OCHEM configurations

[TouchofVersed]

I had trouble with some configurations MCAT Ochem needs u to know:


ok, so lets deal with (+ and -), (L and D), and (S and R)

correct me if I am wrong.

S and R deal with absolute configurations (depends on how substituents are bonded.)

(L and D) deal with the way light is bent.

(-) is another term for L and (+) is another term for D?

also, we have L amino acids and D sugars. Do we specifically have S or R sugars and amino acids?

thanks

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[G1SG2]

S and R deal with absolute configurations (depends on how substituents are bonded.)

correct

(L and D) deal with the way light is bent.

(-) is another term for L and (+) is another term for D?

Yes, it refers to optical activity...

also, we have L amino acids and D sugars. Do we specifically have S or R sugars and amino acids?

Our naturally occurring amino acids have the L configuration.

 

[LaCasta]

All L are S all R are D but these do not indicate whether they are ± as optical rotation can't be predicted by absolute config

 

[medicant]

yes and no. (+) and (-) refer to the rotation of plane polarized light as it passes through an enantiopure solution of the compound in question. L and R are relative terms that relate common biomolecules like amino acids and sugars to glyceraldehyde - it so happens that L molecules turned out to be S, and R molecules R for the naturally occuring molecules...one can imagine non-biological examples, however, where this would not be the case. S and R, as was said, refer to absolute configuration.