Schleyer equation

In Chapter 18, Bentley reviews development of scales of solvent nucleophilicity and applies the Bentley-Schleyer equation to determine N and Y values for sulfuric acid. Also, Bentley examines here the validity of the Taft... 

Froelicher and coworkers215 and Schleyer and coworkers216 calculated the proton affinity of several carbanions (Table 25). Especially, the HF/4-31+G results are in good agreement with experimental values. Calculated proton affinities are compared to that of CH3" with the help of the isodesmic reaction given in equation 20. 

For lack of a better system, the ratio of rate in an ethanol-water mixture of the same Y value as acetic acid to rate in the much less nucleophilic acetic acid, ( Etoii/ acoh) yj has served as a measure of sensitivity to solvent nucleophilicity. More recently, the problem has received renewed attention, and two groups have proposed possible approaches.114 Of the two proposals, that of Bentley, Schadt, and Schleyer is easier to apply. Their scheme defines the solvent nucleophilicity, N, by Equation 5.21, where k is the solvolysis rate constant of methyl tosylate in... 

Although the reactions shown in Equations 6.3 and 6.4, and in some equations and schemes found later in this chapter depict a primary carbocation as an intermediate, it is not certain whether these highly unstable species exist in solution. Both reactions may involve migration concerted with departure of the leaving group. See (a) P. Ausloos, R. E. Rebbert, L. W. Sieck, and T. O. Tiernan, J. Amer. Chem. Soc., 94, 8939 (1972) and references therein (b) P. C. Hariharan, L. Radom, J. A. Pople, and P. v. R. Schleyer, J. Amer. Chem. Soc., 96, 599 (1974). 

More recently, Auner s and Schleyer s groups in a joint effort reported the experimental observation of an alkyl-substituted 6-sila-2-norbomyl cation110. The 6,6-Dimethyl-5-neopentyl-6-sila-2-norbomyl cation 41 was prepared by a hydride transfer reaction via the jr-route 111 from a suitable cyclopentenyl silane derivative at room temperature (equation 10). The toluene solution of the tetrakis(pentafluorotetraborate) salt of 41... 

Schleyer and coworkers investigated the nature of the 9-barbaralyl cation by solvolysis studies of the corresponding tosylate. The acetolysis of 9-deuterio-9-barbaralyl tosylate gave 9-barbaralyl acetate with complete deuterium scrambling, whereas solvolysis in more nucleophilic aqueous acetone gave the product alcohols with the label exchanged to only positions C3, C7 and C9 (equation 50). Solvolysis of 4-deuteriobicyclo[3.2.2]nona-2,6,8-trien-4-yl 3,5-dinitrobenzoate also resulted in the formation of the 9-barbaralols with deuterium scrambled to positions 1, 2, 8, 4, 5 and 6, with only trace amounts at C3 and (equation 51). 

Coalson RD, Beck TL. Poisson-Boltzmann type equations numerical methods. In Schleyer PvR, ed. Encyclopedia of Computational Chemistry. Vol. 3. New York Wiley, 1998 2086-2100. 

The initial objective of our work was to quantify solvent effects (particularly solvent nucleophilicity) by adapting the Grunwald-Winstein equation (2) (5). In equation 2, k is the rate of solvolysis of a substrate (RX) in any solvent relative to 80% v/v ethanol-water (k0) and Y is the solvent ionizing power defined by m = 1.000 for solvolyses of tert-butyl chloride at 25 °C. In this chapter, a discussion of equation 2 and similar free-energy relationships is presented. At the time our work began (1969), in collaboration with Schleyer, mechanisms of solvolytic reactions were close to a high in controversy (6-8). More recent mechanistic developments (9-13) are not reviewed in detail here, but increased recognition of the importance of nucleophilic solvent assistance should be noted. 

From the deviations, a scale of nucleophilicity was derived. Halogenated acetic acids were included, on the basis of reactivities with halonium ions. Other scales appeared from the Schleyer group (5, 6) at about the same time. The various nucleophilicity scales were used to correlate solvolysis rates by now familiar four-parameter equations AG = N + mY or AG = sN + mY. (G — free energy N = solvent nucleophilicity Y = solvent ionizing power s = sensitivity m = sensitivity.) Previously, parameters for such equations had not been determined. 

Values of nAN or nBN for all solvents were obtained from equations 3 or 4, because the y value was available from equation 5, when the nucleophilicity ratio, R, for the reference solvents acetic and formic acid was chosen to be 1. The nN values for solvolysis solvents were compared with the Schadt-Bentley-Schleyer proposed set of nucleophilicity values. The lin-... 

Indeed, Schleyer admits that the application of the above equation to sterically crowded system is dangerous , but this limitation is not extended to 2-exo-norbornyl sulphonates. 

A novel approach to highly symmetrical pentagonal dodecahedrane which involved gas phase isomerization of [l.l.l.l]pagodane over 0.1% Pt/Al203 under an atmosphere of H2 at 360 °C was provided by Prinzbach, Schleyer, Roth and coworkers . Dodecahedrane was obtained in 8% yield (equation 27). The isomerization probably involves carbocationic intermediates. 

Allerhand and Schleyer formd that a proportionality exists between the stretching frequencies of vibrators of the type X=0 (with X = C, N, P or S) and the corresponding stretching If equencies in situations involving hydrogen bonds of the X-H- B type in a variety of solvents. They thought these results to be indicative that the solvents studied interacted in a non-specific manner with both types of vibrator, in contradiction with the specific interaction-only approach advocated by Bellamy et al. They used this information to construct a solvent polarity scale that they called the G scale . Allerhand and Schleyer used an empirical linear fi ee-energy equation to define G ... 

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