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Arrange the following acids in decreasing order of acidity:

List of carboxylic compounds

(a) X > Z > Y
(b) X > Y > Z
(c) Z > X > Y
(d) Z > Y > X

I arrived at option (c) according to -I effect, but the answer given is (a). Why is it so?


marked as duplicate by orthocresol May 26 at 21:45

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In benzoic acid if deprotonation occurs , due to -R property of acid group it will snatch electron cloud from benzene nucleus, increasing its negative charge density and hence getting destabilised........ Where as in acetic acid there is +I group (methyl) which also increases negative charge density on acid functionality. So, it is so much logical that formic acid is the best acid among the others. [ YOU MUST BE wondering why not (b)? If so then think that C- atom being sp2 hybridized will be also giving a slight pull and hence it also attracts the electron cloud from acid group. Hence it becomes better than acetic acid.]


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