Question:
The increasing order of the following compounds towards HCN addition is :
(1) (i) $<($ iii $)<($ iv $)<($ ii $) \quad$
(2) $\quad$ (iii) $<($ iv $)<($ i $)<($ ii $)$
(3) (iii) $<($ i $)<$ (iv) $<$ (ii) $\quad$
(4) $\quad$ (iii) $<($ iv $)<($ ii $)<($ i $)$
Correct Option: , 3
Solution:
-I effect of $\mathrm{NO}_{2}$ increases reactivity towards nucleophilic addition reaction with $\mathrm{HCN} .-\mathrm{OCH}_{3}$ group is electron donating due to resonance effect which decreases the reactivity towards nucleophillic addition.