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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.
In organic chemistry, neighbouring group participation (NGP, also known as anchimeric assistance) has been defined by the International Union of Pure and Applied Chemistry (IUPAC) as the interaction of a reaction centre with a lone pair of electrons in an atom or the electrons present in a sigma or pi bond contained within the parent molecule but not conjugated with the reaction centre.
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 ...
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.
One of the first such racemates studied, by Pasteur in 1853, forms from a 1:2 mixture of the bis ammonium salt of (+)-tartaric acid and the bis ammonium salt of (−)-malic acid in water. Re-investigated in 2008, [ 9 ] the crystals formed are dumbbell -shape with the central part consisting of ammonium (+)-bitartrate, whereas the outer parts ...
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]
Goat Cheese, Pecan, and Mixed Green Salad. This premade salad consists of mixed greens, pecans, dried cranberries, bell peppers, tomatoes, red onions, and goat cheese with a honey vinaigrette. 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 ]