[Koreandude]

Hi I'm currently studying ochem for my pharmacy entering exam in korea.
I was studying about sn1 and sn2 reaction in allylic position.
My teacher told me that if theres carbonyl beside carbon(that you will add nucleophile) it reacts with SN2 reaction then SN1
I was pretty sure that is right cuz of carbony react as Ew
WG.
But how about normal allylic? I googled it but some site said sn1 is major and some said sn2 is major...
I personally think SN2 is major cuz of the stablitiy of transition state in SN2.
BUT.. thinking about SN1 I was so counfused because there is conjugation and resonance..
Which one is major in allylic halide?

Sorry for my bad eng

[hollytara]

Allyl and allylic can react by either SN1 or SN2.  It depends on the conditions. 

The cations are low enough in energy so SN1 is possible.

But the structures are 1o and 2o, so there is little steric hindrance and SN2 works well also.

At lower T, high concentration of Nucleophile and a good SN2 solvent (polar aprotic), definitely SN2.

At higher T, SN1 will start to compete - if the nucleophile and solvent favor SN1, it can be nearly entirely SN1.