(1) CH_3CH=CHCOOH is an α,β-unsaturated carboxylic acid and CH_3CH_2CH_2COOH is a saturated carboxylic acid. The main difference is the presence of a C=C bond in the former. You can differentiate them by bromine water test. CH_3CH=CHCOOH will decolorize bromine water due to the addition reaction with C=C bond, turning bromine water from brown to colourless. CH_3CH_2CH_2COOH will not react with bromine water hence the brown colour remains unchanged.
(2) Benzoic acid (a carboxylic acid), benzyl alcohol (an alcohol) and phenol (a phenol, a stronger acid than alcohol but weaker than carboxylic acid). A simple method to distinguish these three compounds is by using the sodium bicarbonate test. Only benzoic acid will effervesce (Carbon dioxide gas is produced) when reacted with sodium bicarbonate due to the acid-base reaction, whereas benzyl alcohol and phenol will not react. Phenol can be distinguished from benzyl alcohol by using ferric chloride test. Phenol will form a purple complex with FeCl_3, whereas benzyl alcohol will not show any visible reaction.
Distinguish between the following groups of compounds by using a simple chemical method.
(1) CH_3CH=CHCOOH and CH_3CH_2CH_2COOH
(2) Benzoic acid、 benzyl alcohol phenol
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