Question

True or False

1)

Nucleophilic substitution reactions occur at alkyl, alkenyl (vinylic), and aromatic carbons bonded to a halide.

True

False

2)

Experiments involving the formation of a carbocation intermediate indicate that gas phase reactions have activation energies comparable to aqueous solutions. The stability of a carbocation is not influenced by surrounding solvent molecules.

True

False

Answer 1

1. False

Nucleophilic substitution via the S_N1 or S_N2 mechanism does not generally occur with vinyl or aromatic halides. Under certain conditions nucleophilic substitutions may occur, but via other mechanisms such as nucleophilic aromatic substitution.

2. False

For S_N1 reactions the solvent's stabilizes the intermediate carbocation is of direct importance to its viability as a suitable solvent. Polar solvents increases the rate of S_N1 reactions is a result of the polar solvent's solvating the reactant intermediate species, i.e., the carbocation, thereby decreasing the intermediate energy relative to the starting material.