In a
2-l. flask are placed
512 g. (4 moles) of naphthalene and
275 g. (170 cc.) of carbon tetrachloride. The flask is equipped with a stirrer, an
efficient reflux condenser, and a
dropping funnel, the stem of which extends below the level of the liquid. From the top of the reflux condenser a tube leads to a
water trap similar to that described in
Fig. 7 on p. 97. The mixture is warmed on a
steam bath to gentle boiling, and
707 g. (220 cc., 4.4 moles) of bromine is run in at such a rate that practically none of it is carried over with the
hydrogen bromide into the trap. This requires from twelve to fifteen hours, during which time the mixture is gently warmed on the steam bath, with continual stirring, until the evolution of
hydrogen bromide ceases (about six hours). The mixture is now distilled from the steam bath under slightly reduced pressure (using a condenser) until free of
carbon tetrachloride; the residue is mixed with
20–30 g. of powdered or granulated sodium hydroxide and stirred at 90–100° for four hours (Note
1). The liquid is transferred to a flask for fractional distillation and distilled under reduced pressure. The forerun contains a considerable proportion of unchanged
naphthalene, the bulk of which is removed by chilling and filtering with suction; the main fraction,
consisting of
bromonaphthalene, passes over at
132–135°/12 mm. (
145–148°/20 mm.), and a high-boiling fraction, consisting of
dibromonaphthalene, is collected. The intermediate fractions and the filtrates from the foreruns are systematically redistilled; in this way
600–620 g. of colorless
α-bromonaphthalene (
72–75 per cent of the theoretical amount) and about
30 g. of a mixture of dibromonaphthalenes (m.p., about
60°) are obtained.