Organic Chemistry=Rajendra01

8/8/2019 Organic Chemistry=Rajendra01

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An organic compound is one that has carbonas the principal element

e

e

e ee

e

Carbon is unique

It has 6 electrons in its outer shell

arranges 1s2

2s2

sp2

It has room for 4 bonds to 4 other atoms.

Organic compounds have specific geometry

around the carbon to carbon bond


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The carbon atom forms bonds in atetrahedral structure with a bondangle of 109.5 O.

So a chain of carbon atoms makesa zigzag pattern


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Introduction

A hydrocarbon is a compoundconsisting of only hydrogen and

carbon.The carbon to carbon can be single,double, or triple bonds.

The bonds are always nonpolar


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Triple.

Double

Note that in each example, each carbonatom has four dashes, which represent four bonding pairs of electrons, satisfying theoctet rule.

Carbon-to-carbon bonds can be:

Single


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(B) branched

Carbon-to-carbon chains can be

(A) straight

(C) closed ring.


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Identify the longest continuous chain.

The locations or other groups of atoms attached to

the longest chain are identified and numbered bycounting from the end of the molecule which keepsthe numbering system as low as possible.

Hydrocarbon groups that are attached to the

longest continuous chain and named using theparent name and changing the ane suffix to yl

Naming alkanes


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Step-1 Identify the longest continuous chain Where is the longest continuous chain of carbons?


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EndingsEndings

Alkanes (all C-C single bonded parentAlkanes (all C-C single bonded parentchain) end inchain) end in ane ane MethMeth aneane CHCH 44

EthEth aneane CC 22HH66 PropProp aneane CC 33HH88

Attached carbon groups (substituents) endAttached carbon groups (substituents) end

inin yl yl MethMeth ylyl CHCH 33 -- EthEth ylyl CHCH 33CHCH 22 --

PropProp

ylyl

CHCH

33CHCH

22 CHCH

22

3-ethyl pentane


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Step 3. Name the attached groups.Step 3. Name the attached groups.

Carbon (alkCarbon (alk ylyl) groups) groups MethMeth ylyl CHCH 33 --

EthEth ylyl CHCH 33CHCH 22 -- PropProp ylyl CHCH 33CHCH 22 CHCH 22

HalogensHalogens Fluoro (F-)Fluoro (F-) Chloro (Cl-)Chloro (Cl-) Bromo (Br-)Bromo (Br-) Iodo (I-)Iodo (I-)


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Step 4. Designate where the groupStep 4. Designate where the groupis attached to the parent chain.is attached to the parent chain.

Use the numbers of the parent chain fromstep 2 to designate the location of theattached groups to the parent chain.

1 2 3 4 5

2-methyl


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Structural FormulasStructural Formulas

Lazy way to write the Hydrogens Instead of drawing the bonds, just state

how many hydrogens are attached NOTE: The bonds are between

CARBONS in a parent chain, and nothydrogens!

Lewis Structure

Structural Formula


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Order of PriorityOrder of Priority

IN A TIE, halogens get the lower number IN A TIE, halogens get the lower number before alkyl groupsbefore alkyl groups

4-chloro-2-methylpentane or 4-chloro-2-methylpentane or 2-chloro-4-methylpentane?2-chloro-4-methylpentane?

5 4 3 2 1


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Order of PriorityOrder of Priority

IN A TIE between SIMILAR GROUPS, theIN A TIE between SIMILAR GROUPS, thegroup lower ALPHABETICALLY gets thegroup lower ALPHABETICALLY gets thelower number lower number

4-bromo-2-chloropentane or 2-bromo-4-chloropentane ?


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IsomersIsomers

Straight chain alkanesStraight chain alkanes :: AnAnalkane that has all its carbonsalkane that has all its carbonsconnected in a row.connected in a row.

Branched chain alkanes:Branched chain alkanes: AnAn

alkane that has a branchingalkane that has a branchingconnection of carbons.connection of carbons.

Isomers: Compounds with same molecular formula butdifferent structures.


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Petroleumproductsand the

ranges of hydrocar-

bons in

eachproduct.


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There is only one possible wayThere is only one possible waythat the carbons in methane (CHthat the carbons in methane (CH 44),),ethane (Cethane (C 22HH66 ), and propane (C), and propane (C 33HH88))can be arranged.can be arranged.


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However, carbons in butane (CHowever, carbons in butane (C 44 HH1010 ) can) canbe arranged in two ways; four carbons in abe arranged in two ways; four carbons in arow (linear alkane) or a branchingrow (linear alkane) or a branching

(branched alkane). These two structures(branched alkane). These two structuresare two isomers for butane.are two isomers for butane.


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Different isomers are completely differentDifferent isomers are completely differentcompounds. They have different structures,compounds. They have different structures,different physical properties such as meltingdifferent physical properties such as melting

point and boiling point, and may have differentpoint and boiling point, and may have differentphysiological properties.physiological properties.


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Number of possible isomers increases

rapidly with the number of carbons C 30H62 >4 billion possible isomers


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Properties of Alkanes Main property: will burn

C C C


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Types of Carbon AtomsTypes of Carbon Atoms Primary carbon (1Primary carbon (1

oo

)) a carbon bonded toa carbon bonded to

one other carbonone other carbon

Secondary carbon (2Secondary carbon (2 oo )) a carbon bonded toa carbon bonded to

two other carbonstwo other carbons

Tertiary carbon (3Tertiary carbon (3 oo )) a carbon bonded toa carbon bonded to

three other carbonsthree other carbons

C

C

CH

H

H

C C

H

C

C

C

C

H

H

C C

H

HC

C

H

C

C

C

C

H

H

C C

H

H

C

C

C

H


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Unsaturated Hydrocarbons Can have more hydrogen atoms added Very important in biological systems Alkene: hydrocarbon that contains one

or more carbon-to-carbon doublebonds

To show the presence of the doublebond, the ane suffix from the alkanename is changed to ene.

General formula of C n Hn Simplest: ethylene, C 2H4


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Ethylene is the gas that ripens fruit, and a ripe fruitEthylene is the gas that ripens fruit, and a ripe fruitemits the gas, which will act on unripe fruit. Thus,emits the gas, which will act on unripe fruit. Thus,

a ripe tomato placed in a sealed bag with greena ripe tomato placed in a sealed bag with greentomatoes will help ripen them.tomatoes will help ripen them.


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Naming of Alkene is similar to naming alkanesexcept:

The longest continuous chain must containthe double bond.

The base name now ends in ene. The carbons are numbered so as to keep the

number for the double bond as low aspossible.

The base name is given a number whichidentifies the location of the double bond.


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Alkyne: hydrocarbon thatcontains one or more carbon-to-carbon triple bonds

Naming an alkyne is similar tothe alkenes, except the basename ends in yne.

General formula of C n H2n 2 Simplest: acetylene, C 2H2

Alkynes


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Properties of Alkenes and Alkynes

Similar physical properties to alkanes

Undergo more reactions than alkanes

Addition reaction: add compounds across doublebond

Importantly, they can form polymers


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Cyclic Hydrocarbons

Carbon atom chains in form of rings Can be represented by structural

formulas or symbolic representations


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Cycloalkanes and Aromatic Hydrocarbons Cycloalkanes are alkanes (only carbon to carbon

single bonds) which form a ring structure.

The "straight" chain has carbonatoms that are able to rotate freelyaround their single bonds,sometimes linking up in a closedring.

(B) Ring compounds of the firstfour cycloalkanes.


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An aromatic compound is one that is based on thebenzene ring( C 6H6).

Structure: Alternating single & Double Bonding

A benzene ring that is attached to another compound isgiven the name phenyl.

H

H

H

H

H

H


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Functional Groups

Group of atoms that gives a familyof organic compounds itscharacteristic chemical andphysical properties

Alkyl group: derived from alkane byremoving a H R stands for alkyl group in general


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Halogens (F 2, Cl 2, Br 2, I2,) can all add to ahydrocarbon to form am alkyl halide .

When naming the halogen the ine ending isreplaced by o

Fluorine becomes fluoro

Chlorine becomes chloro Bromine becomes bromo Iodine becomes iodo

Halogens


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Common examples of organic halides.


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Alcohol Family hydroxyl(OH) group

Replace - e with - ol CH 3OH, methanol, simplest

Produced industrially

Mainly a chemical intermediate


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C 2H5OH, ethanol

Made industrially and by fermentation

Industrially produced alcohol has noxioussubstances added

Small, simple alcohols tend to be toxic


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Multifunctional Alcohols

Several common alcohols have more than one OHgroup Ethylene glycol: main ingredient in antifreeze Glycerol: used in lotions

Ingredent in some explosives


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Ethers

Two alkyl groups attached to same O Example CH 3CH 2-O-CH 2CH 3

Used mainly as solvent Little chemical reactivity

Insoluble in water

Highly flammable

ld h d d


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Aldehydes and Ketones Both contain carbonyl group (C=O)

Aldehyde: R-CHO Ketone: R-CO-R


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Common Aldehydes Change - e ending to - al

Produced by oxidation of alcohols Formaldehyde used as a preservative

Larger ones used as fragrances Benzaldehyde flavor in maraschinocherries

C

O

H


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Common Ketones Change - e ending to - one

Acetone most common ketone Used primarily as a solvent

Produced by oxidation of alcohols

CH3

C

H3C

O


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Carboxylic Acid

Contains C=O and OH group on samecarbon Change - e to - oic acid

Acetic acid: acid in vinegar

R C

O H

O


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Esters

Derived from carboxylic acids andalcohols

Tend to be fragrant Methyl butyrate apple Ethyl butyrate pineapple Ethyl formate rum

Methyl salicylate wintergreen

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