- SUPPRESSION OF THE CONVERSION OF 3-t-BUTYL-1-METHYL-1-NITROSOTHIOUREA TO 3-t-BUTYL-1-METHYLUREA BY β-CYCLODEXTRIN UNDER ACIDIC CONDITIONS
-
The denitrosation of 3-t-butyl-1-methyl-1-nitrosothiourea (1) was retarded by β-, and γ-cyclodextrins (CDs) at pH 4.70.Decomposition of 1 in the presence of β-CD produced selectively 3-t-butyl-1-methylthiourea (1a), which was remarkably different from the product ratio in the absence of β-CD.These results may be caused by both the protective and the microsolvent effect of β-CD.
- Isobe, Masayoshi
-
-
- Electronic and Steric Effects of Alkyl Group on Denitrosation of 3-Alkyl-1-methyl-1-nitrosothioureas
-
A series of 3-alkyl-1-methyl-1-nitrosothioureas with R=CH3, C2H5, cyclo-C6H11 (3), (CH3)2CH (4), C2H5(CH3)CH, and (CH3)3C were synthesized and their rates of acid catalyzes (pHH:kD is 1.25 for 4.Except 3, a linear plot of log kR/kMe for the denitrosation of RNHCSN(NO)CH3 vs. ?* provides ρ*=-0.98(r=-0.997).The significant factor affecting the rate determining step of the denitrosation of these N-nitrosothioureas at pH 4.6 is the electronic effect of the substituent at the N3 position.
- Isobe, Masayoshi
-
p. 2844 - 2848
(2007/10/02)
-
- Conformational Preferences in Alkylnitrosoureas
-
The spectroscopic properties of several N-alkyl-N-nitrosoureas, N,N'-dialkyl-N-nitrosoureas, and N,N',N'-trialkyl-N-nitrosoureas have been studied in carbon disulfide and chloroform solutions.The NH stretching frequencies in the IR spectra have been observed in both concentrated and dilute solution and in the presence of added dioxane.The results indicate that there is a strong intramolecular hydrogen bond in the mono- and dialkylnitrosoureas.The chemical shifts and line widths of the NMR spectra have also been studied in these solvents.The large chemical shift differences, about 1.3 ppm, for the NH protons in the monoalkylnitrosoureas and other spectroscopic features in the monoalkyl- and dialkylnitrosoureas also indicate that an intramolecular hydrogen bond contributes to a strong conformational preference.The temperature dependence of the NMR spectra of several N,N',N'-trialkyl-N-nitrosoureas establishes that the energy barrier for rotation about the carbon dialkylamide bond is about 13 kcal mol-1.Dipolar resonance interactions are primarily responsible for this barrier.This interaction is augmented by a strong, 8-10 kcal mol-1, hydrogen bond in the mono- and dialkylnitrosoureas.
- Snyder, John K.,Stock, Leon M.
-
p. 886 - 891
(2007/10/02)
-