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In stereochemistry, an epimer is one of a pair of diastereomers. [1] The two epimers have opposite configuration at only one stereogenic center out of at least two. [2] All other stereogenic centers in the molecules are the same in each. Epimerization is the interconversion of one epimer to the other epimer.
Stereochemistry, a subdiscipline of chemistry, studies the spatial arrangement of atoms that form the structure of molecules and their manipulation. [1] The study of stereochemistry focuses on the relationships between stereoisomers, which are defined as having the same molecular formula and sequence of bonded atoms (constitution) but differing in the geometric positioning of the atoms in space.
Traditionally, double bond stereochemistry was described as either cis (Latin, on this side) or trans (Latin, across), in reference to the relative position of substituents on either side of a double bond. A simple example of cis–trans isomerism is the 1,2-disubstituted ethenes, like the dichloroethene (C 2 H 2 Cl 2) isomers shown below. [7]
A racemic mixture is denoted by the prefix (±)-or dl-(for sugars the prefix dl-may be used), indicating an equal (1:1) mixture of dextro and levo isomers. Also the prefix rac- (or racem- ) or the symbols RS and SR (all in italic letters) are used.
The concept of intimate ion pairs is used to explain the slight tendency for inversion of stereochemistry during an S N 1 reaction. It is proposed that solvent or other ions in solution may assist in the removal of a leaving group to form a carbocation which reacts in an S N 1 fashion; similarly, the leaving group may associate loosely with the ...
COOH, R, NH 2 and H (where R is the side-chain) are arranged around the chiral center carbon atom. With the hydrogen atom away from the viewer, if the arrangement of the CO → R → N groups around the carbon atom as center is counter-clockwise, then it is the L form. [ 14 ]
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The two cis stereoisomers of 1,2-substituted cyclohexanes behave like meso compounds at room temperature in most cases. At room temperature, most 1,2-disubstituted cyclohexanes undergo rapid ring flipping (exceptions being rings with bulky substituents), and as a result, the two cis stereoisomers behave chemically identically with chiral ...