Mild reaction conditions are used to stop the
reaction at the amide stage 4 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)