Acid strength in active methylene compounds can be decided by two factors
(i) Presence of electron withdrawing group
(ii) Stability of enolate anion obtained after removal of $H ^{+}$.
Higher the electron withdrawing ability of substitutents attached to electron withdrawing groups higher will be acidic strength of methylene group.
Electron withdrawing ability of $CH _{3} CO -$ is greater than
increases acidic strength of active methyl e ne compound to greater extent than $CH_3CH_2O-\overset{\underset{||}{O}}{C}-$
Number of $CH_3 - \overset{\underset{||}{O}}{C}-$ groups Number of $-\overset{\underset{||}{O}}{C}- OCH_2CH_3$ groups
On the other hand stability of enolate anion obtained after the removal of $H ^{+}$ can be explained as keto group stabilises enolate anion to more extent than ester as ketone group stabilise enolate anion by resonance through one side only while ester stabilises by both side of keto group which can be shown as
less tautomerism will be seen due lesser availability of $C ^{1}$ atom for
tautomerism (as at this $C$ -atom $> C = O$ bond is in conjugation with the lone of neighbouring oxygen attached).
Further, in
as both the C-atoms of $> C = O$ bond have similar
situations hence, tautomerism decreases further.
That's why correct order of acidity can be arranged as II $>I>$ III and correct choice is (c).
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Top Questions on Aldehydes, Ketones and Carboxylic Acids
Aldehydes, Ketones, and Carboxylic Acids are carbonyl compounds that contain a carbon-oxygen double bond. These organic compounds are very important in the field of organic chemistry and also have many industrial applications.
Aldehydes:
Aldehydes are organic compounds that have the functional group -CHO.
Preparation of Aldehydes
Acid chlorides are reduced to aldehydes with hydrogen in the presence of palladium catalyst spread on barium sulfate.
Ketones:
Ketones are organic compounds that have the functional group C=O and the structure R-(C=O)-R’.
Preparation of Ketones
Acid chlorides on reaction with dialkyl cadmium produce ketones. Dialkyl cadmium themselves are prepared from Grignard reagents.
Carboxylic Acid:
Carboxylic acids are organic compounds that contain a (C=O)OH group attached to an R group (where R refers to the remaining part of the molecule).
Preparation of Carboxylic Acids
Primary alcohols are readily oxidized to carboxylic acids with common oxidizing agents such as potassium permanganate in neutral acidic or alkaline media or by potassium dichromate and chromium trioxide in acidic media.
