From Grignard reagents
Grignard reagents react with carbon dioxide (dry ice) to form salts of
carboxylic acids which in turn give corresponding carboxylic acids
after  acidification with mineral acid As we know, the Grignard reagents and nitriles can be prepared
from alkyl halides (refer Unit 6, Class XII) The above methods
Rationalised 2023-24
247
Aldehydes, Ketones and Carboxylic Acids
(3 and 4) are useful for converting alkyl halides into corresponding
carboxylic acids having one carbon atom more than that present in
alkyl halides (ascending the series) 5