{"term":{"id":"04859","title":"prochirality","longtitle":"IUPAC Gold Book - prochirality","doi":"10.1351\/goldbook.P04859","code":"P04859","status":"current","also defines":"<em>also defines<\/em>: proprochirality","definitions":[{"id":1,"text":"This term is used in different, sometimes contradictory ways; four are listed below.The geometric property of an achiral object (or spatial arrangement of points or atoms) which is capable of becoming chiral in a single desymmetrization step. An achiral molecular entity, or a part of it considered on its own, is thus called prochiral if it can be made chiral by the replacement of an existing atom (or achiral group) by a different one. An achiral object which is capable of becoming chiral in two desymmetrization steps is sometimes described as proprochiral. For example the proprochiral $\\ce{CH3CO2H}$ becomes prochiral as $\\ce{CH2DCO2H}$ and chiral as $\\ce{CHDTCO2H}$.The term prochirality also applies to an achiral molecule or entity which contains a trigonal system and which can be made chiral by the addition to the trigonal system of a new atom or achiral group. For example addition of hydrogen to one of the enantiotopic faces of the prochiral ketone $\\ce{CH3CH2COCH3}$ gives one of the enantiomers of the chiral alcohol $\\ce{CH3CH2CHOHCH3}$; the addition of $\\ce{CN^{−}}$ to one of the diastereotopic faces of the chiral aldehyde shown below converts it into one of the diastereoisomers of the cyanohydrin. The two faces of the trigonal system may be described as Re and Si. The term prochiral also applies to a tetrahedral atom of an achiral or chiral molecule which is bonded to two stereoheterotopic groups. For example, the prochiral molecule $\\ce{CH3CH2OH}$ can be converted into the chiral molecule $\\ce{CH3CHDOH}$ by the isotopic replacement of one of the two enantiotopic hydrogen atoms of the methylene group. The carbon atom of the methylene group is called prochiral. The prochiral molecule $\\ce{HO2CCH2CHOHCH2CO2H}$ can be converted into a chiral product by esterification of one of the two enantiotopic $\\ce{–CH2CO2H}$ groups. The carbon atom of the $\\ce{CHOH}$ group is called prochiral. The chiral molecule $\\ce{CH3CHOHCH2CH3}$ can be converted into one of the diastereoisomers of $\\ce{CH3CHOHCHDCH3}$ by the isotopic replacement of one of the two diastereotopic hydrogen atoms of the methylene group. The carbon atom of the methylene group is called prochiral. The stereoheterotopic groups in these cases may be described as pro-R or pro-S. Reference to the two stereoheterotopic groups themselves as prochiral, although common, is strongly discouraged.See: chirality centreThe term prochirality is also applied to the enantiotopic faces of a trigonal system.","links":[{"term":"achiral","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/A00069"},{"term":"chiral","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/C01057"},{"term":"chirality centre","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/C01060"},{"term":"desymmetrization","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/D01623"},{"term":"diastereoisomers","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/D01679"},{"term":"diastereotopic","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/D01685"},{"term":"enantiotopic","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/E02083"},{"term":"methylene","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/M03881"},{"term":"stereoheterotopic","url":"https:\/\/goldbook.iupac.org\/\/terms\/view\/S05981"}],"sources":["PAC, 1996, 68, 2193. 'Basic terminology of stereochemistry (IUPAC Recommendations 1996)' on page 2213 (https:\/\/doi.org\/10.1351\/pac199668122193)"]}],"altoutputs":{"html":"https:\/\/goldbook.iupac.org\/terms\/view\/P04859\/html","xml":"https:\/\/goldbook.iupac.org\/terms\/view\/P04859\/xml","plain":"https:\/\/goldbook.iupac.org\/terms\/view\/P04859\/plain"},"citation":"Citation: 'prochirality' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. 10.1351\/goldbook.P04859","license":"The IUPAC Gold Book is licensed under Creative Commons Attribution-ShareAlike CC BY-SA 4.0 International (https:\/\/creativecommons.org\/licenses\/by-sa\/4.0\/) for individual terms.","collection":"If you are interested in licensing the Gold Book for commercial use, please contact the IUPAC Executive Director at executivedirector@iupac.org .","disclaimer":"The International Union of Pure and Applied Chemistry (IUPAC) is continuously reviewing and, where needed, updating terms in the Compendium of Chemical Terminology (the IUPAC Gold Book). Users of these terms are encouraged to include the version of a term with its use and to check regularly for updates to term definitions that you are using.","accessed":"2026-08-04T23:00:12+00:00"}}