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The Cahn–Ingold–Prelog priority rules, CIP system or CIP conventions (after the scientists;Robert Sidney Cahn, Christopher Kelk Ingold and Vladimir Prelog) are a set of rules used in organic chemistry to name the stereoisomers of a molecule.〔J. March. ''Advanced Organic Chemistry'' 3Ed. ISBN 0-471-85472-7〕〔IUPAC Rules for the Nomenclature of Organic Chemistry. Section E, Stereochemistry (Recommendations 1974). ()〕 A molecule may contain any number of stereocenters and any number of double bonds, and each gives rise to two possible configurations. The purpose of the CIP system is to assign an R or S descriptor to each stereocenter and an E or Z descriptor to each double bond so that the configuration of the entire molecule can be specified uniquely by including the descriptors in its systematic name. The key article by the three authors setting out the CIP rules was published in 1966.〔The following two papers define the CIP system. The papers provide a number of additional rules beyond the main points covered above, such as describing less common forms of stereoisomerism (such as chiral axes and planes), and resolving more difficult priority assignments. For example, note that the above rules fail to generate stereo descriptors for compounds such as (1''s'',2''s'',3''s'')-1,2,3-trichlorocyclopropane (in which all three chlorine atoms are on the same side of the ring).〕 The Cahn–Ingold–Prelog rules are distinctly different from those of other naming conventions, such as general IUPAC nomenclature, since they are designed for the specific task of naming stereoisomers rather than the general classification and description of compounds. ==Steps for naming== The steps for naming molecules using the CIP system are often presented as: # Identification of stereocenters and double bonds # Assignment of priorities to the groups attached to each stereocenter or double-bonded atom # Assignment of R/S and E/Z descriptors 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cahn–Ingold–Prelog priority rules」の詳細全文を読む スポンサード リンク
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