- Kinetic study of the reactions of various types of C-acids with amine bases in acetonitrile. An unusual effect of common BH+ cation on the rate constants
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The rates of proton transfer reactions between C-acids of different types such as 1-(4-nitrophenyl)-1-nitroalkanes, 4-nitrophenylcyanomethanes, and 2,4,6-trinitrotoluene, and organic bases such as 1,1,3,3-tetrametylguanidine, 7-methyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (MTBD), and tri-n-butylamine have been measured in acetonitrile at pseudo-first-order conditions. A general equation for the rates of proton transfer reactions between C-acids and bases with product existing in two forms, ions and ion pairs, has been derived and its applicability tested. The equation works well except for reactions of 1-(4-nitrophenyl)-1-nitroalkanes with guanidines for which the second-order rate constant is diminished with concentration of guanidinium cation, while tetrabutylammonium salts accelerate the reactions. Possible reasons for this are discussed.
- Galezowski, Wlodzimierz,Grzeskowiak, Iwona,Jarczewski, Arnold
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p. 1042 - 1049
(2007/10/03)
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- Comparison of the Intrinsic Reactivities of Carbon and Oxygen Nucleophiles at the 1,3,5-Trinitro-substituted Aromatic Ring
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Kinetic and equilibrium data are reported for nucleophilic attack by nitroalkane anions at unsubstituted ring positions of 1,3,5-trinitrobenzene and of 2,4,6-trinitrotoluene.The results allow the calculation for this reaction type of values for intrinsic rate coefficients, k0' of 0.18 for CH2NO2(1-) and 0.22 for MeCHNO2(1-).The corresponding value for the malononitrile anion, CH(CN)2(1-), is 2.5E4, and for the methoxide ion the value is 1E3.The results are discussed in terms of the electronic-structural and solvational reorganisation occuring during reaction.
- Cox, Jonathan P. L.,Crampton, Michael R.,Wight, Paul
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- A Spectrophotometric Study of 4-Nitro-, 2,4-Dinitro- and 2,4,6-Trinitrobenzyl Carbanions. Decarboxylation of (Nitrophenyl)acetate Anions
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A spectrophotometric study of the reactions of the potassium salts of (2,4,6-trinitrophenyl)acetic acid (3), (2,4-dinitrophenyl)acetic acid (4), and (4-nitrophenyl)acetic acid (5) in Me2SO, THF, and DME is reported, including the effect of catalysis by crown ether 1.These processes are believed to give rise to the corresponding carbanions resulting from decarboxylation.The UV-visible spectrum of the species obtained from reaction of 3 agrees well with literature data for the expected carbanion 6, but there is some discrepancy regarding the species derived from 4 and 5.From the decay of the absorption spectra with time, the stabilities of the benzyl carbanions in these systems correspond to 2,4,6-trinitrobenzyl > 2,4-dinitrobenzyl > 4-nitrobenzyl.
- Buncel, E.,Venkatachalam, T. K.,Menon, B. C.
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p. 413 - 417
(2007/10/02)
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- Kinetic studies of the reactions of 2,4,6-trinitrotoluene and 2,4,6-trinitrotoluene-d3 with ion-paired KOBut and free tert-butoxide ion in tert-butanol
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The reactions of 2,4,6-trinitrotoluene (TNT) and TNT-d3 (deuterated methyl group) with tetra-n-butylammonium tert-butoxide and with potassium tert-butoxide (KOBut), in the absence and presence of the crown ethers 18-crown-6, and dicyclohexyl-18-crown-6, have been studied kinetically in tert-butanol at 30.0 deg C.Evidence is presented to support the suggestion that, at ratios of crown ether to base > 1, the reactive base species is free tert-butoxide ion and that this rapidly reacts with TNT or TNT-d3 to form, in each case, a mixture of ?-complex and purple anion.Specific rate constants for the reactions of free tert-butoxide ion and ion-paired KOBut with TNT and TNT-d3 to form both ?-complex and purple anion are compared.
- Norris, Albert R.
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p. 2178 - 2182
(2007/10/02)
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