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Topic: alpha and beta D Glucose  (Read 9287 times)

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Offline AhmedEzatAlzawalaty

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alpha and beta D Glucose
« on: September 25, 2007, 12:24:48 PM »
is the chair form of alpha D glucose is one in which OH on C1 and CH2OH group on C5 are Trans? and in beta they are Cis?
Is this right? or is there another way to determine alpha and beta D glucose?
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Offline Yggdrasil

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Re: alpha and beta D Glucose
« Reply #1 on: September 25, 2007, 04:10:30 PM »
Yes.  Some people like to remember that they are trans by saying that in the alpha form, the groups on C5 and C1 are anti to eachother. 

It is also worth noting that in beta D-glucose, all the substituents are equatorial.
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Offline AhmedEzatAlzawalaty

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Re: alpha and beta D Glucose
« Reply #2 on: September 27, 2007, 09:06:09 PM »
but i think in Beta form , since C5 and C1 are stereocenters, so the groups they carrying(CH2OH and OH) respectively,could be axial and cis in the same time, you got it? and when OH is axial so it is alpha ,right?
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Offline Yggdrasil

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Re: alpha and beta D Glucose
« Reply #3 on: September 28, 2007, 08:41:44 PM »
Yes, you are correct that they could both be axial and cis.  However, the conformer where all of the substituents are axial is very energetically unfavorable, so all of the constituents of beta-D-glucose should be equatorial (it may be helpful to build a model).
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