Hydrogen bromide, liquid

Other halogen carriers may be used, e.g., 1-2 g. of iron filings, or 1 g. of aluminium amalgam. The bromine must then be added slowly from a dropping funnel to the benzene warmed on a water bath the apparatu.s shown in Fig. II, 13, 9 is suitable and a trap for the hydrogen bromide must, however, be inserted into the top of the condenser. After all the bromine has been introduced, the mixture is heated on a water bath until no red vapours are visible above the liquid. The Subsequent procedure is as above. 

Equip a 1 litre bolt-head flask with dropi)ing fuuncl and a double surface reflux condenser to the top of the latter attach a device (e.g.. Fig. II, 8, 1. c) for the absorption of the hydrogen bromide evolved. Place 100 g. (108 ml.) of dry iso-valeric acid (Section 111,80) and 12 g. of pmified red phosphorus (Section 11,50,5) in the flask. Add 255 g. (82 ml.) of dry bromine (Section 11,49,5) slowly through the dropping funnel at such a rate that little or no bromine is lost with the hydrogen bromide evolved the addition occupies 2-3 hours. Warm the reaction mixture on a water bath until the evolution of hydrogen bromide is complete and the colour of the bromine has disappeared. Pour off the liquid reaction product into a Claisen flask and distil mider the reduced pressure of a water pump. Collect the a-bromo-wo-valeryl bromide at 117-122°/25-30 mm. The yield is 150 g. 

Most metals, concrete, and other constmction materials are corroded by hydrobromic acid. Suitable materials of constmction include some fiber glass-reinforced plastics, some chemically resistant mbbers, PVC, Teflon, polypropylene, and ceramic-, mbber-, and glass-lined steel. Metals that are used include HasteUoy B, HasteUoy C, tantalum, and titanium. The HasteUoys can only be used at ambient temperatures. Liquid hydrogen bromide under pressure in glass at or above room temperature can attack the glass resulting in unexpected shattering. 

Reaction of two or more gases to make a liquid or solid, for example, ammonia plus hydrogen bromide to form ammonium bromide. 

In a 2-1. three-necked, round-bottomed flask fitted with a liquid-sealed mechanical stirrer, a dropping funnel, and an efficient reflux condenser are placed 720 g. (226 cc., 4.5 moles) of bromine (Note i) and 1.5 g. of sulfur (Note 2). A glass tube is connected to the top of the condenser to carry the evolved hydrogen bromide to a gas trap (Org. Syn. 14, 2). Sixty-nine grams (69 cc., 0.52 mole) of dry paraldehyde (Note r) is added slowly, with stirring, over a period of about four hours. The reaction proceeds under its own heat during the addition of the paraldehyde subsequently the mixture is heated externally for two hours at 60-80°. The solution is distilled and a fraction collected over the range 155-175° (Note 3). 

Halogens Although tantalum is severely attacked by flourine at room temperature it does not react with liquid chlorine, bromine and iodine up to 150°C and the metal suffers no appreciable attack in wet or dry bromine, chlorine and iodine below 250°C. It is virtually uncorroded by hydrogen bromide and hydrogen chloride below 370°C, attack starting at about 375 and 410°C respectively. 

During dropwise addition of the bromide to the liquid alcohol, the mechanical stirrer stopped, presumably allowing a layer of the dense tribromide to accumulate below the alcohol. Later manual shaking caused an explosion, probably owing to the sudden release of gaseous hydrogen bromide on mixing. 

To protect the vacuum pump from damage a dry ice-acetone trap and two liquid nitrogen traps are necessary to condense and solidify the hydrogen bromide evolved. 

A. 1 -Bromo-3,3-dimethoxypropane (Note 2). Into a flame-dried, fared, 1-L, round-bottomed flask containing 500 mL of methylene chloride (CH2CI2) (Note 3) at 0°C is bubbled anhydrous hydrogen bromide for approximately 15 min (33.0 g, 0.408 mol of HBr absorbed) (Notes 4,5). Acrolein (22.9 g, 27.2 mL, 0.408 mol) is added rapidly (30 sec) via syringe to the stirred solution (Note 6). After 2 min, a solution of 86.6 g (89.3 mL, 0.816 mol) of trimethyl orthoformate (Note 7) in methanol (100 mL) is introduced into the reaction mixture via cannula over 5 min. The reaction mixture is stirred for 10 min at 0°C, and solid anhydrous calcium carbonate (12.0 g, 0.120 mol) is then added in one portion. The reaction mixture is stirred for an additional 1 hr, the solution is filtered, and the filtrate concentrated under reduced pressure to ca. 50 mL. The residue is distilled through a 25-cm Vigreux column under reduced pressure to give, after a forerun of variable amount (-10 mL) (Note 8), 38.8 g (52%) of 1-bromo-3,3-dimethoxypropane as a colorless liquid, bp 67-69°C at 24 mm (Note 9). 

Evidence in support of a carbonium ion type of mechanism for low temperature polymerization was also obtained in an investigation of the kinetics of the homogeneous liquid phase polymerization of propene in the presence of aluminum bromide and hydrogen bromide at about —78° (Fontana and Kidder, 89). The rate of reaction is approximately proportional to the concentration of the promoter, no polymerization occurring in its absence. During the main portion of the reaction, the rate is independent of the monomer concentration toward the end, it decreases, due apparently to the low-concentration of the monomer, addition of more olefin resulting in an increase in the rate. It was concluded that the reaction involves an active complex, which may be regarded as a carbonium ion coupled with an anion ... 

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