$\mathrm{CH}_3\mathrm{CH}_2\mathrm{OH} \xrightarrow{\mathrm{HBr}} \mathrm{CH}_3\mathrm{CH}_2\mathrm{Br} + \mathrm{H}_2\mathrm{O}$ The reaction follows $\text{SN}^2$ mechanism. It is a single step mechanism which proceeds via the formation of transition state. MECHANSIM:The nucleophile attacks the electrophilic carbon on the backside, resulting in the inversion of configuration. (b) The equation involved in the Reimer-Tieman reaction.