Chm 222 - Clark Science Centerrlinck/Chm222/sec/pset1.pdf · Chm 222 Spring 2016, Exercise Set 1...

Chm 222Spring 2016, Exercise Set 1Preliminaries, Words, Tools

Mr. Linck

c©Boniface Beebe ProductionsJanuary 4, 2016

Version 5.1.

NOTE: An asterisk in the problem title indicates that it is a continuing problem from theprevious one. Two asterisk tells you the problem depends on the last two, etc.

1.1. Electrons in Atoms

Write the electron configuration for Li, Na, Mg, B, Al, C, Si, N, P, O, S, F, Cl, Br. Usea periodic table and appropriate abbreviations for inner shell electrons. This is not a busywork problem. You should learn to assign electronic configurations quickly and accurately,especially for the elements commonly used in organic chemistry.

1.2. Valence Electrons

How many valence electrons does each atom of problem 1 have? It should become secondnature to you to know the number of valence electrons for a given atom. Use the periodictable, but work to make the answers resident in your brain. Look for isoelectronic (iso,from the Greek isos, equal, or same) systems.

1.3. Valence Shell Isoelectronic

Which of the following are valence shell isoelectronic with each other? O2−, F, C, Si, N,N−, N+, F−, Ne, O, S, O+.


Which of the following are valence shell isoelectronic with each other? OH−, NH–2, F−, OH,

CH3, NH2, Cl, SiH3, Br.


Give several groups that are isoelectronic with CH3.

1.6. Lewis Structures

Write Lewis structures for C2H6, CH3OH, CH3NH2, CH2O, C4H8O.

1.7. Valence Shell Isoelectronic Usefulness

If a material X is isoelectronic with CH3, what does that say about substituting X for CH3

in a Lewis structure.

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1.8. Lewis Structures Using the Isoelectronic Rule

Take some of the structures from problem 6 and replace one isoelectronic material withanother. Convince yourself that this leads to an easy way to make new Lewis structures.

1.9. Learning Organic Chemistry

Review your notes from lecture 1. Outline major topics. Rewrite your notes. HINT: Don’thand in the answer to this problem. Keep it and study from it.

1.10. Bond Polarity

Indicate the polarity of the bond (with the δ+ / δ− notation) for each of the following:C-Cl, H-Cl, B-F, C-N, C-O, H-O, B-H, Mg-C, N-F, C-C-F. HINTS: (1) Use the periodictable. (2) What do you think I am getting at with the last example?

1.11. Bond Polarity

Here are a bunch of compounds containing a methyl group. Put them in order from themost positively charged methyl group to the most negatively charged methyl group. HINT:Li is generally a better polarizer than Mg.

CH3CH3 CH3OH CH3Li CH3MgCl CH3F CH3NH2

1.12. Partial Charge

Order the carbon atoms in the structure labeled 1 in Figure 1 in terms of increasing positivecharge. HINT: Referring to organic structures with a number is common since the namescan be clumsy, as we shall see.

1.13. Partial Charge and Chemical Reasoning

The dipole moment of HCl is 1.08 Debye and that of LiH is 6.0 Debye. For each molecule,which end of the molecule is positive and which is negative? HINT: As always in this course,if you don’t know the meaning of something, look it up! In the index of Klein (1st edition),it says“Dipole moments, 30-33.” And believe it or not, even “the web” knows about these.

1.14. Partial Charge and Chemical Reasoning

The dipole moment of FCl and ICl are both about 0.8 Debye. Why are they so similarwhen F and I differ so greatly in electronegativity?

1.15. Dipole Moment and Structure

Why is the dipole moment of CH2Cl2 larger than that of CHCl3, when the latter has threechlorine atoms? HINT: Think structure and remember that a dipole moment is a vector;that is, it has both length and direction.

1.16. Dipole Moment and Structure

Predict the direction of the dipole moment in CCl2Br2. HINT: Again, the dipole momentis a vector.

1.17. Dipole Moment and Chemical Reasoning

Carbon-oxygen bonds are more polar, have larger partial charges, then sulfur-oxygen bonds,yet SO2 has a dipole moment and CO2 does not. Comment. HINT: Think Lewis structureand VSEPR.

Chm 222 Exercise Set 1

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1.18. Dipole Moment and Chemical Facts

To boil a liquid, to convert it into a gas, requires energy to break the bonds, often weak,between the closely spaced liquid molecules. Predict whether CH4 or CH2Cl2 would havethe higher boiling point. Incidentally, what physical property of liquids suggests that themolecules are closely spaced? HINT: Think about squeezing a full capped plastic sodabottle versus squeezing a empty capped empty.

1.19. London Dispersion Forces and Chemical Facts

To boil a liquid, to convert it into a gas, requires energy to break the bonds, often weak,between the closely spaced liquid molecules. Predict whether CH4 or CCl4 would have thehigher boiling point. HINT: Klein under “London ...”

1.20. Lewis Structure of Different Connectivity

If I were to say that you could draw a Lewis structure of C4H9Cl with two different connec-tivities, what would I mean? Do so. Use bond-line structures, hereafter, “line” structures.

1.21. Lewis Structure

Draw Lewis structures of CH3C(O)H, CH3CH(CH3)CH3, CH3CHCH2, C2NH3 (cyclic),CH3F, CH3OCH3, CH3CH2OH, CF3C(O)OH, CH2F2, (CH3)2NH, (CH3)3N. Use line struc-tures. HINT: (X) means that group X is off the main chain.

1.22. Patterns in Bonding

Look at each structure in problem 21 and determine the number of bonds to C, to N, toO, to F, to H. Formulate a rule for the number of bonds to these atoms. NOTE: Pay closeattention to problem 35.

1.23. Using Patterns in Bonding

Use the pattern rule (problem 22 to build a Lewis structure for CH2CHCH2C(O)CH3.HINT: You could start at the left hand carbon, which, because it is bonded to three otheratoms (two H and a C) must be double bonded to the C. That second C is then bonded toan H and a C, and those are both single bonds. Finish the analysis.

1.24. Using Patterns in Bonding*

Use the pattern rule to build a Lewis structure for (CH3)3CCHC(CH3)2.

1.25. Lewis Structures Using Isoelectronic Behavior

Although CF3 is not actually isoelectronic with CH3, it is isolobal (has the same bondingcharacteristics). From the last problem, show this is true. HINT: Take advantage of thisfeature. Get to know what groups can replace what groups in organic structures.


Show that H has similar bonding characteristics as CH3.


Show that OH has similar bonding characteristics as CH3.


Show that NH2 has similar bonding characteristics as CH3.


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Figure 1: Some Structures for Exercises


Show that CH3CH2 has similar bonding characteristics as CH3.

1.30. Using Isoelectronic Features

Show that CH2 and O are isoelectronic and hence you can write the Lewis structure ofCH3CH2CH3 and know, absolutely positively, that you could replace that central “CH2”with an “O” to give CH3OCH3.

1.31. Using Isoelectronic Features

Show that CH2 and NH are isoelectronic and hence you can write the Lewis structure ofCH3CH2CH3 and know, absolutely positively, that you could write .


Past experience teaches me that those of you that draw sloppy Lewis structures are muchmore likely to be in the bottom half of the class than those of you that draw neat ones.HINT: Where is the question in that? Let me try to put in a question: Are you going to belike me (and be rather sloppy with your Lewis structures) or are you going to draw neat,concise Lewis structures that are meaningful to you and to the reader?


Draw Lewis structures of CH3CH2NH2 and of CH3CN, the latter of which is not a cyclicmolecule. As always, use line structures. NOTE: The removal of four hydrogen atoms fromthe first generates the second and, because of the “four bonds to carbon, three to N rule,”this removal is accomplished by the introduction of a triple bond. This is a general resultthat we will formalize soon.

1.34. Formal Charges and Lewis Structures

Until it becomes evident to you which atoms have formal charges and which don’t, calculatethe formal charge on each atom in every Lewis structure you draw. In particular, try iton HN3, CH2N2, BH–

4, BF3. HINT: Klein has lots of index references to “formal charge.”(Perhaps the last time I will point this out.) Be sure to distinguish between formal chargeand the net charge on the molecule.


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Take a look at the charged compounds OH−, NH+4 , and H3O

+. Note that charged com-pounds do not obey the rule that you have formulated from problem 22. Use the concept ofisoelectronic species to make sense of these and formuate a rule for the number of bonds tocharged atoms. NOTE: We will get an exception to this rule at carbon where the positivelycharged species is, for instance, CH+

3 .

1.36. Valence Shell Electron Pair Repulsion Theory–VSEPR

Use VSEPR to specify the geometry around each atom in 2, 3, and 4, which are found inFigure 1.

1.37. Reaction Type

One method of classifying an organic reaction is to ask if it is an addition, in which somethingis added to the carbon framework, or a substitution, in which something attached to a carbonframework is replaced by some other group. What kind of reaction is this overall reaction?

CH3C(O)SCH3 + CH3CH2O− = CH3C(O)OCH2CH3 + CH3S

−

HINTS: 1. (X) means that group X is off the main chain, and the structures are written outto indicate to you the attachment of groups. 2. You should always draw Lewis structuresof compounds unless you are sure you know what the bonding is. 3. In this case, focus onthe uncharged material as your basic “organic” compound.

1.38. Description of Reaction Type*

In the last problem, what has added to what or what has substituted for what on what?HINTS: 1. What?

1.39. Epwa

What are you trying to do with an “epwa?” HINT: Now here is a word that you won’tfind in Klein (or even easily in a Google search), although there are many references to“Arrow-pushing” and “Curved-arrow notation.” We defined it in class.

1.40. Epwa

An “epwa” arrow starts at what? Where does the arrow end of the arrow end? REMARK:Isn’t that a cute play on words?

1.41. Use of epwa

Draw a diagram using epwa that shows how H+ reacts with OH– to form water, H2O.HINT: This looks like busy work, but if you take your time and learn to do epwas clearlyand carefully, you will do well in organic chemistry. Incidentally, most texts draw rathersloppy epwas. Make yours carefully because they really are trying to tell you somethingabout what happens during a reaction.

1.42. Epwa

Use epwa to show how H3O+ is attacked by ammonia, NH3, to form a mole of water and a

mole of ammonium ion. HINT: Where do epwas start?


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1.43. Epwa

Use epwa to show how OH– can attack ClO+2 to form HOClO2. HINT: Either you must

let the last compound violate the octet on the chlorine atom or you must tolerate formalcharge separation in that material.

1.44. Polarization and Epwa

Is any atom on CO2 polarized positively? If so, let OH– attack it to form a product. Useepwa to show what happens. HINT: When an epwa increases the electron count around afirst row atom to more than eight, a second epwa must be used (“One good epwa deservesanother.”) to fix the situation.

1.45. Use of Epwa

The reaction in problem 37 occurs in two steps. The first is an addition reaction. Use epwato show this first step in the reaction of CH3CH2O

– with CH3C(O)SCH3, see problem 37.HINTS: (1) Establish the polarization in CH3C(O)SCH3 and then allow the negative oxygenatom of CH3CH2O

– to attack a positive carbon. (2) This is the first of 492 times I will say“the negatively charged ion attacks the positive carbon atom” this semester; maybe it isalready the third time? (3) See the hint in the last problem.

1.46. Use of Epwa*

The product you made in the last problem is shown, in line structure, here (in both astereochemically correct picture–left–and a picture easier to work with–right):

The second step of the reaction is to break the bond between the central carbon andthe sulfur atom using the negative charge on the oxygen as the “driver”. Use epwa to showthis; make sure your products agree with those in problem 37

1.47. Epwa

Use epwa to show how this reaction occurs.

CH3C(O)Cl + OH− = CH3C(O)OH + Cl−

HINT: In general terms, just like the last couple of problems; that, incidentally, is how tolearn organic chemistry: X is just like Y.

1.48. Reaction Type

What kind of reaction is this, a substitution or an addition?

CH3C(O)CH3 + ”CH−3 ” = CH3C(O−)(CH3)CH3

HINT: Read hint 2 of problem 37


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1.49. Epwa*

Use epwa to describe the equation in the last problem.

1.50. Polarization

What is the polarization in the indicated bond in H3C−−−MgCl? Another way to askthis: That pair of electrons represented by the line in the structure belongs mostly to whichatom, C or Mg?

1.51. Epwa and Reaction*

Use an epwa, starting from those electrons that are mostly on the carbon in the last problem,and let them react with CH3C(O)CH3 to form a negative ion, accompanied by the positiveion MgBr+. The last species suggests that the C—Mg bond breaks; does that make sensefrom your epwa?

1.52. Reaction Type**

What kind of reaction is the process in the last two problems? HINT: Remember we arefocusing on the organic fragment in this course; for this problem, the CH3C(O)CH3.

1.53. Reaction Type

What kind of reaction, addition or substitution, is this?

CH3CH−−CHCH3 + Cl2 = CH3CHClCHClCH3

1.54. Description of Reaction Type*

In the last problem, what has added to what or what has substituted for what on what?HINT: That is called the quadruple plus one “what” statement.

1.55. Some Words Used in Organic Chemistry

The process in problem 53 is often referred to as “addition of chlorine across the doublebond.” Indicate what you think is meant by this. Give a reaction that shows addition ofbromine across a double bond. HINT: Draw the reaction with Lewis structures. REMARK:The adventurous among you might try epwa on this problem. It is a little hard, however,unless you think about who wants electrons (obvious) and which electrons are held weaklyso they can donate to the acceptor. The answer, as we shall see, is the double bond electronsof the carbon compound.

1.56. Some Words Used in Organic Chemistry*

Refer to the last problem and give a reaction that shows addition of water across a doublebond.

1.57. Some Words Used in Organic Chemistry

Give a reaction that shows the substitution of Cl– for I– in CH3I. HINT: I am getting tiredof this hint and will cease after this: Draw Lewis structures.

1.58. Epwa

Use epwa to show how the reaction in the last problem occurs. HINTS: There are severalpossible answers; I don’t care right now which you choose. Remember that carbon atomsare not generally fully bonded to more than four groups at once, in contrast to phosphorous,for instance, which can exist as PF5.


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1.59. Organic Reaction Types

Consider the reverse of the reaction in problem 53,

CH3CHClCHClCH3 = CH3CH−−CHCH3 + Cl2

What shall we call this kind of reaction? A “subtraction” would make sense, but isn’t used.


An elimination reaction, such as that given in the last problem, often produces a doublebond. Is the following reaction an elimination?

CH3C(O−(Cl)CH3 = CH3C(O)CH3 + Cl−

HINT: Remember, a parenthesis means off the main chain, which in this case is threecarbons long.


What this course teaches as much as any other aspect is how to recognize patterns andassociate different things with each other. In pursuit of that goal, classify each of thereactions labeled 0a to 0j–found in Figures 2-4–as an “addition” reaction or an “elimination”reaction or a “substitution” reaction. HINTS: (1) In all cases be sure that you trace whathappens to each and every atom. (2) Sometimes there is an reagent other than the organicspecies of concern. Learn to discriminate and to focus on some carbon center of the majororganic species.


Find the reactions in the set labeled 0a to 0j for which the reaction occurs at, or produces,a carbonyl center. HINT: A “carbonyl” center is a carbon in which two of the bonds are adouble bond to an oxygen.


Find the reactions in the set labeled 0a to 0j for which the reaction occurs at, or produces,an alkene center. HINT: An alkene is a compound in which there is a double bond betweentwo carbons.


What are the three reaction “types” that we have learned? There is only one other generaltype of reaction that you should learn to identify: these are “rearrangements.” In these,often accompanied by something else, there is a change in the basic skeleton of C-C bondsbetween the reactants and products. Not a change in the number of C-C bonds, but theirarrangements. For examples, consider the reaction given in Figure 5. Convince me that itis a “rearrangement” as well as something else.

1.65. Lewis Structure and Acidity

Amino acids (which are used to make proteins) exist in acid solution as a cation. Drawthe Lewis structure of the protonated form of glycine, whose formula in the solid state isNH2CH2C(O)OH. HINT: The extra hydrogen ion must “sit on” a lone pair of electrons.Would you prefer to use a pair on N and make “N+” or a pair on O to make “O+”? Usethe periodic table.


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Figure 2: Reactions for Problem 61


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Figure 5: Reaction for Problem 64


Draw the Lewis structure of neutral glycine in aqueous solution. HINT: It is a zwitterion,a species with both a negative charge and a positive charge in the same molecule.


Draw the Lewis structure of glycine in strong base where it exists as an anion.

1.68. Acidity

Write the reaction that describes the loss of the first proton from protonated glycine. Writethe reaction for the loss of the second proton. HINT: To do flawless acid base chemistry, itis very helpful to write the reactions.


What does your structure from problem 66 say about which of these two reactions proceedsto the right most readily?

+NH3CH2C(O)OH = +NH3CH2C(O)O− + H+

+NH3CH2C(O)OH = NH2CH2C(O)OH + H+

BIGGEST OF HINTS: Since these processes release a proton, the materials on the leftare said to be “acids”. Relative acidity is very important in organic chemistry; it is animportant part of “leaving group ability,” which determines the fate of many intermediates.Also, basicity, the inverse of acidity, had a lot to do with nucleophilicity, or the ability ofan electron-rich group to react. If you want to do well in organic chemistry, learn aboutacidity (and basicity).


Draw a Lewis structure for C6H5NO2 where the carbon skeleton is cyclic. Give formalcharges to all atoms.

1.71. Lewis Structure and Formal Charge

Draw a Lewis structure for (CH3)2SO. Give the formal charge on all atoms. HINT: Youcould end up with formal charge on atoms or you could violate the octet at S.


Draw two Lewis structures for C3H7NO. HINTS: (1) Use four bond to C, three to N, etc.(2) My answer involves “connectivity” differences. Does yours?


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Draw two Lewis structures for CH4N2O where the carbon is attached to both nitrogensand the oxygen. HINTS: (1) Use four bond to C, three to N, etc. (2) My answer involves“connectivity” differences. Does yours?


Do your rules of problem 22 and problem 35 work in the last several problems? HINT:There will be many of you that draw Lewis structures with five bonds to C, 3 bonds toneutral O, etc. Don’t be one of them.

1.75. Bonding and Lewis Structures

In each of the structures 5-7–see Figure 1–choose the strongest C-C bond.

1.76. Bonding and Lewis Structures

In 8 in Figure 1, which C-C is longer. In 9, which N-O bond is longer? Which shorter?HINT: In the last structure there are missing bonds and lone pairs; you should draw themin.

1.77. Classes of Organic Molecules

What is an aldehyde? HINT: There won’t be many of you, but there will be some that bythe end of the semester still do not know what an aldehyde is: Don’t be one of them! Knowwhat it is by yesterday.

1.78. Classes of Organic Molecules and Line Structures

Draw two skeletal (also called a “line”) structures for aldehydes with the formula C4H8O.


What is a ketone?


Draw a skeletal (also called a “line”) structure for at least four ketones with the formulaC6H12O.

1.81. Line Structures

Draw a skeletal structure for a compound of formula C7H12O, which is not a ketone.


Draw the functional group associated with an carboxylic acid derivative.


Draw a skeletal structure for acetyl chloride, CH3C(O)Cl, which is a carboxylic acid deriva-tive (or a carbon level 3 compound); and ethyl acetate, CH3C(O)OC2H5, which is also acarboxylic acid derivative (and a carbon level 3 compound), an ester. Be sure you see thatthese two compounds have a common group in them, CH3C(O)—; that fragment has onecarbon with three bonds. Be sure that you see that in each compound this carbon thatneeds one more bond and is attached to a group that also need one more bond.


Describe the bonding in an ester. Draw the line structure of an ester.


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Figure 6: Structures for Various Problems


Draw a skeletal structure for an alkene with four carbon atoms.


How does a ketone differ from acetyl chloride? Be sure you distinguish between, on the onehand, a ketone and, on the other, a compound in which there is a double bond between aC and an O and an adjacent electronegative element.

1.87. Skeletal Lewis Structures

Draw a Lewis skeletal structure for C5H12, C5H10O, C5H8O2, C5H6O3, C5H12O, C5H13N,C5H12S, C5H10, and C5H8

1.88. Review of Bonding Patterns

How many bonds are there to each C atom in the structures in problem 87?


How many bonds are there to each O atom in the structures in problem 87?


If you have formulated a coherent rule for the number of bonds to C in organic compounds,state it now. If you didn’t yet invent a rule, shame on you. Do so now.


If you formulated a coherent rule for the number of bonds to N, O, and F in organiccompounds, state it now. If you didn’t yet invent a rule, maybe you should drop thiscourse.

1.92. Skeletal Lewis Structure

Draw a skeletal structure for (CH3CH2)2CHCH2OCH3.

1.93. Skeletal Lewis Structure

Draw a skeletal structure for (CH3CH2)2CCH2.


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1.94. Lewis Structures and Classes of Organic Molecules

Draw a skeletal structure for a ketone, an aldehyde, an acid chloride (a carboxylic acidderivative), an alkene.

1.95. Functional Groups

Find all the functional groups in capsaicin, 10, the hot in hot peppers.

We now move on to a brief quantum mechanical description of bonding.

1.96. Coulomb’s Law and Chemistry

Coulomb’s law suggests that positively charged things, such as protons, will want to be nearsources of negative charge, or lacking that, loosely held electrons. Compounds 11, 12, and5 are treated with strong acid. On what atom or (atoms) will the H+ “sit”? HINT: Thelast requires, shudder, thought; also it would help if you recall from earlier courses whatthe nature of a double bond is. We will cover it if you did not.

1.97. Atomic Orbitals

Sketch the angular wave function for a 2s electron; a 2px electron; a 2pz electron. Labelyour axes.

1.98. Molecular Orbitals

Show that a 2pz orbital on one carbon atom overlaps (that is, shows either constructiveor destructive interference) with a 2pz orbital on another carbon if the z axis is theinternuclear axis, the axis between the two carbon atoms. HINT: For some reason, thischoice of axes has bothered students in previous years. Let me point out that you and I arefree to choose our axes anyway we like; I am sure that nature does not care about theselittle exercises of our free will. But if you are going to listen to me talk about a z axis, youhave to know which way I define it; and likewise, when you describe an x axis, you have totell me which way it is pointing.


Show that a 2pz orbital on one carbon atom does not have net overlap with a 2px orbitalon another carbon if the z axis is the internuclear axis.


Show that a 2px orbital on one carbon atom overlaps with a 2px orbital on another carbonif the z axis is the internuclear axis. What is the magnitude of this overlap compared to thatof problem 98? HINT: Since the magnitude of bonding is generally related to the amountof overlap, this assessment is important.


Does a 2pz orbital on one carbon atom overlap with a 2s on another carbon atom if the zaxis is the internuclear axis?


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1.102. Hybridization

Add the angular wave function for a 2s electron of C to that of a 2pz electron of the samecarbon atom. Subtract one from the other. HINT: These statements are exactly what theysay. A wave function is a wave, has sign in space. If two waves come together and bothare positive, then you get a bigger positive. If two waves come together and one is positiveand the other negative, then you get a wave that is smaller in magnitude. Just look at thesigns of the waves and do as instructed.

1.103. Hybridization*

In the last problem, in what direction do the sum and difference functions point? Give mean answer that involves the initial orbitals. Also, what orbitals are “left” unused on the Catom?


Add the angular wave function for a 2s electron of C to that of a 2py electron of the samecarbon atom. Subtract one from the other. In what direction do the functions point? Whatorbitals are “left” unused on the C atom?

1.105. Hybridizations

Add the angular wave function for a 2px electron of C to that of a 2py electron of thesame carbon atom. In what direction does the function point? Subtract the two. In whatdirection does this function point? What orbitals are “left” on the C atom? HINTS: (1)Look for regions of constructive overlap and regions of destructive overlap to determinewhat the new functions (that is the sum of the old ones) look like. (2) This problem istrying to illustrate how our axes are irrelevant to Ms. Nature; see the next problem.


Add the angular wave function for a 2s electron of a C atom to the “sum” result of prob-lem 105. In what direction is this function maximal?


From the last several problems, what do you conclude about the direction that an sp hybridcan point? Who has control over that direction, nature or you? HINT: The answer tothese questions establish clearly how artificial hybrid orbitals are; yet we will find themvery useful.


It is less easy (at this level of your knowledge) to determine directionality for sp2 and sp3

hybrids. Just use what was said in lecture (or can be found in any text) and memorize it.Where in space do sp2 hybrids point? You can answer this next question without ambiguity.What orbital on the atom is “left” over after you make sp2 hybrids? Articulate carefullyyour answer to this last question, recognizing that no axes were defined. Can you give ananswer without specifically defining axes? Where does the “left over” orbital point relativeto the sp2 hybrids?

1.109. sp2 Hybridization and the Leftover Orbital

If two carbon atoms are hybridized sp2 and are bonded to each other, how would youdescribe the total bonding between the two carbon atoms?


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Figure 7: A Correct Tetrahedral Drawing, 15A, and an Incorrect One, 15B

Figure 8: Two Rotational Related Structures. The lighter colored spheres are one kind ofatom, the darker, another.


Where in space do sp3 hybrids on a carbon atom point? What orbital on the atom is “left”over? HINT: The last question is a “trick” question.

1.111. Sketching Molecules

In organic chemistry you need to make accurate drawings of molecules showing their threedimensional shapes. This is especially important for a tetrahedral molecule. Sketch a tetra-hedral molecule, showing the three dimensional character, in at least three ways. HINTS:Use wedges and dotted lines to stress the third dimension. Also, and this is important, ifone atom is in front of another, then the lines describing them should be close to each other;see Figure 7.


How many important points were made in the last lecture? Review your notes from thelast lecture. Connect the important points with each other. Plan on making a one minutepresentation on the flow of the last lecture.

1.113. Structural Flexibility

Consider the molecule HOOH. What happens to the overlap in the σ bond between the twooxygen atoms as one OH group is rotated in a clockwise fashion (looking down the O-Ointernuclear axis) relative to the other OH group? The result of this is that it is easy to“rotate” about a σ bond.


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Is it easy to turn the left hand structure in Figure 8 into the right hand one? Why? HINT:This aspect will be important to us soon in nuclear magnetic resonance, and also later inour study of stereochemistry.


Imagine a π bond between two groups of atoms, say the C=C in C2H4. What happens tothe overlap in a π bond as one CH2 group is rotated in a clockwise fashion (looking downthe C-C internuclear axis) relative to the other CH2 group?


Is it easy to convert structure 23 (see Figure 10, several pages later on) into structure 24?Why or why not?


For the skeletal structures 13, 14, and 15 (in Figure 6), indicate the hybridization of eachC atom.


For the right hand terminal carbon in 13, describe the kinds of bonding orbitals that atomhas.

1.119. VSEPR, Structure, and Hybridization

Use VSEPR to describe the structure of 16 in Figure 9 several pages forward. Whathybridizations are used?

1.120. VSEPR, Structure, and Hybridization

Predict the approximate bond angles and the hybridization used in CH3CH2OH, non-cyclicC3H6, CH3CN.


To do well in organic chemistry is to be proficient at solving logical puzzles. See if you canuse the bonding patterns of molecules to find a molecule of formula C4H10N2 that has noπ bonds and no net dipole. HINT: No net dipole means the molecule is symmetric.


Here is another logical puzzle having to do with the last problem, in particular, with theissue of my request to have no π bonds. Draw the Lewis structure of two compounds withthe formula C6H12, one of which has no π bonds and one of which has one π bond. NOTE:We will use this equivalency extensively later in the course.


Given the number of atoms attached to each carbon atom of cyclopropane, what hybridiza-tion would you use to discuss the bonding? HINT: Upon answering this, the next problemshould occur to you as well as to me.


What is wrong with using sp3 hybridization in cyclopropane?


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1.125. Stability of Molecules**

Given the information in the last two problems, would you like to predict anything aboutthe stability of the C-C bonds in cyclopropane compared to those in propane? If so, do so.If not, maybe this is not the course for you.


A carbon atom is attached to four other groups. What hybridization would it use?


A carbon atom is sp2 hybridized. What bonding characteristics does it have (i.e., how manyσ bonds? how many π?)


Assume an atom has only a pz orbital. Draw an mo diagram for the bonding between twoof these atoms if the internuclear axis is the z axis.


Assume an atom has only pz and px orbitals. Draw an mo diagram for the bonding betweentwo of these atoms if the internuclear axis is the z axis.


Assume you have one atom with only a pz orbital and another with only only pz and px

orbitals. Draw an mo diagram for the bonding between these two atoms if the internuclearaxis is the z axis.


Assume an atom has only two sp hybrids pointing in the plus/minus z direction. Draw anmo diagram for the bonding between two of these atoms if the internuclear axis is the zaxis.


If the C-C axis of 16 is the y axis, and the x axis is up and down in the plane of the paper,what are the atomic orbitals used in the double part of the double bond.


Sketch the molecular orbital for the double part of the double bond in 16. HINT: Makeyour axes the same as those defined in the last problem.


On which atom, C or O, does the π bond of 11 have the largest orbital contribution? Sketchit.


On which atom, C or O, does the π* bond of 11 have the largest orbital contribution?Sketch it.


On which atom, C or Cl, does the σ bond (of a C-Cl bond) have the largest orbital contri-bution?


1.148 19


On which atom, C or Cl, does the σ∗ bond (of a C-Cl bond) have the largest orbitalcontribution?


On which atom, C or B, does the σ bond (of a C-B bond) have the largest orbital contri-bution?

1.139. Partial Charges

In a bond between C and B, which atom is more positively charged?


In a bond between C and H, which atom is more positively charged? HINT: Trick question,or trick answer, take your choice.


In a bond between H and B, which atom is more positively charged? HINT: This is a purelogical deduction if you did the last two problems. Be sure you can articulate the logic.


Draw an mo diagram for the π bonding in H2CCH2 and in H2CO. How are they similar?How do they differ?

1.143. HOMOs

Try to identify the electrons that are least tightly held (that is, the highest occupied m.o.,the homo) in 17-20. For example, in the first compound they would be the C-C π electrons.HINT: Bonding electrons are usually more stable than non-bonding electrons.

1.144. LUMOs

Which compound in the set 17-20 would have the lowest energy empty orbital (lumo)?What kind of orbital (σ, σ∗, non-bonding, etc.) is it?

And now back from our excursion into quantum mechanics, although we will never againbe able to leave it alone!

1.145. Formal Charge and Polarization

Would you expect the hydrogen in BH–4 to be more negative than that in HCl? More

negative than that in NH3? More negative than that in CH4?

1.146. Polarization Review

Would you expect the carbon atom or the oxygen atom of the carbonyl group to be morepositive?

1.147. Predicting Possible Reactivity

If you brought a BH–4 ion up to a carbonyl group, what atoms would be attracted to each

other? HINT: The boron atom in BH–4 is rather effectively shielded by the hydrogen atoms

from the “outside” world.


1.158 20

1.148. Predicting Possible Reaction with More Care

If you brought a NaBH4 molecule up to a carbonyl group, what atoms would be attractedto each other? HINT: How does this problem differ from the last one?

1.149. Reaction and Hybridization

In the reaction

CH3C(O)CH3 + BH−4 = CH3CH(O−)CH3 + BH3

What happens to the hybridization of the central carbon atom? State what electrostaticinteraction occurs between the reactants to facilitate this reaction.

1.150. Describing Reactions with Epwa*

Use epwa to describe what happens in the reaction in the last problem. HINTS: (1) Fromwhere does the epwa start? (2) To what dotted line does it go? (3) Draw your epwacarefully.

1.151. Reaction and Classification of Type

We can complete the reaction of problem 149 by adding dilute acid in a second step. Herethen is both steps

CH3C(O)CH3 + BH−4 = CH3CH(O−)CH3 + BH3

CH3CH(O−)CH3 + H+ = CH3CH(OH)CH3

What kind of reaction is this? How would you describe it? For instance, Boniface Beebe,the great natural philosopher from rural Arkansas, who probably needed eyeglasses, mightanswer: “The net reaction is the substitution of a chlorine for a bromine.”

1.152. Describing Reactions with Epwa

Use epwa to describe what happens in the second reaction in the last problem.

1.153. Predicting Organic Reactions

Predict any reaction between BH–4 and CH3CH2C(O)H. Use epwa to describe it. If reaction

occurs, and we treat the product with H+, use epwa to predict the final product.


When we know the reaction of a pair of molecules, we can often predict what will happen ifwe make slight changes. What would you predict would happen if you reacted BH(CH3)

–3,

which I am imagining is a hydride donor, with CH3C(O)H? Use epwa to describe yourreaction professionally.


Would you make a prediction about how effective BF3H– would be as a hydride donor to

an aldehyde compared to BH–4? Give your reasons.

1.156. Review of Lewis Structure and Hybridization

Draw the Lewis structure of a compound with an sp hybridized C.

1.157. Review of Lewis Structure and Hybridization

Draw the Lewis structure of a compound with an sp2 hybridized C.


1.168 21

Figure 9: Some Structure for Various Problems

1.158. Review of Charge Distribution in a Molecule

In the molecule CH3MgCl, which atom(s) are negative? Which positive?

1.159. Predicting Reactions

If you were to bring a molecule of CH3MgCl up to a carbonyl group, which atoms wouldbe attracted to each other? HINT: There are two general answers to this question, and twosub-answers to one of those. We are ultimately concerned with net reaction, so if you askthe question “Which negative group of the CH3MgCl will most likely give up charge?” youwill be on the right track.

1.160. Reaction Prediction

What might you expect for the immediate products of the reaction

CH3C(O)CH3 + CH3MgCl→

As always, use epwa.

1.161. Reaction Prediction*

Sketch out what would happen (use epwa) if you treated the product of the reaction in thelast problem with H+.

1.162. Preparation for Acidity: Atomic Orbitals

Which orbital is most stable, C 2s or C 2p?

1.163. Preparation for Acidity: Hybrid Orbitals*

Which hybrid orbital contains the most “s character”, sp or sp2?

1.164. Preparation for Acidity: Hybrid Orbitals**

Which hybrid orbital is the most stable, sp or sp2? Why?

1.165. Hybrid Orbitals and Acidity***

In view of the past couple of problems, which compound, 21 or 22, would be most easilyable to tolerate the negative charge it has?

1.166. Hybrid Orbitals and Acidity****

In view of the last problem, which would be the stronger acid, protonated 21, that is,CH3CCH, or protonated 22, CH3CHCH2?

1.167. Review of Molecular Orbitals

Build an mo diagram for the double part of a double bond (the π bond) in 17.


1.177 22


1.168. Using Molecular Orbitals to Predict Chemistry

When light interacts with the molecule 17 and excites an electron from the π bonding orbitalto the π antibonding orbital, what happens to the double bond? HINT: Pay attention toyour diagram in problem 167.

1.169. Conclusions from Molecular Orbital Theory

How would you account for photoisomerization of 23 to 24? HINT: Think about the lastcouple of problems and what the word photoisomerization might mean.

1.170. Hybrid Orbitals

Find the following in the structure 25, which is a penicillin: An sp3 hybridized carbon; ansp2 hybridized carbon; an sp hybridized carbon; an amide; a carboxylic acid group.


Distinguish between an amide and an amine; draw examples.


Distinguish between an amine and an imine; draw examples.


Distinguish between an amide and an imine; draw examples.


Distinguish between an carboxylic acid and an alcohol; draw examples.


Distinguish between an carboxylic acid and an aldehyde; draw examples.


Distinguish between a ketone and an aldehyde; draw examples.


1.190 23

1.177. Skeletal Structures and Nomenclature

Draw the line structure of 4-methyloctane.


Draw the line structure of 2,4-dimethyl-5-propyldecane.


Draw the line structure of 4-(1,1-dimethylethyl)decane.


The trivial name for a propyl group attached by the central carbon is “isopropyl”. Drawthe line structure for 4-isopropyldecane.


The trivial name for a 2-methylpropyl group attached by an end carbon is an “isobutyl”group. Draw the line structure for 5-isobutyldecane.


The trivial name for a 1-methylpropyl group attached by carbon 1 is an “secondary butyl”group, usually abbreviated sec-butyl. Draw the line structure for 5-sec-butyldecane.


The trivial name for a 1,1-dimethylethyl group attached by carbon 1 is an “tertiary butyl”group, usually abbreviated tert-butyl or even t-butyl. Draw the line structure for 5-t-butyldecane.

1.184. Equivalent Groups and Atoms

In the molecule of the last problem, is there easy rotation about the bond connecting thetert-butyl group with the decane? If so, are the methyl groups equivalent on a long timescale? Is there easy rotation about the bond between a CH3 and the central carbon atomof the tert-butyl group? If so, are the hydrogen atoms of the CH3 group equivalent on along time scale?

1.185. Skeletal Structures

Draw the line structure for 3-ethyl-3-hexene

1.186. Nomenclature

Write IUPAC name for 26-31

1.187. Functional Group and Nomenclature

Name the class of compound (the functional group) in compounds 32-38. Then give theIUPAC name for the compounds.

1.188. Skeletal Structure and Nomenclature

Draw a line structure for 1,5-dibromo-2,2-dichloro-4-ethyl-4-methyl-3-hexanol. HINT: Likelywe would never use a name this complicated in practice, we would just draw the structure.


Draw a line structure for tert-butylamine.


1.196 24



Draw a line structure for 3-isobutylcyclopentanol.

1.191. Nomenclature

Name 39-43.


Write a skeletal structure of 4,5-diisopropylnonane; 5,5-dibromo-4-ethyloctane; 4-(1-methylethyl)decane.

1.193. Nomenclature

Name the class of compound in 39-43.

1.194. Predicting Reactions

If you were to bring a molecule of CH3Li up to a carbonyl group, which atoms would beattracted to each other? HINT: There are two general answers to this question.


If we anticipate reaction at the carbonyl carbon atom, what might you expect for theimmediate products of the reaction

CH3C(O)CH3 + CH3Li→

Should I say once more, use epwa.


1.205 25


Carry out the reaction in the last problem as step one of a two step process. The secondstep involves addition of H+. Use epwa to illustrate this second step. What is the netreaction? How would you describe the overall reaction, addition or substitution? Speakingprofessionally, you would say it is . . . .

1.197. Carbon Level

Carbon level is the defined as the “number of bonds from a carbon to an electronegativeelement’.” Give the carbon level in the compounds 39-43.

1.198. Nomenclature and Carbon Level

What is the carbon level of the carbons in acetone (propanone), ethanoic acid, ethanal, andcarbon dioxide?

1.199. Carbon Level

What are the carbon level of carbon atoms in CH3CH2C(O)Cl, CH3C(O)H, CH3C(O)OCH3?

1.200. Carbon Level

For reasons we will justify later in the course, the only odd issue with carbon level concernscompounds with double bonded carbon atoms. The carbon level in each carbon of a doublebond is 1

2 (or the pair has a carbon level of 1, sometimes called a delocalized carbon level 1compound) and that of each carbon in a triple bond between two carbons, the carbon levelof each carbon is 1 (or delocalized carbon level 2). What is the carbon level of each carbonin CH3CHCHCl, HCCCH2CH2OH.

1.201. The Ihd Concept

A concept called the “ihd” is very useful in determining the possible structures of a com-pound. The is an integer greater than zero that is determined by a scary formula whichis easier to use than it looks. Here it is. For a compound of the formula CnHhFfOoNq thevalue of the ihd is given by:

ihd =2n+ 2− h− f + q

2

where Cl, Br, etc behave like F; and S, Se, etc behave like O, which contributes nothing;ad nausem. The only odd think in the formula is the coefficient of N is added rather thansubtracted, hence it has a funny name, “q,” rather than “n,” which has already been usedanyway! Find the ihd of CH3CH2F, CH3OCH3, C6H6. HINT: The ihd tells us the numberof π bonds and rings in a molecule.

1.202. ihd

Find the ihd for each compound in problem 198.

1.203. ihd

Find the ihd for each of the following compounds: C6H10Cl2, C5H10O, C6H14O2, C7H10

1.204. ihd and Lewis Structure

Suggest a possible structure for a compound of formula C6H12O.


1.213 26


1.205. ihd and Lewis Structure

What is the ihd for a compound of formula C4H9N? Suggest a structure.

1.206. ihd

Boniface Beebe, the great natural philosopher from Searcy, Arkansas, looked at a compoundwith the formula C24H48. ”Wow”, he said, ”as big as this is, it must contain a triple bond.”Was Bonnie correct?.

1.207. Nomenclature

Boniface Beebe, in his book, “A Grand View of Organic Chemistry”, published in 1896,described the preparation of a compound he called 4-ethyl-pentane. Although this conveyssufficient information for you to draw the compound, what should he have named it?

1.208. ihd and Structure

Find the ihd and draw a structure for each of the following compounds: C3H4, C10H8,C5H9Cl, C6H10O, C7H10O3, C5H5NH2, C4H5N, C6H12S, C5SiH14, C4H11N, C5H5N. HINT:What structure you draw and that another student draws may be very different, even thoughboth of your could be correct. Life is hard!

1.209. Electrophiles and Organic Species

If you had a positively charged species, E+, which is called an electrophile, and it came upto 23, what atom(s) would it likely attack? How about 41? How about 40? How about2-butyne?

1.210. Nucleophiles and Organic Species

If you had a negatively charged species, N−, which is called a nucleophile, and it came upto 39, what atom(s) would it likely attack? How about 41? How about 44?

1.211. Electrophiles

From the name, what property does an “electrophile” have? HINT: Webster’s Interna-tional Dictionairy says: “Definition of -PHILE: lover: one having an affinity for or a strongattraction to, <acidophile ><Slavophile >”

1.212. Electrophiles

Give some examples of compounds that are likely to be electrophiles and, if appropriate,indicate the electrophilic site in those species.


1.223 27

1.213. Nucleophile

From the name, what property does a “nucleophile” have?

1.214. Nucleophile

Give some examples of compounds that are likely to be nucleophiles and, if appropriate,indicate the nucleophilic site in those species.

1.215. Nucleophiles and Electrophiles

Would you classify the following as electrophiles or nucleophiles? CH–3, H–, CH+

3 , OH–, H+,SH–, NH3.


Compare reaction 0g with 0j. How do you classify them? (See problem 61.) Is Cl2electrophilic or nucleophilic? Is Cu(CH3)

–2 electrophilic or nucleophilic? It should strike

you as odd that both kinds of reagents attack the alkene. Do you anticipate that somethingstrange is happening in one case or the other? HINTS: (1) You should. (2) The heart oflearning organic chemistry (or any other subject for that matter) is to be sure that yourecognize when something looks odd; and to ask yourself “Why?” You may not have theanswer at the moment, but the act of asking still is important.


Past experience teaches me that those of you that draw sloppy epwas, ones in which theelectron pair being used is not obvious (that is where the tail of the arrow is) and, moreimportantly, in which the position in space to which the electrons move (that is where thehead of the arrow goes) is not clear, will generally do poorly in this class. An epwa shouldmean something to you; it is an attempt to represent an important motion of an electronpair. Use the dotted line convention, which most texts DO NOT USE, and make yourepwas neat and concise. Draw an epwa to show how reaction 0f might occur. HINT: Thisprocess occurs in more than one step (as we have seen several similar reactions at a carbonlevel 3 carbon), although that bell may not ring for you at this stage.

1.218. Nucleophile and Electrophiles

What kind of reagent is hydride ion? HINT: See title.

1.219. Polarization of Bonds

What is the charge on the carbon atom which is π bonded to an oxygen atom?


Would you classify the carbon atom in a carbonyl bond as an electrophile or nucleophile?


Consider a reaction between two reagents, one of which is a nucleophile. The other reagent,of necessity, is an .


If one added a proton to a lone pair on the oxygen atom of a carbonyl group, would youclassify the carbon in that group as electrophilic or nucleophilic? Would it be more so orless so than the carbon in problem 220? HINT: Draw a Lewis structure after addition ofthe proton and consider resonance.


1.229 28

Figure 13: A Yucky Epwa (15C) and a Nice Epwa, 15D


How many bonds to a C, a N, an O, a F? How many bonds to an oxygen atom that ispositively charged? to an oxygen atom that is negatively charged? How many bonds to anitrogen atom that is positively charged?


If you had a molecule with a carbon atom attached to three hydrogen atoms and an O−

group, would that molecule react with an electrophile? On which atom would reactionoccur? HINT: Be sure you can do the last problem.

1.225. Nucleophile and Electrophiles*

If you had a molecule with a carbon atom attached to three groups as well as to an O−

group, would that molecule react with an nucleophile? On which atom?

1.226. Epwa and Reaction Prediction

Guess the product of allowing H− to attack butanal, followed by treatment with H+. Useepwa/ogeda. Name the final product. HINT: Another issue with epwa. Most texts makethe head of the arrow for an epwa that is making a bond go to an atom. A few say this isn’tright, but do it anyway. You should not. You should have the head of your epwa pointingto an atom only if a lone pair is being formed, in which case that is where the electrons aregoing. If they are going to a new bond, then the head of the arrow should point betweenthe nuclei where the bond is forming. See Figure 13.

1.227. Epwa and Mechanism

Guess why you have to do these two steps in problem 226 sequentially; that is, why can younot add H−, the aldehyde, and H+ all together? HINTS: (1) Think electrostatic attractionand write a balanced chemical reaction. (2) Most nucleophiles react with H+ faster thanwith other electrophiles.

1.228. Extrapolation of Knowledge

Justify why BH–4 might be used instead of hydride ion, H–.


1.241 29


Would the hydrogen atom in AlH–4 be more or less reactive than that in BH–

4? Why? HINT:As usual, think periodic position.


If I told you that BH–4 was not reactive enough to react with an ester (what is an ester and

what product am I looking for?), which it is not (at least in ethanol as a solvent), wouldyou throw your hands into the air or look for another reagent on the shelf? What would itbe? Why? HINT: Bonnie might throw up his hands, but perhaps you should look at thelast problem.

1.231. Newman Projection

Draw a Newman projection of ethane.


Draw a Newman projection of propane looking down the C1-C2 bond.

1.233. Newman Projection and Stability

Draw the gauche conformation of 1,2-dibromoethane.


Draw the anti conformation of 1,1,1-trifluorobutane looking down the appropriate bond.


If you did the last two problems using Newman projections, draw the line structures. Ifyou did those two problems using line structures, draw the Newman projections.

1.236. Newman Projection and Stabilities

Draw Newman projections for each of the three minimum energies of 2-bromo-1,1-dichloroethaneand indicate their relative stabilities.


Review your class notes from the last lecture. What were the major topics in the lastlecture? Think about them. How can you connect them? How can you connect them towhat has occurred previously in the course?


Make a Newman projection for 3-methylpentane looking down the C1-C2 bond; down theC2-C3 bond. If there is more than one conformer, draw all of them.


Consider oxirane, a cyclic compound of formula C2H4O. Make a Newman projection look-ing down the C1-C2 bond. Can you see any reason why this structure might have someinstability? NOTE: Oxiranes are also called epoxides, three membered rings with two car-bon atoms and one oxygen atom. We shall learn how to synthesize them and how to openthe ring to make interesting compounds.


Draw the zig-zag (line structure) and Newman projections (down the C1-C2 bond) of someconformations of propanal.


1.251 30

Figure 14: Structures for Several Problems

1.241. Isomers and Conformers

How do isomers differ from conformers?


Consider the three Newman projections given in 601-603. Order them in terms of stability.


How many isomers are there of 1-chloro-2-fluoroethane? How many unique conformers?


Is the conformer shown in 604 the most stable about the indicated C-C bond? If not, drawthe Newman projection of the most stable form; otherwise, move on.


What is the name of the compound indicated in 604?


Draw the Newman projection of the most stable conformer of 1-cyclohexylpropane (withrespect to the C1-C2 bond of the propane).

1.247. Review of Epwa and Reaction Prediction

Will BH–4 attack the oxygen atom or the carbon atom of ethanal? Why? Use epwa to show

the product.


Will H3O+ attack the oxygen atom or one of the carbon atoms of ethanal? Why? Use epwa

to show the product.


If H+ does attack the oxygen atom of ethanal, what happens to the electrophilicity of thecarbonyl carbon?


Will OH– attack the carbon atom or oxygen atom of ethanal? Why? Use epwa to show theproduct.


1.263 31

1.251. Epwa and Reaction Prediction*

Will OH– attack a carbon atom of CH3C(O)Cl? Which carbon atom? Why? Use epwa toshow the product. HINT: At the moment I don’t care too much if you plan a “substitution”or an “addition”–see problem 61 although in this case it is rather obvious and we havediscussed it. Later the question you should always ask is: Is there a group that can easilyleave, that is, be stable when it leaves. If so, you have a “good leaving group;” the conceptof acidity is the key to this analysis.

1.252. Epwa and Reaction Prediction**

Here is the only hard problem of this set. Will Br2 be attacked by propene? Use epwa toshow the product. HINTS: Does bromine “want” to be negative? Are there any looselyheld electrons on propene? Think molecular orbitals. Go from there.

1.253. Learning Organic Chemistry***

What is common in the reactions in problems 247, 250, and 251? These cover most of thereactions in the course, although we will get more detail as we go along.

1.254. Learning Organic Chemistry****

How do you fit the result of problem 249 into your knowledge from the last problem?

1.255. Learning Organic Chemistry*5

There is a fundamental difference between the process in problems 247-251 and that inproblem 252. Articulate that difference. HINT: For a concise answer, focus on the whetherthe carbon fragment acts as an electrophile or a nucleophile.


Use epwa to show the reaction of 45 with BH–4, followed by treatment with H+.


Use the already stressed similarity between what happens with BH–4 and what should happen

with CH3MgCl to predict the product of the latter with 45 when you follow the first stepwith treatment with H+.


Use epwa to show reaction of 46 with 47 followed by treatment with H+. Make sure youkeep track of charges.

1.259. Organic Knowledge

How is 47 made?


Use epwa to show reaction of 46 with 48 followed by treatment with H+.


Use epwa to show reaction of 45 with 48 followed by treatment with H+.


Write a mechanism (use epwa) for the reaction of AlH–4 with 2-propanone (better known as

acetone), followed by treatment with H+.


1.274 32

Figure 15: Structures for Several Problems

1.263. Synthesis

How would you prepare 2-pentanol from 46?

1.264. Review of Reaction Prediction

Which would you guess is a more reactive reagent, BH–4 or AlH–

4? Why? HINT: Ever seesomething like that question before?


Write a mechanism (use epwa) for the reaction of C2H5MgBr with ethanal followed bytreatment with H+.


What is the product of reaction of 2-iodopropane with Mg metal?


What is the product of reaction of 1-bromopropane with Mg metal?


What is the product of reaction of 2-chlorobutane with Mg metal?


In the last three problems we could say that we have made a “blank blank” reagent. Fill inthe blanks. HINT: The magnesium reagent in the last few problems is called a “Grignardreagent”, but that is not what I am looking for. I want a more generic answer that is alsomore revealing of general chemistry trends.


What is the product of the reaction of the product of problem 266 with acetone?


What happens if a Grignard reagent is treated with water? HINT: Think “C−” looking forsomething positive.


What happens if a Grignard reagent is treated with CO2? HINT: Same as last problem.

1.273. Synthesis

How would you synthesize 47 from chloroethane?


1.287 33

1.274. Synthesis: First Step

What kind of compound is 49?

1.275. Synthesis: Second Step*

You can make [answer to last problem]s from what kind of compounds? And the answeris?

1.276. Synthesis**

How would you synthesize 49 (also known as Molecular Woman with Lopsided Hat)?

1.277. Synthesis: First Step

What kind of compound is pentan-2-ol?

1.278. Synthesis: Second Step*

What kind of compound can you use to make the kind of compound that is the answer tothe last problem?

1.279. Synthesis**

How would you synthesize pentan-2-ol from 2-pentanone and any other reagent?

1.280. Synthesis

How would you synthesize pentan-2-ol from butanal and any other reagent? HINT: Askthe questions indicated above. Then ask “Do I have a new C-C bond?” Does that limit thepossibilities?

1.281. Synthesis

Given what we have talked about thus far, what questions do you ask yourself to figure outhow to synthesize a compound?

1.282. Synthesis

How would you synthesize pentan-2-ol from ethanal and any other reagent?

1.283. Synthesis and Epwa

How would you synthesize 2-methyl-2-propanol from acetone? Write a mechanism usingepwa.

1.284. Epwa and Reactions

What would be the immediate product if you treated CH3CH2C(O)Cl with CH3MgCl?


Examine your product from the last problem and ask if there is a good leaving group fromthe tetrahedral intermediate? HINT: The best leaving groups are halide ions, followed bymono negative oxygen compounds (but NOT dinegative oxygen). Negative carbon andhydrogen are very poor leaving groups.

1.286. Epwa and Reactions*

Let the good leaving group from the last problem leave. Use epwa to show how it happens.Is the compound that results from your epwa reactive toward the CH3MgCl left in solution?If so, use epwa to show the reaction.


1.287 34


Complete your reaction of the last several problems by adding H+. Use epwa to show thefinal products.


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