October 21, 2021, 05:07:55 PM
Forum Rules: Read This Before Posting


Topic: what s the difference between trans and anti stereochemistry ?  (Read 13707 times)

0 Members and 1 Guest are viewing this topic.

Offline ch_wsc

  • New Member
  • **
  • Posts: 6
  • Mole Snacks: +0/-0
what s the difference between trans and anti stereochemistry ?
« on: October 17, 2006, 05:33:00 AM »
hi , I am sorry to bother u all with a simple question
I am asked what the stereochemistry of 1,2dibromocyclopentane produced by the reaction of cyclopentene and Br2
I know the 2 bromine atoms will go to opposite sides of 2 carbons but i don't know why it's tran but not anti
thx for any explanation

Offline Albert

  • Lonely Wanderer
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1050
  • Mole Snacks: +112/-22
  • Gender: Male
  • Half Decent Pharmaceutical Chemist
Re: what s the difference between trans and anti stereochemistry ?
« Reply #1 on: October 17, 2006, 06:07:03 AM »
When you consider alicyclic compounds, cis means  the substituents are on the same side, while trans isomer has one over and the other under the cyclic structure (http://en.wikipedia.org/wiki/Cis-trans_isomerism).

Anti and syn don't refer to a product but to a reaction (i.e. syn-addition).

Offline movies

  • Organic Minion
  • Retired Staff
  • Sr. Member
  • *
  • Posts: 1973
  • Mole Snacks: +222/-20
  • Gender: Male
  • Better living through chemistry!
Re: what s the difference between trans and anti stereochemistry ?
« Reply #2 on: October 17, 2006, 08:19:09 PM »
Anti and syn don't refer to a product but to a reaction (i.e. syn-addition).

That's not true.  For example, the two diastereomeric products of an aldol reaction are typically referred to as anti and syn.

Offline FeLiXe

  • Theoretical Biochemist
  • Chemist
  • Full Member
  • *
  • Posts: 462
  • Mole Snacks: +34/-7
  • Gender: Male
  • Excited?
    • Chemical Quantum Images
Re: what s the difference between trans and anti stereochemistry ?
« Reply #3 on: October 19, 2006, 08:08:46 AM »
normally anti and syn would describe the conformation as in syn-periplanar, syn-clinical, anti-clinical, anti-periplanar (if those are also the English terms)

I think it's ok to call the product anti. in a ring also trans works. maybe anti makes you think the bond can rotate, i don't know.
Math and alcohol don't mix, so... please, don't drink and derive!

Sponsored Links