1548
BAILEY EXPERIMENTAL
All measurements were performed using a Cary Recording Quartz Spectrophotometer, model 11 M S. Solutions were prepared with 95% ethanol. The author wishes to thank Messrs. Raymond J. Shuba and Peter R. Segatto for obtaining the spectral data. (106) E. A. Braude, W. F. Forbes, and E. A. Evans, J . Chem. SOC.,2202 (1953). (107) J. Gripenberg, Acta Chem. S c a d . , 5, 995 (1951). (108) A. C. Cope, M. Burg, and S. W. Fenton, J . Am. Chem. Soe., 74, 173 (1952). (109) G. Eglinton and M. C. Whiting, J. Chem. Soc., 3052 (1953). (110) PI. A. Plattner, A. Fiirst, A. Eschenmoser, W.
Keller, H. Klaui, St. Meyer, and M. Rosner, Helv. Chim. Acta, 36, 1845 (1953). (111) W. Kuhn and H. Schinz, Helv. Chim. Acta, 35, 2008 (1952). (112) W: Kuhn and H. Schinz, Helv. Chim. Acta, 35, 3395 (1952).
VOL.
22
Samples of ethyl 2,3-dimethyl-5-carbethoxy-6-one-2heptenoate, ethyl 2,3-dimethy1-5-carbethoxy-6-01-2-heptenoate and 5-carboxy-2,3-dimethyl-6-hydroxy-2-heptenoic acid 1,6-lactone were generously provided by Prof. Roger Adams.a2 The sample of pcyclogeranic acid was kindly furnished by Dr. William J. Houlihan and recrystallized from petroleum ether, m.p. 94'; reporkdud m.p., 93-94'. Cyclohexylideneacetic acid was prepared by the procedure of Wallach; rectangular prisms from petroleum ether, m.p. 92-93'.Me-12s Methyl 9-ethyLEhexenoate. A solution of 2-ethyl-2hexenoic acid (Carbide) (100 g., 0.70 mole), 700 ml. of methanol and 50 ml. of concentrated sulfuric acid was allowed to stand at ca. 3" (refrigerator) for one week. The excess methanol was removed in vacuo at 30°, water added, and the ester separated, washed with sodium bicarbonate solution, water and dried. Distillation gave 84 g. (77%) of ester, b.p. 77-78" (15 nun.), n'," 1.4444.'24
NEWBRUNSWICK, N. J.
(113) E. R. H. Jones, T. Y . Shen, and M. C. Whiting, J . Chem. SOC.,763 (1951); the structure of this compound
(119) L. G. Humber and W. I. Taylor, J . Chem. SOC., 1044 (1955). was not established. (120) P1. A. Plattner, A. Fiirst, and K. Jirasek, Helv. (114) H. Heusser, K. Eichenberger, and P1. A. Plattner, Chim. Acta, 29, 730 (1946). (121) P. Bagchi, F. Bergmann, and D. K. Banerjee, Helv. Chim. A c h , 33, 1088 (1950). (115) J. Romo and A. Romo de Vivar, J . Am. Chem. SOC., J . Am. Chem. SOC.,71,989 (1940). 79. 1118 11957). (122) Ch. A. Vodoz and H. Schinz, Helv. Chim. Acta, (116) D. H. hey, J. Honeyman, and W. J. Peal, J . Chem. 33, 1040 (1950); the authors suggest the presence of some ,&y-isomer in the sample. SOC.,185 (1954). (123) Wallach, Ann., 365, 261 (1909), reports m.p. 91(117) D'. I).'E. Newman and L. N. Owen, J . Chem. Soc., 4713 (1952).
(118) R. Ruegg, J. Dreiding, 0. Jeger, and L. Ruzicka, Helv. Chim. Acta, 33,889 (1950).
[CONTRIBUTION FROM
THE
92'. (124) M. Hiiusermann, Helv. Chim. Acta, 34, 1482 (1951) reports b.p. 66-69' (10 mm.), n y 1.4403.
RESEARCH AND D E V E L O P ~ N DIVISION T O F HUMBLEOIL AND REFINING COMPANY]
Ozonolysis of Cyclohexene in Methanol PHILIP S. BAILEY'
Received June 17, 1967 The ozonolysis of cyclohexene in methanol yields polymers of the expected methoxy hydroperoxide. Whenever an aldehyde is formed along with an alkoxyhydroperoxide during ozonolyses in alcohol solvents, it is to be expected that the two will interact.
Criegee and ~o-workers~-~ have shown that ozonolysis of olefins cleaves the double bond to produce an aldehyde or ketone (I) and a zwitterion (11). If the solvent is methanol, the zwitterion (11)reacts with the solvent to produce a methoxy hydroper-
R
R
(1) For reprints of this paper, address the author at the Department of Chemistry, The University of Texas, Austin, Tex. (2) R. Criegee and G. Wenner, Ann., 564, 9 (1949). (3) R. Criegee and G. Lohaus, Ann., 583,6 (1953). ( 4 ) R. Criegee and G. Lohaus, Ann., 583, 12 (1953).
oxide (111).Until recently all of the cases studied using methanol as solvent were those in which I was a ketone. A compound which during ozonolysis would yield an aldehyde as fragment I is phenanthrene. The initial product from the ozonolysis of phenanthrene in methanol is the methoxy hydroperoxide IV.6 It was isolated, however, in the form of the cyclic hemiperacetal Val produced by addition of the hydroperoxy group to the carbonyl group of IV.5b When kept in solution a t room temperature the hemiperacetal reacted further with the solvent to form the peracetal Vb.It is of interest to determine whether such interactions are general during ozo( 5 ) (a) P. S. Bailey, J . Am. Chem. SOC.,78, 3811 (1956). (b) P. S. Bailey and S. B. Mainthia, Results to be published shortly.
DECEMBER
1957
1549
OZONOLYSIS OF CYCLOHEXENE
nolysis, or whether the situation in compound IV is unique.
A simpler compound with a double bond similar to that of the 9,lO bond of phenanthrene is cyclohexene. Criegee and coworkersa have ozonized cyclohexene in inert solvents and have obtained a 6% yield of a monomeric ozonide. The rest was largely a polymeric peroxidic material. Three patents have been issued for the ozonolysis of cyclohexene in methanol.71~ The peroxidic ozonolysis product was analyzed but no structure was assigned t o it. It was described as a complex mixture of monomeric alkoxy peroxides and hydroperoxides. In the present work the ozonolysis of cyclohexene in methanol has been repeated and the product has been shown to be a mixture of polymeric peroxides of types VI and VI1 and/or methylated products intermediate between VI and VII. These are produced by an intermolecular interaction of the
H-C-(
b
'
CH2)4-&-0-0H
\
-6-(
not give simple alkoxy hydroperoxides as final products upon ozonolysis in alcohols as solvents. Instead, hemiperacetals and peracetals from intermolecular or intramolecular interactions generally will be produced. An exception is the ozonolysis of 1,2-dibenzoylethylene. The aldehyde fragment, phenylglyoxal, forms acetals with the solvent preferentially. Structure VI is entirely in the hemiperacetal form. Structure VI1 was produced by reaction of VI with methanol, whereby the aldehyde group WL~B converted to an acetal group and the hemiperacetal groups were converted t o peracetal groups. When the cold reaction mixture from the ozonolysis of cyclohexene was evaporated immediately, and was kept cold during the evaporation, the residue was found to be rich in VI. When, however, the reaction mixture was allowed to stand for a period of time at room temperature before evaporation, the residue was found t o be rich in VII. These products could not be separated and purified. Decomposition, resulting in loss of the peroxidic function, occurred during attempted distillation. The mixtures were sufficiently characterized, however, by elemental analyses, cryoscopic molecular weight determinations, methoxyl group determinations, infrared spectra, and decomposition t o adipic acid by hydrogen peroxide in formic acid solution.
CHz)r-6-0-&
4I
bH
hydroperoxy and aldehyde groups of the methoxy hydroperoxide (VIII). This is t o be contrasted wit11 the intramolecular interaction found in the caae of the hydroperoxide (IV) from ozonolysis of phenanthrene. This difference in behavior of the two hydroperoxides is to be expected on the basis that the two interacting groups in IV are in close proximity, whereas they are not in VIII. It appears that compounds which yield an aldehyde as fragment I do
H
VI
H-C-(
li
/OCH;( CHa)4-C-O0H H
VI11 CH( OCH& (AH&
CHaO-
H-C-(
I
AI - e o -
( ) CH( OCH&
((/&I4
-
-0-0-
XCHa I
-0OH
H
C"dbC& IX
CH( OCH&
L!
- -0OH
I
H (6) R. Clriegee, G. Blust, and G. Lohaus, Ann., 583, 2 (1953). (7) (a) R.E. Foster and H. E. Schroeder (to E. I. du Pont de Nemours and Co., Inc.) U. S. Patent 2,657,240 (Oct. 27, 1953). (b) E. I. du Pont de Nemours and Go., Inc., British Patent 713,344 (Aug. 11,1954). (8) E. E. Fisher (to E. I. du Pont de Nemours and Co., Inc.) U. S. Patent 2,733,270 (Jan. 31, 1956).
CH&-
x H
X
Hydrogen peroxide in basic solution gave only a trace of adipic acid. The fact that a high yield (85%) was obtained in formic acid is excellent evi(9) P. S. Bailey and S. S. Bath, J. Am. Chem. Soc., 79, 3120 (1957).
1550
VOL. 22
BAILEY
TABLE I ANALYTICAL DATAFOR PEROXIDIC PRODUCTS Sirup from Immed. evap.
%C 50.67,50.42 %H 9.15, 9.07 %O voActive 0 % OCHI 26.30,25.95 Mol. Wt. Infrared Strong OH band Spectrum a t 2.951.1 Medium C=O band a t 5 . 8 ~
Theor. for Structure V I (x = 1)
Theor. for Structure VI1 (x = 1)
Sirup from Evap. after 1 hr.
Sirup from Evap. after 4 days
50.88,50.74 8.98, 9.09 38 .O, 37.4 7.44, 7.31
51.94,51.74 9.14, 9.26
51.84 8.70 39.46 9.86
53.55 9.35 37.10 8.56
51.90 9.68 38.42 7.68
36.21,36.02 402,a 5 8 8 Strong OH band a t 31.1 Weak C=O band at 5.75~
41.51,40.92 393a Strong OH band a t 3p Weak C=O band at 5.75~
19.14 486
38.75 56 1
44.71 208
Theor. for StructureIX
a Molecular weight determination by boiling point elevation of benzene. Performed by Miss Jennie M. Chenet of Humble. Molecular weight determination cryoscopically in benzene-probably more accurate, since less chance of decomposition a t the lower working temperature. Performed by Mr. S. B. Mainthia of University of Texas.
dence for the peracetal formulation, which would be readily hydrolyzed under acidic conditions. The high methoxyl group content also speaks for this formulation. Only one other possible polymeric peroxide (X) would have such a high methoxyl group content. Not being a peracetal, however, it would not be expected to be hydrolyzed and oxidized t o adipic acid in so high a yield. The infrared spectra showed a strong hydroxyl band a t 3 p , an extremely weak carbonyl band a t 5.8 p and no band a t 9.4-9.6 p , the region which both CriegeelO and Brinerll and their co-workers have found to be characteristic of ozonides. The molecular weight determinations indicated that the polymers (VI and VII) were primarily trimeric. It is to be noted, however, that in the case of the sample which had stood for four days befofe evaporation of the solvent, the methoxyl group content is so high that one must assume the presence of considerable amounts of the completely methoxylated monomer IX. If this is so, it is reasonable t o assume that the mixtures are composed of monomers (VI11 and/or IX), dimers, and polymers (VI and/or VII) in which "x" varies from 1 to 4 or 5. The analytical data are summarized in Table I. EXPERIMENTAL
The ozone source was a Welsbach T-23 laboratory ozonator. Oxygen dried to a dewpoint of -60" or below was employed. The ozonolysis flask was essentially a tube with the gas inlet at the bottom, a sealed-in fritted disc just above the inlet, and the outlet near the top. The cyclohexene was Phillips Pure (99yo) grade. The peroxidic ozonolysis products. A stream of oxygen containing approximately 6yo ozone by weight was passed through a solution of 4.1 g. (0.05 mole) of cyclohexene and 50 ml. of anhydrous methanol at a rate of approximately f 10'1 R. Crierree. - , A. Kerclrow. and H. Zinke. Chem. Ber., 88, 1878 (1955). (11) E. Briner and E. Dallwigk, Compt. rend., 243, 630 (1956); Helv. Chim. Acta., 39, 1446 (1956).
20 liters per hour and a temperature of approximately -70". The ozone was completely absorbed until one mole per mole of cyclohexene had reacted, after which the gas stream released iodine in the potassium iodide trap adjoining the ozonolysis flask, I n one case the methanol was immediately evaporated from the cold solution at 0.5 mm. pressure, using a Rinco rotary evaporator. The residue was a clear, very viscous sirup weighing 8.9 g. I n two other cases the reaction mixture was allowed to stand for 1 hr. and for 4 days before evaporation. The residual sirups were less viscous and weighed 9.5 g. and 9.9 g., respectively. All three samples strongly oxidized iodide ion to iodine and slowly released oxygen from lead tetraacetate. The latter is a weak, but positive, test for a hydroperoxide.12 Analytical data is summarized in Table I. I n another experiment an attempt was made to purify the sirup by fractional distillation a t 0.5 mm. The clear distillate (b.p. 90-118') gave only weak peroxide tests with sodium iodide. Throughout the distillation gas evolution occurred from the sirup in the still. Attempts were then made, on a fresh batch of the sirup, to prepare crystalline derivatives, such as an oxime, a semicarbazone, and a 2,4dinitrophenylhydrazone involving the carbonyl group and a 3,5-dinitrobenzoate and benzoate involving the hydroperoxy group. I n each case loss of the peroxidic property occurred. Under the alkaline conditions necessary for oxime and semicarbazone preparations no crystalline material was obtained, indicating that the aldehyde group was involved in acetal formation. Conversion to adipic acid. The ozonolysis was carried out on a. 0.05 mole sample and the methanol evaporated as described in the preceding experiments. The peroxidic residue (9.1 9.) was dissolved in 35 ml. of 90% formic acid and 17 ml. of 30Yo hydrogen peroxide was added. Upon gentle warming a vigorous reaction set in (Caution!). After the spontaneous reaction had ceased (30-45 min.) the reaction mixture was refluxed for 30 min., after which time it gave a negative peroxide test with sodium iodide. The mixture was cooled and the initial crop of adipic acid was filtered off. The filtrate was evaporated and the residue was washed with ether and separated by atration. The total yield of adipic acid melting a t 147-150' was 6.2 g. (85% based on cyclohexene). From the filtrates 0.3 g. of acidic material melting at 135140' was obtained. The rest was an oil.
(12) R. Criegee, Fortschr. Chem. Forsch., 1, 536 (1950).
DECEMBER
1957
SOLVOLYSES OF HINDERED ESTERS
1551
Acknowledgment. The author wishes to thank the he worked, for facilitating many things; Doctors E. Humble Oil and Refining Company for inviting him M. Amir and R. H. Perry for sharing their laborato their Baytown laboratories for the summer of tory with him, and Messrs. E. J. Hoffman and R. L. 1956 and placing their research facilities at his dis- Heinrich for sharing their office with him. posal. He is especially grateful t o Mr. J. A. AnderBAYTOWN, TEX. son, Jr., and Dr. J. T. Horeczy, in whose sections [CONTRIBUTION FROM COATES CHEMICAL LABORATORIES, LOUISIANA STATE UNIVERSITY]
Solvolyses of Some Sterically Hindered Aliphatic Esters' JAMES G. TRAYNHAM
AND
MERLE A. BATTISTE2
Received June 6, 1967 Solvolyses, mainly in alkaline solutions, of several methyl, isopropyl, and s-octyl branched aliphatic esters have been studied. Even when the normal reaction path through an addition intermediate (I)was severely hindered, evidence for the alternate .path (alkyl-oxygen fission) was not obtained.
With two modes of fission possible (by three Alkaline hydrolyses of primary and secondary alkyl esters usually occur by acyl-oxygen fis~ion,~paths : acyl-oxygen, alkyl-oxygen by ionization, and probably through an addition intermediate (I). 4 alkyl-oxygen by displacement), the difference in energy requirements in each case will control the course of the reaction. With saturated primary and R- -OR secondary alkyl esters, the addition intermediate appears to be favored energetically. I n other sysAH tems, the formation of relatively stable carbonium I ions or relief of strain in a small ring compound apWith tertiary alkyl,6 and diarylcarbinyl? pear to be favored over the addition intermediate. esters, alkyl-oxygen fission* occurs predominantly When normal acyl-oxygen fission merely regeneror exclusively. For these systems the alternative ates reactants (e.g., methyl benzoate and methoxide mode of fission has been attributed to ion forma- in anhydrous methanol"), alkyl-oxygen fission, tion. A bimolecular displacement reaction, how- much less favored but not prohibitively so, occurs ever, leads to alkyl-oxygen fission in the hydrolysis slowly. of P-lact~nes.~ Even with methyl esters under conI n several types of reactions, including hydrolyditions that mask the usual reaction, slow alkyl- sis of certain aromatic esters, steric factors have oxygen fission has been observed. lo been found to outweigh all other factors in control(1) Taken from the M.S. thesis of M. A. Battiste, Louisi- ling the reaction course among several alternatives. ana State University, August, 1956. Presented in part at the Thus in olefin-forming eliminations with highlySouthwide Chemical Conference, Memphis, Tenn., Decem- branched alkyl derivatives, the less-substituted ber 7,1956. olefin predominates. loAnd highly-hindered aromatic (2) University research assistant, 1955-56. esters which are not hydrolyzed by the usual pro(3) For excellent reviews, see C. K. Ingold, Structure and Mechanism in Organic Chemistry,p. 752 ff, Cornel1University cedure quickly respond, through acylium ion formaPress, Ithaca, N. Y., 1953; and J. Hine, Physical Organic tion, to treatment with concentrated sulfuric acid. l 2 Chemistry, p. 266 ff, McGraw-Hill Book Co., Inc., New The effects of extensive branching on the rates of York, N. Y., 1956. esterification and hydrolysis have been examined (4) M. L. Bender, J . Am. Chem. Soc., 73, 1626 (1951). (5) C. A. Bunton, A. E. Comyns, J. Graham, and J. R. in some detail.13We though it of interest to examine Quayle, J . Chem. Soc., 3817 (1955). the importance of steric factors in controlling the (6) H. W. J. Hills, J. Kenyon, and H. Phillips, J . Chem. course of the hydrolysis reaction with aliphatic esSoc., 576 (1936); J. Kenyon, S. M. Partridge, and H. Phillips, J . Chem. SOC.,207 (1937); M. P. Balfe, H. W. J. ters. The change in mode of fission as the alkyl group Hills, J. Kenyon, H. Phillips, and B. C. Platt, J . Chem. SOC.,556 (1942). is changed from primary t o tertiary may arise in (7) M. P. Balfe, M. A. Doughty, J. Kenyon, and R. Pop- part from an increase in energy requirements for lett, J. Chem. SOC.,605 (1942); M. P. Balfe, A. Evans, J. formation of the addition intermediate (I).FormuKenyon, and K. N. Nandi, J . Chem. Soc., 803 (1946).
1-
(8) A. (3. Davies and J. Kenyon, Quart. Revs. (London), 9,203 (1955). (9) W. A. Cowdrey, E. D. Hughes, C. K. Ingold, S. Masterman, and A. D. Scott, J . Chem. Soc., 1264 (1937); F. A. Long and M. Purchase, J . Am. Chem. SOC.,72,3267 (1950). (10) J. P. Bunnett, M. M. Robison, and F. C. Pennington, J . Am. Chem. Soc., 72,2378 (1950).
(11) H. C. Brown and I. Moritani, J . Am. Chem. SOC.,77 3623 (1955). (12) M:S. Newman, J. Am. Chem. SOC.,63, 2431 (1941). (13) See M. S. Newman, in Steric Effects in Organic Chemistry, ed. by M. S. Newmsn, pp. 205-225, John Wiley and Sons, Inc., New York, N. Y., 1956.
