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Topic: Chiral separation or enatio-selective synthesis  (Read 5926 times)

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suresh46

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Chiral separation or enatio-selective synthesis
« 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


Offline wereworm73

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Re: Chiral separation or enatio-selective synthesis
« Reply #1 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.

Offline Donaldson Tan

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Re: Chiral separation or enatio-selective synthesis
« Reply #2 on: May 22, 2006, 07:18:12 PM »
You can pass your racemic mixture through a chiral column.

What's a chiral column?
"Say you're in a [chemical] plant and there's a snake on the floor. What are you going to do? Call a consultant? Get a meeting together to talk about which color is the snake? Employees should do one thing: walk over there and you step on the friggin� snake." - Jean-Pierre Garnier, CEO of Glaxosmithkline, June 2006

Offline wereworm73

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Offline Will

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Re: Chiral separation or enatio-selective synthesis
« Reply #4 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).

suresh46

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Re: Chiral separation or enatio-selective synthesis
« Reply #5 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??

Offline Will

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Re: Chiral separation or enatio-selective synthesis
« Reply #6 on: May 22, 2006, 08:16:24 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!

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