Pyrazolyltetrazoles—a High-Enthalpy Backbone for Designing High-Energy Compounds: An Experimental Study of the Enthalpy of Formation

The standard enthalpies of combustion and formation of isomeric nitropyrazolyltetrazoles have been measured by combustion calorimetry. Positional isomerism has been shown to have a significant effect on thermochemical characteristics. The contributions of some explosophore groups and moieties to the total heat content of the molecules have been determined. These contributions can be used to correctly calculate the enthalpy of formation of both known and hypothetical energy-intensive compounds.     

Synthesis of 3,4,5-trinitropyrazole

A first representative of exhaustively C-nitrated pyrazoles was obtained by oxidation of 5-amino-3,4-dinitropyrazole.     

Synthesis of compounds with two or more pyrazole rings linked to each other (Review)

Data on the synthesis of compounds containing two or more directly linked pyrazoline rings are summarized.In certain cases the synthesis of pyrazolones, pyrazolines, etc., trom which the pyrazoles can be obtained by known simple methods, is described.N. D. Zelinskii Institute of Organic Chemistry. Russian Academy of Sciences, Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 579-604, May, 1995. Original article submitted November 18, 1994.     

Nitropyrazoles

A preparative method of synthesis of 3-nitro-4-cyanopyrazole (1) from the available 3-amino-4-cyanopyrazole was developed. Chemical conversions of1 were studied, and 3-nitro-4-R-pyrazoles (R = CO₂H, CONH₂, NHCO₂Me, NH₂, Br, NO₂), as well as 3,5-dinitro-4-methoxycarbonylaminopyrazole were obtained starting from1.For part 4 see ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1616–1618, September, 1993.     

Nitropyrazoles

A method for the synthesis of 1-methyl-3,5-dinitropyrazole-4-carbonitrile from 1,4-dimethyl-3,5-dinitropyrazole was developed. Nucleophilic substitution in 1,4-dimethyl-3,5-dinitropyrazole, 1-methyl-3,5-dinitropyrazole-4-carboxamide, and 1-methyl-3,5-dinitropyrazole-4-carbonitrile involves solely the 5-NO₂-group in the ring. 1-Methyl-3,5-dinitropyrazole-4-carbonitrile reacts with thioglycolic acid phenylamide and potassium carbonate to give 4-amino-1-methyl-3-nitro-N-phenyl-1H-thieno[2,3-c]pyrazole-5-carboxamide. The use of glycolic acid phenylamide instead of thioglycolic acid N-phenylamide under analogous conditions resulted in 5-anilino-1-methyl-3-nitro-1H-pyrazole-4-carbonitrile. An explanation for the regiospecificity of the nucleophilic substitution of the 5-NO₂ group in 4-R-1-methyl-3,5-dinitropyrazoles is given. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2004–2014, October, 2007.     

Simulation of the Motion of Groundwater for a Rectangular Bridge with a Screen

Doklady Physics - Within the framework of the steady-state flat filtering of an incompressible fluid according to Darcy’s law, we obtain an accurate analytical solution to the problem of a...     

Bispidine Platform as a Tool for Studying Amide Configuration Stability

In this work, the solution conformations of seventeen 3,7-diacyl bispidines were studied by means of NMR spectroscopy including VT NMR experiments. The acyl groups included alkyl, alkenyl, aryl, hetaryl, and ferrocene moieties. The presence of syn/anti-isomers and their ratios were estimated, and some reasons explaining experimental facts were formulated. In particular, all aliphatic and heterocyclic units in the acylic R(CO) fragments led to an increased content of the syn-form in DMSO-d₆ solutions. In contrast, only the anti-form was detected in DMSO-d₆ and CDCl₃ in the case when R = Ph, ferrocenyl, (R)-myrtenyl. In the case of a chiral compound derived from the natural terpene myrtene, a new dynamic process was found in addition to the expected inversion around the amide N-C(O) bond. Here, rotation around the CO-C=C bond in the acylic R fragment was detected, and its energy was estimated. For this compound, ΔG for amide N-C(O) inversion was found to be equal to 15.0 ± 0.2 kcal/mol, and for the rotation around the N(CO)–C^2′ bond, it was equal to 15.6 ± 0.3 kcal/mol. NMR analysis of the chiral bispidine-based bis-amide was conducted for the first time. Two X-ray structures are reported. For the first time, the unique syn-form was found in the crystal of an acyclic bispidine-based bis-amide. Quantum chemical calculations revealed the unexpected mechanism for amide bond inversion. It was found that the reaction does not proceed as direct N-C(O) bond inversion in the double-chair (CC) conformation but rather requires the conformational transformation into the chair–boat (CB) form first. The amide bond inversion in the latter requires less energy than in the CC form.