- Nitrogen Protonation of N-Nitrosodimethylamine
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Evidence for the presence of the Me2N(H)NO+ ion at kinetically significant concentrations in aqueous solutions of N-nitrosodimethylamine (NDMA) at pH =/ E equilibration in the resulting NDMA-d3 was measured by nuclear magnetic resonance spectroscopy as a function of pD.The reaction was first order in +>, with the plot of observed first-order rate constants versus +> having a slope of k/+> =1E-2 M-1 s-1 at 3 deg C and an ionic strength of 0.2 M.The observed rate date were used to estimate Ka for N-protonated NDMA as 1E12-1E13 M by assuming that the rates of rotation about the N-N bond in Me2N(H)NO+ and of its deprotonation are similar to those for the isoelectronic N-protonated carboxamide function.The trisubstituted nitrogen of the nitrosamine thus appears to be several orders of magnitude less basic than that of the carboxamides.
- Keefer, Larry K.,Hrabie, Joseph A.,Hilton, Bruce D.,Wilbur, David
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- Preparation of a Thallium(I) Diazotate. Structure, Physicochemical Characterization, and Conversion to Novel N-Nitroso Compounds
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Thallium(I) (E)-methanediazotate (4) has been prepared and characterized.In contrast to previously reported methanediazotates, 4 is a highly crystalline material whose physical properties suggest a considerable degree of covalency: it is readily soluble in certain nonpolar solvents; it melts reversibly at a low temperature; it is monomeric and nonconducting in chloroform solution; and ions corresponding to the formula Tl(CH3N2O).+ are found in the electron impact mass spectrum.The crystal structure of 4 revealed Tl-O distances as short as 2.52(3) Angstroem and confirmed the anti stereochemistry; the monoclinic unit cell, space group P21/c-C52h (No. 14), had a=13.233(6) Angstroem, b=11.594(4) Angstroem, c=6.253(2) Angstroem, β=119.45(3)o, V=871.5(6) Angstroem3, and Z=8.The compound's advantageous stability and solubility properties provide important new opportunities for probing the solution chemistry of the alkanediazotates.As an illustration of this potential, 4 has been converted in homogeneous media to unusual N-nitroso compounds including a quaternary ammonium salt of a primary nitrosamine, an isotopic variant of dimethylnitrosamine in which the methyl group syn to the oxygen is fully deuteriated, and the less stable Z conformer of methylbenzylnitrosamine.In contrast to 4 , its Z stereoisomer has until now defied isolation but has been identified in situ by reaction with iodomethane-d3 to produce (E)-methyl(methyl-d3)nitrosamine.
- Keefer, Larry K.,Wang, Shui-mei,Anjo, Takako,Fanning, James C.,Day, Cynthia S.
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p. 2800 - 2806
(2007/10/02)
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