Order factors in organic synthesis. Pattern recognition as a method of factor analysis.
In linear-free-energy relations and free-energy relations, substituents are characterized by so-called electronic parameters. Thus, s1-parameters of substituents, for example, show direct correlations to Tolman's c1-parameters or P-parameters. But by systematic variations at tetrahedral phosphorus, a further set of D-parameters is found by which representative substituents like OMe/SMe and CMe3/SiMe3 with nearly identical c1- or P-parameters may be further characterized. The opposite influence of substituents on chem. behavior is detd. by the +/- sign of D-parameters. By the signs of P- and D-parameters with triphenylphosphine as std., alternative order factors like DO/ACC, EVEN/ODD and S/AS may be identified. Compensation phenomena by self-organization alone make LFER applicable. The importance of pattern recognition and consideration of abs. and relative control make general order control in chem. systems understandable.
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