Substituent

substitutedsubstitutionsubstituentsside chainside-chainchemical groupside-chainssubstituent groups-ylgeneral formula
In organic chemistry and biochemistry, a substituent is an atom or group of atoms which replaces one or more hydrogen atoms on the parent chain of a hydrocarbon, becoming a moiety of the resultant new molecule.wikipedia
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Functional group

groupfunctional groupsmoiety
The terms substituent and functional group, as well as other ones (e.g. side chain, pendant group) are used almost interchangeably to describe branches from a parent structure, though certain distinctions are made in the context of polymer chemistry.
In organic chemistry, functional groups are specific substituents or moieties within molecules that are responsible for the characteristic chemical reactions of those molecules.

Side chain

side-chainside chainsside-chains
The terms substituent and functional group, as well as other ones (e.g. side chain, pendant group) are used almost interchangeably to describe branches from a parent structure, though certain distinctions are made in the context of polymer chemistry.
In organic chemistry and biochemistry, a side chain is a chemical group that is attached to a core part of the molecule called the "main chain" or backbone.

Amino acid

amino acidsresiduesresidue
In proteins, side chains are attached to the alpha carbon atoms of the amino acid backbone.
Amino acids are organic compounds that contain amine (-NH 2 ) and carboxyl (-COOH) functional groups, along with a side chain (R group) specific to each amino acid.

Moiety (chemistry)

moietymoietiesgroup
In organic chemistry and biochemistry, a substituent is an atom or group of atoms which replaces one or more hydrogen atoms on the parent chain of a hydrocarbon, becoming a moiety of the resultant new molecule. The suffix -yl is used in organic chemistry to form names of radicals, either separate species (called free radicals) or chemically bonded parts of molecules (called moieties).
Moieties that constitute branches extending from the backbone of a hydrocarbon molecule, which can often be broken off and substituted with others, are called substituents or side chains.

Organic compound

syntheticorganicorganic compounds
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 chemical nomenclature, an organyl group, frequently represented by the letter R, refers to any monovalent substituent whose open valence is on a carbon atom.

Polar effect

electron-withdrawing groupelectron withdrawing groupelectron-withdrawing
The polar effect exerted by a substituent is a combination of the inductive effect and the mesomeric effect.
The polar effect or electronic effect in chemistry is the effect exerted by a substituent on modifying electrostatic forces operating on a nearby reaction center.

Mesomeric effect

mesomericresonance
The polar effect exerted by a substituent is a combination of the inductive effect and the mesomeric effect.
The mesomeric effect in chemistry is a property of substituents or functional groups in a chemical compound.

Carboxylic acid

carboxylcarboxyl groupcarboxylic acids
The general formula of a carboxylic acid is R–COOH, with R referring to the rest of the molecule.

Alcohol

alcoholssecondary alcoholtertiary alcohol
In these shorthands, R, R', and R" represent substituents, alkyl or other attached, generally organic groups.

Aryl

aryl groupbiarylar
In a chemical structural formula, an organic substituent such as methyl, ethyl, or aryl can be written as R (or R 1, R 2, etc.) It is a generic placeholder, the R derived from radical or rest, which may replace any portion of the formula as the author finds convenient.
In the context of organic molecules, aryl is any functional group or substituent derived from an aromatic ring, usually an aromatic hydrocarbon, such as phenyl and naphthyl.

Ethyl group

ethylEtethylation
In a chemical structural formula, an organic substituent such as methyl, ethyl, or aryl can be written as R (or R 1, R 2, etc.) It is a generic placeholder, the R derived from radical or rest, which may replace any portion of the formula as the author finds convenient.
In chemistry, an ethyl group is an alkyl substituent derived from ethane (C 2 H 6 ).

Radical (chemistry)

free radicalradicalfree radicals
In a chemical structural formula, an organic substituent such as methyl, ethyl, or aryl can be written as R (or R 1, R 2, etc.) It is a generic placeholder, the R derived from radical or rest, which may replace any portion of the formula as the author finds convenient. The suffix -yl is used in organic chemistry to form names of radicals, either separate species (called free radicals) or chemically bonded parts of molecules (called moieties).
Following recent nomenclature revisions, a part of a larger molecule is now called a functional group or substituent, and "radical" now implies "free".

Parent structure

parent compoundparentparent chain
In organic chemistry and biochemistry, a substituent is an atom or group of atoms which replaces one or more hydrogen atoms on the parent chain of a hydrocarbon, becoming a moiety of the resultant new molecule.
To construct a systematic name, affixes are attached to the parent name, which denote substituents that replace hydrogen.

Methanol

methyl alcoholwood alcoholCH 3 OH
It can be traced back to the old name of methanol, "methylene" (from ', 'wine' and ὕλη ', 'wood'), which became shortened to "methyl" in compound names, from which -yl was extracted.
The suffix -yl, which, in organic chemistry, forms names of carbon groups, is from the word methyl.

Methyl group

methylCH 3 Me
In a chemical structural formula, an organic substituent such as methyl, ethyl, or aryl can be written as R (or R 1, R 2, etc.) It is a generic placeholder, the R derived from radical or rest, which may replace any portion of the formula as the author finds convenient. It can be traced back to the old name of methanol, "methylene" (from ', 'wine' and ὕλη ', 'wood'), which became shortened to "methyl" in compound names, from which -yl was extracted. The top 5 most common are the methyl, phenyl, chlorine, methoxy, and hydroxyl substituents.
The reactivity of a methyl group depends on the adjacent substituents.

Phenyl group

phenylphenyl ringPh
The top 5 most common are the methyl, phenyl, chlorine, methoxy, and hydroxyl substituents.
Phenyl groups have six carbon atoms bonded together in a hexagonal planar ring, five of which are bonded to individual hydrogen atoms, with the remaining carbon bonded to a substituent.

Organic chemistry

organicorganic chemistorganic chemical
In organic chemistry and biochemistry, a substituent is an atom or group of atoms which replaces one or more hydrogen atoms on the parent chain of a hydrocarbon, becoming a moiety of the resultant new molecule. The suffix -yl is used in organic chemistry to form names of radicals, either separate species (called free radicals) or chemically bonded parts of molecules (called moieties).

Biochemistry

biochemistbiochemicalbiological chemistry
In organic chemistry and biochemistry, a substituent is an atom or group of atoms which replaces one or more hydrogen atoms on the parent chain of a hydrocarbon, becoming a moiety of the resultant new molecule.

Atom

atomsatomic structureatomic
In organic chemistry and biochemistry, a substituent is an atom or group of atoms which replaces one or more hydrogen atoms on the parent chain of a hydrocarbon, becoming a moiety of the resultant new molecule.

Hydrogen

HH 2 hydrogen gas
In organic chemistry and biochemistry, a substituent is an atom or group of atoms which replaces one or more hydrogen atoms on the parent chain of a hydrocarbon, becoming a moiety of the resultant new molecule.

Hydrocarbon

hydrocarbonsliquid hydrocarbonHC
In organic chemistry and biochemistry, a substituent is an atom or group of atoms which replaces one or more hydrogen atoms on the parent chain of a hydrocarbon, becoming a moiety of the resultant new molecule.

Molecule

molecularmoleculesmolecular structure
In organic chemistry and biochemistry, a substituent is an atom or group of atoms which replaces one or more hydrogen atoms on the parent chain of a hydrocarbon, becoming a moiety of the resultant new molecule.

Pendant group

side grouppendentside groups
The terms substituent and functional group, as well as other ones (e.g. side chain, pendant group) are used almost interchangeably to describe branches from a parent structure, though certain distinctions are made in the context of polymer chemistry.

Polymer

polymershomopolymerpolymeric
The terms substituent and functional group, as well as other ones (e.g. side chain, pendant group) are used almost interchangeably to describe branches from a parent structure, though certain distinctions are made in the context of polymer chemistry.