PHOTOSENSITIZED OXIDATION OF PINE GUM T O YIELD PEROXIDES W A L T E R
H . S C H U L L E R , J A C O B C. M I N O R , A N D
R A Y V.
LAWRENCE
>Vnual %res Laboratory, Southm 1filizotion Risearrh and DruPlopmmt Iltutsion, U S. Department of Atyrculture, Olitstee, Fla.
The photosensitized oxidation of pine gum and gum rosin gives a mixture of peroxides as an off-white, freeflowing solid which may be used wherever a source of low-cost free radicals is desired. The maior peroxidic components of the mixtures are 6,l 4-peroxy-A''*'-dihydroabietic acid, 7 , 1 3 - p e r o ~ y - A ~ ' ~ ~ ' - d i h y d r o a b i e t i c acid, and 1 8-hydroperoxy-6,l 4-peroxy-Ai'"-dihydroabietic acid, derived from levopimaric, palustric, and neoabietic acids, respectively. The photosensitized oxidation of abietic acid, in contradiction to the earlier literature, gives a diperoxide decomposing a t about 60" C. Refluxing 6,14-peroxy-A7'*'-dihydroabietic acid in an inert solvent gives the new and potentially useful 6,7; 8,14-diepoxyabietic acid.
1962, the current status of the field of industrial photochemwas reviewed (5). With respect to photosensitized oxidation. the prrparation of the transannular peroxide, ascaridole (11): from a-terpinene (I) was noted. Also menN
I istry
4 I R t LIGHT
+ DYE
*@ A
A I
ll
tioned was the laboratory synthesis of cortisonr with the photosensitized oxidation of ergosterol as a key step. I n 1963. Schcnck revicwed the phenomenon of photosensitization ( 7 3 ) and emphasized the photosensitized oxidation of a-terpinene to ascaridole as being a commercial process in Europe, where the transannular pcroxide is used as an anthelmintic. T h e photosrnsitized oxidation of three of the four pure major resin acids of pine gum had been studied in our laboratory u p to the time of the prrsent work. Levopimaric acid gave levopimaric acid transannular peroxide [6, I4-peroxy-Ai'*'-dihydroabietic acid (111) (9, 7 0 ) ] , palustric acid gave palustric acid
yn,
19
coon
m
In turn: the rosin portion comprises about 807, by weight of pine gum. the remainder being gum turpentine (a mixture of a- and &pinenes). It was found in the present work that the fourth major resin acid of pine gum~--.abieticacid--does not give levopirnaric transannular peroxide ( I I I ) , as reported by Schenck (72). Instead, a labile diperoxide is formed which rearranges to a nonperoxidic material on vacuum stripping of the solvent a t a pot temperature of 60' C. Esterification followed by high vacuum distillation of the new material gave a product possessing properties consistent with the structure methyl 7,8-dihydr~xy-A~"~~'-dihydroabietate. ' I h e photosensitized oxidation of crude pine gums (as well as gum rosin) was therefore carried out and found to yield products containing over one-half equivalent of peroxide (around 30/, active oxygen), being a mixture of 111. IV. and V. 'l'his mixture was obtained as an off-white, free-flowing solid which is stable on storage a t room temperature and on handling. This peroxidic mixture provides a commercial source of useful and inexpensive free radicals, as the present cost of pine gum is only $0.08 per pound. Thus: another potentially commercial photosensitized reaction would seem available. Refluxirig levopimaric acid transannular peroxide (111) in an inert solvent (xylene) resulted in the formation of the new and potentially useful diepoxide, 5,7(a); 8.14(a)-diepoxyabietic acid ( V I ) .
138'
coon
N
XYLENE
fl -4
V boon
VI
transaiinular peroxide [ 7.13-pero~y-A~~~~'-dihydroabietic acid (I\') (16) 1. and nroabietic acid gave neoabietic acid diprroxide. a hydroperoxy-transannular peroxide [ 18-hydroperoxy-6,14peroxy-Ai'*'-dihydroabietic acid (V) ( 7 I ) J. 'l'hese three resin acids make u p about half of thr rosin portion of pine g u m (2).
Experimental
Photosensitized Oxidation of Slash Pine Gum. A solution of 267 grams of clash pitie gum (containing about 20yc turpentine and 20y0 levopimaric acid on a pine gum basis) VOL. 3
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in 2360 ml. of 95% methanol containing 0.270 gram of rose bengal (lOyc in resin acid solids and 100 mg. per liter in dye) was charged to the 40-watt laboratory reactor. 'The reactor has been described (9). I n addition. four 15-watt fluorescent lamps and a cooling fan were arranged externally. Aeration. with compressed air. and irradiation were carried out simultaneously. Samples were removed a t intervals. stripped under reduced pressure (bath to 60' C . ) , dried. and analyzed for peroxide ( 7 4 by titration. A plot of peroxide content L'S. time leveled off after about 9 hours. T h e solution was then treated with 75 grams of Sorit-A (neutral), filtered. stripped under strongly reduced pressure a t a pot temperature of about 60' C., and then fluffed under a n oil pump vacuum. The friable solid residue \,vas broken u p and air-dried for several days to give an off-white. free-flowing powder containing 0.62 equivalent o peroxide per mole of resin acid present (3.127, active oxygen) f When repeated with longleaf pine gum, active oxygen content was slightly lower. G u m rosin gave a product containing 2.927' active oxygen. Longleaf scrape was found to reduce the dye continuously, even with repeate'd additions of sensitizer, when run as a 107, solution. When run as a 57, alcohol solution. a product exhibiting an active oxygen content of 3.3TG was successfully obtained. Shelf Life of Photosensitized-Oxidized Pine Gum. Samples reanalyzed after 9 months' storage a t room temperature indicated no decrease in peroxide content.
Half Life of Photosensitized-Oxidized Pine Gum. Photosensitized-oxidized pine g u m (1.40 grams) containing 3.027c of active oxygen was dissolved in 48.6 grams of benzene [0.044 gram mole of peroxide group ( - ~ O -0--) per liter] and filtered. Carius tubes of IO-mm. 0.d. and 200-mm. length were each charged Lvith a 3.0-ml. aliquot of the peroxide solution. flushed with nitrogen, and sealed. Each set of tubes bias immersed in a n oil bath held a t the desired temperature. Tubes were removed periodically. opened, and analyzed for peroxide ( 7 3 ) . Half lives were calculated in the usual manner. using T 1;2 = 0.693,'K, bvhere K is the first-order rate constant. Temp.,
c.
155 140 125
Half L if e .Win.
.
12 49 106
of Abietic Acid. L-TNDER CONDITIOSS.A solution of 0.242 gram of abietic acid and 4 mg. of erythrosin B in 40 ml. of 95% ethyl alcohol (0.02,zl in resin acid and 100 mg. per liter in dye) was charged to a vessel (7-1) arrayed for photosensitized oxidation studies. Pure oxygen was passed into the solution and its consumption was noted while irradiation. provided by a 15watt fluorescent lamp and 100-watt incandescent bulb. was impinged on the mixture.
Photosensitized Oxidation
QCASTITATIVE
O n e mole of oxygen per mole of resin acid \,vas absorbed in less than 16 hours. T h e rate then abruptly decreased and a second mole of oxygen was taken up. a t zero order, over the next 160 hours. More extensive and prolonged irradiation did not result in a further uptake of oxygen. The final solution exhibited [ a ] D -22'; no characteristic absorption from 220 to 320 mu, and a peroxide content by titration ( 7 4 of 1.7 equivalents of peroxide per mole of abietic acid. The dissolution of 2.24 grams of potassium hydroxide (solution then 1.\ in KOH) was carried out. The next day the rotation and ultraviolet absorption spectra were essentially unchanged. while the peroxide content was approximately zero.
TVORKUP O F PRODUCT..A solution of 0.605 r a m of abietic acid and 5 mg. of erythrosin B in 100 ml. of 9 5 b ethyl alcohol (0.02.2.l in resin acid and 50 mg. per liter in dye) was charged to a test tube reactor ( 9 ) . Aeration and irradiation (15-watt fluorescent bulb) \vere carried out simultaneously. A steady 98
l&EC PRODUCT RESEARCH A N D DEVELOPMENT
decrease in cy a t 241 mp was observed with little characteristic absorption from 220 to 320 mp noted after 72 hours. -The solvent \vas removed under stronqly reduced prewire (pot temperature to 60' C.) ; the residue could not be crystallized nor could crystalline fractions be obtained via c h r o m s t o p p h y . A \vide variety of primary. secondary, and tertiary amines were added to solutions of the oxidate in ether. acetontx. and alcohol. No precipitates Lverr obtained. Addition of \vater gave oils which resisted crystallization. The ci-ude solid contained essentially no peroxide. A solution of excess (5 to 1) alcoholic sodium hydroxidc exhibited no changr in absorption from 220 to 320 nip after 1 dav and 5 da?-s. respectively. I h e methyl ester was prepared with diazomethanc. 'I'he liquid ester of CY]^)*^ 1 .0' (C 1 .0)waq molccularly distilled in a cold-finger type of vacuum subliinator at 133-43' 0.014 m m . in 7676 vield; [aIDz5-13.0' ( C 0.75). Redistillation in 85% yield resulted in essentially no change in rotation. 'I'he liquid ester exhibited a zero peroxide content and a zero frce arid content; the trst for carbonyl content \,vas nrgative; thr tcttanitromethane test for olefinic unsatiiration was positive; a positive test for 1.2-glycol was obtainrd; there was no characteristic absorption from 220 to 320 m u ; A,,, (CC14 solution) 2.95 microns (rn) (hydroxy-l stretching band) \vas noted ; NMR spectrum. no vinyl hydrogen nor a l l ~ l i cmethyls prcrent, ester methyl absorption a t T = 6.34 exhibited fine splitting; a solution in a 16 to 1 excess of alcoholic potassium hb-droside exhibited no charactrristic absorption from 220 to 320 m u . Analysis. Calculated for C,1F33204: C. 72.4: k1. 9.3. Found: C. 72.1; H. 9.1. BL.ASK E X P ~ R I M E N TNo S . titratablp pcroxidr developed and no change in spectrum from 220 to 320 mw nor in specific rotation was observed of a 0.02.2.1 solutiori of abietic acid in 95c/c ethanol after 6.0 hours of aeration in the dark, irradiation with visible light. contact Lvrth erythrosin €3 in the dark. aeration plus erythrosin B in the dark. irradiation plus erythrosin B. and 72 hours of aeration plus irradiation. A t the end of the blank runs. the abietic acid \\'a4 isolated essentially unchanged. as indicated bv a comparison of its infrared cpectrum with that of the starting material. In addition. a solution of 100 mg. per liter of erythrosin B in 953% ethanol was aerated and irradiated for 43 hours in a 100-watt test tube reactor without the formation of any titratable peroxide in the sb~stem. Thermal Treatment of Levopimaric Acid Transannular Peroxide. A solution of 2.5 grams of levopirnaric acid transannular peroxide in 125 ml. of dry. redistilled x!.lene was refluxed (138 O C.). T h e reaction was followed by analysis for peroxide and change in optical rotation. Anal>-sis of both sets of data showed the reaction to be of first order for the first 10 hours. whereupon all of the peroxide was destroyed and no further change in optical rotation occurred. leveling off a t [aID -44'. The 6.7(a); 8,14(a)-diepoxyabietic acid formed a crystalline tut-butylamine salt i n 9574 yield. which was recrystallized from acetonitrile to constant optical rotation ; weight 2.14 grams (71%) [.ID -42.7' (C0.91 in 95% ethanol); m.p. 18.1-86' C . with decomposition and evolution of gas; no characteristic absorption from 220 to 320 mpc.A,, (Niijol mull) 6.87 (in),11.88 (w),12.0 (w)microns [all epoxy bands ( 8 )I. Analysis. Calculated for CIIHIION: C , 70.7; H, 10.1; N. 3.44; 0.15.7; nrutralization equivalent 408. Found: C, 70.5; H, 10.1; N, 3.65; 0, 15.8; neutralization equivalent 408. The free 6.7(a); 8,14(oc)-diepoxyabietic acid was liberated from the salt in 98% yield? using dilute phosphoric acid in the usual manner (7-l). It was recrystallized to constant rotation from di-n-propyl ether and then from aqueous methanol : [ a ] =-70.3' ( C 0.80 in 9570 ethanol); m . p . 172 -74' C. \rith decomposition and evolution of gas; no characteristic absorp(Nujol mull) 6.92 irhonlderj, tion from 220 to 320 m p ; ,,,A, 8.88 (w), 11.1 (1~): 11.90 (w).12.0 (w)microns [all epoxy bands (8)]. Analysis. Calculated for C20H3004:C. 71.8; €1. 9.0; 0, 19.1 neutralization equivalent 334.4. Found : C. 71.6 ; H: 9.2; 0, 19.3; neutralization equivalent 335.5. T h e methyl ester was made by reaction with diazomethane to give a pure ester of unchanged melting point on rrcrystallization from aqueous methanol: 1n.p. 121' C.; [aIu -72.4' (C 0.60 in 95% ethanol)]; no absorption from 220 to 320 mp; , , A, (Nujol mull) 7.0 (m), 8.04 (s). 8.82 ( m ) , 11.07 im).
+
~
11.85 (w),11.97 (w) micron [all epoxy bands (S)];no bands in ?-micron (no hydroxyl) ; S M R 7 = 6.99 (1 proton; assigned to C-8 hydrogen). a doublet superimposed on a second doublet at about 7 = 7.13. 7.23 (total area equivalent to 1 proton; attributed to splitting of the C-6 proton by the two nonequivalent protons on the C-5 hydrogen). Analysis. Calculated for C2,H3201: C, 72.4; H. 9.3; 0 , 18.4. Found: C. 72.3; H. 9.5; 0 : 18.2. T h e r m a l T r e a t m e n t of Photosensitized-Oxidized P i n e Gum. A solution of 10.0 grams of photosensitized oxidized pine gum in 100 ml. of xylene was refluxed and the disappearance of peroxide followed by titration. After 2 hours little titratable peroxide remained. T h e solution was passed through a Sorit-A column to remove color bodies, the solvent removed by vacuum stripping, and the mixture of diepoxides dried in vacuo. Discussion
T h e photosensitized oxidation of slash and longleaf pine gum. scrape, and gum rosin gave products containing from 0.55 to 0.65 equivalent of peroxide per mole of resin acid present (active oxygen range of 2.8 to 3.376). This compares, for example, \vith a n active oxygen content of 3.97, for lauryl peroxide, 2.17, for a 50% solution of 2.4-dichlorobenzoyl peroxide in dibutyl phthalate, 5.17, for p-menthane hydroperoxide, and 5.77, for dicumyl peroxide. T h e composition of photosensitized-oxidized slash pine gum based on the content of the various resin acids present (2, 9 , 70, 74. 76) is: levopimaric acid transannular peroxide (111), 24% ; palustric acid transannular peroxide ( I V ) , 9y0; neoabietic diperoxide (V). 157,. Since the latter compound is a diperoxide, the value is multiplied by 2 to give 15% X 2 247, 970 or 637, of the total resin acids present as apparently peroxidized on analysis of the total mixture. This is equivalent to an active oxygen content of 3.19y0. Analyses of the Lyhole photosensitized-oxidized slash pine gum approximate this figure. sometimes running slightly lower because of loss of peroxide on charcoal decolorization. T h e turpentine portion of the pine gum does not react under the conditions used. as was demonstrated by experiment. T h e peroxide content of gum rosin, which contains no levopimaric acid ( 2 ) , is palustric acid transannular peroxide (IV), 147,. and neoabietic acid diperoxide (V), 187, (times 2) for a total of 50% of the resin acids present as apparently peroxidized on analysis of the whole product. This amounts to a n active oxygen content of 2.527,. In actual practice, active oxygen contents of about 2.977, are obtained. X o work was done with wood and tall oil rosin because of their very low content of palustric and neoabietic acids. T h e final laboratory process used employed rose bengal as the sensitizer. it being the most efficient of all those tested, although a broad range of dyes can be used (74, 76). Rose bengal was used a t a concentration of 100 mg. per liter, which is about the minimum amount that can be used without decreasing the rate significantly (74). Methanol and 957, ethanol were both used as solvents for the photosensitized oxidation on a large scale. T h e electricity requirement for the light source was about a 2 kw.-hr. per pound of peroxide produced. Daylight fluorescent bulbs were used as the source of visible light. Compressed air was used as the source of oxygen. At a pine g u m concentration of 12.57, in alcohol, no bleaching of the dye occurs throughout the run. Slash pine gum was run in ethanol solution at concentrations u p to 757, pine gum. Hotvever: above a pine g u m concentration of 12.5Oj,. the dye bleaches slo\vly. presumably because of a trace amount of a side reaction ( 7 5 ) -and the dye has to be replaced. T h e amount of dye used per unit weight of pine gum. however. is never
+
+
higher in the higher solids runs than in the 12.57, run. At 75y0 pine gum, some frothing of the solution accompanies aeration. T h e final alcoholic reaction mixture is treated with charcoal to remove the dye, the solvent is removed by stripping under reduced pressure (pot temperature to 60' C.), and the product air-dried. T h e charcoal treatment and air drying were found to be important in providing a free-flowing solid which did not tend to form a cake on standing. I n a modification of the above process, it was found that after the bulk of the ethanol had been vacuum-stripped, the residue could be dissolved in benzene and the peroxidic components extracted with aqueous bicarbonate. Acidification of the combined bicarbonate extracts gives the peroxidic mixture as a solid which can be collected by filtration and air-dried. I n comparing photosensitized-oxidized pine gum with peroxides commercially available it was desirable to know the "half life" of the peroxidic mixture a t varying temperatures. .4ccordingly, solutions of photosensitized-oxidized pine gum in benzene, a t a peroxide concentration often employed in practical polymerization work, were thermally decomposed at varying temperatures and half lives calculated. T h e photosensitized oxidation of abietic acid, the fourth major resin acid of pine g u m ( 2 ) , gave a diperoxide which could not be crystallized a n d was definitely not levopimaric transannular peroxide as claimed by Schenck (72). This was demonstrated by the fact that on treatment of the reaction mixture with a n excess of base? no measurable amount of 6keto-14-hydroxy-A7(*)-dihydroabieticacid was formed, as shown by the ultraviolet absorption spectrum ( 7 0 ) . O n stripping off the alcohol solvent under strongly reduced pressure, a t a pot temperature of about 60' C.: the abietic acid diperoxide decomposed to a new acid, and conversion of the new acid to the methyl ester with diazomethane. followed by molecular distillation, gave a compound in good yield, for which all the evidence was consistent with the structural configuration as 7.8-dihydro~y-A'~~:'~)-dihydroabietic acid. Refluxing levoperoxide transannular peroxide (111) in an inert solvent (xylene) converted the peroxide into the new and potentially useful diepoxide, 6,7(a) ; 8,14(a)-diepoxyabietic acid ( V I ) . This reaction parallels the behavior of ascaridole, as a diepoxide is also obtained in the latter case ( 7 , 3, 4, 6 , 7. 7 7 ) . This reaction would also indicate that, under certain conditions, diepoxides make u p a substantial part of the residue, when transannular peroxides are used as thermally induced sources of free radicals.
Conclusions
A potentially commercial, low-cost process for the preparation of a crude peroxidic product via the photosensitized oxidation of crude pine gum is described. T h e product consists primarily of a mixture of three peroxides obtained from the three major resin acids of pine gum, and has an active ox)-gen content in the neighborhood of 37,, T h e structures of these peroxides have been established. T h e photosensitized oxidation of the fourth major resin acid of pine gum-abietic acidwas shown to give not levopimaric acid transannular peroxide as claimed in the prior literature but a labile diperoxide \vhich rearranges on tvorkup of the crude mixture to a nonperoxide. O n heating in a n inert solvent. levopimaric acid transannular peroxide gives the new and potentially useful diepoxide. 6.7 (a); 8.1 4 ( a )-diepoxyabietic acid. VOL.
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Acknowledgment
T h e NMR spectra were run by Werner Herz, Florida State University, Tallahassee, F]a,, to whom the authors are indebted. literature Cited
(1) Agnello, E. J., Pinson, R., Jr., Laubach, G. D., J . Am. Chem. Soc. 78, 4756 (1956). (2) Baldwin, D. E., Loeblich, V. M., Lawrence, R. V., Ind. Eng. Chem. 3, 342 (1958). (3) Dufraisse, C., Etienne, A., Basselier, J. J., Compt. Rend. 244,
2209 (1957). (4) Fenton, S. W., Runquist, O., “Hydrolysis of Pseudoascaridole,” Abstracts 131st Meeting, ACS, Miami, Fla., April 7-12, 1957, p. 13-0. (5) Ind. Eng. Chem. 54 (8), 20 (1962). (6) Jacob, G., Ourisson, G., Bull. SOC.Chzm. France 1958, 734. (7) Matic, M., Sutton, I). A., J . Chem. SOC.1953, 349.
(8) Mitchell, J., Jr., Kolthoff, I. M., Proskauer, E. S., LYeissberger, A., “Organic Andlysis,” vol. I, p. 151, Interscience, New York, 1953. (9) Moore, R. N., Lawrence, R. v., J . Am. 80, 1438 (19 58) . (10) Ibzd., 81, 458 (1959). (11) Runquist, O., Dzssertatzon Abstr. 16, 2313 (1956). (12) Schenck, G. O., Angew. Chem. 64, 12 (1952). (13) Schenck, G. O., Ind. Eng. Chem. 55 (6). 41 (1963). (14) Schuller, W. H., Lawrence, R. V., J . Am. Chem. Soc. 83, 2563 (1961). (15) Schuller, W. H., Lawrence, R. v’, J’ Org. 28, 1386 (1963). R. v., J . Am. (16) Schuller. w. Moore, R. N., Chem. SOC.82, 1734 (1960). H.j
RECEIVED for review February 19, 1964 ACCEPTEDApril 16, 1964 Division of Organic Coatings and Plastics Chemistry, 147th Meeting, ACS, Philadelphia, Pa., April 1964.
OXIDATION OF SECONDARY ALCOHOLS WITH CARBON TETRACHLORIDE W . J . JACKSON, J R .
Research Laboratories, Tennessee Eastman Co., Division of Eastman Kodak Co., Kingsport, Tenn.
The free-radical oxidation of secondary alcohols to ketones with carbon tetrachloride was studied. The experiments were performed with four model compounds-2-octanol, cyclohexanol, endo-2-norbornanol, and exo-2-norbornanob When 5 mole of a peroxide initiator was added, ketones were obtained in conversions up to 6OY0. A side reaction which took place to a small extent was chlorination of the product. The variables affecting the oxidation are examined, and the mechanism is discussed.
yo
s
oxidation is a free-radical reaction and carbon tetrachloride will yield free radicals, the possibility of oxidizing alcohols with carbon tetrachloride was investigated. When a mixture containing cyclohexanol and carbon tetrachloride was refluxed in the presence of either benzoyl peroxide or ultraviolet light, cyclohexanone, chloroform, and hydrogen chloride were obtained : INCE
e:H +
C C L d 0
0
+ CHC13 f HCI
(1)
A literature search revealed that Razuvaev and his coworkers had observed a similar reaction with methanol and ethanol (76, 78). Later they oxidized 2-propanol in this manner and demonstrated that a chain reaction was involved (73, 75, 77). In all cases the conversions were very low. Their highest conversion (12%) was obtained during the oxidation of 2-propanol to acetone (77). W e studied this reaction to determine whether a new, practical method for oxidizing alcohols could be developed. I t was apparent that such a process would not be as economical as catalytic dehydrogenation or air oxidation, but these procedures are limited in their applicability. I t did appear possible that this process might be more convenient and less costly than the conventional chemical methods requiring oxidizing agents such as nitric acid. chromic acid, and sodium dichromate. Most of these experiments were carried out with one alicyclic alcohol, cyclohexanol (Table I ) , and one aliphatic alcohol, 2-octanol (Table 11). The reactions were conducted by slowly adding various initiators to refluxing carbon tetrachloride 100
l&EC P R O D U C T RESEARCH A N D DEVELOPMENT
solutions of the alcohols. To aid in determining the reaction mechanism, exo- and endo-2-norbornanol (Table 111) were also oxidized. Results from the oxidation of primary alcohols are not reported, since aldehydes were obtained only in negligible amounts. Experimental
Materials. Cyclohexanol and 2-octanol were Eastman grade from the Eastman Kodak Co. exo-2-Worbornanol (4) and endo-2-norbornanol ( 7 7 ) were available as products obtained from Diels-Alder adducts of cyclopentadiene. Carbon tetrachloride and sodium bicarbonate p6wder were obtained from the Allied Chemical and Dye Corp. (B and A quality). Except for diisopropyl peroxydicarbonate, which was prepared (ZO), all of the peroxides were obtained from the Lucidol Division of Wallace and Tiernan, Inc. Acetyl peroxide was available as a 25% solution in dimethyl phthalate. tert-butyl peroxypivalate as a 75% solution in mineral spirits, and bis(2,4-dichlorobenzoyl) peroxide as a 50% solution in dibutyl phthalate. 2,2 ’-Azobis [2-methylpropionitrile] was Eastman grade from the Eastman Kodak Co. Analyses. T h e reaction mixtures were analyzed by gas chromatography with a conventional apparatus. Hydrogen was the carrier gas. T h e column (6 feet X inch) was packed with Carbowax 20M on 35- to 80-mesh Chromosorb P in the ratio of 1 to 4 by weight. Relative molar amounts of ketone, alcohol, and chloroform were determined by measuring the area of each on the chromatogram with a planimeter, dividing by the molecular weight, and multiplying by a calibration factor obtained from known mixtures. Oxidation of Alcohols. Most of these experiments were performed with 0.5 mole of alcohol (Tables I to 111). T h e exceptions were the three experiments in Table I. in which 5.7 mole % of peroxide was added (to 0.1 mole of cyclohexanol), and the first two experiments in Table 111, in which the per-
