“a” gives substitution ; because molecule dominantly exists in diequatoria conformation; in which is no availability of suitable hydrogen for elimination “b” gives elimination; because diaxial existace of -
+
N
Me3 β - Hydrogen encourageselimination c,d,e,f,g → conceptual b)
−
CN → strong nucleophile [ than a base ]; with 2° halides dominantly gives SN2 substitution