Synthesis and X-ray structural study of 1-adamantylmethyl 2-cyanoacrylate and 1,10-decanediol bis-2-cyanoacrylate

I-Adamantylmethyl 2-cyanoacrylate (1) was prepared by the reaction of 2-cyanoacryloyl chloride with 1-adamantylmethanol . 1,10-Decanediol bis-2-cyanoacrylate (2) was synthesized by transesterification of methyl 2-cyanoacrylate with 1,10-decanediol. Esters1 and2 were studied by X-ray structural analysis.Deceased in 1995.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2288–2292, September, 1996.     

Preparation and structure of chlorinated poly(vinyl flouride)

The low-temperature chlorination of poly(vinyl fluoride) (PVF) proceeds readily in CCl₄ suspension. The rate of chlorination is high initially, but the reaction slows down considerably when the chlorine content of the polymer reaches 40–50%. At long reaction times, polymers containing 62% chlorine (1.88 chlorine atoms per monomer unit) can be obtained. As the degree of chlorination increases, the solubility of PVF in organic solvents increases. Polymer crystallinity and polymer softening point decrease with chlorination. Polymers containing 40% chlorine appear to be completely amorphous by x-ray analysis. In this respect, PVF differs from poly(vinyl chloride) (PVC), where chlorination increases the softening point, and it resembles polyethylene where both crystallinity and softening point decrease with chlorination. ¹⁹F NMR analysis of the polymers indicates that up to a degree of chlorination of 1 chlorine atom per monomer unit, 50% of the substitution occurs on the α-carbon of the PVF molecule. This result is very different from the predominant β-chlorination of PVC reported by several workers. The chemical selectivity observed in the chlorination of PVF is in quantitative agreement with the results of free-radical chlorination of organic compounds and can be rationalized by considering the size and the electronic properties of the fluorine atom. The results of ¹H NMR analysis are also in support of a polymer structure where the chlorine atoms are distributed between α- and β-carbons. Based on a comparison of the ¹⁹F and ¹H NMR data, the average composition of chlorinated PVF at the 1 chlorine atom per monomer unit level can be represented as: C₂₀₀H₂₀₀F₁₀₀Cl₁₀₀ = (CH₂)₆₃(CHF)₅₀(CHCl)₂₄(CClF)₅₀-(CCl₂)₁₃.     

Synthesis and structure of 4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]pyrimidines

Kharkov State University, 310077 Kharkov and Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 981–986, July, 1994.Original article submitted May 11, 1994.     

Molecular structure of the alkaloid solasodine

An x-ray structural study of the monohydrate of the alkaloid solasodine has been made. Rings A, C, and F have the chair conformation, ring B half-chair, and rings D and E envelope conformations. The linkages of rings B/C and C/D are trans and that of rings D/E cis. It has been shown that solasodine is a diastereomer of the alkaloid tomatidenol.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Moscow. Institute of Organic Synthesis and Coal Chemistry of the Kazakh SSR Academy of Sciences, Karaganda. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 86–88, January–February, 1989.     

Crystal and molecular structure of 20α-methoxy-16α-21-epoxypregn-5-en-3β-ol-[17α,20β-d]-1′,3′-imidazolidine-2′-thione 3-acetate

The stereochemistry of the substituents at the C20 atom is indicated in accordance with the IUPAC rules for steroids of the pregnane series.     

"Separated" versus "contact" ion-pair structures in solution from their crystalline states: dynamic effects on dinitrobenzenide as a mixed-valence anion

Qualitative structural concepts about dynamic ion pairs, historically deduced in solution as labile solvent-separated and contact species, are now quantified by the low-temperature isolation of crystalline (reactive) salts suitable for direct X-ray analysis. Thus, dinitrobenzenide anion (DNB(-)) can be prepared in the two basic ion-paired forms by potassium-mirror reduction of p-dinitrobenzene in the presence of macrocyclic polyether ligands: L(C) (cryptand) and L(E) (crown-ethers). The crystalline "separated" ion-pair salt isolated as K(L(C))(+)//DNB(-) is crystallographically differentiated from the "contact" ion-pair salt isolated as K(L(E))(+)DNB(-) by their distinctive interionic separations. Spectral analysis reveals pronounced near-IR absorptions arising from intervalence transitions that characterize dinitrobenzenide to be a prototypical mixed-valence anion. Most importantly, the unique patterns of vibronic (fine-structure) progressions that also distinguish the "separated" from the "contact" ion pair in the crystalline solid state are the same as those dissolved into THF solvent and ensure that the same X-ray structures persist in solution. Moreover, these distinctive NIR patterns are assigned with the aid of Marcus-Hush (two-state) theory to the "separated"ion pair in which the unpaired electron is equally delocalized between both NO(2)-centers in the symmetric ground state of dinitrobenzenide, and by contrast, the asymmetric electron distribution inherent to "contact"ion pairs favors only that single NO(2)-center intimately paired to the counterion. The labilities of these dynamic ion pairs in solution are thoroughly elucidated by temperature-dependent ESR spectral changes that provide intimate details of facile isomerizations, ionic separations, and counterion-mediated exchanges.