In organic chemistry and biochemistry, the symbol R denotes a side chain. (The symbol in fact stands for radical.) This is useful when you wish to write a single formula to denote a number of different compounds with a certain structure in common.
Example
All the amino acids that are encoded by DNA have this component: -CH(NH2).CO2H
A convenient way to write the formula for all these amino acids is:
R-CH(NH2).CO2H
where
R = hydrogen (H-) in the amino acid glycine
R = a methyl group (CH3-) in alanine
and so on.
In organic chemistry R means hydrocarbon Alkyl group, such as methly, ethyl, propyl, butyl, (straight or branched chains) or possibly rings such as cycloalkyl, In physical chemistry "R" means Gas constant .
For chemists, the R / S system is the most important nomenclature system for denoting enantiomers, which does not involve a reference molecule such as glyceraldehyde. It labels each chiral center R or S according to a system by which its substituents are each assigned a priority, according to the Cahn-Ingold-Prelog priority rules (CIP), based on atomic number. If the center is oriented so that the lowest-priority of the four is pointed away from a viewer, the viewer will then see two possibilities: If the priority of the remaining three substituents decreases in clockwise direction, it is labeled R (for Rectus, Latin for right), if it decreases in counterclockwise direction, it is S (for Sinister, Latin for left).
An aldehyde
reaction
In Organic Chemistry an oxygen containing compound such as R-O-R' is known Ether.
The Nobel Prize in Chemistry 2005 was awarded jointly to Yves Chauvin, Robert H. Grubbs and Richard R. Schrock for the development of the metathesis method in organic synthesis.
In organic chemistry, the "R" group stands for any alkyl or aryl group. It is used as a placeholder to represent a wide variety of possible substituents in a molecule.
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Ether
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R-O-R' is the general structure for an ether.
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An aldehyde
In chemistry, this chemical compound, R-134A is the symbol for tetrafluoroethane. Tetrafluoroethane can be used as a solvent in organic chemistry.
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