Laboratory Methods of Organic Chemistry - Sciencemadness Dot Org

CHAPTBK VI
PHENOLS AND ENOL8. KETO-ENOLTAUTOMEEI8M
1. CONVERSION OF A SULPHONIC ACID INTO A PHENOL
/3-NAPHTHOL 1
MATERIALS required: 70 g. (0-3 mole) of sodium naphthalene-
/3-sulphonate, 2 210 g. of sodium hydroxide, 20 c.c. of water.
The sodium hydroxide is powdered and, along with the water, is
heated with stirring in a copper or nickel crucible to 280°. The
thermometer, which is at the same time the stirrer, is enclosed in a
copper or nickel tube about 16 cm. long and 0'8 cm. wide.
The bulb of the thermometer, which is maintained in
position by a bored cork, dips into a layer of oil 1 cm.
thick. (See Fig. 55.) Goggles and gloves must be worn. As
soon as the temperature has reached 280° the sodium
naphthalenesulphonate is added rather rapidly with stirring
; heating is continued with a somewhat smaller flame
and the temperature is maintained between 260° and 280°.
After all the salt has been added, the flame is raised
somewhat, causing the molten material to become more
viscous as steam is evolved and bubbles are formed.
Finally, at 310°, the reaction proper sets in. After the
temperature has been kept at 310°-320° for about five minutes
the material becomes more mobile and the reaction is over.
The molten material is at once poured in a thin layer on to
a thick copper plate the edges of which have been bent slightly
upwards. The dark-coloured upper layer consists of the sodium
salt of naphthol. After it has cooled, the material is powdered
and dissolved in water, the naphthol is precipitated from the solution
with concentrated hydrochloric acid, and, after cooling, is extracted
1 E. Fischer, Anleitung zur Darstellung orgamseher Praparate, 9th ed., Braunschweig,
1920. Zeitschnft fur Chemie, 1867, 10, 299.
2 Or the equivalent weight of naphthalene-/3-sulphomc acid, prepared according
to O. N. Witt. See p. 195.
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