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ALDEHYDES AND KETONES

2

Carbonyl Compounds

Ketones

• Ketones have two carbon substituents (akyl,

cycloalkyl, aromatic and not necessarily the same)

C R'

O

R

CH 2

CH 3

C H

C H 3

C H 3

C

O

C

O

H C 3

C

O

H C 3

General formula for ketones:

• Replace the terminal - e of the alkane name with – one
• Parent chain is the longest one that contains the ketone group - Numbering begins at the end nearer the carbonyl carbon

Ketones:Nomenclature

Method of Preparation of Aldehydes

1. Oxidation of Alkenes (Ozonolysis):

Alkenes react with Ozone to give ozonides which

on hydrolysis give aldehydes.

2. Hydration of Alkynes

Hydration of acetylene yield Acetaldehyde.

Hydration of alkynes other than acetylene gives ketones

3. Oxidation of Alcohols

Other Agents Used for Oxidation Reactions:

1. Chromic Acid: H

2

Cr

2

O

7

Prepared in situ by reaction of CrO

3

or Na

2

Cr

2

O

2. PCC

PCC converts primary alcohol to aldehydes. It does not oxidise aldehyde to

carboxylic acids.

3. Oxidation of Alcohols

Johne’s Reagent

Ketones are obtained from Secondary Alcohols by

Oppenauer Oxidation

5. Reduction of Acid Chorides (Rosemund

Reduction)

To prevent further reduction of aldehydes to alcohol, catalyst palladium/BaSO

4

is

poisoned with sulphur to deactivate it partially and prevent further reduction.

Ketones cannot be prepared by this method.

By Hydrogenation of Acid Chlorides in the presence of Pd supported over

Barium Sulphate.

• Friedel–Crafts acylation of an aromatic ring with an acid

chloride in the presence of AlCl

3

catalyst

Aryl Ketones by Acylation

5. Reduction

6. Using Grignard Reagent

From Nitriles