Question

Which of the following is the kinetic rate equation for the addition-elimination mechanism of nucleophilic aromatic substitution? rate = k[aryl halide] rate = k[nucleophile] rate = k[aryl halide][nucleophile] rate = k[aryl halide][nucleophile]2

Answer 1

Answer:

Rate = k[aryl halide][nucleophile]

Explanation:

The simple aryl halides are almost inert to usual nucleophilic reagents but considerable activation on the ring can be produced by the addition of strongly electron-attracting substituents on either the ortho or para positions, or both. These groups deactivate the ring to allow the attack of the nucleophille on the ring.

Thus, these reactions can occur by following addition-elimination mechanism in which the nucleophille first attacks the aryl halide and then the elimination of the leaving group takes place.

Kinetic studies of this type of mechanism demonstrate that the reactions are of second-order kinetics– first order w.r.t. nucleophile and also, first-order w.r.t. aromatic substrate. The rate determining step (r.d.s.) is the formation of the addition intermediate.

Thus,

Rate = k[aryl halide][nucleophile]