[CONTRIBUTION FROM THE CHEMICAL
LABORATORY, UNIVERSITY
OF TORONTO]
FURFURALNITRIMINE J. W. SUGGITT, G. S. MYERS,
AND
GEORGE F WRIGHT
Received November 4, 1946
When camphoroxime is treated with nitrous acid, the conversion R2CNOH --+
RzCN20zoccurs ( l ) , and this was subsequently demonstrated for a number of terpenoid ketones ( 2 , 3 , 14, 15,4,7, 12). Angeli and his co-workers called these compounds “pernitroso” derivatives and considered them to have structures such as R2C=N-0-NO or R2C=(N0)2. These oxime nitrite or geminal dinitroso structures were discarded (17) by Scholl in favor of his nitrimine structure R2C=N-NOa when he prepared (18) an analogous compound from pinacolone several months after Angeli’s first report. Subsequently Harries and Gley (11) prepared from the oxime of mesityl oxide, I, what Scholl specified as mesityl nit,rimine, 11, on the basis of Harries’ structure proof (10). H3C H
I
H3C H
I
HNoz-+ -
CHI-C=C-C-CHa
CH3
I l l CH3-c=C-C=N-NO2
+
II
N-OH
I1
I
HaC H
I
I
CH2
II
CHII-C=C--C-N-NO
2
I
H
III He realized that the isomeric nitramine structure, 111, was possible, but considered it improbable, since the compounds did not react with phenylisocyanate or diazomethane. Nevertheless, the compounds are soluble (frequently with difficulty) in alkali. This might be expected of 111, though not of 11. Indeed, Angeli, and also Hantzch and Barth (9)) found that the potassium salt of “camphenylnitrimine” yielded a labile isomer, perhaps the nitramine, when acidified. This, however, gradually reverted to the original compound. Despite this evidence for nitrimine structure 11,convertible to the unsaturated nitramine, Fusco and Trisoglio (8) have proposed an alternative structure IV for the nitrosated mesityloxide oxime on the basis of its conversion with hydrochloric acid to 3 ,5 5-trimethyl-3 ,4-dichloro-A’-pyrazoline-2-oxide, V. There is, however, no convincing reason why the product could not be the corresponding 1-oxide) in which case it could quite logically have been derived fromthe nitrimine 11. These workers were perhaps influenced by the fact that oximes of benzaldehyde and furfural will not form nitrimines (13), but principally oxime peroxides. Indeed, an unequivocal demonstration of the nitrimine structure has not been developed. )
373
374
SUGGITT, MYERS, AND WRIGHT
HaC H
I
l
H
CHs
l
CHa-C=C-C=N-NO
-+
I
C1-C-C-CHa
-1
0
N
CHs
c1-c
I
I
I
/ \WN
CHs
kv
In view of these differences in opinion it seemed worth while to prepare a nitrimine of reliable structure. We have succeeded in preparing furfuralnitrimine by the simple condensation of furfural with nitramide without catalyst or solvent. The reaction would not take place with solvent present. The nitramide probably reacted as such, because it could not be replaced by hyponitrous acid, a possible contaminant.
The compound is unstable toward both acids and bases. The low yield (41% ' at 0")resulting when equimolar quantities are used, indicates that a mobile equilibrium exists which is largely in the form of the original reactants. This would explain the sensitivity of furfuralnitrimine to acids and bases, since it would derive these properties from the nitramide to which it could easily revert. This equilibrium was demonstrated by yield increase to 70% with fourfold molar nitramide excess and to 62% with the same molar excess of dry furfural. The addition of furfuralnitrimine to furfural and nitramide depressed the yield expected from these latter reagents. The behavior thus conforms to that expected of a mobile equilibrium. Furfuralnitrimine is reasonably stable (for a furan) when it is dry and, in fact, is best purified by sublimation a t 100". It decomposes in sodium bisulfite solution to give the aldehyde-bisulfite addition compound. It also decomposes in water, slowly at room temperature, but rapidly above 40" with formation of nitrous oxide and furfural. addition of sulfamic acid stabilizes the water solution. The compound gives a strong Franchimont (6) test like all the so-called nitrimines and the nitramines, and it reacts in the Liebermann nitrosamine test like all nitramines to give blue-green and blue-violet colors instead of the pure blue given by nitrosamines. When furfuralnitrimine is treated with phenylhydrazine, a vigorous reaction ensues, and furfural phenylhydrazone is formed. Only 14% of the expected nitrous oxide was isolated. When the same reaction was carried out with camphornitrimine, a colorless, non-oxidizable gas was evolved more slowly than with furfuralnitrimine, but after fifteen minutes, 72% of the theoretical quantity had evolved. The residual oil was shown to be camphor phenylhydrazone by conversion to its picrate.
375
FURFURALNITRIMINE
This hydrazone formation must follow the course and is not unprecedented (16) since hydrazine hydrate will form the corresponding camphorazine. The action of hydrazine hydrate on furfuralnitrimine is, however, much too violent to be useful, while the reaction with phenylhydrazine is controllable. Furthermore, the absence of nitric oxide has more significance when phenylhydrazine is used rather than hydrazine hydrate. Either reagent does, however, demonstrate that the compound with which it reacts is not a primary nitramine, since the latter type of compound will react to form simple salts with phenylhydrazine. The similarity in behavior of camphornitrimine, prepared from an oxime and nitrous acid, with an authentic nitrimine such as furfuralnitrimine supports Scholl's viewpoint, so far as camphornitrimine is concerned. Furfuralnitrimine has no enolizable hydrogen. Its greater instability compared with a compound like camphornitrimine may be owing to the stabilizing effect of a hydrogen bridge in the latter compound, VI. Me
I
CH2-C-
' &-H+O
I
H
H VI On the basis of the present work, Scholl's generalization concerning nitrimines cannot be applied either to his own compound, pinacoline-nitrimine, or Harries' mesityloxide-nitrimine, 11. Neither of these compounds evolved gas, even when warmed to 80", with phenylhydrazine. No other aldehyde or ketone was found to condense with nitramide. Benzaldehyde, thiophenaldehyde, cinnanialdehyde, mesityloxide, salicylaldehyde, butyraldehyde, and heptaldehyde were all recovered unchanged under the same reaction conditions which produced furfuralnitrimine. These failures were probably not owing to a catalytic effect since a trace of furfural did not effect the condensation of mesityl oxide with nitramide, nor did a trace of mesityl oxide decrease the amount of furfuralnitrimine formation in a certain time. Possible catalytic effects of acid or peroxide were also excluded, although acid is otherwise deleterious because it destroys the nitramide unless the temperature is well below 0". For the same reason, bases like pyridine cannot be used a t any temperature. Camphor was also treated with nitramide, and no reaction occurred, but this cannot be considered conclusive since the reaction had to be carried out in ether as a solvent. Under these conditions, furfural would not react with nitramide. EXPERIMENTAL
Mesitylnitrimine. The preparation of Harries was repeated in 57% yield. The purified compound, m.p. 141-142', gave a green Franchimont test with dimethylaniline and a
376
SUGGIW,
MYERS, AND
WRIGHT
green-blue Liebermann test. It was not soluble in cold sodium hydroxide, but it dissolved on warming without decomposition. d-Camphornitrimine. The method of Angeli gave yields of 62-70%. The compound dissolves readily in dilute potassium hydroxide without decomposition, and forms the yellow potassium salt melting at 43". Pinacolinenitrimine. Pinacolonoxime, 4.6 g. (0.04 mole), was dissolved in 50 ml. of dry ether and treated with 4.6 g. (0.05 mole) of freshly distilled, liquid x;204at ice-salt temperatures. After standing 45 hours, the green liquid was separated from the precipitated ammonium nitrate and was washed three times with 5 ml. of 2% aqueous sodium hydroxide solution. After drying the ethereal layer with calcium chloride, vacuum fractionation gave 1.8 g. (32%) of pinacoline-nitrimine boiling at 80-83"/11 mm. A Franchimont test was positive, as was a Liebermann nitroso test. A little of the oil was insoluble in cold dilute potassium hydroxide but formed the salt with conc'd aqueous alkali on warming. Furfuralnitrimine. The heart-cut from three repeated distillations of furfural insured a pure dry material. Nitramide was prepared by the method of Booth (5) and was used immediately while it melted at 72-73', and before i t turned brown i n color. To 0.38 g. (0.004 mole) of furfural at 0" was added 0.25 g. (0.004 mole) of nitramide, which dissolved almost immediately. The mixture solidified gradually during fifteen hours at 0". The product was dissolved by addition of 10 ml. of dry acetone. This was vacuum evaporated into the bottom of a test tube. The residue was washed on to a suction filter with 2.5 ml. of icewater and dried at 50°, weight 0.18 g. or 35% yield, m.p. 114'. If the reaction mixture was washed directly on to a suction filter with water, the added washing (15 ml.) necessary t o remove excess furfural reduced the yield to 310/,, m.p. 115-116'. This unused furfural could however be removed by distillation at 25"/0.001 mm., and the yield thus raised to 42%, m.p. 114". This distillation was necessary when four moles of furfural was treated with one mole of nitramide. The distillation a t 0.0005 mm. was carried out after three hours' reaction time t o leave a residue which was crystallized from a-arm benzene to give a yield of 62a/,, m.p. 116". An excess of four moles of nitramide per mole of furfural a t Oo, gave after eight hours a 72% yield by the water-washing technique, m.p. 115". When one mole of nitramide, one mole of furfural, and 0.5 mole of furfuralnitrimine were let stand at 0" for eleven hours, the yield, after deducting the original addend, was only 21%. K O furfuralnitrimine was obtained when water-n-et furfural was used in the reaction. When benzene was used as the reaction solvent, the yield was decreased to 5% after eighteen hours a t 0". The presence of acid traces like acetic acid and hydrogen chloride did not affect the yield if the temperature was low enough to avoid decomposition of the nitramide. Peroxides like ascaridole likewise had no effect,nor did nitrous oxide. Pyridine in trace destroyed the nitramide immediately. Furfural diacetate would not replace furfural in this reaction. The effect of temperature on reaction rate using equimolar quantities of furfural and nitramide is tabulated for a series of experiments all processed identically t o give products map. 114-116.5". Furfuralnitrimine is soluble in warm benzene and ethanol and very soluble in cold acetone or methyl ethyl ketone. It may be purified by crystallization from warm benzene to yield straw-colored m-edge-shaped crystals, m.p. 116.5", or sublimed a t 100°/10 mm. to melt a t 117". The Barger-Rast molecular weight in acetone was found to be 130 (calc'd 140). Anal. Calc'd for ChHJ20a: C, 42.9; H, 2.86; N, 20.0. Found: C, 43.2; H, 2.81; h', 20.0. Hydrolysis of furfuralnitrimine. A 0.1-g. sample was shaken with 1 ml. of distilled water for twelve hours, forming a completely clear solution with no residual solid. The pH was 5.4 compared with 5.5 for the original distilled water. Spot plate tests for nitric acid by
377
FURFURALNITRIMINE
the "brown-ring" reaction and with brucine in dilute sulfuric, showed no nitrate ion. A poor test for nitrous acid was obtained with a drop of sulfanilic acid and a-naphthylamine; only a pale pink color appeared after standing. The addition of phenylhydrazine to the hydrolysate resulted in the precipitation of fine orange crystals of furfuralphenylhydrazone (m.p. 97'). Furfuralnitrimine on warming with a little water begins to evolve gas a t about 40" with decomposition of all the solid present. Nitrimines with phenylhydrazine. Pernitrosocamphor (m.p. 43O), 0.02 g. (0.OOOl mole) was placed in a small test tube with 0.022 g. (0.0002 mole) of freshly distilled phenylhydrazine, taking care not t o mix the reagents. The tube was then connected to a calibrated gas burette and tilted so that the reagents combined in a closed system. No gas evolution was a t first noticeable but after fifteen minutes a t room temperature (25") the burette showed 1.8 ml. of gas, 72?& of the theoretical quantity. To the reaction mixture, an orangeTABLE I EFPECT OF TEMPERATURE ON REACTION RATE
I
TIXE IN HRS.
70YIELD OF PVPPVPALNITPIXINE
0.25 0.5 2 3 4.5 22 48 75
-180
-100
00
2.0 2.8 17
6.7
25
44 28
44 35 36 TABLE I1 SOLUBILITY OF NITROUS OXIDEIN FURFURAL
TEYPEBATUBE
30 15 0
'c.
1
G.
N10 100 6. F W P W A L
5.0 6.1 7.7
I
ML. N
d 100 G. F W F W A L
280 325 390
brown oil, was added an equivalent volume of ethanol and then alcoholic picric acid. The golden-yellow needles which formed melted at 137" and a mixed melt with authentic dcamphor phenylhydrazone picrate gave no depression of the melting point. Similarly, 0.001 g. (7 x 10-6 moles) of furfuralnitrimine was combined with 0.0015 g. (14 X lW6 moles) of phenylhydrazine a t 29'; after eight minutes, 0.25 ml. of the quickly evolved gas was recorded (14%). Reabsorption of some of the nitrous oxide produced was noticed and since it is very soluble in any furfural present this might account for the low yield of gas evolved. The addition of a little warm 50% alcohol-water subsequently gave red-brown crystals (m.p. 97") which were identified by a mixed melt with an authentic sample of furfural phenylhydrazone. The solubilities in Table I1 were determined by saturation of furfural a t the given temperature until no further change in weight occurred. Qualitative color tests with nitrimines. When Franchimont tests were carried out on mesitylnitrimine, pinacolinenitrimine, pernitrosocamphor, and furfuralnitrimine, a green
378
SUGGITT, MYERS, AND WRIGHT
color which rapidly faded was obtained with dimethylaniline. The ruby color obtained with a-naphthylamine in this test was more permanent. I n the Liebermann nitroso reaction, a known nitroso compound gave a pure deep blue color. hlesitylnitrimine on trial gave a dark green color, while pernitrosocamphor, pinacolinenitrimine, and furfuralnitrimine gave greenish-blue t o violet-blue shades.
Acknowledgment. One of the authors (G. S. &isIgrateful .) for a grant-in-aid from the National Research Council. SUMMARY
A true nitrimine has been prepared from furfural and nitramide. It resembles camphornitrimine in its properties but it behaves differently from the compounds reported as mesitylnitrimine and pinacolylnitrimine. TORONTO, ONTARIO REFERENCES (1) ANGELIAKD RIMINI,Ber., 28, 1077 (1895). (2) ANGELIAND RIMINI,Gazz. chim. ital.,26, 11, 29, 517 (1896). (3) ANGELI,ANGELICO,AND CASTELLANA, Atti. R . accad. Lincei Roma, [5], 12, I, 428 (1903). (Zentr. 1903, 11, 373.) (4) FRANCESCONI AKD ANGELUCCI, Gazz. chim. ital.,31, 11, 302 (1901). (5) BOOTH, Inorganic Synthesis, Vol. I, 68. McGraw-Hill, Kew York 1st edition (1939). (6) FRANCHIMONT, Rec. trav. chim., 16, 226 (1897). (7) FRANCESCONI AND FERRULI, Gazz. chim. ital.,33, 188 (1903). (8) (a) Fusco AND TRISOGLIO, Atti. accad. Italia, Rend. classe scifis., mat. nut., [7] 2, 618, 751 (1941). (b) Fusco AND D’ALo, Atti. accad. Italia., Rend. classe sei fis., mat. nut., [7], 3, 113 (1941). (9) HANTZCH AND DOLLFUS, Bey., 36, 226 (1902). (10) HARRIES, Ann., 319, 230 (1901). (11) H.4RRIES AND GLEY,Ber., 32, 1330 (1899). (12) MAHLAAND TIEMANN, Ber., 29, 2807 (1896). (13) PONZIO, Gazz. chim. ital.,36, 11, 287 (1906). (14) RIhfmI, Gazz. chim. ital.,26, 11, 502 (1896). (15) RIMINI,Gam. chim. ital.,30, I, 596 (1900). (16) SACCARDI A N D LATINI, Ann. chim. applicata, 22, 88 (1932). (17) SCHOLL, Ann. 338, 1 (1904). (18) SCHOLL AND BORN, Ber., 28, 1361 (1895).
