May 25, 2019, 03:52:18 PM
Forum Rules: Read This Before Posting


Topic: Organic chemistry  (Read 1618 times)

0 Members and 1 Guest are viewing this topic.

Offline gurmeet.nitk

  • New Member
  • **
  • Posts: 6
  • Mole Snacks: +0/-0
Organic chemistry
« on: November 30, 2016, 01:00:03 PM »
Why p- bromo benzyl alcohol is less reactive to SN2 reaction than benzyl alcohol despite of the -I effect of bromine being dominant ?

Offline Vidya

  • Full Member
  • ****
  • Posts: 723
  • Mole Snacks: +42/-60
  • Gender: Female
  • Online Chemistry and Organic Chemistry tutor
    • Online Chemistry Tutor
Re: Organic chemistry
« Reply #1 on: November 30, 2016, 06:41:17 PM »
For SN2 reaction bulkiness of the group is also a major problem.

Offline gurmeet.nitk

  • New Member
  • **
  • Posts: 6
  • Mole Snacks: +0/-0
Re: Organic chemistry
« Reply #2 on: November 30, 2016, 08:29:47 PM »
Then by that explanation p-nitro benzyl alcohol should be even less  reactive than p- bromo benzyl alcohol , but that is not the case

As far as I know electron withdrawing groups increase sn2 reactivity.

Please help

Offline Vidya

  • Full Member
  • ****
  • Posts: 723
  • Mole Snacks: +42/-60
  • Gender: Female
  • Online Chemistry and Organic Chemistry tutor
    • Online Chemistry Tutor
Re: Organic chemistry
« Reply #3 on: November 30, 2016, 08:33:10 PM »
that is true ..we need to consider both the factors ...he  asked between benzyl alcohol and bromo- benzyl alcohol . now bulkiness factor will decide here ...

Offline gurmeet.nitk

  • New Member
  • **
  • Posts: 6
  • Mole Snacks: +0/-0
Re: Organic chemistry
« Reply #4 on: November 30, 2016, 08:56:11 PM »
Please find the attached image.

As you said bulkiness is the major problem , then the question no 45 in the attached image is having wrong answer .

Could you please justify

Offline Vidya

  • Full Member
  • ****
  • Posts: 723
  • Mole Snacks: +42/-60
  • Gender: Female
  • Online Chemistry and Organic Chemistry tutor
    • Online Chemistry Tutor
Re: Organic chemistry
« Reply #5 on: November 30, 2016, 09:02:08 PM »
Are you checking bulkiness of nucleophiles  or substrate ?
I was talking about the substrate bulkiness .
A bulky nucleophile is not good for SN2.

Offline gurmeet.nitk

  • New Member
  • **
  • Posts: 6
  • Mole Snacks: +0/-0
Re: Organic chemistry
« Reply #6 on: November 30, 2016, 09:06:59 PM »
Bulkiness of neither the substrate nor the nucleophile goes well for sn2 .
Correct if wrong

But how come methoxide ion in the attached image shows least reactivity to sn2

Offline Vidya

  • Full Member
  • ****
  • Posts: 723
  • Mole Snacks: +42/-60
  • Gender: Female
  • Online Chemistry and Organic Chemistry tutor
    • Online Chemistry Tutor
Re: Organic chemistry
« Reply #7 on: November 30, 2016, 09:11:21 PM »
Pl you have to consider bulkiness with other factors
like in nucleophile you need a strong nucleophile also ...check in your question which one is best nucleophile
we have balance out  both factors together.

Sponsored Links