Question

Sodium cyanide reacts with 2‑bromobutane in dimethylsulfoxide to form a substitution product. Draw the substitution product formed when this enantiomer reacts with nacn in dmso. Clearly indicate stereochemistry by drawing a wedged bond, a dashed bond, and two in‑plane bonds per each chiral carbon. Then identify the configuration of the starting material and the product.

Answer 1

The substitution reaction between sodium cyanide and 2-bromobutane involves an SN2 mechanism that inverts the stereochemistry at the chiral center, changing an (R)-configured starting material to an (S)-configured product with a CN group replacing Br.

Step-by-step explanation:

The chemical reaction described involves sodium cyanide (NaCN) reacting with 2-bromobutane in the presence of dimethylsulfoxide (DMSO) to form a substitution product. This substitution reaction is an example of an SN2 mechanism, where the nucleophile (CN-) attacks the electrophilic carbon of 2-bromobutane from the opposite side of the leaving group (Br-), resulting in inversion of stereochemistry at the carbon.

For the stereochemistry, if we assume the starting material, 2-bromobutane, has an (R)-configuration, the product would have an (S)-configuration due to the inversion that occurs during the SN2 mechanism. The chiral center would have a CN group replacing the Br group, and the other substituents on the chiral carbon would be arranged with the appropriate stereochemistry indicating the new configuration.