Form of the dihedral angle dependence of the spin-spin coupling constant JHNNH

Cyclic hydrazides (derivatives of phtalhydrazide,pyrozolidone-3, indazolone, cyclic hydrazide camphoric acid) are studied by the NMR¹H method. The size of the dihedral HNNH angle of several model compounds (pyrozolidone-3, cyclic hydrazide norcamphoric acid) are calculated by the MINDO/3 SSF MO LCAO method. It is shown that in the hydrazides with HNNH dihedral angle 0–70° the magnitude of the HNNH spin-spin interaction constant does not exceed 1 Hz. The form of its dependence on the dihedral angle is determined.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 3, pp. 363–366, 1989.     

Kinetics of the reaction of C6H5 with HBr

The rate constant for the reaction of phenyl radical with hydrogen bromide has been measured with the cavity-ring-down method at six temperatures between 297 and 523 K. The Arrhenius expression for the H abstraction reaction can be effectively given by: . The values of these parameters are similar to those for the H + HBr reaction, but are in sharp contrast to those for alkyl radical reactions. The gross difference between the alkyl radical reactions and the phenyl and H-atom reactions could be rationalized in terms of the inductive effects of these radicals as measured by Taft's σ* (polar) constants. © 1993 John Wiley & Sons, Inc.     

Synthesis of 1-alkyl(aralkyl)-4-acyl-2-piperazinones

1-Alkyl(aralkyl)-4-acyl-2-piperazinones are formed in high yields during selective acylation of N-monosubstituted ethylenediamines by benzoyl and cyclohexylcarbonyl chlorides in the presence of pyridine hydrochloride and treatment of the reaction products with chloroacetyl chloride in the presence of potassium tert-butylate.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 514–517, April, 1986.     

Structure of sevedamine

From the combined chloroform-extracted material of the epigeal part ofKorolkowia sewerzowii Regel the new alkaloid sevedamine has been isolated, with mp 256–258°C (acetone) [α]_D +3.6° (c 1.25; ethanol), C₂₇H₄₅NO₃. On the basis of the results of a study of the UV, IR, PMR, and mass spectra of sevedamine and also performance of a transition to the known alkaloid korseverilinedione it has been established that sevedamine has the structure and configuration of 3β,6α,14α-trihydroxycevanine.     

Mass-spectrometer investigation of 3, 6-dialkyl-2, 5-diketopiperazines

Analysis of mass-spectra of various 2, 5-diketopiperazines gives the basic fragmentation rules for their molecular ions, and the effects of nature and positions of substituents on the process.Mass-spectrometry Laboratory of the Institute of the Chemistry of Natural Compounds.Antibiotics Chemistry Laboratory of the Institute of the Chemistry of Natural Compounds.     

Synthesis and Structure of Triphenylbismuth Bis(Fluorobenzoates)

The reaction between triphenylbismuth, hydrogen peroxide, and 3,4,5-trifluorobenzoic or pentafluorobenzoic acid (molar ratio 1 : 1 : 2, respectively) in ether gave triphenylbismuth bis(3,4,5-trifluorobenzoate) (I) and triphenylbismuth bis(pentafluorobenzoate) (II) in 74 and 89% yields, respectively. The structures of compounds I and II were established by X-ray diffraction. The Bi atoms have a distorted trigonal-bipyramidal coordination with acylate groups in the axial positions. The OBiO angles are 170.2(2)° and 171.5(2)° in I and II, respectively. The Bi–C(Ph)_eq bond lengths vary in the range of 2.187(6)–2.204(5) Å, the Bi–O(acyl) lengths are 2.256(5) Å in I, and 2.281(5) and 2.318(5) Å in II. In the crystals I and II, the Bi and carbonyl O atoms are involved in intramolecular interactions (Bi···O(=C) 2.926(5)–3.176(5) Å), which increase the equatorial CBiC angles on the side of these contacts to 136.2(3)° and 138.6(2)° in I and II, respectively.     

Effects of structural transformations in magnetic emulsions

Structural transformations and relevant changes in the magnetic and optical properties of magnetosensitive emulsions based on magnetic fluids are experimentally studied. Peculiarities of the changes in the magnetic susceptibility of emulsions associated with the deformation of their microdroplets and the effect of phase inversion (the transformation of dispersions of magnetic droplets in nonmagnetic media into dispersions of nonmagnetic droplets in magnetic fluids) are established. Optical effects occurring in magnetic emulsions under the combined action of a shear flow and a magnetic field are studied. It is concluded that optically active composition media may be developed on the basis of magnetic fluids.     

Synthesis ofS-(+)-hydroprene

A novel path toS-(+)-hydroprene (1) starting from the technical gradeS-(+)-dihydromyrcene (2, e.e. 50%) is proposed. The latter was selectively transformed intoS-3,7-dimethyloctanal (5) in three steps including hydroalumination. The reactions of5 with allyl- or methallylmagnesium chloride followed, respectively, either by oxygenation in the presence of PdCl₂/CuCl or by ozonolysis, affordS,E-6,10-dimethyl-3-undecen-2-one (7) which was treated with ethoxyethynylmagnesium bromide to give the title juvenile hormone analogue in 23% overall yield.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No 1, pp. 110–112, January, 1993.     

AB Initio calculations and vibrational spectra of CH3SC≡CH and CH3SC≡CSCH3

Methylthio- (MTE) and bis-methylthioethyne (BMTE) molecules are calculated by the SCF MO method (geometry optimization, basis set 6–31G*/MP2). The calculated internal rotation barriers of methyl groups are 7.12 kJ/lmole for MTE and 12.86 kJ/mole for BMTE (both groups are simultaneously rotated). The s-gosh-orientation of the thiomethyl fragments corresponds to a stable conformation of BMTE. The estimated values of the s-cis- and s-trans-barriers of mutual rotation of SCH₃ groups about the axis of the C≡C bond are 13.61 and 12.54 kJ/mole, respectively. Conformationally sensitive MOs and vibration frequencies are established. An analysis of the experimental IR absorption and Raman spectra and the calculated vibrational spectrum makes it possible to conclude that in the liquid phase the BMTE molecules also have an s-gosh-conformation. Translated fromZhumal Strukturnoi Khimii, Vol. 39, No. 4, pp. 602–609, July–August, 1998.