REACTIONS OF ALDEHYDES AND KETONES BY HARJEET GUJRAL ASSOCIATE PROFESSOR GOVT. COLLEGE ROPAR

Reactions of aldehydes and ketones : oxidation reduction nucleophilic addition 1)Aldehydes are easily oxidized, ketones are not. 2)Aldehydes are more reactive in nucleophilic additions than ketones.

alkanealcohol aldehyde ketone carboxylic acid oxidation reduction addition product nucleophilic addition

nucleophilic addition to carbonyl:

Mechanism: nucleophilic addition to carbonyl 1) 2)

Mechanism: nucleophilic addition to carbonyl, acid catalyzed 1) 2) 3)

Aldehydes & ketones, reactions: 1)Oxidation 2)Reduction 3)Addition of cyanide 4)Addition of derivatives of ammonia 5)Addition of alcohols 6)Cannizzaro reaction 7)Addition of Grignard reagents 8) (Alpha-halogenation of ketones) 9) (Addition of carbanions)

1) Oxidation a)Aldehydes (very easily oxidized!) CH 3 CH 2 CH 2 CH=O + KMnO 4, etc.  CH 3 CH 2 CH 2 COOH carboxylic acid CH 3 CH 2 CH 2 CH=O + Ag +  CH 3 CH 2 CH 2 COO - + Ag Tollen’s test for easily oxidized compounds like aldehydes. (AgNO 3, NH 4 OH(aq)) Silver mirror

Ketones only oxidize under vigorous conditions via the enol.

b) Methyl ketones: test for methyl ketones Yellow ppt

2) Reduction: a)To alcohols

Then + H +  alcohol

Reduction b) To hydrocarbons

3) Addition of cyanide

1) 2)

Cyanohydrins have two functional groups plus one additional carbon. Nitriles can be hydrolyzed to carboxylic acids in acid or base:

4) Addition of derivatives of ammonia

1) 2) 3)

5) Addition of alcohols

6)Cannizzaro reaction. (self oxidation/reduction) a reaction of aldehydes without α-hydrogens

Formaldehyde is the most easily oxidized aldehyde. When mixed with another aldehyde that doesn’t have any alpha- hydrogens and conc. NaOH, all of the formaldehyde is oxidized and all of the other aldehyde is reduced. Crossed Cannizzaro:

7) Addition of Grignard reagents.

1) 2)

#3 synthesis of alcohols. Used to build larger molecules from smaller organic compounds.

Planning a Grignard synthesis of an alcohol: a)The alcohol carbon comes from the carbonyl compound. b)The new carbon-carbon bond is to the alcohol carbon. New carbon-carbon bond

“The Grignard Song” (sung to the tune of “America the Beautiful”) Harry Wasserman The carbonyl is polarized, the carbon end is plus. A nucleophile will thus attack the carbon nucleus. The Grignard yields an alcohol of types there are but three. It makes a bond that corresponds from “C” to shining “C.”