Jan. 5, 1961
221
AMINATION WITH HYDROXYLAMINE-0-SULFONIC ACID
[CONTRIBUTION FROM
THE
DEPARTMENT OF CHEMISTRY AND CHEMICAL ENGINEERING, CASEINSTITUTE OF TECHNOLOGY, CLEVELAND 6, OHIO]
Aromatic Amination with Hydroxylamine-0-sulfonic Acid1 BY PETERKOVACIC AND ROBERTP. BENNETT RECEIVED JULY 25, 1960 Hydroxylamine-0-sulfonic acid aminates toluene in the presence of aluminum chloride to yield toluidines (51% ortho, 13y0meta and 36y0 para). From competitive amination, the relative rate ktaluene/kbenaene was found t o be 3.7. A number of reaction variables were investigated-age of the aminating agent, effect of atmosphere, time, catalysts and solvents. The evidence indicates that amination proceeds by electrophilic substitution involving an attacking species of high activity.
Direct aromatic amination has received relatively disagreement with that determined by Keller and little attention. I n 1901, Graebe2 and Jaubert3 Smith who reported that the product consisted of independently reported the amination of aromatic approximately 96% p-toluidine. I n their work, the compounds with hydroxylammonium chloride in orientation was ascertained by separation of the the presence of Friedel-Crafts catalysts. The use isomers by crystallization of their oxalates. It of hydroxylammonium sulfate is described in the would appear that the oxalate method, possessing patent l i t e r a t ~ r e . ~More recently Keller and the inherent weaknesses of a n analytical procedure Smith6-' investigated hydroxylamine-0-sulfonic based upon chemical reaction and crystallization, is acid (HSA) and some of its derivatives. Com- less accurate than infrared analysis. We are unable, pounds other than those in the hydroxylamine however, to reconcile with our results the finding by class have also been used to effect amination. For Keller and Smith that the crude toluidine is conexample, primary aromatic amines were formed* verted in 96% yield t o a n N-acetyl derivative which, from hydrazoic acid and aromatic compounds in the on the basis of melting point, appears to be the presence of strong Lewis acids. Benzene has been p-isomer of rather good purity. aminated by ammonia in a silent discharge t ~ b e . ~ , ' ~ TABLE I The present study was undertaken to investigate more thoroughly the mechanism of aromatic HYDROXYLAMINE-0-SULFONIC ACID AND TOLUENE^ CataTime, Solvent or Toluidine, Yo amination with hydroxylamine-0-sulfonic acid.
Results and Discussion The aminating ability of HSA was fairly extensively investigated by Keller and They found that a variety of aromatic compounds, including benzene, chlorobenzene, toluene and the xylenes, was aminated by this reagent in the presence of aluminum chloride. I n addition, these authors studied the effectiveness of a large number of catalysts, the variation of yield with time of reaction, and the optimum ratio of catalyst to HSR.
hr. 0.5 .5 .5
lyst AlClr AlCla AlCl: AlCls AlCls AlCls
Mole 0.187
.187
.5 1
His01
.20
2
,187 .187 .187 .187
.5
conditions
...... .
Fresh HSA Under NI DMFb TiCV
. . .. . . . .. . . . . .
Yield 50 40 52
