[2-(3,4-epoxy-cyclohexyl)ethyl]dimethyltert-butylsilane was synthesized, using tert-butyldimethylsilane (TBDMS) and 1,2-epoxy-4-vinylcyclohexane (EVC) as the main raw materials and tris(triphenylphosphine) chlororhodium(I) [RhCl(Ph 3 P) 3 ] as the catalyst. [2-(3,4-epoxy-cyclohexyl)ethyl] dimethyltert-butylsilane is a novel kind of silicon-containing epoxide. The factors affecting the reaction yield, such as catalyst use, reaction time and reaction temperature, were investigated, and the synthesized product was characterized and analyzed by FT-IR and 1 H-NMR. A series of amine-curing resins were prepared with [2-(3,4-epoxy-cyclohexyl)ethyl]dimethyltert-butylsilane, bisphenol A epoxy resin (E-51) and modified amine (593 amine). The mechanical properties of cured splines with the different proportions of amine-curing resins were tested. When the content of 593 amine was 20%, the content of E-51 was 75% and the amount of [2-(3,4-epoxy-cyclohexyl) ethyl] dimethyltert-butylsilane was 5%, the mechanical properties of the cured splines were the best with the tensile strength being 23.3 MPa, the elongation at break being 7.8%, and the Young’s modulus being 421.3 MPa.
Rationale Aromatic hydrocarbons play an important role in the formation and growth of polycyclic aromatic hydrocarbon (PAH) and soot particles. Measurements of their absolute photoionization cross-sections (PICSs), that benefit the quantitative investigation of mass spectrometry, are still lacking, however. Methods PICSs of some aromatic hydrocarbons were measured with tunable synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). Nitric oxide and benzene were chosen as standard references for PICS calibration, since their photoionization cross-sections are well documented in the literature. Binary liquid mixtures of the investigated molecules and their specific solvents were used in the measurements. Results The investigated aromatics include naphthalene, phenanthrene, 1-methylnaphthalene, indene, 2-/3-/4-methylphenylacetylene, 2-methylindene, diphenylacetylene, 1-/2-ethynylnaphthalene and acenaphthylene. Photo-induced fragments from the molecules were also observed with increasing photon energy. Conclusions Based on our measurements and literature data, PICSs of most aromatic molecules have very similar values beyond their ionization energies. However, molecules that contain the phenylacetylene structure have PICSs higher than other aromatics.
Chinese Keemun black tea (KBT) is one of the most renowned black teas worldwide due to its alluring floral/fruity/honey-like odor. However, the key odorants of the so-called Keemun aroma have not been systematically characterized. A comparative sensory-guided flavor analysis was conducted on the aroma compounds in two orthonasally distinguishable KBTs with high and low grades (HG-KBT and LG-KBT). This well-established methodology included the following steps: volatile collection through solvent-assisted flavor evaporation and headspace solid-phase microextraction, aroma identification based on gas chromatography–olfactometry/mass spectrometry, odor contribution calculation according to stable isotope dilution assay, odor activity values (OAVs), and aroma recombination. A total of 42 odorants were characterized, 16 and 10 of which were regarded as key odorants in HG- and LG-KBT, respectively. Among them, dimethyl sulfide, geraniol, β -ionone, 2-/3-methylbutanal, linalool, and 2-methylpropanal showed the highest OAVs and played a pivotal role in ‘ Keemun aroma’. In general, floral odorants had higher OAVs in HG-KBT. In addition, the quantitative changes during the entire preliminary manufacturing step of the tea leaves indicated the great importance of fresh leaves’ quality and withering for the formation of the final aroma quality of the beverage.
危险品化学品经营许可证（带存储）