Cleaning vacuum-pyrolysis

Upon flash vacuum pyrolysis or under silver nitrate catalysis, a variety of 2-ethenyl-sub-stituted cydopropylamines 146 cleanly undergo a vinylcyclopropane to cyclopentene rearrangement [129] and afford high yields (up to 95%) of 4-aminocyclopent-l-enes 147, some of which have unprecedented substitution patterns (Scheme 11.37) [130],... 

The sulfone 80 undergoes clean extrusion of sulfur dioxide on exposure to flash vacuum pyrolysis conditions to produce divinyl compound 81 (Equation 18) <1999J(P1)605>. 

Interestingly, no a,/3-unsaturated thiocarbonyl dimer and no products derived from the 27t thiocarbonyl participation in Diels-Alder reactions were observed although the potential, reversible generation of such products could not be ruled out. In contrast, the low temperature dimerization of a,j8-unsaturated thioketones including methyl vinyl thioketone, generated by flash vacuum pyrolysis (FVP), provided 1 derived from the clean, regiospecific Diels-Alder dimerization with 4tt and 2tt thiocarbonyl participation [Eq. (2)].4... 

The flash vacuum pyrolysis of the monoepoxide of 1,3-cyclooctadiene (362) gave, in a clean and... 

Personnel have to be careful not to damage expensive tooling by spot annealing, mechanical abuse, etc. There are commercial cleaning systems used such as aluminum oxide beds (fluidized beds), salt baths, hot air ovens, and vacuum pyrolysis. As an example, the vacuum pyrolysis cleaner utilizes heat and vacuum to remove the plastic. Most of the plastic is melted and trapped. Remaining plastic is vaporized and appropriately collected in a trap. 

Z)-haloalkenylsilanes afford (Z)-dihaloalkenes], Acetylenic alcohols (122) react with trimethylsilyl iodide to give di-iodoalkenes or unsaturated iodohydrins, depending on the alcohol used. Terminal acetylenic alcohols react cleanly to afford the unsaturated iodohydrins (123) whereas internal acetylene precursors give mixtures of di-iodoalkenes where (124) predominates. Tetrafluoroethylene is conveniently prepared, in excellent yield, from polytetrafluoroethylene by vacuum pyrolysis. ... 

Bicyclo[3,2,0]heptan-6-ones and bicyclo[3,2,0]hept-2-en-7-ones are cleanly iso-merized to cyclohept-2-enones and cyclohepta-2,4-dienones, respectively, in strong acids such as FSO3H and 96% H2SO4, e.g. (174) -> (175), and a useful method of converting phenols into cycloheptane derivatives of type (176) is by flash vacuum pyrolysis of their propiolate esters. Mixtures of isomeric cycloheptadienols are produced when the epoxide resulting from addition of dimethylsulphonium methyl-ide to acylvinyIcyclopropane is heated at 180 °C for 12 h. ... 

The technique of flash vacuum pyrolysis (FVP) is now weU estabUshed as a clean and selective method for bringing about unimolecular thermal reactions. The apparatus required is relatively simple and inexpensive to construct (20147 C1150), and its use is now spreading beyond groups specializing in the technique and finding occasional routine use in target-directed synthesis. In this review, we have aimed to describe aU studies... 

Although many stable sulphines are known, the parent compound, CH2SO, has not been isolated. It is generated cleanly by flash vacuum pyrolysis of 1,3-di-thietan 1-oxide above 300 °C, and of thietan 5-oxide or methanesulphinyl... 

In a world increasingly conscious of the dangers of contact with chemicals, a process that is conducted within the walls of a vacuum chamber, such as the VDP process for parylene coatings, offers great advantages. Provided the vacuum pump exhaust is appropriately vented and suitable caution is observed in cleaning out the cold trap (trace products of the pyrolysis, which may possibly be dangerous, would collect here), the VDP parylene process has an inherently low potential for operator contact with hazardous chemicals. 

Place clean vessels in oven at 60 °C or keep in a desiccator under vacuum. During periods of prolonged non-use, the pyrolysis vessels should be kept in a desiccator to minimize oxidation of nickel surfaces. 

In the preparation of the glass tubes, quartz tubes, and foils prior to sample loading, it is important that none are touched by hand. The method described by Sanglier et al. has proven to work well for foils used inside glass tubes. In this method, pyrolysis foils and tubes are washed in acetone, then dried overnight at 27°C. A single foil is inserted, with flamed forceps, into each pyrolysis tube so as to protrude about 6 nun from the mouth. The tubes may then be stored at 80°C in a clean, dry oven or vacuum dessicator until needed. For each strain, small amounts of biomass (25 Tg) are scraped from three different areas of the inoculated plate and smeared onto the protrading foil. The assembled foils are placed in an 80°C oven for 15 minutes to dry the biomass. 

A 10% solution of each hexafluoropropylene-vinylidene fluoride copolymer is prepared by dissolving 10 g of polymer in 100 ml of reagent grade acetone. A vial 58 mm high is filled with the sample solution. A pyrolysis wire, previously cleaned in a bunsen burner until red hot, then cooled, is dipped into the vial. The dipped wire is then dried in a vacuum oven at 90°C for 30 min. Use of lower drying temperatures or shorter times results in an acetone peak in the pyrogram. This is due to mechanically trapped... 

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