Aldehydes and ketones definition

Question 1

Cyanohydrin

Answer 1

gem-Hydroxynitriles, i.e., compounds possessing hydroxyl and cyano groups on the same carbon atom are called cyanohydrins. Aldehydes and ketones react with hydrogen cyanide (HCN) to yield cyanohydrins. It is catalysed by a base and the generated cyanide ion (CN) being a stronger
nucleophile readily adds to carbonyl compounds to yield corresponding cyanohydrin.

Question 2

Acetal

Answer 2

gem-Dialkoxy compounds in which the two alkoxy groups are present on the terminal carbon atom are called acetals. These are produced by the action of an aldehyde with two equivalents of a monohydric alcohol in the presence of dry HCl gas.

Question 3

Semicarbazone

Answer 3

Semicarbazones are derivatives of aldehydes and ketones and are produced by the action of semicarbazide on them in weak acidic medium.

Question 4

Aldol

Answer 4

Aldols are ẞ-hydroxy aldehydes or ketones and are produced by the condensation two same or different molecules of aldehyde or ketones.

Question 5

Hemiacetal

Answer 5

gem-Alkoxyalcohols are called hemiacetals. These are produced by addition of one molecule of a monohydric alcohol to an aldehyde in presence of dry HCl gas.

Question 6

Oxime

Answer 6

Oximes are produced when aldehydes or ketones react with hydroxylamine in weak acidic medium.

Question 7

Ketal

Answer 7

gem-Dialkoxyalkanes
are called ketals. In ketals, the two alkoxy groups are present on the same carbon within the chain. These are produced when a ketone is heated with ethylene glycol in presence of dry HCl gas or p-toluenesulphonic acid (PTS).

Question 8

Imine

Answer 8

compounds containing >C=N- group are called imines. These are produced when aldehydes and ketones react with ammonia derivative.

Question 9

2,4-DNP derivative

Answer 9

2,4-Dinitrophenylhydrazones (2, 4-DNP derivatives) are produced when aldehydes or ketones react with 2,4-dinitrophenylhydrazine in weakly acidic medium.

Question 10

Schiff’s base

Answer 10

aldehydes and ketones react with primary or aromatic amines to form azomethines or shiffs base.