1,2 addition

[chiddler]

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Book says that only carbons 1 and 3 can be electrophiles. Book also says that a 1,2 and 1,4 addition can occur.

1,4 is very clear. 1,2...not so much.

Say you add a lot of HBr. Alkene can be attacked to make either carbon 2 or 3 carbocations. Both are electrophiles!

So I must have my facts off.

1. How does HBr react with this molecule?

2. How is 1,2 addition possible?

 

[chiddler]

bump for edit.

 

[MedPR]

I haven't reviewed this yet, but it seems to me that if you take off a H from C3, you will get a hydride shift from C2, making C2 a carbocation = 1,2 addition?

 

[NF15]

Oxygen is 1, moves the numbers one up for the rest on the carbons.

 

[chiddler]

Oxygen is 1, moves the numbers one up for the rest on the carbons.

sorry friend i don't think that's accurate.

 

[chiddler]

I haven't reviewed this yet, but it seems to me that if you take off a H from C3, you will get a hydride shift from C2, making C2 a carbocation = 1,2 addition?

take off an H from an alkene? that's not likely to happen is it? also, do you mean c3 with my numbering or c3 with formal numbering

 

[gettheleadout]

Oxygen is 1, moves the numbers one up for the rest on the carbons.

sorry friend i don't think that's accurate.

I agree with chiddler but it's true in rings like furan.

Unfortunately I'm not familiar with addition to unsaturated carbonyls yet, sorry chiddler. 🙁