EXPERIMENT 8: IDENTIFICATION OF ALDEHYDES AND KETONES Flashcards
are representative of compounds which possess the carbonyl group
ALDEHYDES AND KETONES
have at least one hydrogen attached to the carbonyl carbon
ALDEHYDES
No hydrogen attached to the carbonyl carbon, only carbon containing R-groups
KETONES
(TRUE/FALSE) Aldehydes and ketones of low molecular weight have commercial importance.
TRUE
Oxidation of methanol; plastics; preservatives
FORMALDEHYDE
Oxidation of isopropyl alcohol; solvent
ACETONE
Lemon grass oil; fragrance
CITRAL
Oil of jasmine; fragrance
JASMONE
Aldehydes are oxidized to carboxylic acids; ketones are not oxidized.
CHROMIC ACID TEST
(TRUE/FALSE) A positive test is the formation of a blue-green solution from the brown-red color of chromic acid.
TRUE
Tollen’s reagent
ammonia and silver nitrate
This test is sometimes referred to as the “silver mirror” test.
TOLLEN’S TEST
(TRUE/FALSE) Most aldehydes reduce Tollen’s reagent to give a precipitate of silver metal.
TRUE
In Tollen’s test, the aldehyde is oxidized to a ____________.
CARBOXYLIC ACID
Benedict’s reagent
a citrate complex of Cu(II) ion in a base solution
Alipathic aldehydes are oxidized to carboxylic acids with Benedict’s reagent.
BENEDICT’S TEST
(TRUE/FALSE) The Cu (II) ion is reduced to Cu (I) ion and its oxide, Cu2O, precipitates as brick-red solid.
TRUE
(TRUE/FALSE) In Benedict’s test, aromatic aldehydes and ketones react, forming a brick-red precipitate.
FALSE (they do not react; thus, no precipitate is formed)
(TRUE/FALSE) Methyl ketones give the yellow precipitate iodoform when reacted with iodine in aqueous sodium hydroxide
TRUE
Alcohols do not give this test.
2,4-Dinitrophenylhydrazine test
All aldehydes and ketones give an immediate precipitate with 2,4 dinitrophenylhydrazine reagent. The reaction varies from yellow to red.
2,4-Dinitrophenylhydrazine test
4 Compounds involved in experiment 8
ISOVALERALDEHYDE,
BENZALDEHYDE,
CYCLOHEXANONE,
ACETONE,
UNKNOWN
(TRUE/FALSE) Chromic acid are non-corrosive.
FALSE (THEY ARE CORROSIVE)
