Jan. 20, 1959
DECOMPOSITION OF PINANE HYDROPEROXIDE
Examination of the mother liquid provided the second anomer, m.p. 1 5 8 O 1 0 (after recrystallization from chloroform-light petroleum ether), [cY]*~D - 12" in chloroform (c 0.3). The N-phenyl-2,3-di-O-methyl-~-arabinosylamine prepared in the usual way by treatment with ethanolic aniline had m.p. 138O, [aIz4~ -143" after 10 min. in chloroform (c 0.4) changing in 4 hr. to -44' (constant value) (after recrystallization from chloroform-petroleum ether); lit." m.p. 139" for L-isomer. Prolonged Treatment of 3,4-Di-O-methyl-~-mannitol with Sodium Periodate.-When the periodate oxidation of 3,4di-0-methyl-D-mannitol was allowed to proceed longer than 0.5 hr., the molar periodate consumption was: 1.0 mole (after 0.5 hr.), 1.06 (1.5 hr.), 1.35 (12 hr.), 1.47 (24 hr.), 1.52 (37 hr.), 1.60 (49 hr.), 1.66 (61 hr.), 1.71 (88 hr.), oxidation incomplete. Oxidation of 2.3-Di-o-methvl-~-arabinose with Sodium Periodate.-When 2,3-di-O-methyl-~-arabinose (50 mg.) was allowed to react with 0.03 N sodium periodate (25 mi.) these reading changes in specific optical rotation and periodate consumption per mole of 2,3-di-O-methyl-~-arabiriose, respectively, were observed: [ a ] D -110" (after 3 min.); -llOo, 0.03 mole (1 hr.); -llOo, 0.103 mole (4 hr.); - 105' 0.25 mole (18 hr.); -105", 0.35 mole (30 hr.); -loo", 0.43 mole (42 hr.); -85", 0.54 mole (56 hr.); -80", 0.68 mole (5 days); -75', 0.83 mole (9 days); -70°, 0.91 mole (17 days). Reduction of 2,3-Di-O-methyl-~-arabinose with Sodium Borohydride.-To a solution of sodium borohydride (65 mg.) in methanol (2 ml.) was added a solution of 2,3-di-O-methylD-arabinose (298 mg.) in methanol (10 ml.). rlfter 3 hr. the reaction mixture was treated with an additional portion (25 mg.) of sodium borohydride. Since this addition produced no change in rotation (observed for 2 hr.), the reaction mixture was neutralized with dilute acetic acid (tested with universal PH indicator paper) and evaporated to dryness. (10) Cf. H. C. Srivastava a n d F. Smith, THISJOURNAL, 79, 982 (1957). (11) F. Smith, J . Chem. Sac., 753 (1939).
[CONTRIBUTION FROM
THE
445
The residue w3s boiled for 4 hr. with acetic dnhydride (10 ml.) in the presence of anhydrous sodium acetate (0.5 g.) to facilitate'* the isolation of the product. The reaction mixture was poured with stirring into water and the product extracted with chloroform. After washing with dilute sodium bicarbonate and with water, the chloroform extract was drled (MgS04) and evaporated. The 2,3-di-O-methyl-oarabitol triacetate (400 mg.) thus obtained showed [ a I e a D +21° in ethanol (c, 4). The sirupy 2,3-di-O-methyl-~-arabitol triacetate was heated for 0.5 hr. with A' ethanolic potassium hydroxide (0 ml.). After standing overnight the solution was treated with water (10 ml.), deionized by passing successively through a cation (Amberlite IK-120) and an anion (Duolite A4) exchange resin. Evaporation of the solution >ielded 2,3-di-0methyl-D-arabitol as a clear, light-yellow liquid (208 mg.), [ a ] 1 9+5" ~ in ethanol (c, 4), K 0.31 (solvent, butanonewater azeotrope; spray reagent, ammoniacal silver nitrate). Treatment of 2,3-di-O-methql-~-arabitol (26 mg.) n ith P-nitrobenzoyl chloride (67 mg.) in pyridine (1 ml.) in the usual way, gave the corresponding 1,4,5-:ri-p-nitrobenzoatr, m.p. 131.5', [ c Y ] ~ ~+43' D in chlorof~xin(c 0.8) (after rccr)stallization from acetone-ethanol) . A nnl. Calcd. for C ? S H ~ ~ OicNa: C, 53.59; H, 4.02; N, 8.70; OCHz, 9.88. Found: C, 53.99; H, 4.09; S,6.61; OCHI, 9.4. Oxidation of 2,3-Di-O-rnethyl-~-arabitol with Sodium Periodate.-.% solution of 2,3-di-O-methyl-~-arabitol iii 0.044 11 sodium periodate was alloffed to stand a t room temperature. After keeping overnight, 0.91 mole of periodate was consumed per mole of 2,3-di-O-methyl-~-arabitol. Addition of barium chloride to remove iodate and periodate, filtration and evaporation gave a distillate which was shown to contain formaldehyde since it yielded the crystalline dimedone derivative, m.p. and mixed m.p. 190'. The other product of this reaction, namely, 2,3-di-O-rnethyl-~-threoset is being examined and will form the subject of a M e r communication. (12) H. Klosterman and F. Smith, THIS J O U R N A L , 74, 5336 (1952).
ST.PAUL,MINS.
NAVALSTORES STAIIOT\.']
The Decomposition of Pinane Hydroperoxide. 112 B Y GUSTAV A. SCHMIDT3 AND GORDON s. FISHER RECEIVED AUGUST 11, 1088 Further studies of the decomposition of pinane hydroperoxide have revealed that the yield of pinan-2-01s call be increased to nearly 50% by carrying out the reduction in the presence of both pitiane and a base. Evidence also \%.asobtained for attack a t the secondary carbon atoms of uinane during - the oxidation and for isomerization of pinane to monocyclic hydrocarbons during the decomposition.
The previous paper of this series4 reported the In view of the well known instability of the identification of 2,2-dimethyl-3-ethylacetylcyclo-bicyclic terpenes toward acids it seemed reasonable butane as one of the major decomposition products that acids formed during the preparation and deof pinane hydroperoxide. It was observed that in composition of the pinane hydroperoxide conthe absence of pinane up to half of the pinane hydro- tributed to the destruction of the expected bicyclic peroxide decomposed was converted to high boiling products and the formation of tars. This was suptars during decomposition and distillation. Little ported by the fact that the use of a diluent which or no monomeric bicyclic products were obtained lowered the concentration of acids decreased the under these conditions. However, when pinane was production of tars during decomposition and inused as a diluent, the yield of tars was reduced to creased the yield of isopinan-2-01. about 28%, the yield of the ketone was increased In the present investigation, the formation of to about 20% and some isopinan-2-o16was isolated. acids during the peroxidation was minimized by operating a t a relatively low temperature and (1) One of t h e laboratories of t h e Southern Utilization Research & terminating the oxidation before peroxide decomDevelopment Division, Agricultural Researchservice, U. S. Department of Agriculture. Article not copyrighted. position became excessive. Decomposition was (2) Presented before the 6th Southeastern Regional American Chemical Society Meeting, Birmingham. Ala., October 21-23, 1954. (3) General Electric Co., Waterford, N. Y. (4) G. A. Schmidt and G. S. Fisher, THISJOURNAL, 76, 5426 (1954). ( 5 ) The term "iso" has been widely used t o designate +menthane derivatives, such a s isomenthol, in which the methyl and isopropyl
groups are cis, a s well a s t o denote 8 c i s relation of the methyl group t o t h e isopropylidene bridge in t h e 3- and 4-hydroxypinanes. T h e authors feel t h a t use of t h e same convention in naming the two pinan2-01s is preferable t o t h e use of trivial names siich a s mpthyl nopinol or t h e prefixes cis and trans.
GUSTAV A. SCHMIDT AND GORDON S.FISHER
446
Yd.SI
carried out in the presence of sodium methylate to remove acids as they were formed, and the decomposition mixture was washed before distillation. As shown in Tables I and 11, peroxide retention during oxidation was high and recovery of unreacted pinane and products was good.
oxygenated, it was of interest to check the oxygen balance for the decomposition step. -lssuniing t h a t the non-peroxidic products are mono-oxygenated, the oxidate contained 4.78 moles of oxygen. The products recovered after decomposition (see Table 111) contained only 2.97 nioles of oxygen. Therefore, the loss of oxygen was 1.Sl moles or 58 g. TABLE I calculated as niolecular oxygen. 'There is also a net hf ATERIALS BALANCE FOR P R E P A R B T I O N O F P I N A S E HTDRO- loss of hydrogen in the formation of the limonene, PEROXIDE isoverbanone, residue, and acids amounting to Wt., g. Moles about 1.5 moles. Hence, the total deficiency of Pinane charged 2078 15.06 oxygen and hydrogen in the decomposition products Oxidate 2175 14.65 is 61 g., compared to the observed loss in weight Oxidation products 834 4.94" of 65 g. Oxygen as well as water has been reported Pinane unreacted 1341 9.71 as a decomposition product of other tertiary hydroPinane lost 57 0.41 peroxides.6 a 4.63 moles pcrosidc, 0.31 mole uf other oxidatiuri prudAnother noteworthy feature of the decomposition ucts. is the fact that only 9.13 moles of the unreacted pinane (9.71 moles) present in the oxidate was reTABLE I1 hlATERIALS B A L A N C E F O R S E P A R A T I O N OF PIIANEOXIDATES covered after decomposition, while the recovery of oxygenated products was quantitative. This loss AFTER DECOMPOSITION of pinane is almost exactly balanced by the 0.3.; Wt., g. Moles mole of carvomenthene (JV) plus limonene (111) Piiiane recovered 1260 9.13 formed, which indicates t h a t these monocyclic Volatile products" 710 4.67 compounds are formed from pinane during the deResidue 85 0.54 composition step. Both are reasonable products Acids 55 0.30 from the pinan-z-yl free radical in the absence of Total recovery 2110 14.64 oxygen. Loss6 65 0.01 a
See Table 111. * B y difference.
The mixture of decomposition products was coinplex ; b u t careful distillation gave adequate separation for the identification of the major products, and for semi-quantitative analysis on the basis of the infrared spectra (Table 111).
..:\
9 I
TABLE 111 DECOMPOSITION PRODUCTS Product
l-Carvomentheiie I-Limonene 2,2-Diinetliyl-3-ethylacetylcyclobutane I'iiian-2-01 Isopitian-2-ol @-Terpineol a-Terpineol Isoverbanone Pinocamphrols Unidentified alc. and ketones Iiesjdues :\cids
Found in fractions"
11-13 11-12 18-80 29-36 36-43 4 1-43 44-54 44-64 55-58 13-20,3135,35-58 ... . ... . . ... . .
B.p.,b O C .
Moles
>Tole per cent. AC Bd
0.49 0.00
..
84 96 102 108 111 111 115
1.00 0.55 1.86 0.12 .23 .10
20 17 11 9 38 31 2 2 5 4 2 2 1 1
.. .. .
,
.20 .54" .30f
. f! i l
_/'
, '
b'l H.
/+, ~. ". (-1
69 69
.oo
!1
i
..
8 1
3 9 5 - 100 92 4 11 6
'rcltal 5.51 Fraction> 1 I O TWIK ~i,s-yiriaiie.'~ B.p. of purest fmcti(in nt 20 i i i t n . Based o i i moles i i f oxidation products in osidatc. Based on moles of pinane charged-moles of liiiiaiie recovered. Molecular weight of I58 assumed { U I I ICtsis o f elenientar). analysis. f Includes lactones and watvriluhlr I)rotiucts, average nio1ecul:ir weight of 184 assumcd . I'
'I'he low weight recovery after decomposition, accompanied by a good molar recovery suggests that a volatile or water-soluble product was lost. In view of the fact that most of the products were irioiicJ-oxygenated while tlir: hydroperoxide is di-
,Ik
I11
! *.'
'
The most marked eflcct of the use o f sodiuni methylate during the decomposition WRS the illcrease in yield of the pinan-2-01s to nearly SOYc. I n addition, the amount of non-volatile products was reduced to about 16yc. On the other hand, the yield of 2,2-dimethyl-~3-ethylacetylcyclobutaneWLS not changed. The isolation of piiian-2-ol as well as isopinan-2--c)1 was unexpected since the foriner was not detected in the reduction products of the hydroperoxide.' Hence, the catalytic reduction of the hydroperoxide was repeated. When the infrared spectrum of the product was obtained using a double beam spectrophotometer and a suitable concentration of autheiitic isopinan-2-01 in the reference cell, the presence of pinan-2-01 rcadily was apparent. The previous failure to detect it undoubtedly was due to thc use of a less precise speetroi~liototiirterwithout coiu pcnsation for the isopinan-2-01. I n addition, th(. infrared spectra indicated that there was 3 to -I times as much isopinan-2-ol as pinan-2-01 in the. ( 6 ) F H. Seubold, Jr., F. B. Rust and W. E. Vaughan, THISJo1.n73, 18 (1051); 11.S. Kharasch, A. Fono, W. Xudenberg and E. Cizenz.. 17, 207 (1952). h e r . J !< S t i i l r r i n : i i i i l I.. 4 (>uldLilalt, 'l'llls JUlmhh 11 76, 3675 fl(i,53) XAI,,
Jan. 20, 1959
DECOMPOSITION OF PINANE HYDROPEROXIDE
447
Acids and Base-Soluble Neutrals .-The organic materials present in the alkaline mashes were recovered by acidification and extraction with ether in the usual manner. Removal of the ether gave 55 g. of a viscous brown liquid (0.3 mole, assuming a n average molecular wt. of 184). The neutral equivalent was 262, which suggests the presence of lactones or water-soluble neutral oxidation products. Attempts to identify the acids by chromatography13 were unsatisfactory. Peaks corresponding to pinonic and pinic acids were obtained, but the infrared spectra of the fractions indicated that they were mixtures. Distillation of Neutral Products.-The washed product was subjected to a preliminary distillation in ~ U C Z L Oto-remove the bulk of the high boiling components. This distillation left a residue consisting of 59 g. of brown viscous liquid [C, rl a . ( ~ H, ; 10.52, 0 13.73 (difference)]. Thiscorresponds to a n average monomeric molecular weight of 158 g. (CloHle. 701. s a ) ; so the residue represents 0.37 mole of pinane. The crude distillate was then fractionally distilled through a Podbielniak column rated a t 100 theoretical plates, using a high reflux ratio giving the 58 fractions described below. -411 additional 26 g. (0.16 mole) of residue was obtained from this distillation. The results of this distillation are summarized in Table 111. Identification of Volatile Products.-Fractions 1-10 were substantiallv pure czs-l-~inane.'~ The infrared spectra and physical consfants checked with those of the starting material. Pinane recovered in the various cold traps used during decomposition and distillation was included in calculating recovery. The physical properties of fractions 11 and 12 ( n z o D 1.4595, d204 0.8392, [ a ]-104.3') ~ indicated that the major component was I-carvomenthene and this was confirmed by Experimental lo the infrared spectra. However, there was an absorption I-Pinane Hydroperoxide.-The I-pinane hydroperoxide band a t 11.25 p which is not present in the spectrum of mas prepared by oxidation of cis-2-pinane (15.06 moles, carvomenthene. The position and magnitude of this band -19.5', dZo4 0.8570, TPD1.4624)" at 100-105", es- mas correct for about 10% of linionene. sentially as described p r e ~ i o u s l y . ~The reactor consisted of The infrared spectra of fractions 21-28 indicated that they a 5-liter 3-neck flask equipped with two oxygen dispersers, were pure cis-l-2,2-dimeth~~l-3-etli~lacet~lc~-clobutane, but Dean-Stark trap, condenser and stirrer. After 7 hours the optical rotations ( a n , 1 d m . neat) were only -38", to oxidation, the oxidate (2,175 g.) contained 4.63 moles of -26" instead of -59°.7 Inasmuch as other cis-3-substipinane hydroperoxide. Removal of unoxidized pinane from tuted acetylcyclobutanes are known to epimerize in the prea small aliquot at low temperature left the crude oxidation sence of base to give 20-307, of the trans isomer rotating in products as a residue which contained 947, (wt.) of pinane the opposite sense,15it is assumed that the basic conditions hydroperoxide. Hence the total weight of oxidation prodused for decomposition resulted in partial inversion of the ucts would be 834 g. (787 g. of pinane hydroperoxide and cis-~-2,2-dimethyl-3-ethylacet~lcyclobutane to the trans-d 47 g. of by-products). Assuming that the by-products are isomer, which was not separated by the distillation conditions monoxygenated, this corresponds to a total yield of 4.94 -43') used. To confirm this a sample of the ketone (@D moles of oxidation products. On the basis of their infrared prepared frum the I-hydroperoxide under less basic condispectra, the recovered pinane was pure and the hydroper- tions was heated in 2 N methanolic potassium hydroxide oxide1* contained a small amount of carbonyl compound. until the rotation became constant. The recovered ketone Small amounts of alcohols in the hydroperoxide would be dif- had a Z 3-26" ~ and its infrared spectrum was substantially ficult to detect. =Ittempts to separate the isomers by refracDecomposition of l-Pinane Hydroperoxide.-This oxidate unchanged. tionation of fractions 21-28 were unsuccessful. The maxi(2,175 g.) was cooled to 70" in the reactor and 82 E. (1.5 mum rotation was only -41'. moles) o f sodium methylate was added with stirring. -1Vjien Pinan-2-01 and isopinan-2-01 ITere isolated by recrystallithe mixture was warmed to SO", vigorous decomposition zation of the solids which crystallized from fractions 31-%5 occurred. I t was controlled by external cooling with iceThe pure pinan-2-01, n1.p. 58-60 , water. The maximum temperature was 140'. The vigor- and 27-40, respectively. ous reaction subsided after 20 minutes and the reaction mix- and isopinan-2-01, m.p. 81-82', did not depress the melting points of the corresponding authentic samples16 and their ture was allowed to cool slowly to 100". One-fourth of the infrared spectra were identical with the knowns. original peroxide remained undecomposed. The solution P-Terpineol was not obtained pure but was present in high was neutral, but despite the added base the aqueous layer enough concentration in fraction 42 to permit identification in the trap was slightly acidic. Decomposition was com- by comparison of infrared spectra. Characteristic absorppleted by heating the mixture for an additional hour at 100" in the presence of a n additional 20 g. of sodium methylate tion bands mere observed a t 3.20, 6.05, 8.75, 10.95 and 1 1 2 5 mp. The absorption bands not accounted for by P-terpineol and 0.5 g. o f cobalt carbonate. were a t the proper wave length for isopinan-2-01 and isoverAfter cooling, the product was washed with mater to rehanone. The C=CHe stretching band at 6.05 p was used move the excess sodium methylate, sodium salts of the acids for the semi-quantitative estimation of the @-terpineolconformed and any base-soluble neutrals. centration. I-Isoverbanone w u isolated froin fractions 44-54 tlirougl~ (8) H. Schmidt, B e y . , 1 7 , 5-14 ( I g l i ) . the semicarbazone. After recrystallization from ethyl ace(0) 0. Wallach, A n n . , 360, 88 (1908).
reduction product. This is in good agreement with the decomposition data. Hence, the isopropylidene bridge must exert a strong directive influence on the addition of oxygen to the pinan-2-yl radical b u t does not entirely prevent addition in the position cis to it. The isolation of isopinocampheol and isoverbanone from the decomposition mixture indicates that under the oxidation conditions used the secondary positions also were oxidized. Presumably isopinocamphone and isoverbanols also were present and account for part of the alcohols and ketones which could not be separated well enough for characterization. Although only isopinocampheol was isolated in sufficient purity for identification, the levorotary liquid alcohol obtained along with the solid probably contains neoisopinocampheol.8 I n spite of the precautions taken to remove acids as fast as they formed, the aqueous layer in the traps was acidic. Hence i t is assumed that the aand P-terpineol were formed by acid isomerization of the pinan-2-0ls.~ In a separate experiment it was found t h a t even acetic acid is strong enough to isomerize these alcohols a t the temperatures used for the decomposition.
( 1 0 ) Infrared spectra were run on a doublc beam i n s l r u n ~ e n twith NaCl optics by Mrs. Mary N. U'o~droof. Microanalyses were made by L. E. Brown, Southern Regional Research Laboratory, New Orleans, 1.a. All optical rotations are 1 dm. neat unless otherwise specified. (11) G. Chiurdoglu, J. Decot and Mme. van Lancker-Francotte, Bull. SOL. chirn. Belges, 63, 70 (1954), report [ ~ ] * O D 23.1°, d * % 0.8675 and n z o D 1.4628 for cis-d-pinane. (12) By catalytic reduction and infrared spectrophotometric analysis, the cir:trnnr ratiu i,l a similar s i m p l e of pinane hydroperoxide was fuuud to be 3 or -1 lo I .
--
( 1 3 ) D. E . Baldwiu, V . M. 1,oeblich and I--58were cimverted to the p-nitrohcnzoates F, ;r purification. t ive rccr~~stallizatiiin from peiitane yielded an est 84-86*, [ U ] D 29.5" (c 3.8, chlor~~forni), 48" (c 3.31,beiizene).
!CON~~RIUlJ'I'ION FROM THE S O Y E S
VO!.
81
Anal. Calcd. for C17&oOl;\;: C , 67.30; li, 6.97. Found: C, 67.63: €3,7.01). The 3,3-dinitrohenzoatc, 1n.p. 90-91.5", \vas prepared in :t similar manner. Saponificatim of a sample of the g-nitroljenzoate (1n.p. 80-81") gave an alcr>hol in 90yo yield. b.p. 220-221", n z " ~ 1.4843, d2".r0.9568, [ a ]2.8' ~ (c 5.4, benzene). Tlie alcohol on standing partially scilidified in long needles. One recrystallization from pentane gave a solid whicl: me!ted at 54-56'. The infrared spectrum of the solid alcohol was substantially equivalent t o that. o f the mixture from which it W:LS isolated. Attempts t o prepare it solid pheny1uretli;iii were linsuccessful. Anal. Calcd. for Ci;,HlsO; C, 77.87; II, 1123. Found: C, 7 i . 3 5 ; H, 11.66. Sainples c f autiieiitic isi)~,iriocainptiec,iwere pi-elmrcrl ~ J Y reduction of Ii~drosypin'icamphone by the prcicedure of Kuwata,18 arid by catalytic hydrogenation of trans-pitlocarveol.s The s z m i n g materials available were n o t optically liomogeneous; hence tlie products were semi-si)!id. I n frared s:iectra of tlie two reduction products and nf t h coho1 isolatcd froni the decomposition mixture were all siilistantially identical.
CHEMKC.4L
L4UORATORY, ~ ~ N I \ X , I < S I TOF Y ~LLIN1715]
Preparation and Aromatization of Poly-1 ,3-cyclohexadiene1 BY C. S. MARVEL AND GORDOK E. H A m z e L L 2 RECEIVEDJULY 31, 1958 The polymerization of 1,3-cgclohexadiene to a low molecular weight polymer utilizing a Ziegicr catalyst coinposed c - triisubutylalurninu~nand titanium tetrachloride is reported. Although attempted dehydrogenation of the polp-l,3-cyclohcxadietie failed t o give a complete!y aromatized p-polyphenyl rrhich could be isolated, evidence obtained from infrared spectra, analyses and X-ray diffraction stxdies confirmed the presence of p-polyphenyl in the products of the dehydrogenation reactions.
The lower members of the p-polyphenyl series / P LJ \1 possess remarkably high melting points, with p -- > < [ /,, quinquiphenyl and p-sexiphenyl melting without I i r 111 decomposition a t 380 and +L6O4G0, r e s p e ~ t i v e l y . ~ , ~ Numerous preparations of 1 ,3-cyclohexadiene (I) Numerous attempts have been made to obtain high molecular weight p-polyphetiyls. The Ullrnann re- have been reported, including dehydrobromination action has not been successful for the preparation of 1,2-dibromocyclohexane either with quinoline' or of p-polyphenyls larger than p-sexiphenyl.6 A with sodium ethoxide,8 dehydrobrornination of 3polyphenyl having a molecular weight of 2700- bromocyclohexene with quinoline@and pyrolysis of The most convenient 2800 has been reported from the condensation of 1,2-dia~etoxycyclohexane.~~ f)-dichlorobenzene in the presence of a liquid potas- synthesis yielding the highest purity 1,3-cyclohexasium-sodium alloy.6 However, the physical prop- diene was that involving dehydrobromination of 3erties of the polymer indicate that i t was probably broniocyclohexcne, whicli was obtained in 70-80c/;i yield from the reaction of X-broniosuccinimide and not an all-para polyphenyl Research was undertaken to determine the cyclohexene. The bromocyclohexene was heated feasibility of preparing a high molecular weight u i t h quinoline a t 190"to give 1,3-cyclohexadiene in p-polyphenyl (111) by dehydrogenation of poly- 53-6070 yield. Vapor phase chromatography analvsis showed the product to contain a minimum of 1,3-cyclohexadiene (11). 99% 1,3-cyclohexad;cne The other preparations (1) T h e work discussed herein was supported in part by Contracts were judged less convenient and generally gave 1,3A P 33(616)-3772 and -54% with the Materials Laboratory of W r i g h t cyclohexadierie contaminated with cyclohexene Air Development Center, Wright-Patterson Air Force Base, Ohio 1,2and benzene. nehydrobromination of Reproduction of this paper in whole or i n part is permitted for any p u r po5e of the United States Government. T h e paper is abstracted from dibromocyclohexan a portion of a thesis submitted in p x t i a l fulfillment of requirem-nts for containing onily 45 tile P1i.D. degree by Gordon Ellsworth Hartzell to the Graduste Col4070 cyclohexene an lege of the University of Illinois in 1938. 7
,t
d
( 2 ) National Science Foundation Fellow, 1950-1958. ( 3 ) A. E. Cillnm and D. H. Hey. J . Chem..Soc., l i 7 0 (1939). (1) I
