Weygand/Hilgetag Preparative Organic Chemistry

Addition of halogen to C-C multiple bonds 137
as can be recognized by failure of a sample to oxidize KI. The CaCO3 is filtered off and the
solution saturated with NaCl and extracted with ether. The yield is 52% and the b.p. 64.0 to
64.8°/30 mm.
Bis-(3-cMoro-2-hydroxypropyl) ether: 273 CO2 is led into a mixture of diallyl ether
(0.25 mole), water (2.51), and 35% calcium hypochlorite solution (102 g, 0.25 mole) at 3°
with stirring and cooling. A dry-ice condenser is placed on the reaction flask to prevent
loss of diallyl ether. The hypochlorite is consumed in 2 h, then a further amount (51 g) is
added and CO2 is passed in with stirring for a further 2 h. The solution is filtered from
CaCO3, saturated with NaCl, and extracted with ether. The yield is 94.4% and the b.p.
is 150-165°/3 mm or, after a further distillation (138-139°/1 mm).
As well as these simple methods, there are others for preparation of hypochlorous acid
solutions suitable for addition of HOC1, such as passage of Cl2 into an ice-cold slurry of
freshly precipitated HgO 274 or NaHCO3 in ice-water 275 or of bleaching powder and K2CO3
in water. 276
The following procedure may be used for preparing an approximately 20 % hypochlorous
acid solution (HOC1) from chlorine hydrate and HgO: 277 * 278 Chlorine is passed to saturation
into water that is stirred vigorously and cooled in ice-salt freezing mixture. The precipitated
chlorine hydrate is filtered off and mixed, with stirring, with sufficient HgO (about 3/4 of
its weight) to give an aqueous solution and remove the smell of chlorine. This solution is
filtered and distilled at room temperature and 12 mm. The distillate, which contains up to
20% of HOC1, is kept in the dark in the frozen state; it is stable for several months at —10°.
For addition of HOC1 the olefins are stirred with 0.125-0.5 m-HOCl at 10°.
The yields of chlorohydrin from 1-alkenes of higher molecular weight are
considerably increased by addition of pyridine and sulfuric acid (initial pH
6-6.5) 278 . Chlorohydrins of higher molecular weight are also, accessible by
reaction of alkyl hypochlorites with the olefin in an aqueous medium; tertbutyl
hypochlorite (a yellow oil, b.p. 77-78°/760 mm) is suitable for this
purpose; it is obtained by passage of chlorine into tert-butyl alcohol in aqueous
sodium hydroxide at 0-20°.
terf-Butyl hypochlorite may decompose violently under the influence of intense light,
rubber, or overheating! Its preparation (see above) is described in Organic Syntheses; 119
it is important that the temperature and rate of passage of chlorine be controlled; at temperatures
above 20° there is danger of explosions. 280
For addition of HOBr the unsaturated compound is usually stirred for some
hours at room temperature with bromine water, then the excess of hypobromite
is removed by sodium hydrogen sulfite, the solution is saturated with salt,
and the bromohydrin is shaken out of the aqueous phase into ether or CHC13.
A cold solution of hypobromite obtained from bromine and alkali carbonate
may be used in place of bromine water. 281 The tendency of styrene to bromohydrin
formation is so great that a>(bromomethyl)benzyl alcohol is obtained
in excellent yield even in hot water (60-90°) by use of a bromine solution in the
presence of KBr. 261 ' 282
273 J. R. Roach and S. E. Miller, /. Amer. Chem. Soc, 71, 2667 (1949).
274 W. Markovnikov, Ann. Chem., 336, 314 (1904).
275 A. Wohl and H. Schweitzer, Ber. Deut. Chem. Ges., 40, 94 (1907).
276 E. Bamberger and W. Lodter, Ann. Chem., 288, 81 (1895).
277 S. Goldschmidt, Ber. Deut. Chem. Ges., 52, 758 (1919).
278 A. Guyer, A. Bieler, and E. Pedrazzelli, Helv. Chim. Acta, 39, 423 (1956).
279 H. M. Teeter and E. W. Bell, Org. Syn., 32, 20 (1952).
280 C. P. C. Bradshaw and A. Nechvatal, Proc. Chem. Soc, 1963, 213; cf. Org. Synth.,
44, 26 (1964).
281 E. Berner and C. N. Riiber, Ber. Deut. Chem. Ges., 54, 1954 (1921).
282 J. Read and W. G. Reid, J. Chem. Soc, 1928, 1487.