Which is more stable and why: `(CH_(3))_(3)overset(oplus)(C),(CD_(3))_(3)overset(oplus)(C)`?

Explanation

Since D is more electron - releasing than H, - `CD_(3)` is more electron - releasing than `-CH_(3). " " So, (CD_(3))_(3)overset(oplus)(C)` is expected to be more stable than `(CH_(3))_(3)overset(oplus)( C )` . But actually the reverse is true and this can be explained in terms of hyperconjugation. Since the C - H bond is weaker than the C - D bond the hyperconjugative stability of `(CH_(3))overset(oplus)( C )` is greater than that of `(CD_(3))_(3)overset(oplus)( C )`.