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Nucleophilic addition reactions of benzylamines (BA) to benzylidenemalononitrile (BMN) have been studied in acetonitrile at 15.0 degrees C. The rate is first-order with respect to both BA and BMN and no base catalysis is observed. The rate decreases as the electron-withdrawing power of the substituent (Y) in the substrate increases (rho Y < 0). This is in contrast to the similar reactions of beta-nitrostyrenes (NS) with BAs in acetonitrile and the addition reactions of NS and BMN in aqueous solution (rho Y > 0). This sign change of rho Y is considered to result from the strong electron-withdrawing power of the (CN)2 group in BMN, which leads to polarization of C alpha delta+C delta- (CN)2 in the transition state. The mechanism of amine addition to BMN in acetonitrile is radically different from that in water. The reaction is predicted to proceed concertedly in a single step with a hydrogen-bonded, four-center cyclic transition state.

Kinetics and mechanism of the aminolysis of Z-thiophenyl acetates with X-benzylamines are investigated in acetonitrile at 45.0 o C. The magnitudes of Brönsted coefficients βX (=1.3~-1.6) and βZ (= -2.1~-2.4) are all large and cross-interaction constant ρXZ is relatively large and positive (0.90). These trends are consistent with the rate-limiting breakdown of a tetrahedral intermediate, T ± . The proposed mechanism is also supported by adherence of the rate data to the reactivity-selectivity principle (RSP). The kinetic isotope effects, kH/kD, are greater than unity (1.3-1.4) suggesting a possibility of hydrogen-bonded four-centered transition state. The activation parameters, ∆H ≠ and ∆S ≠ , are consistent with this transition-state structure.

Nucleophilic addition reactions of benzylamines (BA; XC6H4CH2NH2) to benzylidene-1,3-indandiones (BID; YC6H4CH=C(C=O)2C6H4) have been studied in acetonitrile at 25.0 degrees C. The rate is first-order with respect to BA and BID, and no base catalysis is observed. The structure-reactivity behaviors (k2, rhoX, betaX, and betaY) are intermediate between the two series of addition reactions of BA to beta-nitrostyrene (NS) and benzylidenemalononitrile (BMN) in acetonitrile. The normal kinetic isotope effects, kH/kD > 1.0, involving deuterated BAs (XC6H4CH2ND2) are smaller than those for the reactions of NS and BMN suggesting a somewhat looser bond formation in the transition state. The reaction is predicted to proceed in a single step with concurrent C(alpha)-N bond formation and proton transfer to C(beta). A hydrogen-bonded, four-center type cyclic transition state is proposed.

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