Atom set which has replaced hydrogen atoms on a hydrocarbon's parent chain
This article is about the term in chemistry. For other meanings, see Substitution (disambiguation).
In organic chemistry, a substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule.[1] (In organic chemistry and biochemistry, the terms substituent and functional group, as well as side chain and pendant group, are used almost interchangeably to describe those branches from the parent structure,[2] though certain distinctions are made in polymer chemistry.[3] In polymers, side chains extend from the backbone structure. In proteins, side chains are attached to the alpha carbon atoms of the amino acid backbone.)
The suffix -yl is used when naming organic compounds that contain a single bond replacing one hydrogen; -ylidene and -ylidyne are used with double bonds and triple bonds, respectively. In addition, when naming hydrocarbons that contain a substituent, positional numbers are used to indicate which carbon atom the substituent attaches to when such information is needed to distinguish between isomers. Substituents can be a combination of the inductive effect and the mesomeric effect. Such effects are also described as electron-rich and electron withdrawing. Additional steric effects result from the volume occupied by a substituent.
The phrases most-substituted and least-substituted are frequently used to describe or compare molecules that are products of a chemical reaction. In this terminology, methane is used as a reference of comparison. Using methane as a reference, for each hydrogen atom that is replaced or "substituted" by something else, the molecule can be said to be more highly substituted. For example:
Markovnikov's rule predicts that the hydrogen atom is added to the carbon of the alkene functional group which has the greater number of hydrogen atoms (fewer alkyl substituents).
Zaitsev's rule predicts that the major reaction product is the alkene with the more highly substituted (more stable) double bond.
^"Definition of SUBSTITUENT". www.merriam-webster.com. Retrieved 4 June 2022.
^D.R. Bloch (2006). Organic Chemistry Demystified. ISBN 978-0-07-145920-4.
^Jenkins, A. D.; Kratochvíl, P.; Stepto, R. F. T.; Suter, U. W. (1996). "PAC, 1996, 68, 2287. Glossary of basic terms in polymer science (IUPAC Recommendations 1996)". Pure and Applied Chemistry. 68 (12): 2287–2311. doi:10.1351/pac199668122287. This distinguishes a pendant group as neither oligomeric nor polymeric, whereas a pendant chain must be oligomeric or polymeric.
In organic chemistry, a substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule...
benzoic acid derivatives with meta- and para-substituents to each other with just two parameters: a substituent constant and a reaction constant. This equation...
non-hydrogen substituent on a cyclohexane occupies the axial position. This axial substituent is in the eclipsed position with the axial substituents on the...
stereoelectronic effect that describes the tendency of heteroatomic substituents adjacent to a heteroatom within a cyclohexane ring to prefer the axial...
position of substituents other than hydrogen in relation to each other on an aromatic hydrocarbon. In ortho-substitution, two substituents occupy positions...
electrons in a conjugated orbital system move away from or towards a substituent group. The effect, which is symbolised by the letter M, is used in a...
In organic chemistry, an aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and...
steric effects, and Es is the steric substituent constant. Polar substituent constants describe the way a substituent will influence a reaction through polar...
In electrophilic aromatic substitution reactions, existing substituent groups on the aromatic ring influence the overall reaction rate or have a directing...
by a synergistic effect of an electron-withdrawing substituent and an electron-donating substituent. The name originates as the electron-withdrawing group...
have from one to six substituents attached to the central benzene core. Examples of benzene compounds with just one substituent are phenol, which carries...
a substituent such as an alkyl or aryl group (these may respectively be called alkylamines and arylamines; amines in which both types of substituent are...
organic and organometallic chemistry, an organyl group is an organic substituent with one (sometimes more) free valence(-s) at a carbon atom. The term...
In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same...
to the anomeric carbon (C1) is in the opposite plane from the CH 2OH substituent in the same ring (C6 of the first glucose). If the glycosidic bond to...
Apicophilicity is the phenomenon in which electronegative substituents of trigonal bipyramidal pentacoordinate compounds prefer to occupy apical (axial)...
alkyl or aryl group and the S(=O)2(OH) group a sulfonyl hydroxide. As a substituent, it is known as a sulfo group. A sulfonic acid can be thought of as sulfuric...
occur naturally and are important in pharmaceutical design. When the substituents are achiral, these conformers are enantiomers (atropoenantiomers), showing...
propyl group is a three-carbon alkyl substituent with chemical formula −CH2CH2CH3 for the linear form. This substituent form is obtained by removing one hydrogen...
as a substituent in numerous organic compounds, though it may also exist independently as an ion or radical. The presence of a methyl substituent may be...
In organic chemistry, a glycosyl group is a univalent free radical or substituent structure obtained by removing the hydroxyl (−OH) group from the hemiacetal...
ring by the substituent is not distributed evenly over the entire ring but is concentrated on atoms 2, 4 and 6, so activating substituents are also ortho/para...
they are not simple hydrocarbons. In chemistry, alkyl is a group, a substituent, that is attached to other molecular fragments. For example, alkyl lithium...
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