Question About Cholesterol

[MissionStanford]

Cholesterol has 8 assymetric centers:
http://www.chemguide.co.uk/basicorg/isomerism/cholesterol2.gif

The one labeled 9 isn't an assymetric center.

Anyway, my book says that because there are 8 assymetric centers, there should be 2^8 = 256 different possible stereoisomers.

But there's also 1 double bond, so wouldn't it be 2^9 = 512 possible stereoisomers since we have to account for the two different stereoisomers that are possible based on whether the double bond is cis or trans?

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[underscore]

Look at the double bond and try to draw the cis and trans forms. You won't be able to, because its stereochemistry is locked by the ring.

 

[Temperature101]

Cholesterol has 8 assymetric centers:
http://www.chemguide.co.uk/basicorg/isomerism/cholesterol2.gif

The one labeled 9 isn't an assymetric center.

Anyway, my book says that because there are 8 assymetric centers, there should be 2^8 = 256 different possible stereoisomers.

But there's also 1 double bond, so wouldn't it be 2^9 = 512 possible stereoisomers since we have to account for the two different stereoisomers that are possible based on whether the double bond is cis or trans?

C9 has 2 CH3 substituents; therefore, that carbon is achiral (not a stereogenic center).

 

[heartsavior]

I'm not sure how you could interchange z/e configuration in a cyclohexene without breaking the intact ring structure. The six atoms about a double bond are all in the same plane, including the vinyl carbons. Still it doesn't make sense to do that. # of possible stereo isomers = 2^n, where n = # of centers of chirality. Keep on the look out for question wording by the way, sometimes it'll be stated as "how many possible pairs of enantiomers"

 

[Temperature101]

I'm not sure how you could interchange z/e configuration in a cyclohexene without breaking the intact ring structure. The six atoms about a double bond are all in the same plane, including the vinyl carbons. Still it doesn't make sense to do that. # of possible stereo isomers = 2^n, where n = # of centers of chirality. Keep on the look out for question wording by the way, sometimes it'll be stated as "how many possible pairs of enantiomers"

I deleted the Z...How the heck I typed it? I dont know.