Question

When ethanol is treated with potassium bromide and concentrated $H_{2}S{O}_4$ , _____ is produced.

• A. ethyl bromide
• B. ethyl hydrogen sulphate
• C. ethylene
• D. ethane

Answer 1

Answer: (A)

The reaction of alcohol with $KBr$ in the presence of concentrated $H_{2}S{O}_4$ is nucleophilic substitution reaction in which $B{r}^{-}$ needs to replace $O{H}^{-}$ , but $O{H}^{-}$ is a poor leaving group, so $H_{2}S{O}_4$ is used to make $OH$ a good leaving group.
Here, instead of taking $HBr$ directly, $KBr$ & conc.$H_{2}S{O}_4$ is taken which produce $HBr$ .