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Chemistry Forums for Students => Undergraduate General Chemistry Forum => Topic started by: owlpower on September 15, 2018, 01:00:33 AM

Title: Which of the following compounds won't rotate plane polarised light
Post by: owlpower on September 15, 2018, 01:00:33 AM

Question : https://imgur.com/a/nGCsjOl

How do I tell which one won't rotate plane polarised light? I know that chiral molecules will rotate plane polarised light. They are all stereo isomers of each other, and I determined 1 to be RR, 2 to be SS, 3 to be RS and 4 to be SR. I also know meso compounds are chiral but do not exhibit optical activity...

Title: Re: Which of the following compounds won't rotate plane polarised light
Post by: sjb on September 15, 2018, 03:58:50 AM

I'd look again at your assignments. Why are 2 and 4 apparently different, for instance?

Title: Re: Which of the following compounds won't rotate plane polarised light
Post by: owlpower on September 17, 2018, 05:32:41 AM

Wait a minute...2 and 4 are conformers, aren't they?

Title: Re: Which of the following compounds won't rotate plane polarised light
Post by: sjb on September 17, 2018, 08:07:47 AM

I think so...

Title: Re: Which of the following compounds won't rotate plane polarised light
Post by: Babcock_Hall on September 25, 2018, 08:54:44 PM

Meso compounds are not chiral.  Is one of your drawings a meso form?

Title: Re: Which of the following compounds won't rotate plane polarised light
Post by: Vidya on September 27, 2018, 03:16:14 AM

Convert all newman projections into Fisher Projections and from there you can easily figure out which one is meso and not chiral.