Substituent

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, though certain distinctions are made in the context of polymer chemistry. 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. 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 substituents.
  • Zaitsev's rule predicts that the major reaction product is the alkene with the more highly substituted (more stable) double bond.

Read more about Substituent:  Nomenclature, Structures, Statistical Distribution

Other articles related to "substituent, substituents":

Strain (chemistry) - Kinds of Strain - Van Der Waals Strain - 1,3-diaxial Strain
... case, the strain occurs due to steric interactions between a substituent of a cyclohexane ring ('α') and gauche interactions between the alpha ... When the substituent is axial, it is brought near to an axial gamma hydrogen ... strain is largely dependent on the size of the substituent and can be relieved by forming into the major chair conformation placing the substituent in an equatorial position ...
Prochirality
... If two identical substituents are attached to a sp3-hybridized atom, the descriptors pro-R and pro-S are used to distinguish between the two ... Promoting the pro-R substituent to higher priority than the other identical substituent results in an R chirality center at the original sp3-hybridized atom, and analogously for the Pro-S substituent ... planar sp2-hybridized atom can be converted to a chiral center when a substituent is added to the re or si face of the molecule ...
Ylidene
... 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, though certain distinctions are made in the ... when naming hydrocarbons that contain a substituent, positional numbers are used to indicate which carbon atom the substituent attaches to when such ...
A Value - Table of A-Values
... The following table lists some common A-values in kcal/mol Substituent A-Value Substituent A-Value Substituent A-Value D 0.006 CH2Br 1.79 OSi(CH3)3 0.74 F 0.15 CH(CH3)2 2.15 OH 0.87 Cl 0.43 c-C6H11 2.15 OCH3 0.6 Br 0.38 C(CH3)3 >4 OCD3 0.56 I 0.43 Ph 3 OCH2CH3 0.9 CN 0.17 C2H 1.35 O-Ac 0.6 NC 0.21 CO2- 1.92 O-TFA 0.68 NCO 0.51 CO2CH3 1.27 OCHO 0.27 NCS 0.28 CO2Et 1.2 O-Ts 0.5 N=C=NR 1 CO2iPr 0.96 ONO2 0.59 CH3 1.7 COCl 1.25 NH2 1.6 CF3 2.1 COCH3 1.17 NHCH3 1 CH2CH3 1.75 SH 0.9 N(CH3)3 2.1 CH=CH2 1.35 SMe 0.7 NH3+ 1.9 CCH 0.41 SPh 0.8 NO2 1.1 CH2tBu 2 S- 1.3 HgBr ~0 CH2OTs 1.75 SOPh 1.9 HgCl 0.3 SO2Ph 2.5 Si(CH3)3 2.5. ...
Substituent - Statistical Distribution
... One cheminformatics study identified 849,574 unique substituents up to 12 non-hydrogen atoms large and containing only C,H,N,O,S,P,Se and the halogens ... Fifty common substituents are found in only 1% of this set, and 438 in 0.1%. 64% of the substituents are unique to just one molecule ...