Anion···π-system interactions in crystals of 4-amino-1-(β-phenylethyl)-1,2,4-triazolium bromide

The character of intermolecular interactions of the bromide anion and organic cation in crystal of 4-amino-1-(β-phenylethyl)-1,2,4-triazolium bromide was studied by a combination of X-ray diffraction data and M06-2X/cc-pvtz quantum chemical calculations. The existence of binding anion...π-system interactions was shown, and their characteristics were studied.     

Crystal,molecular structure and tautomerism of (5-methyl-1H-[1,2,4]triazol-3-ylsulfanyl)-acetic acid

Molecular structure, relative stability of conformers, and tautomers of (5-methyl-1H-[1,2,4]triazol-3-ylsulfanyl)-acetic acid (MTSA) have been investigated by experimental (X-ray diffraction) and theoretical (B3LYP/aug-cc-pVDZ) methods. It was demonstrated that in the solid state MTSA exists in N1H tautomeric form. This tautomer is not the most stable in gas phase and its stabilization is provided by environment effects.     

Principal aspects of the electrodynamic theory of stripline beam-forming lenses

Key electrodynamic problems are solved for calculation of the scattering matrices of stripline lenses with forced refraction for parametric synthesis of a wide range of lenses. The advantages of the method are demonstrated by the example of a Rotman lens.Rostov State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 4, pp. 422–434, April, 1994.     

Reactions of α-aminoazoles with (2<Emphasis Type="Italic">E</Emphasis>)-3-phenylacryloyl chloride

Reaction of 5-amino-3-methylpyrazole, 3-amino-, 5-amino-3-methylsulfanyl-1,2,4-triazole and 5-amino-1,2,4-triazole-3-thione with 3-phenylacryloyl-chloride under mild conditions is characterized by low selectivity and does not lead to the formation of fused heterocyclic systems but gives mixtures of products of mono- and diacylation of the nucleophilic sites in the molecules of α-aminoazoles. Endocyclic monoacyl derivatives of aminotriazoles in DMF undergo a transacylation at the exo-amino-group followed by cyclization into dihydro-1,2,4-triazolo[1,5-a]-pyrimidin-5-ones.     

Halogenation of N-substituted <Emphasis Type="Italic">p</Emphasis>-quinone monoimines and <Emphasis Type="Italic">p</Emphasis>-quinone monooxime esters: VII. Halogenation of 4-aroyl(arylsulfonyl)imino- and 4-aroyl(arylsulfonyl)-oxyimino-2,6-diisopropylcyclohexa-2,5-dien-1-ones

Halogenation of 4-aroyl(arylsulfonyl)imino-2,6-diisopropylcyclohexa-2,5-dien-1-ones gave 4-aroyl-(arylsulfonyl)imino-3-halo-2,6-diisopropylcyclohexa-2,5-dien-1-ones and 4-aroyl(arylsulfonyl)imino-3,5,6-trihalo-2,6-diisopropylcyclohex-2-en-1-ones. The latter were formed as mixtures of two stereoisomers, and the isopropyl group on the sp ³-hybridized carbon atom in one stereoisomer occupies axial position, which is untypical of such compounds. Halogenation of 4-aroyl(arylsulfonyl)oxyimino-2,6-diisopropylcyclohexa-2,5-dien-1-ones leads to the formation of the corresponding addition products with traditional trans-diaxial arrangement of the halogen atoms.     

Conjugation and hyperconjugation in conformational analysis of cyclohexene derivatives containing an exocyclic double bond

The equilibrium geometry, ring-inversion pathway barriers for analogues of cyclohexene with an exocyclic double bond have been studied using the MP2/6-311 G(d,p) level of theory. The equilibrium conformation of the ring depends on conjugation between the endocyclic and exocyclic double bonds. Interactions between conjugated double bonds include the pi-pi conjugation and interactions between the lone pair of the heteroatom of the exocyclic double bond and the sigma-antibonding orbital of the endocyclic single bond. In the case of the tetrahydrocycles with double bonds separated by a methylene group the balance between the pi --> sigma* hyperconjugation interactions between the exocyclic double bond and the neighboring methylene group and the n --> sigma* interaction between the lone pair of the heteroatom and the sigma-antibonding orbitals of the C(sp(2))-C(sp(3)) bond determine the geometrical parameters of the ring. The character of the potential-energy surface around the saddle point depends on the position of the exocyclic double bond and the orientation of the hydrogen atom attached to the heteroatom of the V group of the periodic table in the tetrahydrocycles with double bonds separated by a methylene group.