Rate constants for the reactions of amines and amino acids with substituted benzhydrylium ions have been determined photometrically [1]. The correlation equation log k_{20 °C} = s(N + E), where s and N are nucleophile specific parameters and E is an electrophile specific parameter has been used to determine the nucleophilicity parameters N of various amines and amino acids in aqueous solution and to compare them with N of other nucleophiles [2]. It is found that diethylamine and pyrrolidine have widely differing nucleophilicities despite of comparable Brønsted basicities. Moreover it is shown that α-effect amines [3] like semicarbazide, hydroxylamine or hydrazine do not show enhanced reactivity toward benzhydrylium ions in water. These reactivity parameters are suggested as guidelines for the nucleophilic reactivities of these important molecules in biological and organic chemistry.

[1] S. Minegishi, H. Mayr, J. Am. Chem. Soc. 2003, 125, 286-295.

[2] a) H. Mayr, T. Bug, M. F. Gotta, N. Hering, B. Irrgang, B. Janker, B. Kempf, R. Loos, A. R. Ofial, G. Remennikov, H. Schimmel, J. Am. Chem. Soc. 2001, 123, 9500-9512; b) H. Mayr, B. Kempf, A. R. Ofial, Acc. Chem. Res. 2003, 36, 66-77; c) H. Mayr, A. R. Ofial in Carbocation Chemistry (Eds.: G. A. Olah, G. K. S. Prakash), Wiley, Hoboken, NJ, 2004, Chapt. 13, pp 331-358; d) H. Mayr, A. R. Ofial, Pure Appl. Chem. 2005, 77, 1807-1821; e) For a comprehensive listing of nucleophilicity parameters N and electrophilicity parameters E, see:

http://www.cup.uni-muenchen.de/oc/mayr/DBintro.html.

[3] Reviews: a) N. J. Fina, J. O. Edwards, Int. J. Chem. Kinet. 1973, 5, 1-26; b) A. P. Grekov, V. Ya. Veselov, Russ. Chem. Rev. 1978, 47, 631-648; c) E. Buncel, I.-H. Um, Tetrahedron 2004, 60, 7801-7825.

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