4,747 research outputs found

    Variable temperature 1H and 13C NMR study of restricted rotation in N,N-bis(2-hydroxyethyl)acetamide

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    N,N-bis(2-hydroxyethyl)acetamide shows restricted rotation about the amide bond in both 1H and 13C NMR spectra rendering the two hydroxyethyl groups non-equivalent. A variable temperature study in CD3SOCD3 allowed estimation of the free energy barrier to rotation as 75.6 ± 0.2 kJ mol–1. Previously published data in CDCl3 appears to be erroneous.PostprintPeer reviewe

    Polarization of Thermal Emission from Aligned Dust Grains Under an Anisotropic Radiation Field

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    If aspherical dust grains are immersed in an anisotropic radiation field, their temperature depends on the cross-sections projected in the direction of the anisotropy.It was shown that the temperature difference produces polarized thermal emission even without alignment, if the observer looks at the grains from a direction different from the anisotropic radiation. When the dust grains are aligned, the anisotropy in the radiation makes various effects on the polarization of the thermal emission, depending on the relative angle between the anisotropy and alignment directions. If the both directions are parallel, the anisotropy produces a steep increase in the polarization degree at short wavelengths. If they are perpendicular, the polarization reversal occurs at a wavelength shorter than the emission peak. The effect of the anisotropic radiation will make a change of more than a few % in the polarization degree for short wavelengths and the effect must be taken into account in the interpretation of the polarization in the thermal emission. The anisotropy in the radiation field produces a strong spectral dependence of the polarization degree and position angle, which is not seen under isotropic radiation. The dependence changes with the grain shape to a detectable level and thus it will provide a new tool to investigate the shape of dust grains. This paper presents examples of numerical calculations of the effects and demonstrates the importance of anisotropic radiation field on the polarized thermal emission.Comment: 13pages, 7figure

    N-Benzyl-N-(2-hydroxyethyl)-2-(oxazolidin-2-on-3-yl)-2-phenylacetamide

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    The title compound, obtained by base-induced dimerization of 3-benzyloxazolidin-2-one has been prepared and fully characterised. Its X-ray structure features hydrogen bonded dimers involving the hydroxyl OH and amide carbonyl forming a 14-membered ring.Publisher PDFPeer reviewe

    X-ray structures of 3-acetyloxazolidin-2-one, 3-acetyloxazolin-2-one and oxazolin-2(3H)-one

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    The X-ray structures of three simple heterocyclic compounds have been obtained for the first time. Structures of both 3-acetyloxazolidin-2-one 1 and its unsaturated analogue 3-acetyloxazolin-2-one 3 show a planar imide nitrogen with the exocyclic C=O oriented anti to the ring N–C(=O) bond and negligible intermolecular interactions, a pattern consistent with previously reported analogues. In contrast the parent NH heterocycle, oxazolin-2(3H)-one 4 , exists as hydrogen bonded dimers of two closely similar independent molecules but an unusual type of disorder involving exchange of the ring O and NH positions results in a very high R factor.Publisher PDFPeer reviewe

    3,5-Dithiatricyclo[5.2.1.02,6]decan-2-one

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    The X-ray structure of the title compound has been determined and the structure shows an exo-configured planar dithiolanone ring. This is in contrast to the few previous dithiolanones to be characterised crystallographically which are all twisted.Publisher PDFPeer reviewe
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