Sealing glass tubes

Treatment of resin-bound iminophosphorane 197 with an excess of solid CO2 and CS2 in a sealed glass tube, and with aryl isocyanates afforded I-OXO-, 1-thioxo- 198, and l-arylimino-l//-pyrido[l,2-c]pyrimidine-3-car-boxylates 199 (OlJMClOll). Reaction of iminophosphorane 200, derived from 2-(2-azidophenyl)pyridine with excess PPh3, yielded 6//-pyrido[l,2-c] quinazoline-6-thione (201). 

Fig. A.2. The sequence of making a sealed glass tube, from top to bottom.

To prepare CO solution for the experimental purpose, it is recommended to bubble 20 ml of stock solution in a sealed glass tube with a stream of pure CO gas. The bubbling process lasts for 20 min under the pressure of 100 kPa at 37°C [3]. One microliter of this CO-saturated solution is estimated to contain 30 ng of the gas based on the solubility of CO at 37°C, the extent of dilution of the CO-saturated solution, and the assumption that the loss of the added CO from the bath solution at the time of experiments is negligible. The stock solution of CO should be freshly prepared before each experiment and then should be diluted immediately to the desired concentration with the bath solution or culture media. 

Explds at 60° after 13 sec in a sealed glass tube (Ref 4). Explds spontaneously when frozen and then thawed. Compd is a violent expl, extremely sensitive to impact or friction. It Jalso explds on exposure to strong light (sunlight or diffused), or when in contact with P, As, ozone, fused alkalies, and organic matter such as turpentine rubber, but not with sugar or resins. Metals strong acids do not cause it to expld,... 

On cooling (NH4)2S5 crystallizes as yellow to orange-yellow needles which melt at 95 °C in a sealed glass tube but decompose in air [reverse reaction at Eq. (17)] and on dissolution in water. (Et4N)2Ss is obtained by reaction of Et4NCl with Na2S5 in ethanol [33]. 

Marty, C. and Berset, C., Degradation of rra - 3-carotene during heating in sealed glass tubes and extrusion cooking, J. Food ScL, 51, 698, 1986. 

Interaction is violently exothermic, causing sealed glass tubes at 350°C to explode, and a flow reaction system partially to melt. 

The vapor pressure at 0° (43 mm.) is generally a sufficient criterion for purity. (The checkers also used infrared spectroscopy and noted a trace of impurity of silicon tetrachloride.) Elemental analysis is readily accomplished by heating a weighed sample at 160° for 18 hours with a slight excess of water in a sealed glass tube. A 15 to 20% excess of water over that required by the equation ... 

The cycloaddition of ketone 54 could be effected in a sealed glass tube in a modified microwave oven to afford the tricyclic system stereoselectively. This major adduct arose via the preferred transition state, in which the nonbonded interactions were minimized, because of the alignment of the dienophile beneath the triene unit furthest from the MOM substituent. This pattern of n-facial selectivity implies that, with the natural C2 stereoselectivity, the preferred geometry should provide the relative stereochemistry required for taxol itself. 

Pyrolysis of z-Bu3Ga <- Sb(z-Bu)3 in a sealed glass tube at temperatures between 275 and 450 °C yielded smooth GaSb films with a uniform film morphology as was determined by SEM (Fig. 49). 

Powdery PNT-N was obtained when the unfluorinated compound was refluxed in diphenyl ether solution. When the temperature was raised to 196°C for 24 h, the amount of solid increased with time and there was no observable change in the appearance ofthe solid. However, in the case ofPNT-F, a black solid formed suddenly between 120- 150°C, and no additional solid formed even when the temperature was increased to 190°C. Apparently the fluorinated derivative reacts much more rapidly and exothermically than the hydrocarbon analogue. Care should be exercised when heating such compounds in sealed glass tubes. 

The specimen turns brown very soon if exposed to the air, and must be kept in a sealed glass tube. 

Chemical transport reactions involving the element and/or an elemental subhalide and a transition metal halide/oxyhalide. The components are heated in evacuated sealed glass tubes at 100-300 °C for a period of days to weeks. Applying a small temperature gradient (10-20 °C) leads to gas phase transport and crystallization at the cooler end of the ampoule [19]. 

All solvents for these solution thermolysis reactions were freshly distilled and all reactions were done in sealed glass tubes heated in a thermostatted oven. Over a wide range of solvents (DMF, naphthalene, diphenylmethane, benzene, toluene, and decalin) there was no significant variation in either isomerization rate or product composition. Reactions were done at 125°C, 155°C and 195°C and the only limitation was that DMF could not be used as the solvent in reactions at 195°C it led to substantial substrate destruction (polymer forming reactions of substrate with DMF ). Isomer compositions were ascertained both by HPLC and by NMR. 

The polymerization of our model substrates was studied by heating neat solid samples of each monomer in sealed glass tubes. No pretreatment of the glass was needed to achieve reproducible results and the sealed... 

F. Wohler 23 found that when chlorine hydrate in a sealed glass tube is exposed to sunlight, it forms two liquids, but does not decompose, since, after a summer s exposure, the two liquids re-form chlorine hydrate when winter returns. The same phenomena occur if the chlorine hydrate is warmed and cooled under similar conditions. A cone. soln. of chlorine water is far less prone to decomposition on exposure to sunlight than is a more dil. soln. J. M. Eder found the same to be the case with bromine water, but he also found that a cone. soln. of chlorine water lost 53 95 per cent, of chlorine while a dil. soln. lost 41 87 per cent, under similar conditions, but he does not state the concentration very exactly. A. Pedler further showed that soln. more cone, than one mols. of chlorine with 64 mol. of water had not decomposed perceptibly after a two months exposure to tropical sunlight, and with that increasing dilution, the action became progressively greater, as illustrated in Table VII. 

E. Klimenko 24 has confirmed the observation that dil. soln. of chlorine water decompose more rapidly than cone. soln. and he has studied the influence of hydrochloric acid and various chlorides on the action of sunlight on chlorine confined in sealed glass tubes. J. Billitzer found that the presence of small quantities of... 

Heating the xenon difluoride hexane mixture to 80-90"C in a sealed glass tube leads to its inflammation. If the xenon difluoride and hexane (1 5 mol) are heated in a Teflon tube at 105 "C, the products are 1-, 2- and 3-fluorohexanes (28 42 30) with a total yield of 15-20%.13 Under the same conditions cyclohexane has been converted to fluorocyclohexane in 18 % yield. 

It forms salts, some of which are expl, eg, the silver salt, AgC7Hs NsO, mw 297.06. N 28.3%, wh voluminous ppt obtained by treating the nitroso compd with ale AgNOa, de-comp ca 224° and expl mildly when heated rapidly in a sealed glass tube above the mp... 

Fig. 6. An example showing the use of gas chromatography and mass spectrometry (GC-MS) for identifying reaction products on zeolites. Styrene was first reacted for ca. 30 min on activated zeolite HY at 298 K in a sealed glass tube the sample was extracted using toluene as solvent, and the extracts were then analyzed with GC-MS. The total ion chromatogram of the extracts (a) shows three major peaks eluting at 13.83, 13.93, and 14.31 min, respectively. The peak at 14.31 min was readily identified as the linear dimer. The peaks at 13.83 and 13.93 min show equal ion intensity and nearly identical mass spectra (the mass spectrum of the 13.93-min peak is shown in (b)), and these were assigned to the cis and trans isomers of the cyclic dimer.

Our own liquid-phase studies were carried out at 50°-100°C., where the products are stable (16, 17). We obtained more information on radical interactions and determined the effects of dilution with CC14. Our oxidations were carried out by heating known amounts of isobutane, initiator, and oxygen (sometimes with solvents) in sealed glass tubes as described above. Nearly all conversions of isobutane were kept below 1%. Experimental data are summarized in Table I. 

Kryptopyrrole is very sensitive to oxidation and should be handled with a minimum amount of exposure to the air. It is best stored in sealed glass tubes. If a capillary ebullition tube is used during distillation under reduced pressure, the tube should be connected to a supply of nitrogen. 

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