(a) (i) Cl due to -I effect withdraws electron from O-H bond and decreases electron density in O-H bond. It facilitates the release of
H+ by making O-H bond weaker.
−CH3 group has +I effect. It increases electron density in
O−H bond and this makes the release of
H+ more difficult from acetic acid than chloroacetic acid. Thus,
CI−CH2COOH is a stronger acid than
CH3COOH.
(ii) Carboxylic acid is a resonance hybrid of following structures I and II.
![](https://search-static.byjusweb.com/question-images/byjus/infinitestudent-images/ckeditor_assets/pictures/7925/content_0.png)
Similarly, a carbonyl group of aldehydes and ketones is a resonance hybrid of following structures III and IV.
![](https://search-static.byjusweb.com/question-images/byjus/infinitestudent-images/ckeditor_assets/pictures/7923/content_0.png)
Due to structure IV, the carbonyl carbon of aldehydes and ketones is electrophilic. However due to contribution of structure (II), the electrophilic character of carboxyl carbon is reduced. As a result the nucleophilic addition reactions of aldehydes and ketones do not occur in carboxylic acids.
(b) (i) Rosenmund reduction :
CH3−O||C−Cl+H2Boiling xylene−−−−−−−−→Pd,BaSO4Acetyl chloride CH3−O||C−H+HClAcetaldehyde (ii) Cannizzaro's reaction:
2HCHOFormaldehyde+NaOH(50%)→CH3OHMethyl alcohol+HCOONaSodium fermate CH3CH2CH2COCH3 gives iodoform test due to -
CH3 group attached to -
O||C-group.
CH3CH2CH2COCH3+3NaOINaOH/I2−−−−−−→CH3CH2CH2COONa+CHI3Iodoform+2NaOH