The structure of phosphacymantrene

Proton NMR spectra of phosphacymantrene (π-phospholyl manganese tricarbonyl) orientated in the nematic phases of liquid crystals have been investigated. The derived H-H and H-P direct dipolar coupling constants have been used to determine the relative proton-proton and proton-phosphorus distances. A comparison of the geometrical data of various 5-membered aromatic heterocycles shows that the relative distances between the protons closest to the heteroatom increase with the van der Waals radius of the heteroatom. The results suggest that NMR spectroscopy of orientated molecules can be used to determine van der Waals radii.     

The structure of nitrarine

Summary Dehydrogenation of the alkaloid nitrarine with selenium has given 3-(quinolin-8-yl)--carboline (II) and 3-(5, 6, 7, 8-tetrahydroquinolin-8-yl)--carboline (III).On the basis of the results of a study of the chemical and physical properties of nitrarine, and also from the results of x-ray structural analysis, structure (I) has been established for it.Institute of Heteroorganic Compounds, Academy of Sciences of the USSR, Moscow, Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 334–345, May–June, 1976.     

The structure of luteicine

An investigation of the UV, IR, PMR, and mass spectra and chemical transformations of luteicine have established for it the structure of 11-hydroxy-2,13-dimethoxyhexahydro-1,13-epoxyhomoproaporphine. The structure of the base was confirmed by its partial synthesis from luteidine.     

The structure of silylcycloheptatrienes

Calculations have been made, using the MNDO method, of the structures and energies of four isomeric forms of η⁷-SiH₃C₇H₇ and of η₇-SiH₃C₇H₇. The transition state has been identified for the [1,5] shift of the SiH₃ group in η¹-SiH₃C₇H₇, but no transition state could be located for any other SiH₃ migration pathway: this is consistent with orbital-symmetry control of the rearrangement. Conformational preferences in 7-substituted cycloheptatrienes and 1-substituted cyclohexanes are briefly compared.     

The structure of ulopterol

Chemistry of Natural Compounds - A new coumarin C15H18O5 with mp 141.5–142.5° C (from benzene) has been isolated from the roots and fruit ofPrangos uloptera D. C., and it has been called...     

The structure of naphthalene

The structure of naphthalene has been determined by ab initio gradient computation at the Hartree—Fock level using the 4–21 basis set. Special attention is paid to the small differences between the nearly equal C-C distances and to evaluation of the ability of electron diffraction experiments to distinguish among them. The computed orbital energies are used to assign the photoelectron spectrum.