Furan derivatives of group I elements (review)

Latvian Institute of Organic Synthesis, Riga LV-1006. Translated from Khimiya Geterotsikiicheskikh Soedinenii, No. 4, pp. 435–473, April, 1995. Original article submitted February 22, 1995.     

Kinetics of the thermal desorption of O2, HCl,and H2O from the surface of cobalt chromite

A study has been carried out on the kinetics of the temperature-programmed desorption of O₂, HCl, and H₂O from the surface of cobalt chromite. A mathematic model was obtained for the kinetics of the thermal desorption and a method was developed for determining the kinetic constants. The kinetic parameters of the desorption of O₂, HCl, and H₂O were calculated using these experimental data.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 5, pp. 449–455, September–October, 1993.     

Isomerization of S-2-hydroxyalkyl esters of cyclic phosphorus thioacids

Conclusions The S-2-hydroxyalkyl esters of cyclic P(V) thioacids, which were obtained by reacting a cyclic phosphorus monothioacid with an alkylene oxide, are converted to the 2-mercaptoalkyl esters of cyclic phosphorus acids independent of the size of the ring.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2594–2596, November, 1980.     

Mechanism of oxidation of organic substrates by the rhenium(VI) dithiolate complex in nonaqueous media as determined by EPR using the spin trap method

The mechanism of the reaction of the rhenium(VI) dithiolate complex Re^IV(TDT)₃ with some electron-donating organic reagents in nonaqueous solvents is studied by the spin trap method combined with electron paramagnetic resonance. The reaction products are stable complex rhenium(V) anions, Re^V(TDT)₃-, and short-lived radicals forming long-lived adducts with spin traps as probed by EPR. The possibility of using the radical processes for analytical purposes is discussed.     

Reactions of 5-cyano-1,4,6,9-trioxathia-5-phosphaspiro[4,4]nonanes with compounds containing a labile hydrogen atom

All the investigated reactions of 5-cyano-1,4,6,9-trioxathia-5-phosphaspiro[4,4]nonanes with compounds containing a labile hydrogen atom proceed with the loss of HCN, predominant opening of the oxathiophospholane ring, and formation of 2-oxo-1,3,2-dioxaphospholane derivatives.A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Science Center, Russian Academy of Sciences, 420083 Kazan. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 11, p. 2670–2673, November, 1992.     

On the minimal time function for distributed control systems in Banach spaces

In this paper, it is shown that the minimal time function is locally Lipschitz continuous for the control systemx=Ax+u in a Banach spadeE, under either of two conditions:A is linear and generates aC ₀-semigroup of bounded linear operators; orA is nonlinear, possibly multivalued, and dissipative. The main tool used for the nonlinear case is a result of Barbu concerning the null controllability of the system.     

On the role of collective and local molecular fluctuations in the relaxation of proton intrapair dipolar order in nematic 5CB

We investigate the role that local motions and slow cooperative fluctuations have on the relaxation of the intrapair dipolar order in the nematic 5CB. With this purpose we present a theoretical and experimental systematic study which allow us to quantify the contribution from each type of molecular fluctuation to the intrapair dipolar order relaxation time, T(1D). The experimental work includes measurements of Zeeman and intrapair dipolar order relaxation times (T(1Z) and T(1D)) as a function of temperature at conventional NMR frequencies, in three complementary samples: normal and chain deuterated 4-n-pentyl-4(')-cyanobiphenyl (5CB and 5CB(d11)) and a mixture of normal 5CB and fully deuterated 4-n-pentyl-4'-cyanobiphenyl (5CB(d19)), 50% in weight. Additionally we perform T(1Z) field-cycling Larmor frequency-dependent measurements to obtain the spectral density of the cooperative fluctuations. The obtained results are as follows. (a) The cooperative molecular fluctuations have a strong relative weight in the relaxation of the intrapair dipolar order state, even at Larmor frequencies in the range of conventional NMR. (b) Alkyl chain rotations are an important relaxation mechanism of the intrapair dipolar order at megahertz frequencies. (c) Intermolecular fluctuations mediated by translational self-diffusion of the molecules is not an efficient mechanism of relaxation of the intrapair dipolar order.