Neighboring group participation in solvolyses. 11. Kinetic isotope effect study of the solvolysis of neophyl arenesulfonates

Abstract

Bu), 29.81 ppm (z-Bu) (no other isomer detectable).Compound 5 was obtained by reaction of 10 mL of 1 M (10 mmol) B2H6 solution in THF with 0.63 g (3.8 mmol) of olefin at 0 °C for 3 h, addition of 20 mL of H20, 20 mL of 3 N NaOH, and 20 mL of H202 (30%), extraction with pentane (2 X 50 mL), and destination (57% yield).GLC showed the presence of two epimers (I and II) in 27 ± 4% and 73 ± 4% yields which were separated on a silica gel column (180 X 2.5 cm) with chloroform. Anal. (C12H240, I and II) C, H. NMR (CDC13) for I 0.94 (z-Bu); 3.83 ppm, 61/2 = 14 Hz (H,); for II 0.85 (Z-Bu); 3.98 ppm, é1/2 = 10 Hz (H"). 13C NMR (5-10% in CDC13 with 10% C6F6) C1-C10 for I 71.82,

Chlorine isotope effects in the solvolysis of substituted 1-phenylethyl chlorides

“…The phenyl-C, bond order then becomes 1 + (1 -F)(1 -nl), which simulates partial double bond character for F + 1 .O. Nucleophilic participation by .sr electrons in 1-phenylethyl halide solvolysis was first proposed by Bourns and Stothers (5) to explain an anomalously low carbon isotope effect, and the idea has re-emerged in more recent isotope effect calculations (34).…”

Kinetic isotope effect study of the borderline solvolysis of isopropyl .beta.-naphthalenesulfonate

“…Kinetic isotope effects were determined as described earlier. 19 All carbon-14 kinetic isotope effects were measured by ionization chamber counting. 19,20 For the #3-14C isotope effects in TFE and 97HFIP, both ionization chamber counting and liquid scintillation counting21 were used to assure the reliability of the results.…”

Model calculations of kinetic isotope effects for the solvolysis of neopentyl arenesulfonates

“…By this approach, the TS structures have been estimated for the solvolysis of tert-butyl chloride (SN1),8 elimination of (2-phenylethyl)trimethylammonium salt (E2),9 and for the solvolysis of neophyl brosylate (2, X = p-bromobenzenesulfonate, kA). 10 In the present investigation, the model calculations of the isotope effects in the acetolysis of 1 were carried out for two possible pathways, kA and kc. Likely TS structures were determined by matching the calculated isotope effects with the experimental values.…”

“…A stretching force constant for each reacting bond was calculated by the Pauling-Badger relation15 Fa = niFu (8) where «,• is the order of the bond i and Fh°i s the standard force constant16 for the single bond i. Angle bending force constants were determined by Fa = ga^ny'^Fa0 (9) where Fa°i s the standard angle bending force constant16 for the tetrahedral angle formed by the adjacent bonds i and j and ga is a geometrical or hybridization factor7 given by ga = 1.39 + 1.17 cos a (10) Diagonal force constants used for both reactant and TS models are summarized in Table I. Reaction-Coordinate Generation.…”