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{{#invoke:Hatnote|hatnote}} In organic chemistry and biochemistry, a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon. The terms substituent, side-chain, group, branch, or pendant group are used almost interchangeably to describe branches from a parent structure,<ref>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> though certain distinctions are made in the context of polymer chemistry.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }} This distinguishes a pendant group as neither oligomeric nor polymeric, whereas a pendant chain must be oligomeric or polymeric.</ref> In polymers, side chains extend from a 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. The polar effect exerted by a substituent is a combination of the inductive effect and the mesomeric effect. Additional steric effects result from the volume occupied by a substituent.

The phrases most-substituted and least-substituted are frequently used to describe molecules and predict their products. 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 adds to the carbon of the alkene functional group that 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.

Substituent sections
Intro   Nomenclature   Methane substituents   Structures    Statistical distribution    See also   References  

PREVIOUS: IntroNEXT: Nomenclature
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{{#invoke:Hatnote|hatnote}} In organic chemistry and biochemistry, a substituent is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon. The terms substituent, side-chain, group, branch, or pendant group are used almost interchangeably to describe branches from a parent structure,<ref>{{#invoke:citation/CS1|citation |CitationClass=book }}</ref> though certain distinctions are made in the context of polymer chemistry.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }} This distinguishes a pendant group as neither oligomeric nor polymeric, whereas a pendant chain must be oligomeric or polymeric.</ref> In polymers, side chains extend from a 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. The polar effect exerted by a substituent is a combination of the inductive effect and the mesomeric effect. Additional steric effects result from the volume occupied by a substituent.

The phrases most-substituted and least-substituted are frequently used to describe molecules and predict their products. 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 adds to the carbon of the alkene functional group that 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.

Substituent sections
Intro   Nomenclature   Methane substituents   Structures    Statistical distribution    See also   References  

PREVIOUS: IntroNEXT: Nomenclature
<<>>