1835
179
KCETKCET 2014Aldehydes Ketones and Carboxylic Acids
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Solution:
Iodoform reaction is a type of haloform reaction which can be defined in a general way as
Important facts related to haloform reaction are as
(i) KOH may also be used as alkali.
(ii) The compounds which can give this test must contain either one of these:
i.e., any compound containing CH3CO - group of any compound which on oxidation give such group or their halogen derivatives in which halogen is substituted from CH3 group give this reaction.
(iii) CH3COCH2COOC2H5 does not give haloform reaction active methylene group. Insipite of the presence of CH3CO group in it. The reason is the presence of active methylene −CH2− group which prevents the conversion of CH3CO− to CX3CO− a necessity for the reaction).
(iv) The outline of the mechanism is seen as
Step I Halogen first oxidises (only in case of alcohols to carbonyl compounds) and then halogenated the compound to get CX3O∣∣C− group.
(If CH3−X∣CH− is taken it is frist convertsed to CH3−OH∣CH− by alkali and oxidised followed by halogenation) i.e.
Step II This CX3−O∣∣C− is then hydrolysed by alkali as
Step III The −O∣∣C−OH is further reacts with alkali to give salt and water as
Hence, among given form choices only (d) will give iodoform test.
