Question

Can anyone explain how no. of chiral carbons in β - D + glucose is 5?

Answer 1

@Woodward

Answer 2

@Woodward , I just needed you and you came online. O wuv you man :D

Answer 3

https://upload.wikimedia.org/wikipedia/commons/thumb/b/bb/Beta-D-Glucose.svg/620px-Beta-D-Glucose.svg.png

So each of these carbons on the ring have 4 different substituents since even though they might be attached to carbons, those carbons they're attached to don't have the same connectivity! Maybe a smaller example will help, but chiral centers are more than just "is this attached to a carbon or not, for instance, this molecule is chiral: even though each atom is attached to only carbons, if this helps.

I can try to clarify more, since I know I'm kind of vague about this I am not entirely sure what you needed clarification on. :D

Answer 4

Actually, I tried finding no. of chiral carbons and every where got the answer 4 with following reason but the actual answer is 5. I don't know how. Your explanation seems to make sense.

http://wps.prenhall.com/wps/media/objects/3313/3393159/blb2510.html

Answer 5

*No of chiral corbons in glucose molecule

Answer 6

Ah, the difference is that the linear form of the molecule has 4 and the closed-chain form has 5.

Answer 7

Oh, I see... Can you link me something where I can learn how to find chiral carbons in closed chain compound?

Answer 8

Hmm, I don't know of any off the top of my head. All I can say is that the extra chiral carbon comes as a result of when the ring closes it turns the \(sp^2\) hybridized carbonyl carbon at the aldehyde into an \(sp^3\) carbon, which is really what appears to be the difference between \(\alpha\) and \(\beta\) -D-glucose.

Answer 9

You should be able to do something similar to how it was done here to determine if the carbons are chiral or not, http://wps.prenhall.com/wps/media/objects/3313/3393159/imag2510/AABAAST0.JPG

I can walk you through how to show that each carbon is chiral, or actually if you could draw it out it might be simpler that way to show me how you'd do it so I can help you realize where you're going wrong.

Answer 10

Ok, so here it is how I am doing, wait, do you want me tell why I think there are 4 chiral carbons because that's what I understand till this moment. I don't know how to figure it out in closed rings because according to me chiral carbons are those which have four different species attached to them.

Answer 11

Whichever, just make sure you specify which form you're talking about since the linear and cyclic forms have a different number of chiral carbons. The linear has 4, and the cyclic has 5, so whatever I just said doesn't make sense or you're unsure of just show me how you'd do it I guess.

Answer 12

Also, here's a mechanism so you can see a little bit how the carbonyl carbon is turned into a chiral carbon, which is where we're getting that extra chiral center from:
http://web.campbell.edu/faculty/nemecz/323_lect/sugars/images/Glucose_cycl.jpg

I realize you're probably doing biology and don't understand organic chemistry too well so if that confuses you just forget about it haha.

Answer 13

Ohh...I get it now......I saw this video
https://www.khanacademy.org/science/organic-chemistry/stereochemistry-topic/chirality-r-s-system/v/chirality-center-jay

Answer 14

Yes, you are right ;D

Answer 15

Thank you very Much!!!! c:

Answer 16

Cool, glad I could help! :P

Answer 17

@woodward great job!