quick sterochem question
Started by ihatebluescrubs
R and S can be found by looking at the molecular structure. +/- can only be found experimentally. However, if you know the optical orientation (+/-) of one molecule, then its enantiomer has the opposite sign.
Assuming that it has one chiral center, otherwise things get more complicated
French physicist used the Rotation of Light to distinguish between enantiomers using the + / - system.
An enantiomer that rotates plane-polarized light in the positive direction, or clockwise, is called dextrorotary [(+), or d-], while the enantiomer that rotates the light in the negative direction, or counterclockwise, is called levorotary [(-), or l-]. When both d- and l- isomers are present in equal amounts, the mixture is called a racemic mixture. DO not mix Recemic with Meso
Left rotation: (-) or l or levorotatory.
Right rotation: (+) or d or dextrorotatory.
Caution: (+) or (-) does NOT correspond to R/S configurations.
Caution: d and l is NOT the same as D and L. The upper case letters denote absolute configurations in sugars.
Absolute configuration is the (R) or (S) that's labeled on the chiral centers
Relative configuration used before the mid-1800s, people did not have an understanding of the tetrahedral carbon atom, so they did not have absolute configurations. Instead, they used the relative configurations of which way a compound rotates plane-polarized light.
An enantiomer that rotates plane-polarized light in the positive direction, or clockwise, is called dextrorotary [(+), or d-], while the enantiomer that rotates the light in the negative direction, or counterclockwise, is called levorotary [(-), or l-]. When both d- and l- isomers are present in equal amounts, the mixture is called a racemic mixture. DO not mix Recemic with Meso
Left rotation: (-) or l or levorotatory.
Right rotation: (+) or d or dextrorotatory.
Caution: (+) or (-) does NOT correspond to R/S configurations.
Caution: d and l is NOT the same as D and L. The upper case letters denote absolute configurations in sugars.
Absolute configuration is the (R) or (S) that's labeled on the chiral centers
Relative configuration used before the mid-1800s, people did not have an understanding of the tetrahedral carbon atom, so they did not have absolute configurations. Instead, they used the relative configurations of which way a compound rotates plane-polarized light.
