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121.
Aluminium chloride-catalysed acylations and alkylations of monohalogenobenzenes with cinnamoyl chloride has been studied. Under strictly homogeneous conditions, alkylation was increasingly favoured relative to acylation as the primary reaction along the series: benzene <fluorobenzene<bromobenzene<chlorobenzene. Changing to heterogeneous conditions (excess catalyst with CS2 as diluent) preserved this order but primary alkylation was relatively enhanced. The addition of nitrobenzene to the homogeneous reaction restrained alkylation more than acylation.Primary acylation may be followed by alkylation giving asymmetrical 1,3,3-triarylpropan-1-ones but the possibility that these are formed by alkylation followed by acylation is ruled out. These ketones may subsequently undergo α,β-ketonic fission.Primary alkylation may be followed by cycliacylation producing 3-arylindan-l-ones with the halogeno substituent at the side-chain aryl group and this observation rules out their alternative mode of formation, cyclialkylation of the primary acylation product.An example of a para → meta bromine shift is discussed. 相似文献
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Bromolactonization of 4-hexenoic acids gives a greater percentage of δ-lactones than does iodolactonization. Substituents in the 3-position favor the formation of δ-lactones while substituents in the 6-position favor the formation of γ-lactones. 相似文献
124.
The effect of the separating shear-layer thickness and shape on the structure of the flow in the reattachment region of a backward-facing step is examined using wall static-pressure profiles and turbulence data for a range of Reynolds number (800 < Re H< 40,000) and upstream boundary-layer thickness (0 < δ/H < 2). The reattachment pressure and the peak pressure in the reattachment zone decrease in a continuous manner as the upstream boundary layer thickens. The thinnest boundary layers follow the correlation of Roshko and Lau. Using the pressure data, correlations are developed which can be used to predict the level of turbulent shear stress in the near-wall region at reattachment, a location in which experimental data are extremely difficult to obtain. 相似文献
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The superconducting transition temperature, Tc, of NaCl structure compounds in the series Ag1?xSn1+xSe2 is found to be exceptionally sensitive to hydrostatic pressures up to 21 kbar. For five samples of varying composition, Tc is suppressed smoothly at a rate of ?(6?8)×10?5K·bar?1. These results are discussed with respect to the volume sensitivity of the electron-phonon interaction responsible for superconductivity. 相似文献
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