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The solvolysis rates of 5-(Y)-substituted indan-2-yl (Z)-benzenesulfonates were determined in a variety of protic solvents at 45.0, 55.0 and 65.0 °C. Application of an extended Grunwald–Winstein equation indicates that kinetic responses to both solvent ionizing power, YOTs and solvent nucleophilicity, NOTs, are relatively low but increase in parallel with increasing leaving ability, m= 0.39–0.46 and l= 0.32–0.41 for Z=p-Me ∼p-NO2. The magnitude of cross-interaction constant. ρYZ, is also relatively small (0.16–0.32), which is, however, much more dependent on the nucleophilicity rather than the ionizing power of the solvent. These are consistent with the typical SN2 mechanism proceeding through a transition state in which solvent participates in both bondmaking and -breaking processes.

Nucleophilic substitution reactions of 1-(Y-phenyl)ethyl chlorides with X-anilines have been investigated in methanol at 65.0 °C. An isokinetic point is obtained at σY+=ca.– 0.23 with ρx= 0; the sign of ρx changes at this point from positive for the relatively strong electron donating Y substituents to negative for the more electron withdrawing Y substituents.The magnitude of the cross-interaction constant, ρxy, between the substituents X and Y is unusually large with the relatively small magnitude of ρx° resulting in an observable isokinetic point at σY+=–ρx°//ρxy=–0.23. These results are interpreted in terms of a transition state (TS) structure in which nearly complete bond formation between the nucleophile and cation formed in an ion-pair preequilibrium is coupled with a TS imbalance phenomenon. The results of kinetic isotope effect studies involving deuteriated anilines and methanol are also in line with this mechanism.

The nucleophilic substitution reaction of cumyl arenesulfonate with aniline has been investigated. The reaction in acetonitrile proceeds by the SN2 mechanism with probable frontside nucleophilic attack. The large magnitude of ρxz(=–0.75) obtained results in an observable sign reversal of ρz at x= 0.83, with a negative ρz value for σx > x. This rather unusual phenomenon can be rationalized by a strong interaction between the nucleophile and leaving group due to their close proximity in the transition state, which in turn is a result of the frontside nucleophilic attack. The reactions in methanol indicate that the SN1 channel competes with the SN2 pathway and ion-pair return is observed when the aniline nucleophile concentration is low.

Kinetic studies of the reaction of Z-phenyl cyclopropanecarboxylates with X-benzylamines in acetonitrile at 55.0 °C have been carried out. The reaction proceeds by a stepwise mechanism in which the rate-determining step is the breakdown of the zwitterionic tetrahedral intermediate, T±, with a hydrogen-bonded four-center type transition state (TS). These mechanistic conclusions are drawn based on (i) the large magnitude of ρX and ρZ, (ii) the normal kinetic isotope effects (kH/kD > 1.0) involving deuterated benzylamine nucleophiles, (iii) the positive sign of ρXZ and the larger magnitude of ρXZ than that for normal SN2 processes, and lastly (iv) adherence to the reactivity–selectivity principle (RSP) in all cases.

Kinetic studies have been carried out on the solvolysis and aminolysis with anilines of anilino thioethers, N-methyl-N-[(Z-phenylthio)methyl]-Y-anilines, YC6H4N(CH3)CH2SC6H4Z, I, in methanol at 45.0°C. In contrast to the iminium cations with significant lifetimes produced in water, the solvolysis proceeds by a direct displacement (SN2) mechanism in methanol. In the aminolysis, both bond formation and cleavage are well under way in a late SN2 transition state with high ρX (βX) and ρZ (βZ) values. However, cross interactions between the nucleophile and leaving group are extensive with large negative constants (ρXZ=−1.7, βXZ=−0.27), which are suggestive of an SN2 reaction with frontside attack. The inverse secondary kinetic isotope effects involving deuterated anilines (kH/kD=0.84–0.88) along with low ΔH≠ (4.2–5.2 kcal mol−1) and ΔS≠ (−46–−59 e.u.) values are consistent with the proposed mechanism.

The aminolysis of Z-aryl cyclobutanecarboxylates (II) with X-benzylamines is investigated in acetonitrile at 55.0 °C. The rates are uniformly greater by 2.2 times than the corresponding rates of aryl cyclopropanecarboxylates (III). All the selectivity parameters, ρX (βX), ρZ (βZ) and ρXZ, are quite similar for the two substrates II and III. The kH/kD values involving deuterated benzylamines (XC6H4CH2ND2) are greater than unity, but are marginally smaller than those for the reactions of III. Low ΔH‡ and large negative ΔS‡ values are obtained and adherence to the reactivity–selectivity principle is observed. All these results are consistent with a stepwise mechanism with rate-limiting expulsion of a leaving group (aryl oxides) from a tetrahedral intermediate, T±, with a hydrogen-bonded, four-center transition state.

The aminolysis reactions of Z-aryl phenyldithioacetates (C6H5CH2C(S)SC6H4Z) with benzylamines (XC6H4CH2NH2) are investigated in acetonitrile at −25.0 °C. The reactions are predicted to proceed by a stepwise mechanism with rate-limiting expulsion of the thiophenolate anion from the zwitterionic tetrahedral intermediate, T±, based on (i) large magnitudes of selectivity parameters, βX (ρX) and βZ (ρZ), (ii) positive and large cross-interaction constants ρXZ (=2.05), and (iii) adherence to the reactivity–selectivity principle. The significant normal kinetic isotope effects (kH/kD = 1.14–1.81) involving deuterated amines and low activation enthalpies (ΔH‡ ≈ 3 kcal mol−1) together with large negative activation entropies (ΔS‡ = −37 to −53 e.u.) are consistent with concurrent proton transfer of amine hydrogen with the leaving group departure in the transition state.

Effet des substituants des groupes phenyles: des anilines et des benzenesulfonates de phenyl-1 ethyle