# Which is more stable out of the given carbocation?

I have read in Solomon's Fryhle that +I effect of D is more than H but here in this problem it is given that (CH3)3C+ is more stable. How is it possible when Deuterium enriches the electron density over central Carbon resulting in diminishing of + charge eventually making second structure more stable. Second explanation can be on the basis of hyperconjugation which says that -CH3 is better in showing hyperconjugation than -CD3, but WHY? Please explain.

## 1 Answer

$\ce{C-D}$ bonds are stronger. Hyperconjugation is thus more easily seen with hydrogen rather than deuterium.
Hyperconjugation> Inductive effects at stabilization.I believe you can reason the rest out by yourself.
To see why $\ce{C-D}$ bonds are stronger.
See this

• While true, this answer is extremely unsatisfying. The link from bond strength to hyperconjugation is not obvious to me at all. (And I'm not saying I have any better explanation. This is something which I have never seen a good explanation for.) – orthocresol Jan 28 '18 at 18:33
• @orthocresol Maybe this contains the required answer. – Apoorv Potnis Jan 29 '18 at 5:51