2460
JOHN
F.RROWT”,JR.
to the formation of electrolytes on reaction n-ith oxygen or with light. An attrdctive interpretation of the oxygenation reaction assumes that this represetits an extreme case of attack on the solvent. Much less extensive attack on other solvents, prcsumably involving triphenylmethylperoxy radica126is well established. The present data suggest that a triphenylcarbonium salt of a dinegative anion is formed. I n the absence of knowledge concerning the nature of the anion or even the stoichiometry of oxygen consumption,3f the system cannot be more completely defined. ( 2 6 ) Cf. N. K.Lichtin and G R 7 1 1 o m ~ THISJ O I J R N A L , 76, 3011 (19541. (27) A single rough quantitative oxygenatlon experiment indicated conslimption of 0.7 mole of 01 per mole of hexaphenSlcthanr. Adiiitional experiments by P Pnppns lieldrd rpsults of poor preciw3n
[ COWTRIBUTION FROM
THE
LTol. 79
The product of irradiation 111 the absence of oxygen apparently is different from that obtained 111 other media M herc triI’lienylnietliane d i i t l tliphenyl-bis-diphenyleneethane result from induced disproportionation. X reasonable hypothesis is that generation of conducting species in the present c‘ise involves attack on the solvent but dia,mostic data are not now available. Acknowledgment.-This work was made possible by a Frederick Gardner Cottrell grant by the Research Corporation, Mr. Peter Pappas assisted in some of the experiments. 1-aluable discussions were held with Dr. George R. Thomas. which fell in the raiiqe I ileth in?
;t
0 5 mole of C h per mole of hexaphert
Iiosiov 15, RIlss
GENERALELECTRIC RESEARCH LABORATORY 1
The Reaction of Nitric Oxide with Isobutylene BY JOHN F. BROWN,JR. RECEIVEDNOVEMBER 28, 1956 Nitric oxide containing traces of nitrogen dioxide reacts readily with liquid isobutylene t o give nitrogen and a mixture of nitrated products. This mixture is believed t o contain 6-nitrqisobutylene (22%) ; nitro-t-butanol (9%) ; traces of isobutylene pseudonitrosite, nitro-t-butyl nitrate and a-hydroxyiinbutyraldoxime; and major amounts (6B70) of a substance having the partial structure (nitro-t-butyl)4iY202. The latter is very unstable and decomposes on standing or gentle warming t o give a-nitrotsobutylene and N-(nitro-t-butyl)-hydroxylamine, which also decomposes on standing or heating. Thus, the net result of treating isobutylene with nitric oxide and then distilling the product is the formation of nitroisobutyleiies (74y0) and small quantities of substances having nitro-t-butyl groups joined t o nitro, nitroso, nitrate ester, hydroxyl, hydroxylamino and oximino groups. It is suggested that the (nitro-t-butyl)4NzOn is representative of the unidentified unstable oils which have frequently been obtained by treating olefins with X2OZor N204. A mechanism for the SO-isobutylene reaction is proposed.
In the past, the nature of the reaction between nitric oxide and olefins has been virtually unknown. There are about a dozen references in the technical literature suggesting the possibility of such a reaction, but the only workers to identify any products were Bloomfield and Jeffrey,’ who obtained 1-nitrocyclohexene and cyclohexene pseudonitrosite from cyclohexene. As late as 1949, an authoritative text stated that reactions between nitric oxide and the normal ethylenic double bond did not occur.2 An extensive study of the nitric oxide-olefin reaction lias recently been made in this Laboratory. This study established three general characteristics of the reaction. First, the reaction is initiated by nitrogen dioxide. Scrupulously purified nitric oxide can be stored in contact with liquid olefins for da.ys without reaction, but in the presence of traces of NO%,such as are usually present in nitric oxide, reaction occurs readily with many types of olefins and other hydrocarbon^.^ Second, the product of a nitric oxide-olefin reaction is usually a mixture of the crystalline pseudonitrosite (dimeric nitro nitroso adduct) and an unstable liquid mixture which will undergo a “fume-off’’ or low-order explo( 1 ) G. F. Bloomfield and G. A. Jeffrey, J. Chem. Soc., 120 (1944). (2) N. V. Sidgwick. “The Organic Chemistry of Nitrogen,” T h e Clarendon Press, Oxford, 1940, p. 213. (3) C. A. Rurkhnrd, 1. F.Brown, Jr., C. S. Herrick, R. L. Myers a n d r? T. Xiird., Abstracts of P.ipers, 126th Meeting American Chemical :;oc:rty, Srptcmtier i2-17. 1954, p 41 0.
sion upon attempted distillation. It was found that the decomposition of these liquids could be controlled by steam distillation or passage through a falling film still, but no means of fractionating any significant quantity without decomposition was discovered. Third, the distilled liquid reaction products consist mainly of mixtures of nitroolefins. For example, 1-octene gives 1-nitro-1-octene and 1nitro-2-octene. I n general, the linear olefins give fair yields of both nitroolefins and pseudonitrosites, while the branched olefins give good total yields of nitroolefins but little pseudonitrosite. It was evident, however, that any detailed understanding of the nitric oxide-olefin reaction would require considerably more information about the nature of the reaction products. The present investigation of the products from the nitric oxide-isobutylene reaction was undertaken iii order to obtain such information. Basically, this objective required that a detailed analysis be made on a complex mixture which was changing composition continually during the course of the analysis. In order to accomplish this, a large batch of nitric oxide-isobutylene reaction product was prepared and the stoichiometry of the reaction determined. The product was fractionated, mainly by distillations under mild conditions, until a large number of fractions representing individual compounds or simple mixtures had been obtain1 d. -Inalysi, of tliesc tlien 1;eriiiitted a
l f L i y20, IO;r7 HONO
R E s C T I O N OF
ON-c
7
I
I
0.3%
CC-OH C
NITRICOXIDE
HON=C CC-OH 4 C XV
C
/I cc c
NnOa
ON-c cc-ON02 C
----f
0.670
ozx-c
CC-OK0
02N-c CC-ON02 XIV
NO2
+
c
HzO OzN-c CC-OH c XI11
+
2481
WITH ISOBUTYLENE
stable oil having the partial structure (nitro-t-butyl)dN202 (I) and hence referred to as the RdN202 compound. Upon standing or gentle warming it undergoes elimination and decomposition to give aTABLE I ESTIMATED COMPOSITION OF THE PRODUCT FROM THE REACTION OF NITRICOXIDE WITH EXCESS LIQUIDISOBUTYLENE AT 28’ IntermediInitially a t e present stage
Compound
.. * . 66.4 (Nitro-t-butyl),N~O~ (I) K-(Nitro-t-butyl)-hydroxylamine 1.0 . . 15 (11) 0,N-Bis-(nitro-t-butyl)-hydroxyl.. 0.4 .. amine (111) .. 1.8 .. Nitromethane (IV) .. 0.8 .. Acetone (V) .. 0.2 .. Acetorime (VI) .. 2.3 .. 0-(Nitro-t-butyl)-acetoxime (VII) , . ca. 1 .. Regenerated isobutylene 0.8 .. 1,2-Dinitroisobutane (VIII) .. .. 2 Unidentified ( I X ) 49.7 . . 49 a-Nitroisobutylene (X) 24.2 21.8 21.8 p-Nitroisobutylene (XI) 2.7 2 . 1 2.1 Isobutylene pseudonitrosite ( X I I ) 8.8 8.8 8 . 8 Nitro-t-butanol (XIII) 0.6 0.6 0.6 Nitro-t-butyl nitrate (XIV) 0.3 0.3 0.3 a-Hydroxyisobutyraidoxime (XV) .. 7.3 Liquids b.p. > 100’ (1 mm.) (XVI) I
02N-c CC
+ HNOs
& XI Fig. 1.-Proposed
NO
+
NOi,+ H20
Recycles 4
J
course of the reaction between nitric oxide and liquid isobutylene.
complete identification and estimation of the constituents of the separated fractions. During the fractionation, the refractive indices, infrared spectra and other properties of the mixtures were followed closely in order to detect changes in product composition as they occurred. The nature of the changes that the individual product constituents underwent under the conditions of the fractionation were then determined and used as the basis for estimates of the product composition a t earlier stages. Finally, the resulting estimate of the initial product composition was checked by comparing the stoichiometric ratios which it predicted against those actually observed. Results The results of this investigation are summarized in Table I. The composition “after fractionation” shows corrected analytical values for the aggregate composition of 45 liquid and solid organic fractions separate from the crude product. The composition “initially present” represents these values adjusted for all the changes that were observed to be occurring during the fractionation, while that a t the “intermediate stage” represents a somewhat hypothetical product in which the decomposition of I, the most sensitive constituent, has gone to completion, while that of 11, the next most sensitive, has not yet begun. The major primary product of the reaction between nitric oride and isobutylene is a thick, un-
After fractionation
.
nitroisobutylene (l-nitr0-2-methyl-l-propene~ X) and K-(nitro-t-butyl)-hydroxylamine(11). (CaHsN02)rNzOz + 3c,HrP\’oz
+ (CdHaN0z)NHOH + (HNO)
However, as might be expected for a p-nitroalkylamine,4 I1 is also rather unstable and undergoes three further types of decomposition under conditions like those employed in the fractionation. These may be termed disproportionation, dealdolization and reversion to starting materials. The disproportionation occurs mainly when solutions of I1 are allowed to stand in the cold and gives the 0,N-bis-(nitro-t-butyl)-hydroxylamine (111). Z(C~HsN02)NHOH+ (C&HsNOz)NHO(C4HsN02)
+ “*OH
Dealdolization occurs on heating and results in a cleavage of the I1 into nitromethane and acetoxime. (CHs)zC( CHzN0Z)NHOH +CHjNOz 4-(CH$)zC=NOH
A similar reaction of the dialkylhydroxylamine I11 gives 0-(nitro-t-butyl)-acetoxime (VII) . (CHa)rC(CHzNOz)NHO(CaHsNOz) ----f CH3NOz (CHa)2C=NO( CnHsNO1)
+
The reaction termed “reversion t o starting materials” is a complex autocatalytic process which is induced by heating with nitrogen oxides. It appears to involve the steps (CHa)zC(CHsNO2)NHOH
+ NO2
--f
(CHs)zC(CH7N02)NO (XII) (4) A. Lambert and J. D. Rose, J . C h e w SOC.,1611 (1047).
2182
JOHN
F. BROWN,JR.
Yol. 79
stable oil which produced diisobutylamine and 0hydroxyisobutylamine upon hydrogenation. (CH3)2C(CHiSO2)SO + KO2 --+ There are no prior reports of any R4N20aconiSO (CH3)zC(CH2NOz)S02 ( Y I I I ) pounds, but many preparations of materials having all of the attributes of I have been described in the iCII:V2==CII.! -L S O ----+ Sz, (CI€~j)2C=CJIT02, etc. literature. The addition of “nitrous fumes” or The net result of this process is the formation of 3 2 0 3 to an olefin gives good yields of crystalline gaseous products such as isobutylene, nitrogen and pseudonitrosites in only a few cases; usually, the nitric oxide, along with XII, VIII and considerable major product is a viscous, unstable oil referred to tar. The thermal dissociation and disproportiona- as an “oily nitrosite” or “liquid pseudonitrosite.” tion of the pseudonitrosite, represented by the last The fact that such oils form a-nitroolefins on standthree equations, was examined independently and ing or gentle warming has been recognized for those found to give good yields of dinitroisobutane VIII, obtained from camphene.9 /3-pinene, styrene. along with regenerated isobutylene, X, Nz and NO. indene,l 2 l-methylindene,13 1,1-diphenylethylene’3 Finally, it was noted that a little isomerization5 and l-arylcyclohexenes.14 Since none of these oils of the a-nitroisobutylene (X) to the more volatile were analyzed, none possessed the intense blue /3-nitroisobutylene (XI) occurred during one dis- color characteristic of tertiary nitroso compounds tillation in which the base 11was present. in solution and no isolated pseudonitrosite has By adjusting the values of the final composition ever been observed to undergo a spontaneous elimilisted in Table I for the observed conversions of I1 nation to a-nitroolefin, it seems likely that these and IX into 111-X and XVI, of X into XI and of I oils were not simply different forms of the nitrointo 11, X and probably IX, the composition listed nitroso adducts but were instead R4S?Oz comin Table I as “initially present” was calculated. pounds corresponding to the !nitro-t-butyl~4S202 This composition predicts that the stoichiometric obtained from isobutylene. ratios of isobutylene consumed to nitric oxide conThe R4N202Cornpound.--The RiS20scompound suinrd to nitrogen produced to water produced is thus of interest not only as the majar primary should be 1.00:2.54:0.58:0.063. The observed product of the NO--isobutylenereaction but also as values, 1.00:2.r50:0.60:0.0G4, are within experi- a possible example of an unrecognized major mental error of these and hence provide independ- product in many S20a - and Nz04-olefin reactions. ent support for the estimated initial composition The formation of such products means that mixof the product. tures of NOz, olefin and YO can combine in the ratio 2 : 2 : 1 , as well as in the knomx ratios 1 : 1 : 1 Discussion Relationship to Other Nitrations.-It would (giving pseudonitrosites) and 2 : 1 : I ) (gil-ing nitroappear from Table I that the products of the sates, nitro nitrites arid dinitro compounds). The available data do not seem t o permit an nitric oxide-olefin reaction are qualitatively, though unambiguous structural assignrnent to our R4S202 not quantitatively, the same as those obtained in other olefin nitrations. Except for the hydroxyl- compound, but a fairly good case can bc made for .’R amine derivatives, all of the NO-isobutylene the structure ?X
