Consider the following carbocations: I. 2-Methylbutan-2-yl cation II. 4-Chloro-2-methylbutan-2-yl cation III. 2-Methylpropan-2-yl cation The correct decreasing order of their stability is:

Step-by-step solution

The stability of alkyl carbocations is determined by the number of -hydrogens (hyperconjugation) and inductive effects. III. 2-Methylpropan-2-yl cation ( tert -butyl cation) has 3 methyl groups attached to the positively charged carbon, giving 3 + 3 + 3 = 9 -hydrogens. I. 2-Methylbutan-2-yl cation has two methyl groups and one ethyl group attached to the positively charged carbon, giving 3 + 3 + 2 = 8 -hydrogens. II. 4-Chloro-2-methylbutan-2-yl cation also has 3 + 3 + 2 = 8 -hydrogens. However, the presence of the