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In organic chemistry, a 'substituent' is an atom or group of atoms substituted in place of a hydrogen atom on the parent chain of a hydrocarbon. The suffix ''-yl'' (meaning "attached to") is used when naming organic compounds that contain a substituent. Additionally, when naming hydrocarbons that contain a substituent, positional numbers are used to indicate which carbon atom the substituent is attached to when such information is needed to distinguish between structural 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.
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 in a set of 3,043,941 molecules. 50 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. The top 5 consists of the phenyl, chlorine, methoxy, hydroxyl and ethyl substituent. The total number of organic substituents in organic chemistry is estimated at 3.1 million creating a total of 6.7×1023 molecules.
★ Functional groups are a subset of substituents
★ Side chain
★ Database of 21,000 substituents and 49,000 linkers extracted from bioactive molecules
# ''Cheminformatics Analysis of Organic Substituents: Identification of the Most Common Substituents, Calculation of Substituent Properties, and Automatic Identification of Drug-like Bioisosteric Groups'' Peter Ertl J. Chem. Inf. Comput. Sci.; '2003'; 43(2) pp 374 - 380 Abstract Download reprint
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.
| Contents |
| Number crunching |
| See also |
| External links |
| References |
Number crunching
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 in a set of 3,043,941 molecules. 50 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. The top 5 consists of the phenyl, chlorine, methoxy, hydroxyl and ethyl substituent. The total number of organic substituents in organic chemistry is estimated at 3.1 million creating a total of 6.7×1023 molecules.
See also
★ Functional groups are a subset of substituents
★ Side chain
External links
★ Database of 21,000 substituents and 49,000 linkers extracted from bioactive molecules
References
# ''Cheminformatics Analysis of Organic Substituents: Identification of the Most Common Substituents, Calculation of Substituent Properties, and Automatic Identification of Drug-like Bioisosteric Groups'' Peter Ertl J. Chem. Inf. Comput. Sci.; '2003'; 43(2) pp 374 - 380 Abstract Download reprint
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