Residual reaction exotherm solvent

Solution polymerizafion. Highly exothermic reactions can be handled by this process. The reaction is carried out in an excess of solvent that absorbs and disperses the heat of reaction. The excess solvent also prevents the formation of slush or sludge, which sometimes happens in the bulk process when the polymer volume overtakes the monomer. The solution process is particularly useful when the polymer is to be used in the solvent, say like a coating. Some of the snags with this process its difficult to remove residual traces of solvent, if that s necessary the same is true of catalyst if any is used. This process is used in one version of a low-pressure process for high-density polyethylene and for polypropylene. 

A pressure safe glass bottle containing 7.4 g (0.05 mol) of potassium thio-phenoxide and 50 mL of dimethylformamide is placed under vacuum The bottle IS charged with 2 7 bars of bromotnfluoromethane and shaken for 3 h. The reaction is slightly exothermic. The mixture is poured in 100 inLof 17% hydrochloric acid The aqueous phase is extracted with hexane. The organic layer is washed with water and dried over potassium carbonate The solvent is evaporated, and the residue is distilled to give 5 5 g (62%) of trifluoromethylthiobenzene (bp, 77-78 C at 754 mm of Hg). 

A solution containing 741 g (5.0 mols) of 1-phenyl-2-propylidenylhydrazine, 300 g (5.0 mols) of glacial acetic acid and 900 cc of absolute ethanol was subjected to hydrogenation at 1,875 psi of hydrogen in the presence of 10 gof platinum oxide catalyst and at a temperature of 30°C to 50°C (variation due to exothermic reaction). The catalyst was removed by filtration and the solvent and acetic acid were distilled. The residue was taken up In water and made strongly alkaline by the addition of solid potassium hydroxide. The alkaline mixture was extracted with ether and the ether extracts dried with potassium carbonate. The product was collected by fractional distillation, BP B5°C (0.30 mm) yield 512 g (68%). 

A solution of 13.5 g (21 mmol) of diisopinocamphenylborane in 250 mL of hexane is treated at 0 C with 7.1 g (47 mmol) of trifluoromethanesulfonic acid in a dropwise fashion which results in the evolution of hydrogen gas. The mixture is stirred for 3 h at 0 "C and then at r.t. overnight. At OX the reaction proceeds with slow, but steady, hydrogen evolution without problem (an induction period which results in a rapid exotherm in the Mukaiyama procedure has been reported30). After stirring overnight, a small amount of solid material appears. The solvent is evaporated and the residue is used without further purification 99.8% ee. 

During evaporation of solvent hydrogen fluoride, an exothermic reaction between residual ketone and bromine trifluoride set in and accelerated to explosion. 

Carbon disulphide was used as an extraction solvent when analysing epoxy resins. On one occasion, adding to a hardener produced a vigorous fume-ofif leaving a residue looking like sulfur [1], Amines and complexes thereof are used as hardeners, and the reaction with, especially, polyamines to give dithiocarbamates is surprisingly exothermic [2],... 

Dining chlorination of styrene in carbon tetrachloride at 50°C, a violent reaction occurred when some 10% of the chlorine gas had been fed in. Laboratory examination showed that the eruption was caused by a rapid decomposition reaction catalysed by ferric chloride [1], Various aromatic monomers decomposed in this way when treated with gaseous chlorine or hydrogen chloride (either neat, or in a solvent) in the presence of steel or iron(III) chloride. Exotherms of 90°C (in 50% solvent) to 200°C (no solvent) were observed, and much gas and polymeric residue was forcibly ejected. 

TeClf catalysed Friedel-Crafts aromatic alkylation (typical procedure. To a solution of 1-phenylethanol (3.7 g, 30 mmol) in toluene (30 mL) is added slowly TeCl4 (9.7 g, 36 mmol), keeping the temperature at 25°C (exothermic reaction). Small amounts of white precipitate appear immediately, and after a few minutes the colour of the mixture becomes dark brown. The mixture is stirred for 3 h and then quenched with HgO (20 mL). The organic layer is separated, washed with brine (2x20 mL) and dried (MgS04). Evaporation of the solvent leaves an oily residue which is distilled under vacuum, giving a mixture of 1-phenyl-1-tolylethanes (4.9 g (83.3%) b.p. 117-128°C/1 torr). GLC analysis (silicone OV-101, 0.24 mm X 30 m capillary column at 100-260°C, 4°C min i) reveals an ortholpara ratio of 12 88. 

The reaction mixture is cooled in a water-ice bath, and a saturated aqueous ammonium chloride solution is added at such a rate as to maintain the temperature below 35°C. Ammonium chloride solution is added in portions until addition produces no further exothermic reaction (Note 3). The supernatant solution is decanted through glass wool onto 400 g of ice in a 4-L separatory funnel. The residual solids are washed with three portions of hexane, approximately 1000 nt total, and the washes are decanted into the separatory funnel. After the phases are separated, the aqueous phase is washed with an additional 500-mL portion of hexane. The combined organic extracts are washed with 500 nl of saturated ammonium chloride, and then with 500 nl. of brine. The organic layer is dried over anhydrous magnesium sulfate and filtered. Most of the solvent is removed by a rotary evaporator and the residual oil is distilled at reduced pressure using an ice water-cooled fraction cutting head. After a small forerun, approximately 390-392 g (94% of theory) is collected as a colorless oil, bp 116°C/1.6 nm (lit. 155°C/17 rim). ... 

The monazite sand is heated with sulfuric acid at about 120 to 170°C. An exothermic reaction ensues raising the temperature to above 200°C. Samarium and other rare earths are converted to their water-soluble sulfates. The residue is extracted with water and the solution is treated with sodium pyrophosphate to precipitate thorium. After removing thorium, the solution is treated with sodium sulfate to precipitate rare earths as their double sulfates, that is, rare earth sulfates-sodium sulfate. The double sulfates are heated with sodium hydroxide to convert them into rare earth hydroxides. The hydroxides are treated with hydrochloric or nitric acid to solubihze all rare earths except cerium. The insoluble cerium(IV) hydroxide is filtered. Lanthanum and other rare earths are then separated by fractional crystallization after converting them to double salts with ammonium or magnesium nitrate. The samarium—europium fraction is converted to acetates and reduced with sodium amalgam to low valence states. The reduced metals are extracted with dilute acid. As mentioned above, this fractional crystallization process is very tedious, time-consuming, and currently rare earths are separated by relatively easier methods based on ion exchange and solvent extraction. 

To a stirred mixture of 7.4 gm (0.1 mole) of l-butyl alcohol and 13.0 gm (0.2 mole) of sodium cyanate in 50 ml of benzene is slowly added 15.5 ml (0.21 mole) of trifluoroacetic acid. The reaction is exothermic and some gas bubbles are formed. The reaction is stirred for 3 hr, then 15 ml of water is added, the organic layer separated, dried, the solvent removed under reduced pressure at a pot temperature of 40°-50°C the resulting residue solidifies to afford 10.7 gm (92%), m.p. 98°-101°C. Recrystallization of the entire product from water affords 8 gm (69%), m.p. 107°-108°C. 

To 1,3-diazadiene 5 (10 mmol) was slowly added dropwise a solution of MC l BA (12 mmol) in anhyd CHClj (20 111L) at rt. An exothermic reaction ensued and decolorization occurred as an indication of the end of the oxidation. The solution was washed with coned itq NaIIC03 (lOmL), H20 (10 ml.,), and then dried (Na2S04). After removing the solvent, the residue was recrystallized (hexane) to give the product 6. 

L, round-bottomed flask equipped with a magnetic stirrer, reflux condenser, and a 250-mL addition funnel are placed 56.3 g (0.26 mol) of MCPBA (80%) and 350 mL of dichloromethane. The suspension is stirred and a solution of 38.0 g (0.16 mol) of 9-n-butyl-1,2,3,4,5,6,7,8-octahydroacridine in 120 mLof dichloromethane is added rapidly (exotherm). When the reaction mixture ceases to boil gently from the heat of reaction, it is heated to extend the reflux period to a total of 2.5 hr. The reaction mixture is cooled to room temperature, extracted with 0.5 M aqueous sodium hydroxide (4 x 450 mL), and dried over anhydrous sodium sulfate. The drying agent is removed by filtration, the filtrate is concentrated with a rotary evaporator, and the residual solvent is removed at 0.1 mm pressure to afford 40 g (99%) of yellow crystalline product, mp 96-100°C. 

To a solution of 3.4 g of KOH pellets in 75 mL boiling EtOH, there was added a solution of 10.0 g 2,5-dimethoxythiophenol in 60 mL EtOH followed by 10.9 g ethyl bromide. The reaction was exothermic with the immediate deposition of white solids. This washeated on the steam bathfor 1.5 h, added to 1 LH O, acidified with HC1, and extracted with 3x100 mL CH2C12. The pooled extracts were washed with 100 mL of 5 % NaOH, and the solvent removed under vacuum. The residue was... 

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