Which would undergo S_N2 reaction faster in the following pair and why?

Give reasons:

n-Butyl bromide has higher boiling point than t-butyl bromide.

Give reasons:

Racemic mixture is optically inactive.

Give reasons:

The presence of nitro group (–NO₂) at o/p positions increases the reactivity of haloarenes towards nucleophilic substitution reactions.

Which alkyl halide from the following pair is chiral and undergoes faster S_N2 reaction?

428.

Out of S_N1 and S_N2, which reaction occurs with

(a) Inversion of configuration

(b) Racemisation 

Draw the structure of major monohalo product in each of the following reactions: 
i) 


ii) 

 

Write the IUPAC name of