A HIGH YIELDING, REPRODUCIBLE SYNTHESIS OF TRIMETHYLSILYLKETENE
ABSTRACT A two-step sequence for the preparation of trimethylsilylketene, from chloroacetaldehyde diethyl acetal via ethoxyacetylene, has been modified and optimized.
Reaction of ynolate anions derived from silylketenes with electrophiles: a facile preparation of silyl ynol ethers and functionalized silylketenes
Reaction of the ynolate anions 2a,b, generated from the silylketenes 1a,b, with a variety of electrophiles 3 is investigated. The reaction with bulky and/or hard silyl chlorides, such as ButMe2SiCl, PriSiCl, (Thexyl)Me2SiCl and ButPh2SiCl, exclusively gives the silyl ynol ethers 4, while that with small or soft silyl chlorides and stannyl chlorides gives only the functionalized silylketenes 5 in modest to high yields, respectively. In the case of the reaction with small and hard Me3SiCl, initial formation of the O-trimethylsilyl ynol ether 4b and the subsequent rapid isomerization to the bis-silylketene 5a are proposed by the trapping of 4b as a cobalt complex 7b.
Growth and Characterization of β-RDX Single-Crystal Particles
1,3,5-Trinitrohexahydro-s-triazine (RDX) single-crystal particles crystallized in the β phase have been successfully grown by sublimation–recrystallization. Synchrotron X-ray diffraction results confirm that the recrystallized products are β-RDX single crystals. Compared to the traditional solution deposition methods, the sublimation method used in this work breaks through the mass limitations during the growth of β-RDX. The distribution of α- and β-RDX on different substrates reveals that hydrophilic substrates are prone to grow β-RDX single crystals and that hydrophobic substrates prefer α-RDX single crystals. The sublimation rate dominates the growth of pure β-RDX. The mechanisms of the phase transition from β-RDX to α-RDX during the process of sublimation–recrystallization have been studied. The current results can promote the potential application of β-RDX in the propellant, explosives, and military fields.