HYDROGEN BROMIDE 47% solution

Allyl chloride is then converted to cliloro-brom-propane by heating in a sealed tnbo with a slight excess of cone, hydrogen bromide solution at 100° for seven to eight hours. The mixture is then washed, dried and fractionated. 

A mixture of 2-(di-n-propylamino)-5-methoxy-2,3-dihydro-lH-phenalene, (1.65 g 5.55 mmol), released from the hydrochloride salt, and 20 ml of 48% aqueous hydrogen bromide solution was heated for 15 min in an oil bath at 125°-130°C. The reaction mixture was evaporated, the residue was dissolved in a minimum amount of methanol, diethyl ether was added until the mixture became cloudy, and the mixture was filtered through a filter aid (CELITE) to remove some oily impurity. The filtrate was diluted with diethyl ether and seeded. There was obtained 1.28 g (63% yield) of the 2-(di-n-propylamino)-2,3-dihydro-IH-phenalen-5-ol hydrobromide, melting point 233°-234°C (dec.). 

Caesium Brom-palladite, Cs2PdBr4, is precipitated as a dark brown mass on mixing concentrated solutions of caesium bromide and palladous bromide.2 Upon recrystallisation from dilute hydrogen bromide solution, fine reddish brown needles are obtained, which are anhydrous, and very soluble in wrater. 

Epoxy resins are characterised by two or more epoxy groups in the structure. To cure an epoxy resin with a suitable hardener, accurate estimation of epoxy groups is crucial. Epoxy equivalent is defined as the amount of resin that contains one mole of epoxy. Epoxy equivalent of an epoxy sample is determined by a standard titration method [6] using hydrogen bromide solution in acetic acid. The method is briefly described next. 

About 100 mg of anhydrous sodium carbonate, 20 ml of chlorobenzene and 10 ml of glacial acetic acid are taken in an Erlenmeyer flask and magnetically stirred until all the carbonate dissolves. Four drops of 0.1% solution of crystal violet in acetic acid are added. The purple-coloured solution is titrated with hydrogen bromide solution (prepared by diluting about 6 ml of commercial reagent with 250 ml of acetic acid). The titre value is noted at the blue-green end point. About 300 mg of epoxy sample is titrated in a similar way. A blank titration is also carried out without any sample. 

The oxidative bromination of Cs-Cg olefins can be carried out using a system composed of catalytic thallium(iii) oxide (0.2 M of Tl(iii)) and a vanadium-based heteropolyacid cocatalyst (HPA-n = H3+ PMOi2 V 04o n = 2-8) in the presence of hydrogen bromide solution (1.0 M of Br ) and oxygen as co-oxidant. The HPA-n cocatalyst can promote oxidation of thal-lium(i) to thallium(iii) in the presence of bromide ions. For instance, the reaction of 1-hexene with the thallium(iii)/HPA-6/bromide system at 100 °C and 8 bar of oxygen led to a mixture of 1,2-dibromohexane and hex-enebromohydrin along with a small amount of 2-hexanone in different ratios. In the absence of thallium(m) species, the oxidation process proceeds slowly, presumably due to the HPA-6 anion-mediated oxidation of bromide to bromine. 

Hydrogen Bromide, anhydrous Hydrogen Bromide Solution 1048 1788 15 60 Hydroquinone Hydrosilicofluoric Acid 2662 53... 

A solution prepared by dissolving 2 g. of biomine in 100 g. of carbon tetra. chloride is satisfactory. Carbon tetrachloride is employed because it is an excellent solvent for bromine as well as for hydrocarbons it possesses the additional advan. tage of low solubility for hydrogen bromide, the evolution of which renders possible the distinction between decolourisation of bromine due to substitution or due to addition. 

SO, + 2H,0 + Br, — HjSO, + 2HBr Alternatively, the acid mixture may be obtained from the reaction between potassium bromide solution and concentrated sulphuric acid below 76° the potassium hydrogen sulphate crystallises out and is removed by filtration ... 

I hour. Finally raise the temperature of the bath to 65-70° for a further 45 minutes or until all the bromine has disappeared (no red vapours visible) and the evolution of hydrogen bromide has almost ceased. Keep the solution of hydrogen bromide in the beaker (2). 

Lead dioxide in acetic acid solution gives lead tetra acetate which oxidises hydrogen bromide (and also hydrogen iodide), but has practically no cflFect under the above experimental conditions upon hydrogen chloride. 

Bromine test. Dissolve 0 2 g. or 0 2 ml. of the compound in 2 ml. of carbon tetrachloride, and add a 2 per cent, solution of bromine in carbon tetrachloride dropwise until the bromine colour persists for one minute. Blow across the mouth of the tube to detect any hydrogen bromide which may be evolved (compare Sections III,6 and 111,11). 

Names such as hydrobromic acid refer to an aqueous solution, and percentages such as 48% HBr denote the weight/volume of hydrogen bromide in the solution. 

Metaldehyde [9002-91-9] a cycHc tetramer of acetaldehyde, is formed at temperatures below 0°C in the presence of dry hydrogen chloride or pyridine—hydrogen bromide. The metaldehyde crystallizes from solution and is separated from the paraldehyde by filtration (48). Metaldehyde melts in a sealed tube at 246.2°C and sublimes at 115°C with partial depolymerization. 

Bromination of aldehydes (qv) is more compHcated because bromination can take place on the aldehyde carbon as weU as the a-carbon. Acetals are brominated satisfactorily in cold chloroform solution in the presence of calcium carbonate, which reacts with the hydrogen bromide formed (24). 

A. 2-f2-Bmmoetkyl)-l,3-diozane (1), A 2-L, three-necked flask Is equipped with a mechanical stirrer, thermometer, and gas Inlet tube. In the flask are placed 750 ml of dichloromethane, 112 g (2.00 moll of acrolein (Note 1), and 0.10 g of didnnamalacetone Indicator (Note 2) under nitrogen. The yellow solution is cooled to 0-5°C with an Ice bath. Gaseous hydrogen bromide (Note 3) is bubbled Into the solution with stirring until the Indicator becomes deep red (Note 4). The Ice bath is removed and 1.0 g of p-toluene-sulfonic acid monohydrate and 152.2 g (2.00 mol, 144 mL) of 1,3-propanediol (Note 11 are added. The yellow solution is stirred at room temperature for 8... 

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