Asymmetrical nonbridgehead nitrogen—IV : Chiroptical properties of the amines,N-chloroamines and cyanamides

The ORD and CD spectra of 2-methyl-aziridine, azetidine, pyrrolidine, piperidine, their N-Me, N-Hal, N-CN derivatives as well as those of camphidine, N-methyl- and N-cyano-camphidine have been investigated. The possibility of application of the quadrant rule for N-chloroamines is discussed. A similar rule is proposed for the N-CN chromophore.     

ac Conductivity of mixed spinel NiAl0.7Cr0.7Fe0.6O4

ac Conductivity measurements are carried out across the metal to insulator transition in NiAl_0.7Cr_0.7Fe_0.6O₄. The low frequency data is analyzed using Summerfield scaling theory for hopping conductivity. The exponent of the scaling behavior has significantly different values in the conducting and insulating regimes. The hopping frequency and the zero frequency conductivity are found to increase with temperature, slowly in the metallic regime and rapidly in the insulating regime.     

On the theory of slowing down gracefully

We discuss the transport of a tracer particle through the Bose?CEinstein condensate of a Bose gas. The particle interacts with the atoms in the Bose gas through two-body interactions. In the limiting regime where the particle is very heavy and the Bose gas is very dense, but very weakly interacting (??mean-field limit??), the dynamics of this system corresponds to classical Hamiltonian dynamics. We show that, in this limit, the particle is decelerated by emission of gapless modes into the condensate (Cerenkov radiation). For an ideal gas, the particle eventually comes to rest. In an interacting Bose gas, the particle is decelerated until its speed equals the propagation speed of the Goldstone modes of the condensate. This is a model of ??Hamiltonian friction??. It is also of interest in connection with the phenomenon of ??decoherence?? in quantum mechanics. This note is based on work we have carried out in collaboration with D Egli, I M Sigal and A Soffer.     

Asymmetric nitrogen

The molecular structure of 3-methyl-1-((S)-1-tosylprolyl)1,2-diazacyclohex-2-ene, the product of the reaction of 5-methyl-1,6-diazabicyclo[3.1.0]hexane with (S)-N-tosylproline chloride, has been established by X-ray structural analysis. The pyrrolidine cycle has a half-chair conformation with the pyramidal nitrogen atom; the tosyl and pseudo axial carbamoyl groups havetrans orientations. The diazacyclohexene cycle has an envelope conformation with folding along the C(7)...C(9) line. The stereochemistry of the transition state of the above-mentioned reaction is discussed.For the previous communication, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 500–503, March, 1995.     

Asymmetrical nonbridgehead nitrogen—XXIV: Complete separation into antipodes and absolute configuration of chiralic N-alkoxyaziridines

Optically active derivatives of 1 - methoxyaziridine - 2,2 - dicarboxylic acid have been obtained: the diethyl ester S-(? 1a) by kinetic enrichment under the action of 1-ephedrine; the diamines R-(+2d) and S-(?2f) by crystallization from 1-methyllactate; the diamide S-(?2g) by asymmetric inversion reaction at the N atom while heating in 1-methyllacetate. The basic possibility of 1-alkoxyaziridine reactions with retention of optical activity (ammonolysis and reduction with LAH₄) has been demonstrated for S-(?1a) and R-(+1). 1-Methoxy - aziridine - 2,2 - dicarboxylic acid cis-ethyl ester 4 has been completely separated into antipodes 1R, 2S-(+4) and 1S, 2R-(?4) which under the effect of diazoethane afford diethyl esters R-(+1) and S-(?1) with optical purity of 96.2 and 93.8% (determined by PMR using a chiralic shift-reagent). On the basis of X-ray analysis of monoamides of 1 - methoxyaziridine - 2,2 - dicarboxylic acid ethyl ester and of salt +7 the trans-specificity of ammonolysis and hydrolysis of 1 and the absolute configurations of all the optically active derivatives obtained were established.     

Mass spectrometry of organic compounds of group V elements 7—N-alkoxyamines

The suggestion of participation of the participation Ione electron pair of the nitrogen atom in amine-type stabilization has been confirmed by a decrease in amine-type fragmentation and a drastic change in the decomposition routes under electron impact of N-alkoxyamines.