Mechanism doubts.

1) Can SN1 reaction take place with E2 ? If yes, then when and why ?

2)What would be the effect of increasing solvent polarity on the rate of the given substitution reaction:-

R------L+ → R+ + :L

3)Why phenyl halide is unreactive towards SN1 reaction?

4)In Solomons its given that 2- Methylpropene is more stable than trans-2-Butene. Why so?
Won't there'll be strain in 2- Methylpropene because both the methyl groups are attached to the same carbon. But in the case of trans-2-Butene methyl groups are in trans position, won't it should be more stable?

9 Answers

1
shubhi gupta ·

hey yaar....
stability of carbocation--

CCl3+ or +CH2 - CCl3

1
shubhi gupta ·

(3) bcz in SN1 there is formation of carbocation and we knew that pheny carbocation does n't exist and as well it does not undergoes sn2 also, but it undergoes sn reaction

(1) True, i can give u explanation tomorrow!!!

11
Khyati ·

@ Shubhi

I think it will be CCl3+

1
shubhi gupta ·

hey wat's the reason here electron density at Carbon is so positive, and we knew these are less stable!

39
Pritish Chakraborty ·

1) I don't think SN1 can compete with E2. E2 takes place via transition state which means the "intermediate" has partial charges. A carbocation has a full blown positive charge. Thus the transition state is favoured. Though this question is quite natural as both the mechanisms favour 3 degree carbocations the most..

2) I think increasing solvent polarity would help in the formation of the carbocation. The solvent molecules would douse the fire (carbocation's desire for electrons) to some extent.

3) Another reason for this is the loss of aromaticity.

4) Something to do with hyperconjugation?

1
shubhi gupta ·

No yaar nothing associated with hyperconjugaton.....

1
shubhi gupta ·

CCl3+ is more stable than +CH2-CCl3 bcz of +R.... is this rigt

11
Khyati ·

Thanks Pritish [1]

1
aman_deep ·

CCl3+ will b more stable than +CH2-CCl3 bcz of resonance in CCl3+ bt still both will b lesser stable than CH3+ bcz exceptionally in case of halogens inductive effect is more stronger than the resonance effect.....

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