Org. Synth. 1946, 26, 92
DOI: 10.15227/orgsyn.026.0092
SALICYL-o-TOLUIDE
[o-Salicylotoluide]
Submitted by C. F. H. Allen and J. VanAllan.
Checked by H. R. Snyder and R. L. Rowland.
1. Procedure
In a 250-ml. flask attached to a Vigreux column 30 cm. in over-all length (Note 1), a mixture of 42.8 g. (0.2 mole) of phenyl salicylate ("Salol," m.p. 42–43°), 26.7 g. (0.25 mole) of o-toluidine, and 60 g. of 1,2,4-trichlorobenzene (m.p. 15–16°), is heated at the boiling point, so that the phenol formed slowly distils. The temperature rises from 183° to 187° during the first hour, and 22–23 g. of distillate is collected. Heating is continued until the temperature rises to 202° and a total of 45–46 g. of distillate has been collected (Note 2). The flask is then removed, and to it are added 3 g. of Norit and 10 ml. of trichlorobenzene. The mixture is heated to boiling and filtered hot by suction. The filtrate is allowed to stand in the ice chest overnight. The crystalline amide is filtered by suction, slurried with 75 ml. of ligroin (b.p. 90–120°) at 35–40°, and filtered. After being dried to constant weight, the salicyl-o-toluide, m.p. 143–144°, amounts to 33–35 g. (73–77%) (Note 3), (Note 4) and (Note 5).
2. Notes
1.
These are measurements of standard ground-glass equipment.
2.
The checkers preferred
α-methylnaphthalene (Eastman, practical) as the diluent. When it is used in the apparatus described the
phenol does not distil, so that a reaction flask fitted with an
air-cooled condenser is more convenient. The reactants in
60 g. of α-methylnaphthalene are heated in an
oil bath at 230° for 1.5–2 hours.
Three grams of Norit and
20 g. more of α-methylnaphthalene are then added, and the mixture is treated as described under Procedure. The yield and melting point of the product are identical with those described.
3.
Since the pure material
1 melts at
144°, the product needs no further purification for ordinary purposes. It has a faint odor, which can be removed by recrystallization from aqueous
ethanol (suitably by solution in
8–10 ml. of ethanol per gram of material and the addition of water just short of precipitation from the hot solution). The loss in recrystallization is only about 5%; the melting point is unchanged.
4.
By working up the filtrate, only about 2 g. of material of poor quality can be secured.
5.
Other anilides can be prepared by this procedure.
|
|
Amine Used
|
M.p of Anilide
|
Yield, %
|
|
|
Aniline
|
131–132°
|
70
|
|
2,5-Dichloroaniline
|
228°
|
89
|
|
β-Naphthylamine
|
188°
|
84
|
|
2-Aminopyridine
|
206°
|
86
|
|
1-Aminoanthraquinone
|
278–284°
|
79
|
|
When the boiling point of the amine is widely different from that of phenol, a diluent is unnecessary though it facilitates purification. In the absence of a diluent, the hot melt is poured into ethanol and recrystallized, using a decolorizing carbon; there is considerable tendency towards crystallization during the filtration from the charcoal.
Salicylanilide (m.p. 131–132°) is obtained by heating the mixture without a diluent for 3 hours at 180–200° with a short air condenser, pouring the melt into 100 ml. of ethanol, and working up as above. The persistent pink color is not easily removed.
3. Discussion
Salicyl-o-toluide has been prepared only by the action of
phosphorus oxychloride upon a mixture of
salicylic acid and o-toluidine. The useful methods of preparation of
salicylanilide are by the interaction of
salicylic acid and
aniline in the presence of
phosphorus trichloride,
2,3,4 by heating
phenyl salicylate and
aniline,
5 and from
o-hydroxybenzamide and
bromobenzene in the presence of small amounts of
sodium acetate and metallic
copper.
6 A number of these and other anilides have been described.
7
Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)
ligroin
ethanol (64-17-5)
sodium acetate (127-09-3)
aniline (62-53-3)
phenol (108-95-2)
salicylic acid
copper (7440-50-8)
decolorizing carbon,
Norit (7782-42-5)
Phosphorus Oxychloride (21295-50-1)
bromobenzene (108-86-1)
phosphorus trichloride (7719-12-2)
2-aminopyridine (504-29-0)
phenyl salicylate (118-55-8)
1-aminoanthraquinone (82-45-1)
1,2,4-trichlorobenzene (120-82-1)
trichlorobenzene (87-61-6)
α-methylnaphthalene (90-12-0)
2,5-Dichloroaniline (95-82-9)
Salicylanilide (87-17-2)
β-naphthylamine (91-59-8)
o-toluidine (95-53-4)
Salicyl-o-toluide,
o-Salicylotoluide (7133-56-4)
o-hydroxybenzamide (65-45-2)
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