[mana]

hi all
in this reaction the addition of halohydrin must be Markovnicov but we have no hydrogen here  so how I can guess the product, and about the stereochemistry of Br and OH must be anti because the intermediate is bromonium ion am I right?

[chenbeier]

Think what is halohydrin and what happens partly if bromine and water is mixed.

[kriggy]

What does it have to do with hydrogens?

And yes, the itermediate is bromonius and therefore they are anti

[mana]

What does it have to do with hydrogens?

And yes, the itermediate is bromonius and therefore they are anti

now the problem is why OH has added to more substituted carbon, I mean it should be added to carbon bonded to D, isn't it?

[Babcock_Hall]

I don't see deuterium versus hydrogen as making much of a difference in this reaction; in other words, I think you will see the same product formed at a very similar rate, no matter which one is present.  Why do you think that the reaction followed the regiochemistry that it does?

[mana]

I don't see deuterium versus hydrogen as making much of a difference in this reaction; in other words, I think you will see the same product formed at a very similar rate, no matter which one is present.  Why do you think that the reaction followed the regiochemistry that it does?

you mean I should have mixture of products?

[Babcock_Hall]

I think that one product will be the sole or at least the predominant product.  I made my previous comment because it does not seem to me that the presence of deuterium is important in this instance.

[mana]

Is it right to say that OH is added to more substituted carbon because of markovnikov rule?

[Babcock_Hall]

That is correct.

[clarkstill]

Is it right to say that OH is added to more substituted carbon because of markovnikov rule?

It is related, but Markovnikov's rule is really for addition of a protic acid (HX) across an alkene. The mechanism for halohydrin formation is completely different, and goes through (as mentioned above) a bromonium ion. The question is really, why does a bromonium ion undergo nucleophilic attack at the more substituted carbon? It is counter to what you'd normally expect for an SN2-like reaction.