Question

In the below reaction, the reactivity of alcohols is;
$ROH + HX \to RX + {H_2}O$ ;
A) $Tertiary{\text{ }} > {\text{ }}secondary{\text{ }} > {\text{ }}primary$
B) $Tertiary{\text{ }} < {\text{ }}secondary{\text{ }} < {\text{ }}primary$
C) $Tertiary{\text{ }} > {\text{ }}primary{\text{ }} > {\text{ }}secondary$
D) $Secondary{\text{ }} > {\text{ }}primary{\text{ }} > {\text{ }}tertiary$

Answer 1

Alcohols are compounds in which a hydroxyl (– OH) group is attached to saturated carbon atom.
General Formula: $R - OH$
Monohydric alcohols are classified as primary (1°) secondary (2°), or tertiary (3°), depending upon whether the –OH group is attached to a primary, a secondary, or a tertiary carbon.

Complete step by step answer: Alcohols are reactive compounds. They are attacked by polar or ionic reagents. This is because:
The C–O and O–H bonds of the alcohols are polar since oxygen is highly electronegative.

They oxygen atoms of alcohols is an electron-rich centre because it has two unshared pairs of electrons
Alcohols react with hydrogen ($HX$) to form the corresponding alkyl halides
Eg; $C{H_3}C{H_2}OH + HBr \to C{H_3}C{H_2}Br + {H_2}O$
In general, tertiary alcohols react rapidly with hydrogen halides; secondary alcohols react somewhat slower; and primary alcohols, even more slowly.
The reaction is acid catalyzed. Alcohols react with the strongly acidic hydrogen halides $HCl,{\text{ }}HBr$ , and {\text{ }}HI], but they do not react with non acidic $NaCl,{\text{ }}NaBr,{\text{ }}or{\text{ }}NaI$ . Primary and secondary alcohols can be converted to alkyl chlorides and bromides by allowing them to react with a mixture of a sodium halide and sulfuric acid:
The order of reactivity of alcohols is $3^\circ > 2^\circ > 1^\circ$ methyl.

So,Option “A” is correct.
Note: The order of reactivity of hydrogen halides$is{\text{ }}HI{\text{ }} > {\text{ }}HBr{\text{ }} > {\text{ }}HCl$ . $HCl$ reacts only in the presence of a catalyst anhydrous$(ZnC{l_2})$ .No catalyst is required in the case of $HBr{\text{ }}or{\text{ }}HI$.
Primary alcohols react with hydrogen halides by an ${S_N}1$ mechanism.