Patented Nov. 16, 1948 2,454,047

UN STATES PATENT OFFICE 2,454,047 CONVERSION OF ALICYCLIC ALDEHYDES Harry do V. Finch, El Cerrito, Seaver A. Ballard, Orlnda, and Theodore W. Evans, Oakland, Calif., assignors to Shell Development Com pany, San Francisco, Calif., a corporation of t Delaware No Drawing. Application May 9, 1947, Serial'No. 747,128 20 Claims. (Cl. 260-514) i 2 . ., This invention relates to a process for the con aldehydes. The alcohols produced in the course version of alicyclic aldehydes, the production of of the present process, as hereinafter described, alicyclic acids and alcohols, and the production are of a new and useful variety. of aliphatic dicarboxylic acids. More particu The present invention provides an e?icient and larly, this invention provides a process whereby economical process for producing dicarboxylic alicyclic aldehydes may be converted simultane acids which obviates the objections to prior art ously to alicyclic acids and alcohols, and whereby processes, and which is especially adaptable to the.v the alicyclic acids so produced may be further commercial production thereof, and in the course acted upon to produce aliphatic dicarboxylic of which alicyclic acids and new and valuable acids. alicyclic alcohols are produced. I ‘ Certain reactions for the conversion of alde According to our invention, more fully de hydes to acids are well known, and various proc- ~ scribed hereinafter, an alicyclic aldehyde is con esses for these reactions have been described. tacted with a substantially anhydrous molten or However, these heretofore known reactions are "fused” alkali metal hydroxide, or mixture of two not generally applicable to alicyclic aldehydes, 25 or more alkali metal hydroxides. The resulting especially where the alicyclic aldehyde contains alkali metal carboxylate may or may not be sep one or more unsaturated linkages of ole?nic char arated from the reaction mixture. If separated. acter. between two nuclear carbon atoms, since it constitutes a valuable product which may be the necessary reagents or reaction conditions converted by methods known to the art to the commonly cause ring cleavage in such cases, corresponding acid if desired, or it may be further. thereby precluding formation of alicyclic acids, acted upon with an aqueous solution of an alka‘ and usually result in the formation of an aliphatic line material, as hereinafter fully described, to monocarboxylic acid. Accordingly, it is an object produce the salt of an aliphatic dicarboxylic acid. of the present invention to provide a process for This salt may be converted, also by methods the conversion of alicyclic aldehydes, and espe 25 known to the art, to the corresponding-acid if cially those alicyclic aldehydes having at least one desired. If the alkali metal carboxylate is not unsaturated linkage ofole?nic character between separated from the reaction mixture, the salt of ‘ two nuclear carbon atoms, to alicyclic acids. A a dlcarboxyllc acid, and subsequently the dicar further object is the production of alicycllc alco boxylic acid, may be prepared directly therefrom hols in the same step of the process. A further 80 by treating the reaction mixture with watenwlth object, is to react the alicyclic acids so produced adjustment of the concentration of the alkali if so that aliphatic dicarboxylic acids are produced. necessary and heating the resulting mixture, as A further object is to produce aliphatic dicar hereinafter described. The aliphatic dicar boxylic acids from alicyclic aldehydes without boxylic acid, prepared by either process, may be separating the intermediate alicyclic acid from 35 recovered by any convenient means, as by extrac the reaction mixture. tion of the acid salts with ether, acidi?cation with The aliphatic dicarboxylic acids produced ac hydrochloric acid, extraction of the acid with cording to the process of the present invention are ether, and evaporation of the ether. well known, and various methods for their prepa In carrying out the process of our invention we ration have been described. For example, have made the surprising discovery that, on con methods for the preparation of pimelic acid, a tacting an alicyclic aldehyde with a bath com- - typical dicarboxylic acid representative of those prising a. molten alkali metal hydroxide, or a mix herein contemplated which have been heretofore ture of such hydroxides, signi?cant yields of all described, include its preparation from penta cyclic alcohols are obtained. These alcohols may methylene dibromide through the cyanide proc 45 be separated from the reaction mixture,- which ess, and from trimethylene dibromide by means comprises chie?y the alkali metal carboxylate, of the malonic or acetoacetic ester synthesis. the desired alcohol, and unreacted alkali metal However, these methods are commonly suitable hydroxide, by dissolving the cooled reaction mix for laboratory scale preparation only, since the ture in, water,--acidifying with hydrochloric acid, cost of the reactants and the necessity for close 60 extracting with ether, and distlllating the ether control over the reaction conditions prevent sat extract. The acid and alcohol are separated by isfactory commercial scale operations. These the distillation. ' known processes for producing aliphatic dicar The initial reactants of the present invention‘, boxylic acids do not indicate that such acids alicyclic aldehydes, preferably have from 4 to 8 might successfully be prepared from alicyclic 55 carbon atoms in the nucleus or ring, though com-. s 2,464,047 3 4 pounds with larger rings may be used, and pref droxide baths should be operated in the lower erably the reactants have one double bond of region of the recited temperature limits. oleilnic character between two of the nuclear car In converting the alicyclic acid formed in the bon atoms, though alicyclic aldehydes with one or above-described step to the aliphatic dicarbox with two or even more such double bonds may be ylic acid, the acid and an aqueous solution of an employed and are within the scope of the present alkaline material are introduced into a vessel invention. The term "alicyclic," as used herein designed to withstand the pressure developed on with respect to aldehydes, acids and alcohols, is heating to the desired temperature, hereinafter meant to include those aldehydes, acids, and alco described. The proportions of acid, alkaline ma- hols which have a cyclic portion of aliphatic terial and water may be varied considerably, but character, and which may have one or more may advantageously be within the range of from double-bonds of ole?nic character between two about 0.5 to 2 mols of the acid, about 1.3 to 4 nuclear carbon atoms, but which excludes all mols of alkaline material and about 35 to 85 mols compounds having three conjugate double bonds of water. If the acid was not separated from the in a six membered ring, 1. e., compounds of aro 15 reaction mixture in the above-described step, the matic character. The alicyclic aldehyde react composition of the reaction mixture containing ants may be obtained from any convenient source. the alkali metal salt of the acid and free alkali For example, 3-cyclohexenecarboxaldehyde, used metal hydroxide may be adjusted usually by hereinafter to illustrate preferred embodiments adding water and, if necessary, an additional of the present invention, may be obtained by 20 quantity of an alkaline material, to bring the methods known to the art, as for example by composition substantially within the above re the addition reaction between butadiene and cited limits. In carrying out this step, we pre acrolein. fer to use an aqueous solution of an alkali metal In converting an alicyclic aldehyde to an all hydroxide. However, excellent results may be cyclic acid with simultaneous formation of an 25 achieved with aqueous solutions of other alkaline alicyclic alcohol, according to the process of our materials, such as the alkaline earth hydroxides, invention, the aldehyde is contacted with a molt e. g., barium hydroxide or ‘strontium hydroxide, en bath of any of the alkali metal hydroxides, or and aqueous solutions of salts of weal: acids and any mixture of said hydroxides, e. g., molten sodi strong bases, e. g., sodium phosphate. The reac um or potassium hydroxide, or a mixture thereof. 30 tion mixture is then heated under ambient pres We have found that molten mixtures of sodium sure, though higher or lower pressures may be and potassium hydroxides give excellent results, employed if desirable, to a temperature of from and the mixture may advantageously comprise 1 about 250° C. to about 450° C. In most instances mol of potassium hydroxide to 1/2 to 4 mols of temperatures of from about 280° C. to about 380° sodium hydroxide, which is the preferred range. C. give excellent results and are preferred. After Technical grade hydroxides may be used. since sufficient time for reaction has been allowed, we have found that the usual impurities do not usually from 2 to 10 hours, the dicarboxylic acid deleterlously a?ect the process. formed may be separated by any convenient _ In carrying out the process of our invention, we means. For example, the acid salt may be ex prefer to contact the aldehyde reactant with the tracted with ether, the ether extract acidified molten alkali metal hydroxide by passing the va with hydrochloric acid, the acid extracted with pors of the aldehyde into a bath of molten hydrox ether, and the ether evaporated. ide. However, other methods of contacting the al The products prepared according to the proc dehyde with the molten bath may be employed. ess of our invention have many uses. For ex For example, an aldehyde, and especially those 45 ample, the alicyclic acids may be treated to form aldehydes with a relatively high boiling point, esters, useful as plasticizers for various resins, may be contacted with the molten bath by intro the new alicyclic alcohols are useful as solvents, ducing the aldehyde in liquid form beneath or and form derivatives useful in detergent com upon the surface of the molten bath, in which positions, as emulsifying agents, and as driers in method the liquid may or mayinot be preheated 50 resins and varnishes, and the aliphatic dicar before contacting. A further modification which boxylic acids may be used in the production of may be desirable in some instances is to contact polyamide-type resins, as intermediates in the the aldehyde in solid form with the molten bath. production of other resins, and on esteri?cation The temperature of the bath is not critical, but yield esters which are valuable as plasticizers should be su?iciently high so that adequate mix 55 in resins and rubber compositions. ing may be achieved, and may advantageously In order to illustrate a preferred embodiment be from about 200° C. to about 470° C. We have of the present invention, the processing of 3 found that relatively low temperatures favor for cyclohexenecarboxaldehyde to produce 3-cyclo mation of the alcohol. The rate of addition of hexenemethanol and pimelic acid is described the vapors of the alicyclic aldehyde to the molten hereafter. The~vapors of 3-cyclohexenecarboxal hydroxide is not critical, and may advantage dehyde are passed into a bath comprising molten ously be varied for example from about 1 to 5 potassium and‘sodium hydroxide in mol ratio of mols per hour per 1000 grams of the molten from 1:0.5 to 1:4,--at a rate of from 1 to 5 mols hydroxide bath. per hourperlOOO grams of the molten bath. The As above stated, when alicyclic aldehydes are reaction ‘is ‘stopped while there is still excess al contacted with the molten alkali metal bath at._ kali, the reaction mixture cooled, diSSOliVBd in relatively low temperatures, formation of the ali water, acidified with an aqueous solution of a cyclic alcohols arefavored. This is illustrated in mineral acid, extracted with ether, and the ether Examples I and II, wherein the molten baths were extract fractionated. Fractionation yields 3-cy held at 250° C. and 200° C., and the yields of 70 clohexenecarboxylic acid and 3 - cyclohexene the alicyclic alcohols, in these examples 3-cyclo methanol. An aqueous solution of an alkaline hexenemethanol, were 10 and 18%, respectively. material, e. g., sodium or potassium hydroxide, is In carrying out the process of our invention, added to the 3-cyclohexenecarboxylic acid so that therefore, if the alcohols of our invention are de the resulting mixture has a mol composition of airous as products, the molten alkali metal 11? 76 acid: sodium or potassium hydroxide: water 2,454,047 6 . within the range of from about 0.5 to 2:13 to 4:35 nuclear carbon atoms. However, the tendency of to 85. This mixture is heated in a pressureves alicyclic aldehydes to form'products with a dif-' sel. such as a stainless steel bomb, to from about ierent number of carbon atoms, in the processfof 250° C. to 450° C. for from about 2 to 10 hours. our invention, is not marked, and may be con The reaction mixture is then acidified with an trolled to a considerable extent by proper choice aqueous solution of a mineral acid, e. g., hydro of the reaction conditions. such vas the tempera; chloric acid,v extracted with ether, and the ether ture of the molten alkali metal hydroxide bath. evaporated. The pimelic acid product may be The preferred process of our invention, there further puri?ed if desired. The 3-cyc1ohexene fore, contemplates the processing of alicyclic 'al- ' . methanol. prepared as above-described in accord 10 dehydes to produce corresponding alicyclic acids, ance with the process of our invention, is a new alcohols, andaliphatic dicarboxylic' acids, i. e., I composition of matter, and possesses properties the products contain the same number of carbon which make it especially usefull as an emulsify atoms as the alicyclic aldehyde reactant. ' ing agent, a drier for resins and varnishes, and Various modi?cations may be made in the a. solvent for a wide variety of organic materials, 15 present invention as herein described without de In a substantially identical manner other all parting from its scope. For example, various cyclic aldehydes may be processed according to mixtures of alkali metal hydroxides may be em the present invention to produce alicyclic acids, ployed in either step, and various alkaline mate alicyclic alcohols, and dicarboxylic acids. Ex rla‘s may be employed in the second step, i. e., amples of alicyclic aldehydes which may be em 20 in converting the alicyclic acid to the aliphatic ployed in our invention include: 1-cyclobutene dicarboxylic acid; the ?rst step, the conversion carboxaldehyde, 2 - cyclobuteneca'rboxaldehyde, of an alicyclic aldehyde to an alicyclic acid, may 1-cyclopentenecarboxaldehyde, 2 - cyclopentene be carried out at super or sub-atmospheric pres carboxaldehyde, 3 - cyclopentenecarboxaldehyde, sure; and continuous or intermittent instead of l-cyclohexenecarboxaldehyde, 2-cyclohexenecar the batchwise ‘process herein described may be boxaldehyde, 3-cyclohexenecarboxaldehyde, 1, employed. Other modi?cations will be apparent cycloheptenecarboxaldehyde, 2-cycloheptenecar to those skil‘ed'in the art. boxaldehyde, 3-cycloheptenecarboxaldehyde,‘ 4 The following examples illustrate preferred cycloheptenecarboxaldehyde, 1 - cyclooctenecar - embodiments of our invention, which is not to be boxaldehyde, 2 -cyclooctenecarboxaldehyde, 3 considered as limited thereby: cyclooctenecarboxaldehyde, 4-cyc‘ooctenecarbox aldehyde, cyclobutanecarboxaldehyde, cyclopen= ' Example I vtanecarboxaldehyde, cyclohexanecarboxaldehyde, 0.98 mol of vaporized 3-cyclohexenecarboxal~ cycloheptenecarboxaldehyde, cyclooctanecarbox dehyde were passed into a molten mixture com-i aldehyde, and their analogues and homologues. 35 prising 4.0 mols-of sodium hydroxide and 3.11 Substituted alicyclic aldehydes may also be em mols of potassium hydroxide held to a temper ployed, such as 3-methyl-l-cyclobutenecarbox ature of about 250° C. at a rate of 0.9 vmol per‘ aldehyde, 2-methyl - 3 - cyclohexanecarboxalde hour. Some hydrogen was evolved. The cooled hyde, 2-ethyl-3-cyclohexenecarboxaldehyde, 2,5 reaction mixture was dissolved in water, acidi?ed dimethyl-3-cyclohexenecarboxaldehyde, 2-ethyl 140 with aqueous hydrochloric‘ acid, and extracted 3-oyclohexenecarboxaldehyde, 2-isopropyl-3y-cy with ether. Fractionation of the ether extract clohexenecarboxaldehyde, 3-cyclohexene - etha yielded 3-cyclohexenecarboxylic acid and 3 nal, cyclohexane-ethana‘», 1 - cyclobutene-3-pro cyclohexenemethanol. Conversion to 3-cyclo ponal, cyclopentane-4-butanal, and the like. hexenecarboxylic acid was 82% I and to In carrying out the process of our invention, the 3 -cyclohexenemethanol was 10%. products, namely the alicyclic acids and alcohols, The acid thus obtained melted at from 13 to'14° and the aliphatic dicarboxylic ‘acids, will gen (7., boiled at from 85 'to 88° C. (1 mm.), and had erally have the same number of carbon atoms as an equivalent weight of 129. The infra-red the initial alicyclic aldehyde reactant. For ex spectrum indicated the structure to be that of ample, in the conversion of ’3-cyclohexenecarbox 50 3-cyclohexenecarboxylic acid. - - aldehyde, the products, 3-cyclohexenecarboxylic Properties of the new alcohol, 3-cyclohexene acid, S-cyclohexenemethanol, and Dimelic acid, vmethanol. were determined to be as follows: all contain the same number of carbon atoms as boiling point=70.6° C. to 74.0° C. at 5 mm. meri the 3-cyclohexenecarboxaldehyde. However, in cury pressure; bromine number=151 grams per some instances, products containing fewer car 55 100 grams: melting point of the alpha-naphthyl bon atoms than the alicyclic aldehyde reactant urethane derivative=104° 0.; hydroxyl value=' may be produced without departing from the 0.854 equivalent per 100 grams. _Analysis for car scope of our invention. For example, if 3-cyclo bon and hydrogen gave 74.3 and 10.8 weigh hexene-3-propanal be employed as the initial re~ percent. respectively. actant, the resulting products may contain the 00 A solution of 0.149 mol of the 3-cyclohexene same number of carbon atoms, or they may, in carboxylic acid and 0.38 mol of sodium hydroxide‘ dividually or in any combination. contain a fewer in 7.2 mols of water was heated to from 325° C. number of carbon atoms. In this case 3-cyclo to 340° C. for, 4 hours in a stainless steel bomb. hexene-3-propionic acid, 3 - cyc10hexene-3-pro The resulting reaction mixture was acidi?ed with panol, azelaic acid, 3-cyclohexenecarboxylic acid, 65 aqueous hydrochloric acid and extracted with 3-cyclohexenemethanol, and pimelic acid may be ether. . Evaporation of the ether yielded pimelic among the products obtained, depending some acid, the conversion being 66%. . what upon the reaction conditions. The forma Example I! tion of products containing a fewer number of carbon atoms than the initial alicyclic aldehyde 70 Example I was repeated with the following reactant is especia'ly noticeable when employ modi?cations: the temperature of the molten ing alicyclic aldehydes characterized by a rela alkali metal hydroxide was held to about 200° C., tively large ring, e. g., a ring containing '7 or more 1.13 mols of 3-cyclohexenecarboxaldehyde vapor carbon atoms, and particularly if such compounds was introduced into the molten caustic, and the contain more than one double bond between 75 temperature of the 3-cyclohexenecarboxylic acid 2,454,047 8 sodium hydroxide-water mixture was held to perature and pressure at a temperature of from from about 300° C. to about 325° C. for 8 hours. about 250° C. to about 450° C. A substantially identical conversion to pimelic 10. The process for converting an alicyclic alde acid was obtained as in Example I, and a higher hyde containing one unsaturated linkage of ole conversion to 3-cyclohexenemethanol was ob ?nic character between two nuclear carbon atoms tained. namely 18 % . to an aliphatic dicarboxylic acid, which comprises contacting said alicyclic aldehyde with amolten Example III mixture of sodium and potassium hydroxide at a The vapors of 3-cyclopentenecarboxaldehyde temperature of from about 200° C. to about 470° are contacted with molten sodium hydroxide at C., separating the produced alicyclic acid, and ' a temperature of about 350° C. at a rate of about heating said alicyclic acid with an aqueous alka 3 mols of the vapor per hour per 1000 grams of line material to a temperature of from about 250° the molten sodium hydroxide. The reacted C. to about 450° C. at an elevated pressure. I mixture is treated according to the procedure of 11. The process for converting an alicyclic alde Example I, and 3-cyclopentenecarboxylic acid, 15 hyde to the corresponding ‘aliphatic dicarboxylic 3-cyclopentenemethanol, and adipic acid are acid, which comprises introducing said alicyclic recovered as products. , aldehyde into a molten mixture of sodium ny-, The invention claimed is: > droxide and potassium hydroxide at a temperature 1. A process for converting an alicylic aldehyd of from about 200° C. to about 470° C., stopping the to an alicyclic acid which comprises contacting 20 reaction before complete consumption of the al said alicyclic aldehyde with a molten alkali metal kali, acidifying the reaction mixture, separating hydroxide at a temperature not greater than the produced alicyclic acid, and heating said about 470° C. alicyclic acid with an alkali metal hydroxide and 2. A process for converting an alicyclic alde water to from about 280° C. to 380° C. for from 2 hyde to an alicyclic acid which comprises con 25 to 10 hours at an elevated pressure, tacting said alicyclic aldehyde with a molten 12. The process for converting an alicyclic alde alkali metal hydroxide at a temperature of from hyde to an aliphatic dicarboxylic acid, which com about 200° C. to about 470° C. prises introducing said alicyclic aldehyde in vapor 3. A process for converting an alicyclic alde form into a molten alkali metal hydroxide at a hyde to an alicyclic acid which comprises con 30 temperature of from about 200° C. to about 470° tacting said alicyclic aldehyde with a molten C., stopping the introduction of said alicyclic alde mixture of sodium hydroxide . and potassium hyde into said molten alkali metal hydroxide be hydroxide at a temperature not greater than fore complete consumption of said hydroxide, ad about 470° C. justing the composition of the reaction mixture so 4. A process for converting an alicyclic alde 85 that the moi ratio of acid: alkali: water is within hyde to an alicyclic acid and an alicyclic alcohol the range of about 0.5 to 2:13 to 4:35 to 85, and which comprises contacting said alicyclic alde heating said reaction mixture to from about 250° hyde with a molten alkali metal hydroxide at C. to about 450° C. at an elevated pressure. a temperature not greater than about 470° C. 13. The process for converting 3-cyclohexene 5. A process for converting an alicyclic alde 40 carboxaldehyde to 3-cyclohexenecarboxylic acid, hyde to an alicyclic acid and an alicyclic alcohol which comprises contacting 3-cyclohexenecarbox which comprises contacting said alicyclic alde aldehyde with a molten alkali metal hydroxide hyde with a molten alkali (metal hydroxide at a at a temperature not greater ‘than about 470° C., temperature of from about 200° C. to about 470° and acidifying the resulting reaction mixture. C., and separating alicyclic acid and the alicyclic 45 14. A process for producing pimelic acid, which alcohol. comprises reacting 3-cyclohexenecarboxaldehyde 6. A process for converting an alicyclic alde with molten alkali metal hydroxide at a tempera hyde which contains one double bond of ole?nic ture of from about 200° C. to 470° C., acidifying the character between two nuclear carbon atoms to resulting reacted mixture, separating 3-cyclo an alicyclic acid, which comprises contacting said hexenecarboxylic acid therefrom, and reacting alicyclic aldehyde with molten alkali metal hy said B-cycIohexenecarboxylic acid with water and droxide at a temperature not greater than about an alkaline material at a temperature of from 470° C. 250° C. to about 450° C. and an elevated pressure. 7. A process for simultaneously converting an 15. A process according to claim 14 wherein the alicyclic aldehyde which contains one double 55 alkaline material is an alkali metal hydroxide. bond of ole?nic character between two nuclear 16. A process for producing pimelic acid, which carbon atoms to the corresponding unsaturated comprises contacting the vapors of 3-cyclohexene aliphatic acid and the corresponding unsaturated carboxaldehyde with a molten mixture of sodium alicyclic alcohol, which comprises contacting said hydroxide and potassium hydroxide at a tempera unsaturated aliphatic aldehyde with molten 00 ture of from about 200° C. to about 470° C. stop alkali metal hydroxide at a temperature of about ping the reaction before the alkali is completely 880° C. . consumed, adding water to the reacted mixture, 8. A proces for converting an alicyclic aldehyde and heating the resulting aqueous mixture to a to an alicyclic alcohol, which comprises contacting temperature of from about 250° C. to about 450° said alicyclic aldehyde with a molten alkali metal 65 C. at an elevated pressure, acidifying the resulting hydroxide at a temperature not greater than about reacted mixture, and separating pimelic acid 300° C. therefrom, 9. The process for converting an alicyclic alde 17. A process for converting 3-cyclohexanecar hyde to an aliphatic dicarboxylic acid, which com boxaldehyde to 3-cyclohexenecarboxylic acid and prises contacting said alicyclic aldehyde with a 70 3-cyclohexenemethanol which comprises contact molten alkali metal hydroxide at a temperature ing 3-cyclohexenecarboxaldehyde with a. molten not greater than about 470° C., acidifying the re alkali metal hydroxide at a temperature not great sulting reaction mixture, separating the produced er than about 470° C. alicyclic acid, and reacting said alicyclic acid with 18. A process for converting B-cyclohexenecar an aqueous alkaline solution at an elevated tem 76 boxaldehyde to 3-cyclohexenemethanol which 2,404,“? 10 comprises contacting B-cyclohexenecarboxalde REFERENCES CITED hyde with a molten alkali metal’hydroxide at a temperature not greater than about 680° C. The following references are of record in the 19. A process for converting an alicycllc alde _?1e of this patent: hyde to an alicyclic alcohol which comprises con 5 UNITED STATES PATENTS .tacting an aldehyde which contains one double bond of ole?nic character between two nuclear ' Number . _ Name I __ Date v carbon atoms with a molten alkali metal hy 2,285,601 McAllister ______'__> June 9, 1942 droxide at a temperature not greater than about 2,286,559 McAllister ______.._ June 16, 1942 380° C. - 10 I OTHER REFERENCES 20. A process for-the preparation of 3-cyclo hexenecarboxylic acid which comprises contacting Fiesselmann, Ber. Deut. Chem. GeselL, vol. '75, 3-cyclohexenecarboxalclehyde with a molten al pages 881-889 (1942). , ' ' kali metal hydroxide at a temperature not greater French et al., J. Am. Chem. Soc. vol. 64, mes 1479-1499 (1942). than about 380° C. 15 HARRY M: V. 'FINCH. SEAVERA.BALLARD. THEODORE W. EVANS.