The crystal structure of octamethylcyclotetrasilane was determined at 87 K by X-ray diffraction methods: C8H24Si4, monoclinic, P21/n, a 7.650(2), b 7.452(1), c 13.320(10), Å, β 103.48(2)°, Z = 2, dx 1.046 g cm?3. In the crystal, Si4Me8 molecules are located at crystallographic inversion centers, which constrains the Si4-ring to be planar. 相似文献
The 1H and 13C nmr spectra of the rotational isomers 3a and 3b of 6‐N‐methyl‐N‐formylaminomefhyl)‐thioquinanthrene were completely assigned with a combination of 1D and 2D nmr techniques. The key‐parts of this methodology were long‐range proton‐carbon correlations and NOE experiments with N‐methyl‐N‐formylaminomethyl substituent. The X‐ray study of 4‐methyl‐2‐N‐methyl‐N‐formylaminomethyl)quinoline 4a as well as 1H and 13C nmr spectra show that N‐methyl‐N‐formylaminomethyl substituent in 4a and 4b has a different steric arrangement than the same substituent in 3a and 3b . 相似文献
n‐Propylammonium dihydrogenphosphate, C3H7NH3+·H2PO4?, crystals are ferroelastic at room temperature. The phase transition into the prototypic phase takes place at approximately 378 K. All atoms except two H atoms are linked by the lost symmetry operations derived from the prototypic space group P2/b21/n21/a. Each of these two different H atoms is involved in an asymmetric hydrogen bond between an oxygen pair. Ferroelastic switching is concomitant with jumps of these H atoms from the donor to the acceptor O atoms. The compound belongs to the structural family of n‐alkylammonium dihydrogenphosphate and in particular to the structure type of pentylammonium dihydrogenphosphate, which differs by localization of alternating layers from the rest of the known alkylammonium dihydrogenphosphates. The crystal was slightly twinned; the proportion of the minor domain was approximately 3.5%. 相似文献
The reactivity ratios for the bulk free‐radical copolymerization of n‐butyl acrylate (BA)/n‐butyl methacrylate (BMA) are estimated at 80 °C. By performing a series of low conversion runs including replicate runs, the reactivity ratios are estimated as rBA = 0.460 and rBMA = 2.008. Runs to high conversions are then conducted at three different feed compositions (fBMA = 0.2, 0.5, and 0.8) to validate the reactivity ratios. The composition data from the high conversion experiments show good agreement with the estimated reactivity ratios in the integrated form of the Mayo–Lewis model. The molecular weight, gel content, and glass transition temperature of BA/BMA copolymers are also determined.