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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: suresh46 on May 22, 2006, 05:34:01 PM

Title: Chiral separation or enatio-selective synthesis
Post by: suresh46 on May 22, 2006, 05:34:01 PM

Hi,
I'm new to this and really impressed by forum.

RS-CO-OCHR*-OAc How to separate them or do a entio selective synthesis?
Recemic synthesis is as follows: RSH+ClCOOCH2Cl to RSCOOCH2Cl then react with AcONa to give the recemic compound.

Your input is appreciated

Title: Re: Chiral separation or enatio-selective synthesis
Post by: wereworm73 on May 22, 2006, 07:09:20 PM

You can pass your racemic mixture through a chiral column.  Because the material in the column is optically active, one of the enantiomers will pass through it slower than the other.

Title: Re: Chiral separation or enatio-selective synthesis
Post by: Donaldson Tan on May 22, 2006, 07:18:12 PM

Quote from: wereworm73 on May 22, 2006, 07:09:20 PM

You can pass your racemic mixture through a chiral column.

What's a chiral column?

Title: Re: Chiral separation or enatio-selective synthesis
Post by: wereworm73 on May 22, 2006, 07:29:14 PM

http://www.chromtech.se/

Title: Re: Chiral separation or enatio-selective synthesis
Post by: Will on May 22, 2006, 07:46:17 PM

Read P.402 - 404 of this chapter of my organic chemistry book- http://www.willcornforth.com/organicchem_chapter16.pdf.
I read this book almost every day, I was going to post here before but I got delayed reading up about the Hammett relationship!
Theres a whole chapter on Asymmetric synthesis (chapter 45) and it sums up the methods at the end of it (see pic below).

Title: Re: Chiral separation or enatio-selective synthesis
Post by: suresh46 on May 22, 2006, 08:00:01 PM

Thanks Will17, I don't see the attached page#402-404.

Thanks Wereworm73,
we did some chiral column screening (polysacaride column), analytical works fine, but prep.column doesnot work in our case. May be silica based column??

Title: Re: Chiral separation or enatio-selective synthesis
Post by: Will on May 22, 2006, 08:16:24 PM

Quote from: suresh46 on May 22, 2006, 08:00:01 PM

Thanks Will17, I don't see the attached page#402-404.

Sorry, its pages 22-24 in the pdf file, but 402-404 in the actual book.

On page 24, you may also want to have a look at question 3- it is rather ridiculous!

The solutions manual provides rather a large answer for it.

Quote

Question:
Cinderella's glass slipper was undoubtedly a chiral object. But would it have rotated the plane of polarized light?
Purpose of problem:
Revision of the cause of rotation and optical acitivity.
Suggested solution:
No. The macroscopic shape of the object is irrelevant. Only the molecular structure matters as light interacts with electrons in the molecules. Glass is not chiral (usually made up of inorganic borosilicates these days). Only if the slipper had been made of a single enantiomer of a transparent substance would it have rotated polarized light. The molecules in Cinderella's left foot are of the same absolute configuration as those in her right foot despite her feet being macroscopically enantiomeric.

Surely it would have rotated a plane of polarized light if it was made up of a chiral substance with an ee!