Propylene bromide

Methylene bromide. Ethylidene bromide Ethylene bromide. Propylene bromide, Bromoform wo-Butylene bromide 2 3[Pg.296]

In a 3-I. round-bottom flask, a hydrobromic add solution is made by the sulfur dioxide reduction of 480 g. of bromine in the presence of 510 g. of ice water or a mixture is made of 1000 g. of aqueous 48 per cent hydrobromic acid and 300 g. of concentrated su. furic acid. To this are added 385 cc. of aqueous allyl alcohol, which, according to bromine titration, contain 233 g. of pure allyl alcohol. The 3-I. round-bottom flask is fitted with a mechanical stirrer (Fig. 1, p. 4, see also Notes), separatory funnel, and an efficient condenser set for downward distillation. Stirring is started and 300 g. of concentrated sulfuric add are added gradually through the separatory funnel to the warm solution. The allyl bromide distils over completely in about one-half to one hour. The crude allyl bromide is washed with dilute sodium carbonate solution, is dried over calcium chloride and is distilled. The yield of product boiling at 60-72° from a number of experiments varies from 443 to 465 g. (92-96 per cent theory). A small high-boiling fraction is also obtained and examination has shown this to consist of propylene bromide. 

In the preparation of allyl bromide, appreciable loss may occur, not only because of carbonization but primarily because of the reaction of the allyl bromide with hydrobromic acid to form propylene bromide. Stirring during the formation of the alkyl bromide prevents the formation of two layers in the reaction mixture and thus assures a rapid and smooth distillation. An efficient condenser is of course essential. 

The action of propylene bromide and eodium acetacetlc or benzoylacetic esters proceeds as would be expected and methyIcycloprop nc=2-benzoyl-2 acid and methylcyclopropane-2-acetyl-2-acid are the products. The latter on boiling with water loses carbon dioxide with ring cleavage and acetolsobutylalcohol result 1... 

Phosphorus oxychloride, 22 Phosphorus pentachloride, 21, 22 Potassium hydroxide, 29 Propylene bromide, 3, 11... 

The following pairs have neither a maximum nor a minimum vapour pressure water and acetone, ethyl alcohol and acetone, ethyl alcohol and carbon disulphide, acetic acid and benzene, ether and benzene, etc. The following pairs have rectihnear vapour pressure curves benzene and chlorbenzene, benzene and brombenzene, toluene and chlorbenzene, ethylene bromide and propylene bromide. Thus, for very similar pairs, the vapour pressure curve is a straight line. 

A classical example is a mixture of ethylene bromide (EB) and propylene bromide (PB). Figure 5.2a shows the partial and the total pressures of these mixtures as a function of the mole fraction of (PB) at 85 °C, Based on the work of von Zawidzki (1900) quoted by Guggenheim (1952). These two components clearly cannot be considered as being identical, or very similar. Yet, the fact that they form an SI solution in the entire range of compositions is equivalent... 

Figure 5.2 The partial vapor pressures and the total pressure of a system of (a) ethylene bromide (EB) and propylene bromide (PB) as a function of composition x (mole fraction PB) at T— 85 °C, based on data by von Zawidski (1900) cited by Guggenheim (1952) (b) benzene (B) and bromobenzene (BB) at 80 °C. Note that although the two components have widely different vapor pressures the mixture is nearly SI. (Based on data from McGlashan and Wingrove 1956.)...

Chem. Soc. 87, 859 (1905) Johnson, McEwen, Org. Syn. 5, 99 (1925). By gentle heating of propylene bromide with bromine in the presence of iron wire Kronstein. Ber. 54, 7 (1921) Tapley, Giesy, J. Am. Pharm. Assoc. 15, 173 (1926) by reaction of bromotrichloromethane with allyl bromide initiated by y-rays Heiba, Anderson, J. Am. Chem. Soc. 79, 4940 (1957). 

Colorless liquid d 5 1.9712 bp 60 167° (mp —36°) 1.5249, Slightly sol in water (1.68 g/t at 30 ) sol in ale, ether. Upon prolonged heating trimethylene bromide dec and part of it is converted to propylene bromide (1,2-dibro-mopropane). Boiling with water yields trimetbylene glycol. 

There are not many systems that even approximately follow Raoult s Law. Even those systems that do approximately follow Raoult s Law such as benzene-toluene and ethylene bromide-propylene bromide will be found to have small deviations if very accurate measurements are made. Raoult s Law is an ideal concept that real systems are compared to. 

---