Assertion (A): The reaction of $CH X_{3} CH X_{2} Br$ with $NaN X_{3}$ is much faster in DMF than in methanol. Reason (R): DMF is a hydrogen-bond donor and stabilises azide ion strongly in the ground state. Choose the correct option.

AA is true but R is false.
BBoth A and R are true and R is the correct explanation of A.
CA is false but R is true.
DBoth A and R are true but R is not the correct explanation of A.

Answer: A

A is true: the rate increase is several orders of magnitude. R is false: DMF has no O-H or N-H bond and cannot donate hydrogen bonds; the reason for the rate increase is the weak solvation of the anion in DMF, whereas methanol stabilises azide through hydrogen bonding.

Practice Organic Reaction Mechanisms III: Nucleophilic Substitution More on SN1 vs SN2: substrate, nucleophile, solvent, leaving group

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Assertion (A): The reaction of CHX3​CHX2​Br with NaNX3​ is much faster in DMF than in methanol. Reason (R): DMF is a hydrogen-bond donor and stabilises azide ion strongly in the ground state. Choose the correct option.

Answer: A

More questions on SN1 vs SN2: substrate, nucleophile, solvent, leaving group

Assertion (A): The reaction of $CH X_{3} CH X_{2} Br$ with $NaN X_{3}$ is much faster in DMF than in methanol. Reason (R): DMF is a hydrogen-bond donor and stabilises azide ion strongly in the ground state. Choose the correct option.