dentalmagnet

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TeamGuo

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A would be the optimal answer since the only other possible answer is the primary halide but you know that will never go under SN1 since primary carbocations will almost never be formed.

Good choice!
 

dentalmagnet

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I read that SN1 occurs on halides attached to double bonds. Like aromatic halides because the intermediate is SP2. But then I remembered that there is no way that SN2 would occur and that SN1 was rare in that situation. So the allylic halide does do SN1 and SN2?

Also, a secondary carbon does both as well right?
 
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shoombol tallah

Big Boy
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Since my exam was standardized, we don't get to see the answers..just our scores.
This is going to bug me so I thought I would ask you guys. On the ACS there was a question where they asked which halide would readily undergo SN2 and SN1...I don't remember the choices completely, but I think they were something like:
A. first degree allylic halide
B. a halide on a double bond
C. a regular primary halide
D. A tertiary halide

I picked (A) the allylic primary halide..but that was a guess. SN1 doesn't normally undergo primary, but it could possibly rearrange right? If a second degree carbon was on there, I would have picked that. I just want to know because this is a pretty good question and I might see it on the DAT.

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You got it right.

B) vinyl halide are unreactive for SN1 and SN2
C) Great for SN2 but bad for SN1
D) Great for SN1 bad for SN2 (too bulky)


choice A is resonance stabilized and thus the best answer :)
 

dentalmagnet

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