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Chemistry · 2025 · 3 marks
Aldehydes, Ketones and Carboxylic AcidsNomenclature and Structure of Carboxyl Group3 marksUnderstandshort answer
CBSE 2025 · Region 7 · Set 1 · Q27
Give reasons for the following: (a) Benzoic acid does not undergo Friedel-Crafts reaction. (b) HCHO is more reactive than CH_3 CHO towards addition…
Give reasons for the following :
(a)
Benzoic acid does not undergo Friedel-Crafts reaction.
(b)
HCHO is more reactive than $\displaystyle \mathrm{CH}_{3} \mathrm{CHO}$ towards addition of HCN.
(c)
Vinyl group directly attached with carboxylic acid should decrease the acidity of corresponding carboxylic acid due to resonance, but on the contrary it increases the acidity.
Marking-scheme solution
(a)
Because the carboxyl group is deactivating and the catalyst aluminium chloride (Lewis acid)
gets bonded to the carboxyl group.(forms salt)
(b)
Because carbonyl carbon of HCHO is more electrophilic than CH3CHO/ due to +I effect of
methyl group/ steric effect of methyl group, CH3CHO is less reactive.
(c)
Because of greater electronegativity of sp2 hybridised carbon to which carboxyl carbon is
attached.
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