Would you expect the reaction of propyl bromide with NaCN , which is :

1.	Would you expect the reaction of propyl bromide with NaCN , which is :-CH3CH2CH2-Br + NaCN -----> CH3CH2CH2-CN + NaBr to occur faster in DMF or in ethanol ?explain
Answer» The REACTION will occur faster in DMF. This is because the reaction between Propyl bromide (CH3CH2CH2-Br) and Sodium cyanide (NaCN) follows the SN2 MECHANISM. The SN2 mechanism is a single-step nucleophilic substitution reaction mechanism. The SN2 mechanism is promoted by polar aprotic SOLVENTS and hindered by polar protic solvents. DMF is a polar aprotic solvent and will favor the reaction. Ethanol is a polar protic solvent and will HINDER the reaction. Polar aprotic solvents dissolve the substrate and nucleophile but they do not participate in HYDROGEN bonding with the nucleophile. Polar protic solvent will form hydrogen bonds with the nucleophile and prevent the nucleophile from binding to substrate.

Would you expect the reaction of propyl bromide with NaCN , which is :-CH3CH2CH2-Br + NaCN -----> CH3CH2CH2-CN + NaBr to occur faster in DMF or in ethanol ?explain

Answer»

The REACTION will occur faster in DMF.

This is because the reaction between Propyl bromide (CH3CH2CH2-Br) and Sodium cyanide (NaCN) follows the SN2 MECHANISM.
The SN2 mechanism is a single-step nucleophilic substitution reaction mechanism.
The SN2 mechanism is promoted by polar aprotic SOLVENTS and hindered by polar protic solvents.
DMF is a polar aprotic solvent and will favor the reaction.
Ethanol is a polar protic solvent and will HINDER the reaction.
Polar aprotic solvents dissolve the substrate and nucleophile but they do not participate in HYDROGEN bonding with the nucleophile.
Polar protic solvent will form hydrogen bonds with the nucleophile and prevent the nucleophile from binding to substrate.