SnCl2/HCl is used in which of the following methods of preparing aldehydes?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Stephen reaction
In the Stephen reaction a nitrile is reduced by stannous chloride and hydrochloric acid to an imine, which is hydrolysed to the aldehyde:
\( \displaystyle \ce{R-C#N} \xrightarrow{\ce{SnCl2 + HCl}} \ce{R-CH=NH} \xrightarrow{\ce{H3O+}} \ce{R-CHO} \)
NCERT (2026-27 edition):
8.2.2 Preparation of Aldehydes – “Nitriles are reduced to corresponding imine with stannous chloride in the presence of hydrochloric acid, which on hydrolysis give corresponding aldehyde. … This reaction is called Stephen reaction.”