Hot reactions

Rinse the walls of the flask with a httle water and complete the reaction by heating the mixture (which consists of two layers and a precipitate of sodium chloride) on a boiling water bath for 15 minutes with vigorous mechanical stirring. Pour the hot reaction mixture into 1500 ml. of glacial acetic acid contained in a 4-htre round-bottomed flask rinse the flask with 250 ml. of acetic acid. Cool the solution in an ice bath to 5° (11), stir mechanically, and add a solution of 125 g. of sodium nitrite in 250 ml. 

Vote 3. If more HMPT is used the yield of the cumulene will be lower the compound can remain longer in the hot reaction mixture, where it can polymerize. Mote 4. It is essential to follow the instructions given. The reaction sometimes starts very soon if in such a case the desired pressure (10-20 mmHg) has not yet been achieved, part of the cumulene may polymerize in the hot reaction mixture. 

CVD processing can be accompanied by volatile hot-reaction by-products such as HCl or HF, which, along with unused precursor gases, must be removed from the exhaust gas stream. This is done by scmbbing the chemicals from the gas using water to dissolve soluble products or by burning the precursor gases to form oxides. 

Safety is often a primary concern in CVD processing because of the ha2ardous nature of some of the gases and vapors that are used and the hot reaction products generated. 

Monocalcium phosphate [10031-30-8] Ca(H2P0 2 H2O, used in baking powder (see Bakeryprocesses and leavening agents), is crystallized from a hot reaction mixture of concentrated (electric furnace) phosphoric acid and lime, or it is made by spray-drying a slurry of the product of reaction of lime and phosphoric acid (14). 

This heating prior to distillation obviates the necessity of intermediate isolation of the carbinol. The dehydration is evidenced by small explosions when the water drops on the hot reaction mixture. 

The hot reaction mixture is poured with stirring over about 0.75 1. of crushed ice in a 2-1. beaker. The beaker is filled with water, and the mixture is stirred to dissolve inorganic salts (Note 5). The insoluble red-brown solid is collected on a suction filter. This crude product, even while damp, is transferred to a 2-1. round-bottomed flask, and 500 ml. of a mixture of 75% (375 ml.) of petroleum ether (b.p. 90-100°) and 25% (125 ml.) of benzene is added. The flask is provided with a reflux condenser, and the mixture is heated at reflux for 15 minutes by means of an electric mantle (Note 6). The resulting solution is decanted into a second 2-1. flask, leaving in the first flask some water and a red-brown solid residue. Po the slightly cooled liquor in the... 

The following example illustrates in detail the preparation of amino benzoic acids from the hot reaction product obtained by the oxidation of a xylene and containing a mixture of salt, amide salt and diamide of a phthalic acid. 

A mixture of 800 g of potassium o-bromo-benzoate, 1,500 ml of bis-(2-methoxyethyl)ether, 355 g of N-ethyl-morpholine, 375 g of 2,3-dimethylaniline, and 30 g of cupric acetate is heated gradually with stirring to 140°C over a period of 90 minutes. The hot reaction mixture is then acidified with 260 ml of concentrated hydrochloric acid and the acidified mixture divided into 2 equal portions. One liter of water is added to each portion and the mixtures allowed to cool. The N-(2,3-dimethylphenyl)anthranllic acid which separates upon cooling is collected by filtration and recrystallized from bis(2-methoxyethyl)ether MP 229° to 230°C (corr.). 

Pour the hot reaction mixture onto 4 liters of crushed ice. Pour slowly and stir the ice mixture. What remains in the flask can be worked up by adding ice to it and swirling the contents. After approximately % of an hour, the solid is filtered and washed with approximately 600 ml water. 

This same conclusion was reached for this system by Siekierska, Halpem and Siuda who were, in addition, able to include hot reactions in their analysis, as was shown in Table 4. 

Analysis of soluble Pd by ICP. A series of reactions was initiated according to the procedure described above. After 20 s, 1 min, 3 min or 1 h, the hot reaction mixture was passed quickly through a 0.45 pm syringe filter to remove solid BaCei cPd c03.x, then the solvent was removed under reduced pressure. A mixture of BaCei cPdx03. cand K2CO3 in IPA/H2O, heated at 80 °C for 1 h, was subjected to the same workup procedure. Each of the solid residues was suspended in 12 mL 10 M aqueous HCl. The mixtures were filtered to produce clear solutions for subsequent analysis on a Thermo Jarrell Ash (TJA) High Resolution ICP spectrometer. A ICP standard solution of Pd (Aldrich) was diluted to 10 ppm for use as the high standard. 

Maitlis filtration test. To investigate whether the Pd-doped perovskite is the actual catalyst, or a reservoir of soluble Pd, a Maitlis filtration test (10) was performed. The reaction of 4-bromoanisole with 4-phenylboronic acid, catalyzed by BaCeo 95Pdo os02 95, was intemipted at 20 s and 1 min, corresponding to conversions of 16 and 45%, respectively, by filtering the hot reaction mixture to remove the solid perovskite. The filtrates were allowed to cool to room temperature without stirring. After 3 h, the biatyl yields in both samples were estimated to be 100% by H NMR. 

The first stage of a reaction involved the addition of sodium dispersed in toluene to a solution of adipic ester in toluene. The subsequent addition of iodomethane (b.p. 42°C) was too fast and vigorous boiling ejected some of the flask contents. Exposure of sodium particles to air caused ignition, and a violent toluene-air explosion followed [ 1 ]. When a reagent as volatile and reactive as iodomethane is added to a hot reaction mixture, controlled addition, and one or more wide-bore reflux condensers are essential. A similar incident involving benzene was also reported [2]. 

Aryloxy-l,2-diarylethanones can be cyclodehydrated to diarylbenzofurans by heating with sodium acetate and acetic anhydride in polyphosphoric acid. Quenching the hot reaction mixture with water leads to initially violent acid-catalysed hydrolysis of the excess anhydride. 

A challenge of a different kind was encountered in the internal vinylation of various vinyl triflates and bromides as depicted in Eq. (11.13) [27]. The electron-rich structures obtained from the reactions were of interest for further use in Diels-Alder reactions, but the risk of degrading the products in the hot reaction medium posed a problem and a prudent choice of energy input was imperative. It turned out that single-mode microwave heating for 5 min at the very low power of 5 W was sufficient to yield 64% of the product with excellent regioselectivity. Measurements with a fluor-optic probe revealed an unexpectedly high temperature of 76 °C [27]. 

Most tars in the product gas are destroyed by thermal cracking as they pass through the hot reaction zone, and the raw product then exits the gasifier at high temperature. The particulate levels in the product gas are typically low due to the absence of turbulence in the gasifier, but the gas may contain alkali vapors as it exits the hot reaction zone. 

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