In the following pairs of halogen compounds which is faster undergoing S_N2 reaction?

Predict the order of reactivity of the following compounds in S_N1 and S_N2 reactions:
(a) The four isomeric bromobutanes.
(b) C₆H₅ H₂Br, C₆H₅CH (C₆H₅Br, C₆H₅CH (CH₃)Br, C₆H₅C(CH₃)(C₆H₅)Br.

Why (-NO₂) group shows its effect only at ortho- and para-position and not at meta–position?

Explain the reason:

The reactivity order of alkyl bromides is tert alkyl bromide > sec alkyl bromide > primary alkyl bromide.

Write the chemical equations for the following conversions:
Chloroform to acetic acid

Write the chemical equations for the following conversions:
Acetaldehyde to chloroform