Alkyl Halides - Result Question 42

####42. List-I contains reactions and List-II contains major products.

Q. $> _{ONa}$

Match each reaction in List-I with one or more products in List-II and choose the correct option.

(2018 Adv.)

(a) $P \rightarrow 1,5 ; Q \rightarrow 2 ; R \rightarrow 3 ; S \rightarrow 4$

(b) $P \rightarrow 1,4 ; Q \rightarrow 2 ; R \rightarrow 4 ; S \rightarrow 3$

(c) $P \rightarrow 1,4 ; Q \rightarrow 1,2 ; R \rightarrow 3,4 ; S \rightarrow 4$

(d) $P \rightarrow 4,5 ; Q \rightarrow 4 ; R \rightarrow 4 ; S \rightarrow 3,4$

Show Answer

Answer:

Correct Answer: 42. $(b)$

Solution:

For this reaction 1 and 4 are probable products.

Product 1 i.e., $OH _{OH}$ is formed due to substitution while product 4 i.e., 1 is formed due to elimination. A tertiary carbocation i.e, + formed during the reaction. Remember for $3^{\circ}$ carbocation ions elimination product predominates.

For $Q$, i.e. $\chi _{OMe}^{+HBr}$

Correctly matched product for this reaction is 2 i.e., $>Br$. The reaction proceeds as

$$ \searrow _{OMe}+HBr \rightarrow MeOH+\searrow _{Br} $$

For $R$ i.e., $\chi _{Br}^{+NaOMe}$

Correctly matched product is 4 i.e., 1 . It is a normal elimination reaction and proceeds as

$$ \chi _{Br}^{+\underset{\begin{array}{c} \text { (Alkali in } \\ \text { alcohol) } \end{array}}{++-} NaOMe} \rightarrow $$

Column I Column II Explanation
P. $NaOEt(2)$ $\overline{O}$ Et (strong
nucleophile) causes
dehydrohalogenation
of $3^{\circ}$ alkyl halide
Q. $Ia \rightarrow\rangle$ $EtBr(3)$ $3^{\circ}$ butoxide undergoes
$S _N$ reaction with $1^{\circ}$
alkyl halide

$3^{\circ}$ alkyl halide preferes elimination.

For $S$ i.e., $\chi _{ONa}^{+MeBr}$

The correct match is 3 i.e., OMe. The reaction proceeds as



NCERT Chapter Video Solution

Dual Pane