Academic Integrity: tutoring, explanations, and feedback — we don’t complete graded work or submit on a student’s behalf.

1. Which is the most stable cation and which is the least stable cation? Cation

ID: 849290 • Letter: 1

Question

1. Which is the most stable cation and which is the least stable cation?

Cation 2 is most stable; cation 3 is least stable.

Cation 3 is most stable; cation 2 is least stable.

Cation 1 is most stable; cation 2 is least stable.

Cation 2 is most stable; cation 1 is least stable.

Cation 1 is most stable; cation 3 is least stable.

Cation 3 is most stable; cation 1 is least stable

a.

Cation 2 is most stable; cation 3 is least stable.

b.

Cation 3 is most stable; cation 2 is least stable.

c.

Cation 1 is most stable; cation 2 is least stable.

d.

Cation 2 is most stable; cation 1 is least stable.

e.

Cation 1 is most stable; cation 3 is least stable.

f.

Cation 3 is most stable; cation 1 is least stable

Explanation / Answer

The stability order of carbocations bearing only alkyl groups is
3o > 2o > 1o > CH3.          where o=degrees

Cation stability is influenced by three factors:
a) Hyperconjugation:
Increasing the number of alkyl substituents increases the stability of the carbocation. This is due to orbital overlap between the ? bond and the empty p orbital on the sp2 carbon.
b) Inductive Effects:
Neighbouring alkyl groups contain electrons that are polarizable, and these can shift towards the positive charge. (Small Hydrogen substituents cannot do this as well).
c) Resonance Effects:
Conjugation with a multiple bond or lone pairs of electrons increase the stability of a carbocation.