Question
Explain the reaction of alcohols with hydrogen halides.Short note: Lucas test
✓
Answer
$\rightarrow$ Alcohols react with hydrogen halides to form alkyl halides.
$\ce{R - OH + HCl \xrightarrow{ ZnCl _2} R - Cl + H _2 O}$
$\rightarrow$ The difference in reactivity of three classes of alcohols with $\text{HCl}$ distinguishes them from one another.
$\rightarrow$ Alcohols are soluble in Lucas reagent $($conc. $\text{HCl}$ and $ZnCl_2)$ while their halides are immiscible and produce turbidity in solution.
$\rightarrow$ In case of tertiary alcohols, turbidity is produced immediately as they form the halides easily.
$\rightarrow$ Primary alcohols do not produce turbidity at room temperature.
$\rightarrow$ This is how alcohols can be distinguished by Lucas test.
$\ce{R - OH + HCl \xrightarrow{ ZnCl _2} R - Cl + H _2 O}$
$\rightarrow$ The difference in reactivity of three classes of alcohols with $\text{HCl}$ distinguishes them from one another.
$\rightarrow$ Alcohols are soluble in Lucas reagent $($conc. $\text{HCl}$ and $ZnCl_2)$ while their halides are immiscible and produce turbidity in solution.
$\rightarrow$ In case of tertiary alcohols, turbidity is produced immediately as they form the halides easily.
$\rightarrow$ Primary alcohols do not produce turbidity at room temperature.
$\rightarrow$ This is how alcohols can be distinguished by Lucas test.
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