PHARMACEUTICAL ORGANIC CHEMISTRY-1 TOPIC ALCOHAL, Assignments of Pharmaceutical Chemistry

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ALCOHOLS

Alcohols

• Alcohols R-OH

Compounds in which hydroxyl group is attached to saturated

carbon atom.

Alcohols are a homologous series of organic compounds

with the general formula C n H 2 n OH and names ending – ol.

Classification of Alcohols: Number of hydroxyl groups

Monohydric Alcohols

Dihydric Alcohols

Trihydric Alcohols

CH 2 CH 2

OH OH

1,2-ethanediol

• The functional group of an alcohol is an -OH

group bonded to an sp^3 hybridized carbon

– C-O-H bond angles 105°.

• Oxygen is sp^3 hybridized

– two sp^3 hybrid orbitals form sigma

bonds to carbon and hydrogen

– the remaining two sp^3 hybrid orbitals each contain

an unshared pair of electrons

O

C

H

H

H

H

Structure - Alcohols

OH

CH

CH

CH

-OH

n -propyl alcohol

CH

-OH

Methyl alcohol

CH

HO-CHCH

CH

sec-butyl alcohol

CH

CCH

CH

Nomenclature

tert -butyl alcohol

1. Common names: “alkyl alcohol”

Useful only for small alkyl groups.

Nomenclature-Alcohols

• Examples

1 - Propanol (Propyl alcohol) 2 - Propanol (Isopropyl alcohol) 1 - Butanol (Butyl alcohol)

OH

OH

OH

2 - Butanol ( sec- Butyl alcohol) 2 - Methyl- 1 - propanol (Isobutyl alcohol) 2 - Methyl- 2 - propanol (tert- Butyl alcohol)

OH

OH

OH

cis- 3 - Methylcyclohexanol

OH

OH

Bicyclo[ 4. 4. 0 ]decan- 3 - ol 1 4 5 8 10 9 1 2 2 3 3 4 5 6 7 6 Numbering of the bicyclic ring takes precedence over the location of - OH

Chapter 10 8

Nomenclature-Alcohols

CH 3 CH

CH 3

CH 2 OH

CH 3 C

CH 3

CH 3

OH

CH 3 CH

OH

CH 2 CH 3

2-methyl-1-propanol 2-methyl-2-propanol 2-butanol OH Br CH 3 3-bromo-3-methylcyclohexanol =>

Chapter 10 10

Naming Priority

• Acids

• Esters

• Aldehydes

• Ketones

• Alcohols

• Amines

• Alkenes

• Alkynes

• Alkanes

• Ethers

• Halides

Chapter 10 11

Hydroxy Substituent

• When -OH is part of a higher priority class of

compound, it is named as hydroxy.

• Example:

CH 2 CH 2 CH 2 COOH

OH

4-hydroxybutanoic acid also known as GHB =>

2. Hydration of Alkenes:

3. Catalytic Hydrogenation of Aldehydes and Ketones

• Add H 2 / Pd-C
• (^) Aldehyde I^0 Alcohols
• (^) Ketones 20 Alcohols

4. Hydrolysis of Grignard Reagent Grignard + formaldehyde yields a primary alcohol with one additional carbon. C O H H C CH 3 H 3 C CH 2 C MgBr H H H CH 3 CH CH 3 CH 2 CH 2 C H H O (^) MgBr HOH CH 3 CH CH 3 CH 2 CH 2 C H H OH Synthesis of 1° Alcohols RMg l reacts with Propanal to form 2-Butanol ( 0 alcohol)

4. Hydrolysis of Grignard Reagent Reduction of RMgX with Ketones

5. Reduction of Carbonyl Compounds with Metal Hydrides

Reduction of a carbonyl compound with NaBH 4 or LiAlH 4 add the equivalent

of H 2 to a molecule

19

Mechanism of Reduction

• (^) The reagent adds the equivalent of hydride to the carbon of C=O and polarizes the group as well 20