What's with deuterium? an organic problem

1. Apr 23, 2015

mooncrater

1. The problem statement, all variables and given/known data
I did a question in which positive charge was unstable near to $-CD_3$ group but was stable near to $CH_3$ group.

2. Relevant equations

3. The attempt at a solution
Why is it like that? Is deuterium less active for hyperconjugation or it causes more steric hindrance? What's wrong with deuterium?

2. Apr 23, 2015

Raghav Gupta

How many neutrons or protons Deuterium has?

3. Apr 23, 2015

mooncrater

It has a proton and a neutron. So steric hindrance?

4. Apr 23, 2015

Raghav Gupta

I am not sure but it looks that it is the only reason. What do you think?

5. Apr 23, 2015

mooncrater

Yup.. it seems to me it's steric hindrance only, as it's heavier(thus bigger) than hydrogen. And it can't be hyperconjugation as it has the same configuration. That's what I think.

6. Apr 23, 2015

Staff: Mentor

Do I understand correctly that you assume deuterium is larger than protium, because it has an additional neutron in nucleus? That must be off. The size of nucleus is negligible.

The only (in such cases) important difference is that D is twice heavier, so its reactions (broadly understood, not only in terms of pure chemistry, but also shape shifts) are much slower. I don't know what is the correct answer here, but that's the only valid approach IMHO.

7. Apr 23, 2015

mooncrater

What is IMHO? Something molecular hybrid orbital?

8. Apr 23, 2015

Raghav Gupta

In my humble opinion.

9. Apr 23, 2015

mooncrater

Really? Okay....!!