
The reaction proceeds through the following stages:
1. Step 1: \({CH3CH2CH2Br} \xrightarrow[\Delta]{\text{alc. KOH}} {A}\)
Alcoholic KOH under heating conditions facilitates an elimination reaction. Specifically, 1-bromopropane undergoes dehydrohalogenation with alcoholic KOH to yield propene, designated as A.
\({CH3CH2CH2Br} \xrightarrow[\Delta]{\text{alc. KOH}} {CH3CH=CH2(A)}\)
2. Step 2: \({A} \xrightarrow{\text{HBr}} {B}\)
Propene (A) reacts with hydrogen bromide (HBr). Adherence to Markovnikov's rule dictates the addition of the hydrogen atom to the carbon with a greater number of existing hydrogen atoms, resulting in 2-bromopropane as the predominant product, labeled B.
\({CH3CH=CH2(A)} \xrightarrow{\text{HBr}} {CH3CHBrCH3(B)}\)
3. Step 3: \({B} \xrightarrow[\Delta]{\text{aq. KOH}} {C}\)
2-Bromopropane (B) reacts with aqueous potassium hydroxide (KOH) in the presence of heat. This process drives a nucleophilic substitution reaction, favoring an SN1 mechanism due to the secondary alkyl halide nature and the use of aqueous KOH, ultimately forming propan-2-ol, denoted as C.
\({CH3CHBrCH3(B)} \xrightarrow[\Delta]{\text{aq. KOH}} {CH3CH(OH)CH3(C)}\)
Consequently, propan-2-ol is identified as the principal product C.
The correct order of the rate of reaction of the following reactants with nucleophile by \( \mathrm{S_N1} \) mechanism is:
(Given: Structures I and II are rigid) 