Theoretically toluene should yield three isomeric mono sulphonic acids,
in which the entering sulphonic acid group occupies the positions
ortho, meta, or para to the methyl group.
The action of sulphuric acid on toluene was first investigated by
Jaworsky, (Ztschr. Chem. 1,272), who described one toluene sulphonic
acid as the resulting compound. In 1869 Engelhardt and Latschinoff
(Ibid. 617), heated toluene with sulphuric acid and made and studied
the potassium salt of the resulting acid. They obtained two forms, and
identified them by fusion with caustic potash which converted them into
the ortho and para cresols, showing that sulphonation had taken place
in the positions ortho and para to the methyl group.
Barth (Ann. chem. (Liebig) 152,91), working similarly but fusing under
different conditions which also caused oxidation of the methyl group to
a carboxyl group obtained para hydroxy benzoic acid and salicylic acid
(ortho hydroxy benzoic acid.) This also proved that the sulphonic acid
group had entered in the ortho and para positions.
Anna Wolkow (Ztschr. Chem (1870) 321), confirmed this work but ascribed
the meta position to the sulphonic acid that passed into salicylic
acid. She also made two acid chlorides and amides and recorded their
melting points.
Fittig and Ramsay (Ann. chem. (Liebig) 168,242) studied this result
of Anna Wolkow, and to determine and settle the constitutions of the
sulphonic acids, carefully prepared and purified their sulphonic
acids; they proved definitely that no meta acid was formed, and that
the products were only the ortho and para toluene sulphonic acids.
Hubner and Post (Ann. chem. (Liebig) 169,47) worked on pure para brom
toluene, and obtained two para brom toluene mono-sulphonic acids, one
of which they proved to be the ortho acid by removal of the bromine by
metallic sodium, and oxidation to salicylic acid. By exclusion they
decided that the other acid must be one containing the sulphonic acid
group in meta position to the methyl group.
F.C.G. Müller (same as Hubner and Post) made the barium salt of ortho
brom toluene sulphonic acid, and then removed the bromine by treatment
with sodium amalgam. The excess of alkali was removed by sulphuric
acid, the sodium sulphate removed by evaporation and crystallization,
and the residue dried. On treatment with phosphorus pentachloride
an oily toluene sulphonchloride was obtained; this was decomposed
by heating with water, the hydrochloric acid removed by repeated
evaporations, and the syrup thus obtained evaporated to a crystalline
condition. Several salts were made and studied. His amide melted at
90-91. Because this acid differed in properties from the two previously
mentioned, Müller considered it to be the meta toluene sulphonic acid.
About this time F. Gervor (Ann. chem. (Liebig) 169,383), made ortho
diazo toluene sulphonic acid by subjecting ortho toluidine sulphonic
acid to nitrous fumes. This was decomposed with alcohol under
pressure, and a sodium salt of the acid obtained; this was converted
into the chloride and an amide which melted at 148, differing in this
and other properties from the amides of the ortho and para toluene
sulphonic acids previously known.
In 1874 Pechmann (Ibid., 173,195) obtained a quantity of para toluidine
meta sulphonic acid by heating para toluidine with sulphuric acid,
and crystallizing out the para toluidine ortho sulphonic acid and
disulphonic acids, leaving the meta acid in solution because of its
greater solubility. The diazo compound was made by treatment of the
acid in alcoholic suspension with nitrous fumes, and decomposed with
alcohol under pressure. Various salts of the resulting sulphonic
acid were made and studied, also the chloride and amide which melted
"somewhere below 100".
In 1875 Pagel (Ann. chem. (Liebig) 176,297) working on ortho toluidine
sulphonic acid, made a toluene sulphonic acid which resembled Muller’s.
His amide melted at 104.
In 1877 Beckurts (Ber.d.che. Ges. 10, 943), seeking for a good method
of obtaining pure ortho toluene sulphonic acid, heated toluene and
sulphuric acid in the ordinary way, and made the potassium salts of the
resulting acids. By treatment with phosphorus pentachloride he obtained
the acid chlorides which he separated by cooling to -15, and filtering
off the solid para compound. The remaining liquid was transformed into
an amide and purified by fractional crystallization. Two compounds
were obtained with sharp melting points of 153 and 104. From this work
he concluded that the sulphonation of toluene yielded all the three
possible acids.
Fahlberg (Am. Chem. J. 1, 170), doubted Beckurts’ statement, because
although his acid showed different properties he neglected to prove
its constitution by converting it into the hydroxy benzoic acid. He
therefore repeated Beckurts’ work, and identified the amide melting at
154 as coming from ortho toluene sulphonic acid, by conversion into
salicylic acid. The other amide with a sharp, constant melting point
of 108 was oxidized, and the products separated and identified as para
sulphamine benzoic acid, anhydro ortho sulphamine benzoic acid, and
acid potassium ortho sulphobenzoate. These were the products one would
expect from an oxidation of a mixture of the ortho and para toluene
sulphonamides. Further proof that his acid was a mixture was obtained
by mixing amounts of pure ortho and para toluene sulphonic acids, and
by repeated crystallizations a form was obtained which melted at 108.
F.H.S. Muller (Ber. d. chem. Ges. 13, 1348), mentioned the formation of
meta toluene sulphonic acid by the action of sulphurous acid upon the
corresponding diazo compound, but gave no details except the melting
points of his amide, anilide, and toluide.
Claesson and Wallin in 1879 (Ibid. p. 1848), claimed that they had
obtained meta toluene sulphonic acid by the action of chlorsulphonic
acid upon toluene. They used very large quantities of materials. They
obtained three acids, and identified them as the ortho and para,
and called the third the meta acid, despite the fact that they had
knowledge of Fahlberg’s work.
The next step was undertaken by R. Otto (Ibid, 13, 1292), at the
request of Beckurts. He examined some of the latter’s supposed meta
toluene sulphonamide, and found it to be a mixture of the amides of the
ortho and para acids.
Nevile and Winther (Ibid. 13, 1940), while investigating the formation
of amino sulphonic acids, obtained a toluene sulphonic acid by heating
ortho diazo toluene sulphonic acid with alcohol under pressure, and
also by reducing brom toluene sulphonic acid with sodium amalgam. It
was converted into the chloride and amide,--the latter melting at
106.5-107.5.
In 1886, Valin (Ibid. 2952), convinced by the work of Otto that
Fahlberg’s views were correct, and that he and Klason had not obtained
meta toluene sulphonic acid, again attacked the problem; an acid was
made and salts described.
In 1891, Metcalf (Am. Che. J. 15,301) (Dissertation, 1892), proved
that decomposition of para diazo toluene meta sulphonic acid with
ethyl alcohol under pressure resulted in the formation of para ethoxy
meta toluene sulphonic acid in far greater quantity. Consequently the
toluene meta sulphonic acid could not have been obtained by either
Pechmann or Valin.
Griffin, (Dissertation, 1895), prepared what he thought was a solution
of the meta toluene sulphonic acid from the amide, and made and studied
several salts as well as the anilide and toluide. However he did not
investigate his solution to find out what it contained, but went ahead
on the assumption that he had a solution of this acid. It is on the
basis of his lack of investigation that I am working.
The derivatives of para toluene sulphonic acid have been made and
studied by Newell, (Dissertation, 1895), and are being investigated
further. He prepared para tolyl phenyl sulphone by the Friedal-Crafts
reaction, para phenyl sulphone benzoic acid by oxidation of the
sulphone with chromic acid, its salts, chloride, amide, and anilide,
and para benzoyl diphenyl sulphone from the acid by the Friedal-Crafts
reaction, and studied their reactions and properties.
The analogous derivatives of ortho toluene sulphonic acid were made
and studied by Canter, (Dissertation, 1900). He prepared ortho tolyl
phenyl sulphone by the Friedal-Crafts reaction, ortho phenyl sulphone
benzoic acid by oxidation of the sulphone by potassium permanganate,
its chloride, amide, and anilide, and ortho benzoyl diphenyl sulphone
from the acid by the Friedal-Crafts reaction.
The analogous derivatives of the meta toluene sulphonic acid with one
or two exceptions have not been made or studied, nor has the acid
itself been prepared in a form which could be recognized. The following
derivatives of meta toluene sulphonic acid have been made and studied;
the amide by Müller, Pechmann, Pagel, Beckurts, F.H.S. Muller, Nevile
and Winther, Chase Palmer, Klason, Valin, Noyes and Walker, Metcalf,
and Griffin; meta sulphamine benzoic acid by Limpricht and Uslar,
and Griffin; meta toluene sulphon anilide and toluide by Muller and
Wiesinger, (Ber. d. chem. Ges, 12,1348), and by Griffin; the latter
also made and studied several metallic salts.
The literature on the ortho and para toluene sulphonic acids and
their derivatives is voluminous, and covers a great many derivatives
which have been thoroughly studied and whose structure has been
determined. The literature on meta toluene sulphonic acid is very
meagre, comparatively, and all that could be found is mentioned in this
paper. This would seem to indicate that investigators have avoided
this series, and apparently the reason is due to the difficulties
encountered in isolating the free acid.