Functional Groups A functional group is a small group of atoms that lend characteristic properties to the molecule Properties of the molecule are dictated.

Functional GroupsA functional group is a small group of atoms that lend

characteristic properties to the molecule

Properties of the molecule are dictated by the functional groups; allows for systematic study of organic molecules

Halides: R-Xwhere R is any alkyl group, and X a halogen

CH3Cl - chloromethane

C6H5Cl - chlorobenzene

Synthesis: radical chain reaction between an alkane and a halogen

CH4 + Cl2 CH3Cl + HCl

Cl2 2Cl•

•Cl + CH4 HCl + •CH3

•CH3 + Cl2 CH3Cl + •Cl

Cl

h or heat

h or heat

Alcohols: R-OH hydroxyl functional group

Nomenclature - use the suffix “ol”

CH3-CH2-OH ethanol

CH3-CH2-CH2OH 1-propanol

H3C CH2

CH2 CH2

OH

H3C CH2

CH CH3

H3C C

OH

OH

CH3

CH3

1-butanol (1o alcohol)

2-butanol (2o alcohol)

2-methyl-2-propanol(3o alcohol)

Primary alcohol

Secondary alcohol

Tertiary alcohol

Presence of OH group allows hydrogen bonding

As the C chain becomes longer the OH group becomes less important

Synthesis of alcohols

Hydrolysis of a alkyl halide with a strong base

OH- + CH3Br CH3OH + Br-

Addition across a double bond

CH2=CH2 + H2O CH3CH2OH

Charge distribution in ethanol; red indicates negative charge

300 - 400oC

60 - 70 atm

OH

Phenol (C6H5OH)

weak acid, Ka = 1 x 10-10; stability of the phenolate ion (C6H5O-)

Phenols: hydroxyl group attached directly to an aromatic ring

Oil of thyme

Oil of clove

Ethers: R - O - R

C2H5 - O - C2H5 diethylether

C6H5 - O - C2H5 ethylphenylether

Synthesis:

2 R-OH R - O - R + H2OH2SO4

CH3-CH2-OH

CH3-CH2-OH+

H2SO4

140oCCH3-CH2-O-CH2-CH3 + H2O

H2SO4 180oC

2CH2=CH2 + 2 H2O

Kinetics vs thermodynamics

Aldehydes and Ketones

C

H

R

O

C O

C

R

R

O

carbonyl group

aldehyde

ketone

HCHO: formaldehyde

CH3CHO: acetaldehyde

CH3COCH3: dimethlyketone (acetone)C

H3C

H3C

O

C

H3C

H

O

C

H

H

O

Properties of aldehydes and ketones differ because of the aldehyde H atom

CH3CH2OH CH3CHO

1o alcohol aldehyde

ethanol acetaldehyde

(CH3)2CHOH (CH3)2CO

2o alcohol

2-propanol dimethylketone

O2, catalyst,

high temperatures

O2, catalyst,

high temperatures

almond and cherries

cinnamon

vanilla

Carboxylic acids: -COOH functional groupC

O

OH

HCOOH - formic acid (ant venom)

CH3COOH - acetic acid (vinegar)

Carboxylic acids hydrogen bond - “dimers”

Synthesis

Catalytic oxidation of aldehydes

CH3CHO CH3COOHO2, Mn2+

C

O

OH

H

C

O

OH

H3C

Esters: R-COO- R’C

O

OR

R'

C

O

OH

H3C CH2CH3

OHCH3C

O

OCH2CH3

+ H2O

acetic acid + ethanol ethylacetate

Tristearin: animal fatty acid tri-esters

CH2OHCHOHCH2OH + 3 CH3(CH2)16COOH

glycerol stearic acid

Fats (solids) and oils (liquids) are triesters formed from glycerol and three carboxylic acids (fatty acids)

Saturated - C-C single bonds

Unsaturated - one (mono-unsaturated) or more (polyunsaturated) C=C bonds

Amines:

NH

HR

NH

R'R

NR

R'R"

NH

HH ammonia

primary amine (1o)

secondary amine (2o)

tertiary amine (3o)

CH3NH2 methylamine

(CH3)2NH dimethylamine

(CH3)3N trimethylamine

C6H5NH2 aniline

Amines are bases:

NicH2+(aq) + 2 NH3(aq)

Nic(aq) + 2 NH4+(aq)

Synthesis of amines

a) Naturally occurring

b) NH3 + CH3Cl CH3NH2 + HCl

NH2

nicotineN

N

CH3

Amino acids: carboxylic acid containing an amine group

Glycine: NH2CH2COOH

H3NCHCOOH+

R

H3NCHCOO+ -

R

H2NCHCOO-

R

- H3O+ - H3O+

+ H3O++ H3O+

cationic form

predominant in acidic solutions

anionic form

predominant in basic solutions

dipolar form - zwitterion

Amides: -CONH2- group

Formed by reaction between NH3 or 1o or 2o amine and acid

CR' N

O

H

R

CH3C

O

O

H NHH

CH2CH3 CH3C

O

NHCH2CH3

+ H2O

C

O

HOCH2

N

H

H

+ C

O

HOCH2

NH2 C

O

HOCH2

NH

C

O

CH2

NH2

+ H2O

Proteins: polypeptides with CONH linkage between amino acids

glycine + glycine diglycine + H2O

http://www.cryst.bbk.ac.uk/pps97/course/section3/helix.pdb