D&L/R&S/+&- stereochemistry

[97spooncivic]

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I just have a quick question, I know +&- for optical rotation has no relationship with D&L or R&S in regards to stereochemistry. My questions is are D&L and R&S related? If they are, I'm assuming D &R go together just based upon their names.

 

[PiBond]

I just have a quick question, I know +&- for optical rotation has no relationship with D&L or R&S in regards to stereochemistry. My questions is are D&L and R&S related? If they are, I'm assuming D &R go together just based upon their names.

in carbohydrates, for D-isomers the penultimate carbon has an R configuration. For L-isomers, the penultimate carbon has an S configuration. this is just for carbohydrates though...we don't use this R/S and L/D relationship to describe your run-of-the-mill stereocenters in other molecules

for amino acids, L-amino acids has S-stereochemistry (exception is cysteine which has R-stereochemistry but still considered an L amino acid, also glycine isn't chiral so it's an outlier as well)

don't worry about this too much for the MCAT

 

[boaz]

D&L is unrelated to R&S.

 

[Isoprop]

D&L (capitals) are relative configuration. They describe the stereochemistry relative to a glyceraldehyde.

R&S are absolute configurations based on rules.

+/- or d/l (lower case) is the optical rotation. It is determined whether plane polarized light

So...
A molecule can be R but be either D or L.
A molecule can be R but be either + or - (d or l).

 

[JmanDO]

Don't worry, it's all pretty EZ to deal with.