(a). Which of the following two compounds would react faster by S_(N^(2)) pathway, 1-bromobutane or2-bromobutane and why? (b). Allyl chloride is more reactive than n-propyl chloride towards nucleophilic substitution reaction. Explain why?

(a). Which of the following two compounds would react faster by S_(N^(

1.	(a). Which of the following two compounds would react faster by S_(N^(2)) pathway, 1-bromobutane or2-bromobutane and why? (b). Allyl chloride is more reactive than n-propyl chloride towards nucleophilic substitution reaction. Explain why?
Answer» Solution :(a) In `S_(N^(2))` pathway, steric hindrance is involved. The order of reativity of the alkyl halides is `:1^(@) lt 2^(@) lt 3^(@)` 1-Bromobutane being a primary alkyl halide will offer less steric hindrance to the attacking nucleophile and will react faster than 2-bromobutane in `S_(N^(2))` reaction. (b). ALLYL chloride is more reactive than n-propyl chloride TOWARDS nucleophilic substitution reaction, (`S_(N^(1))` reaction). it readily ionises to GIVE a carbocation which is resonance stabilised. The other COMPOUND n-propyl chloride `(n-C_(3)H_(7)Cl)` is very little ionides since the n-propyl carbocation is not resonance stabilised. therefore, ionisation leading to `S_(N^(1))` reaction is quicker in allyl chloride than in n-propyl chloride.