Secondary structure of crystals

Published experimental data on the dependence of the properties of crystal substances on crystal size are discussed. The dependence is of the same form for different properties and different crystal substances. When the crystal diminishes in size, its properties remain constant until the size decreases to 10⁻⁵–10⁻⁶ cm; smaller crystals considerably change their properties. It is shown that the currently available experimental data are sufficient to substantiate the notion of an “elementary unit of a solid crystal” (“crystal quantum”). The elementary unit of a crystal is regarded as a basis for the secondary structure (macrostructure) of a solid and an elementary carrier of its “crystal” properties. Due to this notion, we can interpret the vast experimental material on the real structures and properties of solids from a single viewpoint. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 4, pp. 724–730, July–August, 1995. Translated by L. Smolina     

Chemistry of ethyleneimine

The mechanism of the reaction of N-aminoethyleneimine with some aliphatic aldehydes and with acrolein have been studied. It has been shown that the reaction takes place at the carbonyl bond C=O with the formation of hydrazones.For part II, see [1].     

Herbicidal hydroxylamine derivatives

The synthesis of 2-alkyl(dialkyl)amino-4-chloro-sym-triazine derivatives of hydroxylamine, N-methylhydroxylamine, and N-phenylhydroxylamine has been effected and their properties have been studied. The thermal and catalytic polycondensation of the 2-alkyl(dialkyl)amino-4-chloro-6-N-phenyl(methyl)hydroxyamino-sym-triazines accompanied by the liberation of hydrogen chloride and the formation of linear polycondensates with 3–4 members has been observed.For part IX see [9].     

Photochemical reactions of 7-aminocoumarins. 5. [2+2]-Cycloadducts with trans-stilbene

The photocycloaddition of trans-stilbene to 7-diethylaminocoumarin, 4-methyl-7-diethylaminocoumarin, and 4-(N-morpholino)-7-diethylaminocoumarin was investigated. Adducts involving stereospecific (2+2)-cycloaddition at the 3–4 bond were isolated. On the basis of the PMR spectra and an x-ray diffraction study, it was established that the phenyl groups in the cycloadducts occupy 1-endo and 2-exo positions.For Communication 4, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1022–1027, August, 1990.     

Synthesis of organocyclosiloxanes containing cyanoalkyl groups on the silicon atom

The cohydrolysis of-cyanoethyl- and-cyanopropylmethyldichlorosilanes with dimethyldichlorosilane has been studied and the optimum conditions ensuring the maximum yield of rings containing cyanoalhyl groups have been determined.B is(-cyanoethyl)hexamethylcyclotetrasiloxane,-cyanopropylpentamethylcyclotetrasiloxane, and bis(-cyanopropyl)hexamethylcyclotetrasiloxane have been obtained for the first time and characterized.     

Efforts to expand the genetic alphabet: identification of a replicable unnatural DNA self-pair

Six unnatural nucleotides featuring fluorine-substituted phenyl nucleobase analogues have been synthesized, incorporated into DNA, and characterized in terms of the structure and replication properties of the self-pairs they form. Each unnatural self-pair is accommodated in B-form DNA without detectable structural perturbation, and all are thermally stable and selective to roughly the same degree. Furthermore, the efficiency of polymerase-mediated mispair synthesis is similar for each unnatural nucleotide in the template. In contrast, the efficiency of polymerase-mediated self-pair extension is highly dependent on the specific fluorine substitution pattern. The most promising unnatural base pair candidate of this series is the 3-fluorobenzene self-pair, which is replicated with reasonable efficiency and selectivity.     

Highly regioselective construction of spirocycles via phosphine-catalyzed [3 + 2]-cycloaddition

A direct entry to spirocycles with low to moderate regioselectivity was achieved by triphenylphosphine-catalyzed [3 + 2]-cycloaddition of active exo-methylenecycles (1) and ethyl 2,3-butadienoate (2). The regioselectivity of the reaction was greatly improved by using the bulky tert-butyl ester of the 2,3-butadienoate (5). The regioselectivity of the reaction was further enhanced by using the tert-butyl 2-butynoate as the substrate. This protocol provided an efficient entry to the skeleton of spirocarbocycles, especially spiro[4.n]alkanes.     

Preparation and steric structure of 2-Alkoxy-2,5-dioxo-4,4-bis(trifluoromethyl)-7(8)-chloro-1,3,2λ5-benzodioxaphosphepins

The reaction of hexafluoroacetone with 2-alkoxy-6(7)-chloro-1,3,2-benzodioxaphosphorin-4-ones yielded 7-and 8-chloro-substituted 2-alkoxy-2,5-dioxo-4,4-bis(trifluoromethyl)-1,3,2λ⁵-benzodioxaphosphepines. Their steric structure was studied by single-crystal X-ray diffraction. The effect of fluorinated substituents on the crystal packing of the benzophosphepines was demonstrated. Hydrolysis of these compounds gave the corresponding 4-and 5-chloro-substituted 2-(2-hydroxyphenyl)-2-oxo-1,1-bis(trifluoromethyl)-ethanols; the structure of 2-(2-hydroxy-5-chlorophenyl)-2-oxo-1,1-bis(trifluoromethyl)ethanol was also proved by single-crystal X-ray diffraction.     

On the origin of the splitting of the second maximum in the radial distribution function of amorphous solids

The splitting of the second maximum of the radial distribution function of an irregular atomic packing is regarded as an indication of the amorphous state of a substance. This paper describes the splitting-forming atomic configurations using Delaunay simplices, representing chains of elementary configurations. It is shown that the splitting is formed of chains in which all simplices are nearly regular tetrahedra and quartoctahedra. Translated fromZhumal Struktumoi Khimii, Vol. 38, No. 1, pp. 78–88, January–February, 1997.     

Structure of aconifine

The structure of the new alkaloid aconifine, which has been isolated from the tubers and epigeal part ofAconitum karakolicum Rapcs. has been established on the basis of the results of chemical transformations and spectral characteristics. Some features of the selective acetylation of aconitine and aconine have been elucidated. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 665–672, September–October, 1980.