Electrosynthesis of N-tert-Butyl-2-benzothiazolesulfenamide

Conditions for the production of N-tert-butyl-2-benzothiazolesulfenamide (TBBS) in an oxidative condensation of 2-mercaptobenzothiazole and tert-butylamine are determined. The electrosynthesis occurs during electrolysis of a 4.5–5.0 M NaCl solution containing a water-immiscible organic solvent extracting TBBS. The process efficiency is the highest at the following conditions: a 1 : 8 ratio between 2-mercaptobenzothiazole and tert-butylamine, a DSA, a stainless-steel cathode, a current density of 300 A m^–2, and a continuous extraction of TBBS into a 3 : 1 mixture of carbon tetrachloride and acetonitrile. Under these conditions, the TBBS yield is 98–100%, the current efficiency is 74%, the process productivity is 0.9 kg m^–2 h^–1, and the electricity consumption is 1.9 kW h kg^–1. Repeated use of the aqueous phase corrected for the source products jeopardizes neither the process characteristics nor the product quality.     

Electrochemical Reduction of Arsenic Acid

It is found that arsenic acid in aqueous solutions is reduced chiefly to arsine, whose yield substantially depends on the cathode material nature and electrolysis conditions. The yield increases with the acid concentration and catholyte temperature. The maximum yield (current efficiency of about 50%) is obtained on a cadmium cathode. Hydrochloric acid or cationic surface-active substances present in the catholyte raise the arsine yield on a copper cathode by more than two times and make no impact on the yield on a cadmium cathode. A possible mechanism of the observed phenomena is discussed.     

Recyclization of 2-imino-2h-1-benzopyrans under the influence of nucleophilic reagents. 1. New approach to the synthesis of 3-(1,3,4oxadi-, thiadi-, and triazolyl-2)coumarins

It has been found that under the action of hydrazides of carboxylic acids, 2-iminocoumarin-3-carboxamides are recyclized to N⁽¹⁾-acylamidrazones of coumarin-3-carboxylic acids. The use of N⁽¹⁾-acylamidrazones is proposed as a simple and effective means of synthesizing 3-(1,3,4-oxadi-, thiodi-, and triazolyl-2)coumarins. The possibilities of alternate schemes of synthesis are discussed, and a mechanism is suggested for the recyclization.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 186–192, February, 1996.     

Influence of the quantum size effect for grazing electrons on the electronic conductivity of metal films

The thickness dependence of the electronic conductivity of thin (5–150 nm) single-crystal (100) films of refractory metals is investigated at different temperatures ranging from 4.2 K to room temperature. Regions of square-root, quasilinear, and quadratic dependences are observed. The quasilinear thickness dependence is explained by the influence of quantum effects on the transverse motion of electrons in the case when electron scattering by the film surfaces dominates. For macroscopic film thicknesses 30–50 nm, much greater than the Fermi wavelength of an electron, quantum corrections to the electronic conductivity reach values of the order of 50%. This is a consequence of the quantum size effect for grazing electrons, which leads to an anomaly in electron scattering by the film surfaces. The region of the quadratic thickness dependence corresponds to the quantum limit, and the square-root region corresponds to the classical limit. The effect is explained in a quasiclassical two-parameter model (the effective angle α* for small-angle electrons and the parameter γ, equal to the ratio of this angle to the diffraction angle) that takes into account the diffraction angular limits for grazing electrons. The effect occurs for parameters α*≪1 and γ∼1 and differs from the “ordinary” quantum size effect. Pis’ma Zh. éksp. Teor. Fiz. 66, No. 11, 693–698 (10 December 1997)     

Electroreduction of Nitriles: The Reduction of Furfurylidene- and Benzylidenemalonodinitriles and Esters of Substituted 1-Cyanoacrylic Acids

The electrochemical reduction of compounds with a common formula R¹(H)C=C(CN)R², where R¹ is C₆H₅, n-CH₃OC₆H₄, n-FC₆H₄, or -furyl; and R² is CN or COOC₂H₅ is studied. The reduction of these compounds at a zinc cathode in the water–acetonitrile KH₂PO₄ solution yields both cyclic and linear hydrodimers. The relative yield of the linear hydrodimer increases with lowering the temperature and acetonitrile content in the catholyte. The obtained data well correlate with the suggestion that the cyclic products form in the catholyte bulk from linear hydrodimers.