Question

Question: Rank the species in each group in order of increasing leaving group ability.

a. Br^-,Cl^-,I^-

b. NH₃,H₂S,H₂O

Short answer

Answer

a. Cl^-< Br^-<I^-

b. NH₃ < H₂O <H₂S

Step-by-step solution

Leaving group ability

When the size of the leaving group atom increases, it attains stable and independent existence.

Another measure to identify the better leaving group is its pK_avalue.

Lesser the value of pK_a , the greater the ability it has to act as a leaving group.

The given molecules

a. In this set of ions, the size of I^-is the largest and next Br^-is larger than Cl^-.

Thus, the leaving group ability is as shown below:

Cl^-< Br^-< I^-

b. The values of the given compounds are as follows:

NH₃ 35

H₂O 15.7

H₂S 7

The best leaving group is the one that has less pK_a (acid dissociation constant) value, The order is shown below:

NH₃< H₂O < H₂S