i) Which alkyl halide from the following pairs would you expect to react rapidly by an mechanism and why?

ii) Racemisation occurs in reactions. Why?

i)

2-bromobutane (a) is a secondary alkylhalide and 1-broobutane (b) is a primary alkylhalide. The reaction takes place between Carbon and the nucleophiles. The presence of bulky groups near the Carboncauses an inhibiting effect. Therefore, as the transfer or resonation of nucleophilic groups takes faster in the primary alkylhalides, reaction occurs rapidly.

The reactivity for the reaction takes place in the order:

1^o halide > 2^o halide > 3^o halide

ii) Carbocation is formed in the reaction as an intermediate. This is rate determining step in the reaction. The upcoming nucleophile attacks the carbocation. This give rise to the formation of equal proportion of D and L products. As the formed product is racemic mixture containing equal amounts of optically active enantiomers. Therefore, racemisation occurs in reactions