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Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: NoCode. on February 05, 2008, 06:18:35 PM

Title: Chiral Centers in Cholesterol
Post by: NoCode. on February 05, 2008, 06:18:35 PM

When I went to find the chiral centers in cholesterol, I found 7 of the 8. Why is the circled carbon a chiral center? It looks to me that it is bonded to 2 of the same molecule.

(http://aycu28.webshots.com/image/44227/2000006575761083614_rs.jpg)

Thanks.

Title: Re: Chiral Centers in Cholesterol
Post by: macman104 on February 05, 2008, 06:22:42 PM

It does?  You have to look past just the direct carbon it is attached to also.  I think you'll see that it is not in a symmetric position at all.  For example, they both connect to a CH, but after that, the paths differ.

Title: Re: Chiral Centers in Cholesterol
Post by: agrobert on February 05, 2008, 06:23:25 PM

Refer here for numbering.

http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=stryer.figgrp.3660

C-8 (circled) has a hydrogen going back (into the plane) and is connected to four different substituents.  Chirality has to do with symmetry and C-8 is not a symmetric center.  C-14 which you knew was chiral is chiral for the same reason as C-8.

Title: Re: Chiral Centers in Cholesterol
Post by: agrobert on February 05, 2008, 06:24:42 PM

It might help to draw the stereochemistry of all centers including protons.

Title: Re: Chiral Centers in Cholesterol
Post by: NoCode. on February 05, 2008, 06:37:10 PM

Thanks a lot. I wasn't thinking and didn't look past the direct carbon that it was attached to.

Title: Re: Chiral Centers in Cholesterol
Post by: lucky09 on September 30, 2009, 05:41:53 PM

wait why is  C attached to HO a chiral???? ???

Title: Re: Chiral Centers in Cholesterol
Post by: sjb on September 30, 2009, 05:44:53 PM

Quote from: lucky09 on September 30, 2009, 05:41:53 PM

wait why is  C attached to HO a chiral???? ???

Because ultimately it's attached to 4 different groups (in this case). What is it attached to?

Title: Re: Chiral Centers in Cholesterol
Post by: lucky09 on September 30, 2009, 05:47:39 PM

well one side is attached OH and two sides are attached to CH2 and one side H? rite

Title: Re: Chiral Centers in Cholesterol
Post by: sjb on October 01, 2009, 02:03:29 AM

Quote from: lucky09 on September 30, 2009, 05:47:39 PM

well one side is attached OH and two sides are attached to CH2 and one side H? rite

At "radius" one atom, yes, how about further out? Do you appreciate why the circled atom is chiral?