Org. Synth. 1933, 13, 90
o-PROPIOPHENOL AND p-PROPIOPHENOL
[Propiophenone, o- and p-hydroxy-]
Submitted by Ellis Miller and Walter H. Hartung.
Checked by W. W. Hartman and L. J. Roll.
In a 2-l. three-necked, round-bottomed flask, fitted with a reflux condenser, a mechanical stirrer (Note 1), and a 100-cc. dropping funnel, are placed 374 g. (2.8 moles) of anhydrous aluminum chloride and 400 cc. of carbon bisulfide (Note 2). To the stirred suspension is added slowly through the dropping funnel 375 g. (2.5 moles) of phenyl propionate (Note 3). Reaction sets in almost at once with the evolution of hydrogen chloride (Note 4), and the carbon bisulfide begins to reflux from the heat of reaction (Note 5). When all the propionate is in (one and one-half hours is required), the mixture is further heated to gentle refluxing on a steam bath until the evolution of hydrogen chloride has practically ceased (about two hours). The reflux condenser is then turned downward, and the carbon bisulfide is distilled. The steam bath is replaced by an oil bath which is heated to 140° and maintained at 140–150° for three hours (Note 6). During this period a fresh evolution of hydrogen chloride takes place. The mixture thickens and finally congeals to a brown resinous mass. Stirring is continued as long as possible (Note 7).
The solid is then allowed to cool, and the aluminum complex is decomposed by slowly adding first a mixture of 300 cc. of concentrated hydrochloric acid with 300 cc. of water and then 500 cc. of water (Note 8), whereupon a black oil collects at the surface. After standing overnight in the ice box, a large portion of this layer solidifies and can be separated by filtration. This solid (p-propiophenol) is recrystallized from 400 cc. of methyl alcohol. The yield is 129–148 g. (34–39 per cent of the theoretical amount) of a light yellow product melting at 145–147°. A second recrystallization raises the melting point to 147–148°.
The oily filtrate combined with the concentrated mother liquors of the above recrystallization is dissolved in 500 cc. of 10 per cent sodium hydroxide and extracted with two 100-cc. portions of ether to remove non-phenolic products. The alkaline solution is acidified with hydrochloric acid and the oily layer is separated, dried over anhydrous magnesium sulfate, and distilled. The o-propiophenol boils at 110–115°/6 mm. The yield is 120–132 g. (32–35 per cent of the theoretical amount). About 40 g. of p-propiophenol boiling at 135–150°/11 mm. is obtained. The total yield of crude p-propiophenol is thus 169–188 g. (45–50 per cent of the theoretical amount) (Note 9).
The stirrer should be made of sturdy glass rod, bent preferably in the shape of a golf-club head
, to provide for heavy duty when the reaction mass becomes thick.
was used as a solvent the products were always tarry.
Crude, undistilled phenyl propionate
, made by gently heating a mixture of equivalent quantities of phenol
and propionyl chloride
until hydrogen chloride
evolution ceases, is satisfactory for rearrangement. The ester can also be made conveniently by slowly adding one mole of thionyl chloride to a mixture of 1.05 moles each of phenol and propionic acid
, driving off all the hydrogen chloride
and sulfur dioxide
, and distilling.
Because of the large volume of hydrogen chloride
evolved, it is desirable to work under a good hood
. If this is not available, the gas-trap
described on p. 4
may be used.
The addition of the phenyl propionate
is regulated so as to maintain gentle refluxing.
The temperature of the reaction mixture is about ten degrees lower than the bath temperature, or 130–135°. The reaction temperature determines the yield ratio of the two isomers. In general, higher temperature (above 160–170°) favors the formation of the ortho isomer.
It is necessary to stir the thickening mass continuously to permit the escape of hydrogen chloride
formed during the heating; otherwise it may swell rapidly and choke the outlets of the flask.
This decomposition is strongly exothermic, and the dilute acid should be added slowly.
The above procedure has been found satisfactory for the preparation of a number of the homologs of o- and p-propiophenol
, such as aceto-, butyro-, and caprophenol
Ortho and para propiophenols
have been previously prepared by condensing propionic acid
in the presence of zinc chloride
and from phenol
and propionyl chloride
The procedure described above is an adaptation of one described by Cox3
and by Hartung, Munch, Miller, and Crossley.4
In an alternative procedure phenyl propionate
is added directly to aluminum chloride
; no solvent is used.5
This preparation is referenced from:
Chemical Abstracts Nomenclature (Collective Index Number);
aceto-, butyro-, and caprophenol
Ortho and para propiophenols
Propiophenone, o- and p-hydroxy-
o- and p-Propiophenol
hydrochloric acid (7647-01-0)
methyl alcohol (67-56-1)
sodium hydroxide (1310-73-2)
thionyl chloride (7719-09-7)
propionic acid (79-09-4)
sulfur dioxide (7446-09-5)
aluminum chloride (3495-54-3)
zinc chloride (7646-85-7)
magnesium sulfate (7487-88-9)
propionyl chloride (79-03-8)
phenyl propionate (637-27-4)
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