What is the order of ease of dehydrohalogenation of alkyl halides?

What is the order of ease of dehydrohalogenation of alkyl halides?
  1. $3^{\circ}\gt2^{\circ}\gt1^{\circ}$
  2. $2^{\circ}\gt1^{\circ}\gt3^{\circ}$
  3. $3^{\circ}\gt1^{\circ}\gt2^{\circ}$
  4. $1^{\circ}\gt2^{\circ}\gt3^{\circ}$

Solution

According to Saytzeff elimination, the ease of dehydrohalogenation depends on the stability of the alkyl substituted alkenes which is given as, $\mathrm{R}_2 \mathrm{C}=\mathrm{CR}_2 \gt \mathrm{R}_2 \mathrm{C}=\mathrm{CHR} \gt \mathrm{R}_2 \mathrm{C}=\mathrm{CH}_2, \mathrm{RCH}=\mathrm{CHR} \gt \mathrm{RCH}=\mathrm{CH}_2$ $\therefore \quad$ The ease of $\alpha, \beta$-dehydrohalogenation is: $3^{\circ} \gt 2^{\circ} \gt 1^{\circ}$

Asked in: MHT CET 2024 (10 May Shift 1)

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