Ingold nomenclature

In the former (Ingold) nomenclature this was called the SRN1 mechanism (see IUPAC, 1989a). This scission may consist of two steps, forming first an aryldiazenyl radical and the phenylthiolate radical (see Sec. 8.6). 

By heterolytic dissociation into carbocations and dinitrogen followed by the addition of a nucleophile (called Dn + An mechanism in the new IUPAC nomenclature103, Sjyl in the former Ingold nomenclature). 

The prefix (RS) is used to denote a racemic modification. For example, (RS)-Sec butyl chloride. The symbols R and S are applied to compounds whose absolute stereochemistry has been determined. However, while applying the nomenclature to projection formulae of compounds containing several asymmetric centres Cahn, Ingold. Pielog procedures are supplemented by the following conversion rule. 

FIGURE 1.1 Chemical and stereochemical nature of amino acids. Substituents in (a) and (b) are on opposite sides of the plane N-Ca-C, the bold bond being above the plane. Interchange of any two substituents in (a) changes the configuration. For the Cahn-Ingold-Prelog system of nomenclature, the order of preference NH2 > COOH > R2 relative to H is anticlockwise in (a) = (S) and clockwise in (c) = (R). 

See Shoppee, "Christopher Kelk Ingold," 351 and Seddon, "The Development of Electronic Theory," 32. Ingold s note (603620) was added to R. M. Beesley and J. F. Thorpe, "The Formation and Stability of Associated Alicyclic Systems. Pt. I. A System of Nomenclature, and Some Derivatives of Methane-II-Cyclopropane and of Methane-III-Cyclopropane," JCS 117 (1920) 591620 also see C. K. Ingold, R. M. 

The discussion and classification of reagents is masterful in identifying Ingold s new nomenclature and principles with more widely known oxidation-reduction and acid-base theory. The 1953 lectures at Cornell University, published as Structure and Mechanism in Organic Chemistry, follow this same strategy, showing how old classification schemes overlap with each other and how apparent inconsistencies disappear as old schemes are incorporated into the new one. Nineteenth-century Berzelian electrochemical dualism, revived by Lapworth and Robinson in the cationic/anionic schema, disappears into the electrophilic/nucleophilic language. 

But using Ingold s nucleophilic-electrophilic nomenclature, all "basic" reagents, organic or inorganic, are nucleophilic and "basicity" ("affinity" for... 

With respect to the nomenclature and classification system that Ingold set up, it is interesting to note the incorporation not only of traditional anthropomorphic metaphors of love and war (italicized), but also (without making too much of it) ones suggesting the modem capitalist marketplace (bold-face) ... 

Scheme 2.1 Kinetic resolution of glycidyl butyrate catalyzed by porcine pancreatic lipase, PPL The preferential conversion of (S)-glycidyl butyrate into (R)-glycidol and butyric acid results from the stereochemical nomenclature rules under the Cahn, Ingold, Prelog convention, the configuration around the chiral centre is not affected.

In response to this nomenclature dilemma, the Cahn-Ingold-Prelog (IUPAC, International Union of Pure and Applied Chemistry) system of nomenclature was developed and is now the standard mediod to specify the relative configuration of chiral centers in molecules. Each chiral center will have two possible mirror-image configurations, which are designated as eidter R or S. 

In both of the pre-rate-determining equilibria, (7) and (8), the position of equilibrium must lie well to the left. Ingold and co-workers3 wrote this anion-catalysed reaction as SEl-2Br", and, since there appears to be no simple method of experimentation to allow a choice between the two possible mechanisms, this nomenclature can conveniently be allowed to cover both. 

Notice that in the previous examples, the atom of the higher atomic weight is given the higher priority (Br = 79.1 versus Cl = 15.5, and I = 126.0 versus N = 14.0). These assignments are based on the priority rules of Cahn-Ingold-Prelog nomenclature. 

The d, l nomenclature is chosen in this chapter in order to unmistakably distinguish homochiral stereoisomers. According to the specifications of the Cahn-Ingold-Prelog nomenclature L-l would equal (S)-l, while L-2 equals (J )-2. 

Deprotonation of a-alkylated acetic acid esters (e.g., the propionic acid ester of Figure 10.13) with LDA at —78°C selectively yields the -enolatcs.Thc quotation marks indicate that this application of the term is based on an extension of the E/Z-nomenclature here, the Cahn-Ingold-Prelog priority of the O I, i1 substituent is considered to be higher than the priority of the OR group. The deprotonation of the ester shown in Figure 10.13 occurs via the strain-free transition state A. The alternative transition state B is destabilized by a 1,3-diaxial interaction. 

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