Chemistry 262

Quiz 1

Winter 2018

The following quiz contains 30 questions valued at 3 point/question, and 4 bonus

problems valued at 1 point/question, and space for you to demonstrate 3 2-step

functional group interconversions at 1 point each.

Name: KEY

CLASSIFICATION OF ALKYL HALIDES, ALCOHOLS, THIOLS, ETHERS, AND SULFIDES

1. Which of the following is benzyl methyl sulfide?

a.

b.

c.

d.

e.

The dreaded benzyl (as opposed to phenyl) group

NOMENCLATURE OF ALKYL HALIDES, ALCOHOLS, THIOLS, ETHERS, AND SULFIDES

2. The correct IUPAC name for tert-butyl alcohol is

a. 1-butanol

b. 2-methyl-1-propanol

c. 2-methyl-2-propanol

d. 2-butanol

e. 1,1-dimethyl-1-ethanol

Hard to believe so many forgot about assigning the longest parent chain

NOMENCLATURE OF ALKYL HALIDES, ALCOHOLS, THIOLS, ETHERS, AND SULFIDES

3. Which of the following is the correct structure for the compound commonly referred

to as dioxane?

a.

O

b.

O

c.

d.

e.

None of the above corresponds to dioxane

Dioxane is also known as 1,4-dioxacyclohexane, or [6]-crown-2

HOMOGENEOUS INTERMOLECULAR INTERACTIONS – BOILING POINTS AND MELTING POINTS

4. Which of the following would have the greatest boiling point?

a. (CH3)3CCl

b. (CH3)3COH

c. (CH3)3COK

d. (CH3)2CHOCH(CH3)2

e. CH3CH2CH2CH2OH

Really should be a straightforward problem once the metal atom indicating ionic bonding

has been identified

HOMOGENEOUS INTERMOLECULAR INTERACTIONS – HYDROGEN BONDING

5. Which of the following compounds has the highest boiling point?

a. Hexane (MW = 86, BP = 69 oC)

b. Glycerol (1,2,3-propanetriol) (MW = 92 g/mol, BP = 290 oC)

c. Propylene glycol (1,2-propanediol) (MW = 76, BP = 188 oC)

d. Isobutyl alcohol (MW = 74, BP = 108 oC

e. Ethylene glycol (MW = 62 g/mol, BP = 197 oC)

Largest with the most extensive hydrogen bonding network

HOMOGENEOUS INTERMOLECULAR INTERACTIONS – MELTING POINTS

6. Xylene is another name for the dimethyl benzenes. Which of the following would have

the highest melting point?

a. ortho-xylene

b. meta-xylene

c. para-xylene

d. ethylbenzene

e. toluene

Largest with the most extensive hydrogen bonding network

HETEROGENEOUS INTERMOLECULAR INTERACTIONS – SOLUTIONS AND SOLUBILITY

7. Which of the following solvents would dissolve NaCl to the greatest extent?

a. Hexane ( = 1.9)

b. Dichloromethane ( = 8.9)

c. Diethyl ether ( = 4.3)

d. Ethyl Acetate ( = 6.0)

e. Formic acid ( = 59)

Please see table 8.2. NaCl is highly soluble in formic acid (95 % HCO2H, 58 g/100 mL)

HETEROGENEOUS INTERMOLECULAR INTERACTIONS – SOLUTIONS AND SOLUBILITY

8. Which of the following has the greatest solubility in water?

a. Pentane

b. Diethyl ether

c. Dichloromethane

d. n-propyl chloride

e. None of the solvents listed dissolves > 0.1 % w/v

4:1 C to O ratio gives saturation at 6.0 g/100 mL or since d = 0.71 g/mL or 8.4 % v/v

Diethyl ether has a lower dipole moment and dielectric constant than dichloromethane, but

can hydrogen bond with water. Dichloromethane’s solubility limit is 1.8 g/100 mL @ 25 oC

HETEROGENEOUS INTERMOLECULAR INTERACTIONS – SOLUTIONS AND SOLUBILITY

9. Which of the following compounds would have the poorest water solubility?

a. Diethyl sulfide

b. Diethyl ether

c. 1-butanol

d. 1,2-butanediol

e. 4-mercapto-1-butanol

Polarizable yes, polar no, hydrogen bonding no – diethyl sulfide is insoluble in water.

Being polarizable, it has a boiling point of 92 oC. For comparison, with a molar mass =

90 g/mol, a similarly sized hexane (MW = 86) boils at 69 oC, similarly sized pentanol

(MW = 88) boils at 138 oC…the power of hydrogen bonding

HETEROGENEOUS INTERMOLECULAR INTERACTIONS – SOLUTIONS AND SOLUBILITY

10. Which of the following compounds would have the greatest solubility in water?

a. Diethyl sulfide

b. Diethyl ether

c. 1-butanol

d. 1,2-butanediol

e. 4-mercapto-1-butanol

Water can act as the hydrogen bond donor – a Godsend, since all we have to do is

establish the C:O ratio as a first approximation (but be on the lookout for esters).

Again, thiols or thioethers cannot hydrogen bond, but thiols can be ionized. Pay

attention to high pH conditions

HETEROGENEOUS INTERMOLECULAR INTERACTIONS – HOST/GUEST RELATIONSHIPS

11. Please name the following compound

Name: [15]-crown-5

BONUS (1 EC): THE COMPOUND SHOWN BELOW WAS AN UNFORTUNATE SIDE PRODUCT IN THE

MANUFACTURE OF THE BROADLEAF HERBICIDE 2,4,5-T ((2,4,5-TRICHLOROPHENOXY)ACETIC ACID,

ANALOGOUS TO 2,4-D SHOWN ON PAGE 441 OF YOUR TEXT). THE SIDE PRODUCT WAS NOT REMOVED

FROM THE PRODUCT MIXTURE, AND A COMBINATION OF 2,4,5-T AND 2,4-D CONSTITUTED THE VIETNAM

DEFOLIANT AGENT ORANGE. THE SIDE PRODUCT IS A WELL-ESTABLISHED DEVELOPMENTAL TOXIN AND

CARCINOGEN AND GOES BY THE NAME TCDD. WHAT DOES THE ACRONYM TCDD STAND FOR?

TCDD: TetraChloroDibenzoDioxin

A benzene attached at 2 places is a benzo group. Obviously, I would have accepted

dioxane instead of dioxin

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS - OVERVIEW

12. What is the name of the functional group formed when the conjugate base of a

butanethiol displaces iodine from iodobutane in an SN2 reaction?

a. Thiol

b. Thiolate

c. Thioether

d. Sulfide

e. (c) & (d)

A deprotonated thiol is a good nucleophile. Since this happens readily (pKa thioethane =

10.6, this is a common motif in biochemistry)

BONUS (1 EC): NAME THE COMPOUND FORMED

NAME: Dibutyl sulfide, Dibutyl thioether

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – REACTION RATES

13. The rate equation for a nucleophilic substitution reaction of a tertiary alkyl bromide (R-

Br) with I ion would be

a. Rate = k [RBr]

b. Rate = k [I]

c. Rate = k [RBr][I]

d. Rate = k [RBr]2[I]

e. Rate = k [RBr][I]2

Tertiary alkyl halide – think SN1 or E1 (in this case iodide is a poor base and thus SN1 is

favored). It is always the formation of the carbocation that is rate limiting in these

reactions.

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – REACTION RATES

14. Which of the following statements is/are true of SN1 reactions of alkyl halides in

general?

a. The rate of an SN1 reaction depends on the concentration of the alkyl

halide

b. The rate of an SN1 reaction depends on the concentration of the nucleophile

c. SN1 reactions of alkyl halides occur faster in polar aprotic solvents compared to

protic solvents

d. Statements (a) and (c) are true

e. Statements (a) (b) and (c) are true

Given carbocation formation is always rate limiting, if (b) were true it couldn’t be SN1.

Polar protic solvents give rise to the greatest forces of intermolecular interaction with ions

and so work best to promote unimolecular reactions by stabilizing the transition state

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – TRANSITION STATE THEORY

15. For the typical SN2 reaction Y + RX RY + X, it can be predicted S‡ will

be

a. > 0

b. = 0

c. < 0

d. 0

e. Unpredictable as to algebraic sign

In an SN2 reaction, the reactants are part of a single complex – as such, the number of

moles decreases and the entropy decreases

BONUS (1 EC): THE RELATIVE NUCLEOPHILICITIES OF SPECIES DO NOT NECESSARILY PARALLEL THE

RELATIVE BASICITIES OF THE SAME SPECIES BECAUSE

a. NOT ALL NUCLEOPHILES ARE BASES, AND VICE VERSA

b. EXPERIMENTAL MEASUREMENTS OF SUFFICIENT ACCURACY ARE NOT AVAILABLE TO MAKE THE

COMPARISONS

c. NUCLEOPHILICITY IS A THERMODYNAMIC MATTER; BASICITY IS A MATTER OF KINETICS

d. BASICITY IS A THERMODYNAMIC MATTER; NUCLEOPHILICITY IS A MATTER OF

KINETICS

e. ACTUALLY, THE RELATIVE VALUES DO PARALLEL ONE ANOTHER

Ask yourself, “What does the Ka in pKa actually represent?”

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – THE SN2 REACTION

16. What is the principal product of the following reaction?

CH2Cl

H OCH3

CH3

OH

CH2OH

H3CO H

CH3

CH2Cl

HO H

CH3

I

III IV

CH2Cl

H OH

CH3

II

CH2OH

H OCH3

CH3

SN2?

a. I

b. II

c. III

d. IV

e. An equimolar mixture of I and II

Semi-tricky I suppose, but the attack is not on a chiral center.

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – THE SN2 REACTION

17. When 1,4-diiodo-2,2-dimethylbutane (0.10 mol) is treated with 0.10 mol of NaCN in

dimethyl sulfoxide at 30 C, the product(s) formed is/are

a.

NCI

b.

ICN

That extra C “spacer” makes a big difference (see table 9.3)

c.

NCCN

d.

I

e. Both (a) and (b) in equal amounts

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – STEREOCHEMISTRY

18. What would be the major product(s) of the following reaction?

a. I

b. II

c. III

d. IV

e. None of the above

2o alkyl halide, no -substituents, weak base, decent nucleophile in acetone (recall SN2

reactions speed up in aprotic polar solvents). SN2 – look for inversion of configuration

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – CRITICAL FACTORS

19. Which of the following is not a polar aprotic solvent?

a.

H3CC

CH3

O

b. H3C C N

c.

H3CS

CH3

O

d.

HC

N

O

CH3

CH3

e.

H3CCH

OH

CH3

It’s an alcohol – analogous to water, yes?

BONUS (1 EC): TO THE RIGHT OF THE STRUCTURE, WRITE THE COMMON NAME OF EACH SOLVENT; IF THE SOLVENT

GOES BY AN ACRONYM, INCLUDE IT AS WELL

I II III IV

Br

I II

NaI

Acetone

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – CRITICAL FACTORS

20. Which alkyl halide would you expect to react most slowly when heated in aqueous

solution?

a. (CH3)3C-F

b. (CH3)3C-Cl

c. (CH3)3C-Br

d. (CH3)3C-I

e. They would all react at the same rate

Probably the one with far and away the worst leaving group

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – E2 ELIMINATION STEREOCHEMISTRY

21. What is the principal product of the following reaction?

a.

b.

c.

d.

e.

Anti periplaner reaction mechanism, concerted: (1) rotate C2 so Cl is in the plane of the

paper down (2) rotate C3 so H (no shown obviously) is in the plane of the paper up – this

puts methyl groups on opposite sides (3) collapse to alkene, retaining relative positions

Cl

EtOH, EtONa

heat

OEt

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – E2 REGIOCHEMISTRY

22. What is major product outcome for the following reaction?

a.

b.

c.

d.

e.

Question is a bit silly at some levels (SN2 inversion followed by elimination) but does

show how care must be taken when planning a synthesis. tBuOK gives the anti-Zaitsev

(least substituted) alkene product. Note the initial position of the Cl (d) is the product

rotated 180o

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – FACTORS INFLUENCING SN1 AND E1 REACTIONS

23. Carbocations are frequent intermediates in acidic reactions of alkenes, alcohols, etc.

Which of the following is characteristic of carbocations?

a. Rearrangement to a more stable carbocation

b. Loss of a proton to form an alkene

c. Combination with a nucleophile

d. Reaction with an alkene to form a larger carbocation

e. All of the above

This is actually a decent summary of the behavior of carbocations

Cl

1. NaI, acetone

2. t-BuOH, t-BuOK

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – FACTORS INFLUENCING SN1 AND E1 REACTIONS

24. Which mechanistic step in the acid-catalyzed dehydration of 3,3-dimethyl-2-butanol is

the rate determining step?

a.

b.

c.

Step 3:

d.

Step 4a:

+ H3O+

+ H2O

e.

Step 4b:

+ H3O++ H2O

Again, carbocation formation is the rate determining step – recall the analogy of the

impatient, strong, base or nucleophile that is not going to wait around for carbocations

to form, but who is blocked by the tertiary structure which provides enough time for

the more stable (and thus more stable transition state faster) tertiary carbocation to

form. Also recall the treatment of partial inversion that occurs figure 9.13

OH

+ H3O+

OH2

+ H2O

Step 1:

OH2

+ H2O

Step 2:

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – GENERAL PRODUCT PREDICTIONS 5

25. What is the major product of the reaction between methanol and (2R,3S)-2-bromo-

3-methylpentane at room temperature?

a.

b.

c.

d.

e. Both (a) and (c)

(1) Draw out the structure. (2) Assess the structure – substitution slows down SN2

reaction (3) Do I have a good base? Nope (4) Is the system being heated to promote

elimination? Nope (5) Are there any other potential nucleophiles around? Nope – looks

like a solvolysis reaction proceeding through a carbocation with the potential to

rearrange to a 3o carbocation

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – GENERAL PRODUCT PREDICTIONS

26. What is the principal product outcome for the following reaction?

a.

b.

c.

OCH3

H3CO

ClEtOH, heat

OEt

d.

e.

Assess as for #25, only heat promotes elimination, and ring expansion relieves ring

strain and provides a tertiary carbocation prior to elimination

NUCLEOPHILIC SUBSTITUTION AND -ELIMINATION REACTIONS – GENERAL PRODUCT PREDICTIONS

27. What would be the principal product for the following reaction?

HH3C

H Br

HH3C

H CN

CNH3C

H Br

I II

III IV

CNH3C

H H

HH3C

NC Br

C

25oC

a. I

b. II

c. III

d. IV

e. Equal amounts of I & II

Good nucleophile at room temperature with 2o alkyl halide with no blockers (that my

friends, is humor of the highest order) – straight up SN2 with inversion of configuration

ORGANOMETALLIC COMPOUNDS – FORMATION OF GRIGNARD AND ORGANOLITHIUM REAGENTS

28. Which of the following solvents would be least effective in generating a Grignard

reagent?

a. I

b. II

c. III

d. IV

e. V

No non-bonded pairs of electrons, no Grignard reagent formation

ORGANOMETALLIC COMPOUNDS – REACTIONS OF GRIGNARD AND ORGANOLITHIUM REAGENTS

29. What is the structure of product (D) in the following reaction sequence?

a.

b.

c.

d.

e.

CH3CH2OCH2CH3O

(CH3CH2)3N

CH3(CH2)4CH3 CH3OCH2CH2OCH3

I II III

IV V

CH3CHOH

CH3

CH2

O

CH2

PBr3A

etherB C

H3O+

DMg

CH3CHOCH2CH2OH

CH3

CH3CHCH2CH2Br

CH3

CH3CHCH2CH2OH

CH3

CH3CHOCH2CH3

CH3

CH3CHCH2CH3

CH3

Now would be a good time to start counting carbons. In case it isn’t perfectly clear,

the purpose of the Grignard reaction is to form carbon to carbon bonds. By using PBr3

to convert an alcohol to an alkyl halide, you remove the alcohol from the “main chain”.

By coupling the Grignard reagent to oxirane (epoxide) you extend your carbon chain by 2

carbons. Opening the strained ring by nucleophilic attack gives an alkoxide…or alcohol

upon exposure to acid

CARBENES, CARBENOIDS, AND THE SIMMONS-SMITH REACTION

30. What is the major product for the following reaction?

a.

b.

c.

d.

e.

More than one of the above

Simmons-Smith reaction, a concerted syn addition to alkenes to form cyclopropane rings

I2CH2

Zn(Cu)

I I

I

BONUS: 2 STEP TRANSFORMATIONS

Please neatly list up to 3 2 step functional group interconversions you have learned. You

must proceed from the initial functional group to a second functional group and then in the

2nd reaction from the 2nd functional group to a 3rd. Full credit will be given for

transformations that include conditions

Interconversion 1

Reaction 1:

Reaction 2:

Interconversion 2

Reaction 1:

Reaction 2:

Interconversion 3

Reaction 1:

Reaction 2: