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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.
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]
In LCP theory a lone pair is treated as a ligand. Gillespie terms the lone pair a lone pair domain and states that these lone pair domains push the ligands together until they reach the interligand distance predicted by the relevant inter-ligand radii. [1]
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.
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.
[7] Racemic compound (sometimes true racemate) If molecules have a greater affinity for the opposite enantiomer than for the same enantiomer, the substance forms a single crystalline phase in which the two enantiomers are present in an ordered 1:1 ratio in the elementary cell. Adding a small amount of one enantiomer to the racemic compound ...
There are three common naming conventions for specifying one of the two enantiomers (the absolute configuration) of a given chiral molecule: the R/S system is based on the geometry of the molecule; the (+)- and (−)- system (also written using the obsolete equivalents d- and l-) is based on its optical rotation properties; and the D/L system is based on the molecule's relationship to ...
A molecule may contain any number of stereocenters and any number of double bonds, and each usually gives rise to two possible isomers. A molecule with an integer n describing the number of stereocenters will usually have 2 n stereoisomers, and 2 n−1 diastereomers each having an associated pair of enantiomers.