Editing Substituent (section)

== Statistical distribution ==
One [[cheminformatics]] study identified 849,574 unique substituents up to 12 non-hydrogen atoms large and containing only [[carbon]], [[hydrogen]], [[nitrogen]], [[oxygen]], [[sulfur]], [[phosphorus]], [[selenium]], and the [[halogen]]s in a set of 3,043,941 molecules. Fifty substituents can be considered common as they are found in more than 1% of this set, and 438 are found in more than 0.1%. 64% of the substituents are found in only one molecule. The top 5 most common are the [[Methyl group|methyl]], [[phenyl]], [[chlorine]], [[methoxy]], and [[hydroxyl]] substituents. The total number of organic substituents in organic chemistry is estimated at 3.1 million, creating a total of 6.7×10<sup>23</sup> molecules.<ref>{{cite journal|last1=Ertl|first1=P.|title=Cheminformatics Analysis of Organic Substituents: Identification of the Most Common Substituents, Calculation of Substituent Properties, and Automatic Identification of Drug-like Bioisosteric Groups|journal=Journal of Chemical Information and Modeling|volume=43|pages=374–380|year=2003|doi=10.1021/ci0255782|pmid=12653499|issue=2}}</ref> An infinite number of substituents can be obtained simply by increasing carbon chain length. For instance, the substituents methyl ({{chem2|\sCH3}}) and pentyl ({{chem2|\sC5H11}}).