Question

Give structures of the products you would expect in the following reactions:

A $HCl-ZnC{l}_2$ with Butan-$1$-ol

B $HCl-ZnC{l}_2$ with $2$-Methylbutan-$2$-ol

C $HBr$ with Butan-$1$-ol

D $HBr$ with $2$-Methylbutane-$2$-ol

E $SOC{l}_2$ with Butan-$1$-ol

F $SOC{l}_2$ with $2$ Methylbutan-$2$-ol

Answer 1

Solution of $ZnC{l}_2$​ in conc. $HCL$ is known as Lucas reagent. It is used to differentiate primary, secondary and tertiary alcohols.
On adding the alcohol to Lucas reagent, a tertiary alcohol reacts immediately forming a precipitate of alkyl chloride. If the precipitate appears after few minutes, the alcohol is secondary. If no precipitate is obtained in cold, the alcohol is primary.

The reaction can be given as –


Primary alcohols do not react appreciably with Lucas reagent $(ZnC{l}_2+conc.HCl)$ at room temperature. So, no product will be obtained here.


Solution of $ZnC{l}_2$ in conc. $HCl$ is known as Lucas reagent. It is used to differentiate primary, secondary and tertiary alcohols.

On adding the alcohol to Lucas reagent, a tertiary alcohol reacts immediately forming a precipitate of alkyl chloride. If the precipitate appears after few minutes, the alcohols is secondary. If no precipitate is obtained in cold, the alcohol is primary.

Tertiary alcohol reacts immediately with Lucas reagent to given alkyl chloride.

The reaction can be given as –



When treated with $HBr$, alcohols typically undergo a nucleophilic substitution reaction to generate an alkyl halide and water.

The relative reactivity order of alcohols is :
$3^{\circ }>2^{\circ }>1^{\circ }>$ methyl

The product obtained when $HBr$ reacts with Butan-$1$-ol can be given as -



When treated with $HBr$, alcohols typically undergo a nucleophilic substitution reaction to generate an alkyl halide and water.

The relative reactivity order of alcohols is :
$3^{\circ }>2^{\circ }>1^{\circ }>$ methyl

The product obtained when $HBr$ reacts with $2$-Methylbutan-$2$-ol can be given as –



Alcohols when react with thionyl chloride $SOC{l}_2$, gets converted into corresponding alkyl chloride. The by-products here are hydrochloric acid $\left(HCl\right)$ and sulphur dioxide $\left(S{O}_2\right)$. Both the by-products are gaseous in nature.

The product obtained when $SOC{l}_2$ reacts with Butan-$1$-ol can be given as –



Alcohols when react with thionyl chloride $SOC{l}_2$, gets converted into corresponding alkyl chloride. The by-products here are hydrochloric acid $\left(HCl\right)$ and sulphur dioxide $\left(S{O}_2\right)$. Both the by-products are gaseous in nature.

The product obtained when $SOC{l}_2$ reacts with $2$-Methylbutan-$2$-ol can be given as –