Patented Sept. 7, 1954 2,688,627

UNITED STATES PATENT OFFICE 2,688,627 DCYCLOPENTADENE CARBOXYFLIC ACDS Charles A. Cohen, Roselle Park, Louis A. Mikeska, Westfield, and Frederick Knoth, Jr., Sayreville, N. J., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application May 8, 1952, Serial No. 286,834 13 Claims. (C. 260-429) 1. 2 This invention relates to novel dicyclopenta- diene is used as the starting material. In the diene carboxylic acids and to a process for pro- case of pure dicyclopentadiene the hydrogenation ducing the same. Specifically, this invention re- product is 9,10-dihydrodicyclopentadiene boiling lates to tetrahydrodicyclopentadiene carboxylic at 177° to 178° C., at atmospheric pressure and acids and process for producing these products. 5 inelts at 50 to 50.5° C. On titration with bromine In the practice of this invention the starting it absorbs bromine in an amount equal to 119 material is Substantially pure dicyclopentadiene centigrams of bromine per gram. The mixed Or a copolymer of methyl cyclopentadiene and products of hydrogenation are liquid at Ordinary cyclopentadiene (hereinafter referred to as temperature due to the mutual depression of the methyldicyclopentadiene) or a dimer made from 10 melting point. methyl cyclopentadiene (hereinafter referred to For purposes of purification and elimination of as dimethyldicyclopentadiene) or mixtures of two any unhydrogenated dimers present in the crude or more of these products normally found in dihydro product it is desirable but not necessary petroleum refinery streams originating from to distill the crude hydrogenation product at at either vapor phase, gas phase, or steam cracking 15 mospheric or higher preSSure So as to crack any processes. The production of the starting mate- unhydrogenated material to monomers which Will rials and methods of concentrating these dinners boil between 40 and 75° C. and thus effect a sepa is not an intrinsic part of this invention. For ration of a pure dihydro dimer which is stable most purposes, 60 to 90% alpha-dicyclopenta- against cracking when distilled at atmospheric diene available commercially Will Suffice. It is a 20 pressure. primary object of this invention to convert the The next stage in the preparation of these acids individual or mixed dimers to the tetrahydro- is to ester-CXonate the dihydro derivative to a carboxylic acids by a series of reactions involving carbaikoxy derivative of the tetrahydro dimer. hydrogenation to the dihydro derivative, ester- This is effected by bringing into intimate mixture OXOnation of the dihydro derivative, and hy- 25 in a pressure resistant vessel capable of having drolysis or Sagonification of the ester to the cor- its contents agitated, the dihydro derivative and responding acid. an excess of a monohydric aliphatic alcohol in the The hydrogenation of the dicyclopentadiene or presence of a cobalt catalyst while Subjecting the alkyl Substituted dicyclopentadiene to the dihydro contents of the vessel to a pressure of carbon derivative is effected by means of ordinary hy- 3G monoxide at a pressure of preferably 3000 pounds drogen in the presence of catalysts such as Raney per square inch gauge and a temperature of pref nickel, nickel on kieseguhr or other supporting erably 150° C. medium, or noble metal catalysts such as plati- The monohydric alcohol may be any aliphatic num oxide and the like. Temperatures for the alcohol of from one to 12 carbon atoms, pref hydrogenation may be from ambient temperatures erably 1 to 3 carbon atoms, and may be a normal to about 100° C. and pressures may be from one 3) primary alcohol, a branched primary alcohol, or atmosphere to as high as 1000 pounds per Square a secondary alcohol. Examples of these alcohols inch pressure. The upper limit expressed is not are methanol, ethanol, isopropanol, isooctyl alco limiting. Hydrogenation may be accomplished on hol, dodecanol, etc. Since the primary purpose the raw material as such or in the presence of an of the process is to recover the acids, it is of ad inert, diluent and solvent. On hydrogenation vantage to use the lowest molecular weight alco to the dihydro derivative two hydrogen atoms hol available and for this reason methanol is the enter the ring in the 9,10 position as shown in preferred alcohol. The quantity of alcohol to be the Structural formula, below: used in this reaction should be in excess of at

6 6 45 least One molar equivalent of the dihydro nate 10 N 01 rial utilized in the reaction and is preferably pres 7 CH, -- Ha - ent in a volume ratio of three parts of alcohol to 9 2 one of the dihydro material. Under these condi N-1N/ 8 3. tions, a large part of the dihydro product is solu 50 ble in the alcohol but is not completely so. It has Dicyclopentadiene Dihydrodicyclopentadiene been found that complete solubility of the re to give 9-10 dihydro dicyclopentadiene or a actants in the alcohol phase is not necessary for mono- or dialkyl substituted dicyclopentadiene Successful operation of the reaction. depending on whether pure dicyclopentadiene, a The cobalt catalyst used in this reaction may be mono alkyl derivative, or a dialkyl dicyclopenta- 5 5 present preferably in a concentration of between 2,688,627 3 4. 0.1 and 5.0 Weight percent as metal based on the The acids prepared by the process described dihydro product and is added to the reaction nix above are novel and have many useful proper ture either in the form of finely powdered cobalt ties not hereinbefore shown by products of sini metal or as cobalt carbonyl or as a cobalt Salt lar molecular Weight. In performance chara,c- of an organic acid readily soluble in at least one terstics they are best approached by the naph of the reaction materials Such as the alcohol or thenic acids isolated by alkali extraction from dihydro material. For this purpose we use cobalt certain gas oils, but suffer from none of the acetate, cobalt oleate, cobalt naphthenate or the drawbacks of these naphthenic acids in that the cobalt Salt of the novel acids forming the subject naphthenic acids are odoriferous to an unde of this invention. 0 sirable degree, possess poor color initially, and The reaction as set forth hereinbefore is run become worse in storage and contain appreciable under the conditions set forth until at least one quantities of reactive sulfur compounds which molar equivalent of carbon monoxide has been interfere seriously with their extended use. absorbed as indicated by pressure drop. On cool ihese new acids readily form oil- and hydrocar ing and removing the reaction mixture from the bon-soluble salts of all of the heavy metals and pressure vessel, there is obtained a mixture Com accordingly are a suitable material for the pro prising excess alcohol and the alkyl ester of the duction of paint driers such as the cobalt, lead tetrahydrodicyclopentadiene carboxylic acid cor and manganese salts, and in addition are Suitable responding to the alcohol employed in the reac for the production of hydrocarbon-Soluble cop tion. The point of attachment of the carboxyl 20 per and zinc salts which are of the utmost in group to the dicyclopentadiene ring is in the 1 or portance for the treatment of textiles, leather, 2 position as shown in the structural formula, and other material exposed to humid climatic below: conditions. The zinc salt in addition to use in fungicides, mildew preventatives and in paints 1.N COOR 1N 25 is also suitable for incorporation into lubricant CH CI compositions where they act as inhibitors. It is within the province of this invention to utilize l l"Uloor these acids for any uses where the naphthenic Ester of tetrahydrodicyclo- Ester of tetrahydrodicyclo acids have hitherto been used, since a unique pentadiene 1: Carboxylic Acid pentadiene 2: Carboxylic Acid 30 feature of the acids described in this invention In the case of pure dihydrodicyclopentadiene and is their ability to readily form oil and hydrocar methanol, the methyl ester may be readily Sepa bon-soluble derivatives of metal salts. The acids rated from excess methanol by distillation. The may further be esterified with other alcohols or methyl esters of the mixture of the 1- and 2 glycols to form plasticizers, Synthetic lubricants carboxylic acids boils at 97 to 99 C. at 2 mm. 35 and the like. They are capable of rendering preSSure and shows On analytical Saponification, basic dyes, namely, those containing an aimino a saponification equivalent equal to 288 mgm. group, which are normally water soluble in the KOHAgm. With the conditions shown above a form of their salts with inorganic acids, oil or yield of 78 mole percent of the ester was obtained hydrocarbon-soluble by reaction of the basic dye in a typical run based on the quantity of dihydro 40 With this acid. alpha-dicyclopentadiene charged to the pressure Wessel. Eacample 1-ox-Dicyclopentadiene For recovering the corresponding acids these Commercially available dicyclopentadiene esters are then hydrolyzed by Conventional meth which . On analysis was found to contain (ex ods such as the use of moderately dilute acids, pressed as monomer) 75% of cyclopentadiene Such as 20% Sulfuric acid used. With or without and 15% methyl cyclopentadiene was cracked in the addition of an agent capable of depressing the liquid phase by distillation under a fraction the interfacial tension such as mahogany Sul atting tower containing 30 plates. Using a re fonates, Twitchell agents and the like. Or, the flux ratio of 15:1 rejected any methyl cyclo esters may be Saponified in Conventional nan pentadiene formed during the Cracking process ner by means of an excess of alkali. In the case and substantially pure cyclopentadiene boiling at of the former method the acids are obtained di 40-40.5° C. at atmospheric pressure was taken rectly and are separated from the inorganic acid overhead. The distillate was permitted to stand medium and purified by distillation. Where for three days at room temperature at which saponification is utilized for converting the ester 55 time the major portion of the monomer had di to the acid, the acid is recovered from the sa merized to dicyclopentadiene. The undimerized ponification mixture by acidification with a min diene was removed by application of vacuum at eral acid such as H2SO4, HCl and the like. The ordinary temperature resulting in solidification crude acids as obtained by either method are of the residue. It was distilled at reduced pres heavy viscous oils, nearly colorless, and are ob 60 tained in Water-White state by distillation pref Sure, boiling at 170° C. extrapolated to atmos erably under reduced pressure. The mixed acids pheric pressure and melted at 32-32.5° C. obtained from pure dihydro-alpha-dicyclopenta Eacample 2-Dihydro a-dicyclopentadiene diene boil at 131° to 132° C. at 1.5 mm., are water One hundred and thirty-two grams of ox-di white in color, and nearly odorless. On stand 65 ing, preferably at reduced temperature, the dis cyclopentadiene prepared in Example 1 Was dis tilled acid crystallizes into a snow-white Solid solved in 400 ml. of anhydrous ethanol contained and on recrystallization of the solid acid from in a hydrogenation bomb, 50 mgm. of PtCl2 cata petroleum ether there is obtained a single acid lyst added, the air exhausted from the System melting at 102 to 103° C. having neutralization 70 and replaced with hydrogen under 60 pounds per equivalent equal to 311 mgm. KOHAgm. ASSign square inch guage pressure. The free Space in - ment of this Solid acid to either the 1- or 2-po the system was equal to 7.63 liters. The bomb sition cannot be done at this time with certainty was agitated at room temperature with immedi since oxidative degradation of either the 1 or 2 ate absorption of hydrogen. Hydrogenation to acid leads to the same end products. 75 the dihydro a-dicyclopentadiene was complete in 2,688,627 5 6 20 minutes as indicated by a pressure drop of of mineral acid (Congo red indicator) and the 47 pounds guage pressure. ether removed on the steam bath. The residue The bomb was opened, the solution filtered to was distilled under high vacuum yielding a remove suspended platinum and the alcohol re water-white, Wiscous oil which boiled at 131-132° moved by distillation at atmospheric pressure. 5 C. at 1.5 mm. Hg pressure and weighed 173 grams. The crude product from four hydrogenation runs Titration of a sample with standard alkali gave was combined and distilled at atmospheric pres a neutralization equivalent of 0.1812 compared to Sure. Prior to taking any distillate overhead, the a theoretical equivalent of 0.1802. After standing distillation was run under total reflux in order to for Sometime the acid solidified to a white crystal crack any unhydrogenated dicyclopentadiene. O line mass. Recrystallization from petroleum The dihydro-alpha-dicyclopentadiene boiled at ether gave pure white crystals melting at 102 177-178° C. G. 760 mm., weighed 502 grams, and 103 C. (Copper Bar). The acid as prepared solidified on cooling. It had a melting point of appears to be a mixture of tetrahydro-alpha 50 to 50.5° C. and absorbed bromine by A. S. T. M. dicyclopentadiene 1:carboxylic acid and tetra procedure. D875-46T in an amount equivalent hydro alpha-dicyclopentadiene 2:carboxylic to 119.8 centigrams of bromine per gram. The acid. Assignment of the acid melting at 102 theoretical equivalent for pure dihydro-alpha 103° C. to either the 1 or 2 position cannot be dicyclopentadiene is 119.1 centigrams of bromine done with certainty at this time. per gram. Eacample 5-Copper salt of tetrahydro-or-dicy Eacample 3.-Methyl ester of tetrahydro ox-di 20 clopentadiene 1: (2) carboacylic acid cyclopentadiene 1: (2) carboacylic acid Eighteen grams (0.1 mol) of the acid prepared Two hundred and one grams of the dihydro in Example 4 were dissolved in 100 ml, of 1.0 alpha-dicyclopentadiene prepared in Example 2 N NaOH, the pH adjusted to 6 and diluted to was dissolved with the aid of heat in 667 ml. of 250 ml. with water. The solution of the sodium anhydrous methanol and charged to a 2 liter Salt was heated nearly to boiling and to it was stainless-steel high pressure autoclave. To the added, with efficient agitation a solution of 8.5 mixture was added 4.3 grams of finely powdered grams of culpric chloride (CuCl2.2H2O) in 250 cobalt metal, equivalent to 0.5% by weight on ml. of water heated nearly to the boiling point. the total reaction mixture. The air was dis 30 The copper Salt precipitated as pale bluish-green placed from the System and the autoclave crystals. The precipitate was washed twice by charged with carbon monoxide to a pressure of decantation with 400 ml. Of hot water and then 2400 pounds per square inch guage at 20 C. collected on a Bichner funnel. After pressing Agitation was started and the temperature raised dry it was allowed to stand in a desiccator over over the course of One-half hour to 150° C. at CaCl2 for One week. Chemical analysis showed which temperature the pressure in the system rose a copper content of 14.3 weight percent copper to 3500 pounds pressure per Square inch guage. against a theoretical copper content of 15.05. Absorption of the CO was steady at the Work The copper salt is Soluble in the cold in most of ing temperature of 150° C. and the System was the common organic solvents such as ether, repressured to 3500 pounds each time the pres 40 benzene, hexane, petroleum spirits, etc. Sure dropped to 3000 pounds pressure. Absorp A Solution of the copper salt in a petroleum tion of the CO was continued until approximate naphtha boiling between 240 and 290° F. Was ly 120% of the theoretical quantity of CO had made. So as to contain 4% of Cu in the Solution been absorbed as indicated by pressure drop. and then padded into cotton duck in an amount The autoclave was allowed to cool, the crude re equal to a 50 weight percent take up. On drying action product filtered from a small amount of the cloth showed on analysis a take up of 2 unreacted cobalt metal and fractionally dis Weight percent of copper. It was stable against tilled. After removing the excess methanol the leaching when Washed with Water and when product boiled at 97-99 C. at 2 mm. pressure, Subjected to Soil burial tests showed no tender was water white in color, had a mild fruity odor ing of the fabric in the time required to cause and weighed 244 grams. About 50 grams of ma nearly complete disintegration of the untreated terial representing column holdup, which boiled cloth. at somewhat higher temperature probably due Eacample 6.-Cobalt Salt of tetrahydro cy-dicyclo to superheating, was discarded. Analysis by sa pentadiene 1: (2) carboacylic acid ponification with standard alkali gave a saponi 5 5 fication equivalent of 288 mgm. KOH per gram. The cobalt salt of the distilled acid prepared Eacample 4-Tetrahydro a-dicyclopentadiene, in Example 4 was made in the same manner as 1: (2) carboarylic acid the copper Salt in Example 5 except that 11.9 One hundred and ninety-four grams of the grams of cobaltous chloride (CoCl2.6H2O) was methyl esters of tetrahydro alpha-dicyclopen 60 substituted for the copper chloride. The pre tadiene carboxylic acid prepared in Example 3 cipitated cobalt Salt which was a pale pink in was added to 100 grams of KOH (85%) dis color was taken up in petroleum naphtha after Solved in 500 ml of absolute alcohol. The solu Washing and filtration, water held in the filter tion was heated on a steam bath under reflux for cake separated from the naphtha solution, and 4 hours, the alcohol removed by distillation under the Solution dehydrated by distillation under reduced pressure and the residue dissolved in a Dean-Stark Water trap. The clear Solution of 500 ml. of cold water. The cold aqueous Solu the cobalt salt which was deep purple in color was tion was extracted twice with 200 ml. portions of analyzed for cobalt content and adjusted to a petroleum ether and then acidified with about 6 weight percent Solution of the metal. 135 ml. of concentrated HC1. The carboxylic Eacample 7-Manganese Salt Or tetrahydro on-di acid appeared as a milky precipitate which on cyclopentadiene, 1: (2) carboacylic acid standing collected as a pale yellow oil on the The manganese salt of the distilled acid pre bottom of the flask. The mixture was extracted pared in Example 4 was prepared in the same with ethyl ether, the ether extract washed free 75 manner as the cobalt salt in Example 6 2,688,627. 7 8. except that 8.5 grams of manganous sulfate pressure. After removing some low boiling ma (MnSO4.H2O) was used instead of the cobalt. terial, there was obtained a water-White product The precipitated manganous salt was perfectly boiling at 177-184° C. which weighed 824 grams. White in color and when dissolved in cold hex In contradistinction to pure dihydro-alpha di ane gave a colorless solution. On heating a Cyclopentadiene which is a Solid at Ordinary tem Solution of the manganous salt in petroleum peratures, the dihydro methyl dicyclopentadiene naphtha in the presence of air the color grad remains liquid. It had a bromine number by ually darkened (probably due to a change in val A. S. T. M. procedure D875-46T equivalent to 17 ence State of the manganese) to a reddish-brown centigrams of bromine per gram, Color. The Solution in the naphtha, was ad 10. When Subjected to ester-OXOnation in the justed to contain 6 weight percent of manganese. manner described in Example 3 a water-White liquid acid was obtained on Saponification of the Eaccinaple 8-Dirging tests on Cobalt and manga ester. The metal salts of the acid had substan 126Se Sdlts tially the same solubility characteristics as the A Series of tests Were run on the time required 15 Salts made from pure tetrahydrodicyclopenta for uniform films of linseed oil and a synthetic diene 1: (2) carboxylic acid. drying oil made by the polymelization of buta Eacample 10-Dialkyl tetrahydro dicycloperatadi diene to set to tack-free condition. For pur ene carboacylic acid pOSes of comparison two driers available com mercially, Nuodex 6% cobalt and Nuodex 6% 20 A high boiling bottoms obtained from the manganese Were used in Companion experiments. liquid phase Cracking of commercial dicyclopen tadiene was cracked in the vapor phase and a The table below gives the drying times found: fraction rich in methyl cyclopentadiene boiling at (a) SYNTHETIC DRYING OIL 73° C. was continuously removed as a side stream 25 during fractionation of the cracked products. Conc. of Metal, The crude methyl cyclopentadiene was allowed to Wt. Percent Drying Time to Tack Drier Free State, hours dimerize at room temperature and the dimer purified by distillation at reduced pressure. It boiled at 207-210° C. extrapolated to atmospheric preSSure. Analysis showed the following compo 30 sition (expressed as monomer) : Weight percent Methyl cyclopentadiene------93.2 Cyclopentadiene ------2.6 35 C7 cyclodiene------2.8 Acyclic C5 dienes------1.4 (b) LINSEED OIL One hundred and fifty grams of the above di methyl dicyclopentadiene was charged to a hy Conc. of Metal, drogenation bomb with sufficient absolute etha Wt. Percent Drying Time to Tack 40 nol to make a total volume of 500 ml, and 100 Free State mgm. of PtC2 hydrogenation catalyst added. Co Hydrogenation Was started at room temperature Not tack free in 15 days. and continued for a pressure drop of 46 pounds 15 days. per Square inch gage from an initial 60 pounds Do. 45 DO. pressure. The catalyst was removed by filtration, ------4 days. alcohol removed by atmospheric distillation and .04 50 hours, .02 DO. the product fractionally distilled at atmospheric D0------.. 04 D0. preSSure So as to Crack and remove as monomer any unhydrogenated dimer. Distillate boiled at The above data indicate that for fast drying 50 215-218 C. Weighed 140 gms. and on redistilla oils such as the Synthetic drying oil, both the tion under reduced pressure boiled at 48-49 C. at Nuodex catalyst and the experimental salts are 2 mm. preSSure. equivalent. For slow drying oils such as linseed When Subjected to ester-oxonation in the oil, the metal salts of the acids forming the sub manner described in Example 3 a. Water-white ject matter of this invention are superior. 55 liquid acid was obtained on saponification of the ester. The metal Salts of the acid had substan Eacample 9.-Alkyl tetrahydrodicyclopentadiene tially the same solubility characteristics as the carboacylic acids SaltS made from pure tetrahydrodicyclopenta One liter (965 grams) of a commercial grade of diene 1: (2) carboxylic acid. dicycloperatadiene found to contain on analysis 60 What is claimed is: 75% cyclopentadiene and 15% methyl cyclopen 1. A process for the production of tetrahydro tadiene (expressed as monomer but combined as alpha-dicyclopentadiene carboxylic acids which copolymers) was charged to a 2-liter hydrogena comprises reacting a material selected from the tion bomb together with approximately 50 grams group consisting of dicyclopentadiene and alkyl of Raney nickel hydrogenation catalyst. Hy 65 derivatives thereof with hydrogen to form a hy drogen was admitted to the system to 1800 pounds drogenated material selected from the group con per Square inch guage and agitation started. sisting of dihydrodicyclopentadiene, dihydroal Absorption of hydrogen began immediately with kyldicyclopentadiene and dihydrodialkyldicyclo a simultaneous rise in temperature which gradu p&ntadiene, reacting the hydrogenated material ally leveled out at 85°C. The system was repres 70 With CO and a monohydric aliphatic alcohol in sured each time the pressure dropped to 1000 the presence of a cobalt-containing catalyst at a pounds until a total pressure drop of 2900 pounds temperature of 100-200 C. and at a pressure of had taken place. The catalyst was removed by 2500-4000 p. S. i. g. to form a carbalkoxy deriva filtration from the crude dihydrodiene and the tive of the hydrogenated material and converting filtrate Subjected to fractionation at atmospheric 75 the carballkoxy derivative to a carboxylic acid se 2,688,627 10 lected from the group consisting of tetrahydrodi 10. Salts of tetrahydro-alpha-dicyclopentadi cyclopentadiene carboxylic acids, alkyl tetrahy ene:1 (2) carboxylic acid, wherein the metal of drodicyclopentadiene carboxylic acids and dial the salt is one selected from the group consisting kyl tetrahydrodicyclopentadiene carboxylic acids. of Copper, manganese, Cobalt, zinc, and lead. 2. A process for the production of tetrahydro 11. Salts of tetrahydro - alkyl - dicyclopenta dicyclopentadiene:1 (2) carboxylic acid which diene:1 (2) carboxylic acid, comprises reacting dicyclopentadiene with hydro 12. Salts of tetrahydro-alkyl-dicyclopentadi gen to form dihydrodicyclopentadiene, reacting ene:1 (2) carboxylic acid, wherein the metal of dihydrodicyclopentadiene with CO and methyl the Salt is one selected from the group consisting alcohol in the presence of a hydrocarbon-soluble 10 of copper, manganese, Cobalt, zinc, and lead. Salt of cobalt at a temperature of about 150° C. 13. Tetrahydro - alpha-dicyclopentadiene car and a pressure of 3000 to 3500 p.s. i. g. to form carbo-methoxy tetrahydrodicyclopentadiene, and boxy compounds having the formula: converting the carbo-methoxy derivative to tet 6 5 rahydrodicyclopentadiene:1 (2) carboxylic acid. 5 101 3. A process according to claim 2 in which the R-- C COOM hydrocarbon-soluble salt of cobalt is cobalt oleate. N 2NY2 4. A process according to claim 2 in which the 8 3 R. hydrocarbon-soluble salt of cobalt is the cobalt wherein the COOM group is attached to a carbon Salt of tetrahydrodicyclopentadiene:1 (2) car 20 atom selected from the 1 and 2 carbon atoms, boxylic acid. wherein R and R' represent substituents selected 5. Tetrahydro - alpha - dicyclopentadiene:1 (2) from the group consisting of hydrogen and alkyl carboxylic acid. groups, and wherein M is a substituent selected 6. Tetrahydro - alkyl - dicyclopentadiene:1 (2) from the group consisting of alkyl groups, hydro Carboxylic acid. 25 gen and an equivalent weight of metal. 7. Alkyl esters of tetrahydro-alpha-dicyclo pentadiene:1 (2) carboxylic acid, wherein the References Cited in the file of this patent ester group contains an alkyl radical of 1 to 12 Carbon atoms. UNITED STATES PATENTS 8. Alkyl esters of tetrahydro-alkyl-dicyclo 30 Number Name Date pentadiene:1 (2) carboxylic acid wherein the 2,448,368 Gresham et al. ------Aug. 31, 1948 ester group contains an alkyl radical of 1 to 12 2,514,533 Bloch ------July 11, 1950 carbon atoms, OTHER REFERENCES 9. Salts of tetrahydro-alpha-dicyclopentadi 35 Elsenier's Encyclopedia of Organic Chemistry, ene:1 (2) carboxylic acid, Wol. 13, pages 1030-1031.