INDUSTRIAL AND ENGINEERING CHEMISTRY
April, 1946
ACKNOWLEDGMENT
The author wishes t o acknowledge the suggestions and criticisms of the members of the Development Section of the Ethyl Corporation in the preparation of this paper, and to thank the management of the Ethyl Corporation for the aid extended in publishing this paper. Thanks are also due Ruth Seglin for assistance in the early part of this work. NOMENCLATURE
L P P, P,
= molal latent heat of vaporization, B.t.u./lb. mole
= vapor pressure, lb./sq. in. abs. = critical pressure, lb./sq. in. abs.
= reduced pressure, P/P,.
T = saturatian temperatye R. T, = critical temperature, k. T = reduced temperature, T/T,. O
405
Unprimed symbols refer to material whose properties are being investigated (the unknown), primed symbols refer to the reference material whose properties are being correlated with those of the unknown. LITERATURE CITED
(1) Gordon, IND.ENO.CHEM.,35, 851 (1943). (2) Herzog, Ibid., 36,997 (1944). (3)
Keenan and Keyes, “Thermodynamic Properties of Steam”, New York, John Wiley & Sons, 1936. Meissner and Redding, IND.ENO.CHEM.,34, 521 (1942). Othmer, Ibid., 34, 1072 (1942). Quinn and Jones, “Carbon Dioxide”, A.C.S. Monograph 72. New York, Reinhold Pub. Corp., 1936. Sage and Lacey, IND.ENG.CREM.,30, 673 (1938). Ibid., 34, 730 (1942). Stearns and George, Ibid., 35, 602 (1943). Tanner, Benning, and Mathewson, Ibid., 31, 878 (1939). U. 8. Bur. of Standards, Circ. 142 (1923).
Composition of Gum Turpentine
of Coulter Pine N. T. MIROV California Forest and Range Experiment Station‘, Berkeley, Calif.
Analysis showed that the turpentine of a rare Coulter pine growing in California consists of two terpenes: I-apinene and 1-8-phellandrene with an admixture of two paraffin hydrocarbons, n-heptane and n-undecane. The presence of paraffins in Coulter pine turpentine shows once more that turpentine as obtained from pine oleoresins is not always a mixture of terpenes alone. Probably an admixture of paraffin hydrocarbons to the terpenes is more common than earlier investigations had indicated.
T
H E oleoresin composition of only aboul twenty of the seventy or more species of pines has been investigated. Each new study of a species is a contribution to our knowledge of oleoresins and may help to explain the processes of formation of oleoresin in the living tissue of trees. This is of fundamental importance to the naval stores industry. Although only a few pine species are now used for commercial gum turpentine production, the future may see many more pressed into service with consequent adjustment of turpentine specifications. The oleoresins of pines are important not only from an industrial point of view; a study of the biochemistry of the genus Pinus promises to be of far-reaching importance in various other ways, such as in breeding studies. Coulter pine (Pinus coulteri D. Don) has been used in several breeding experiments a t the Institute of Forest Genetics, a branch of the California Forest and Range Experiment Station. To facilitate these experiments, an investigation was made of the biochemical characteristics of Coulter pine oleoresin, especially the volatile part. Previous work with the oleoresin of the various pines showed that its specific peculiarities could be used to advantage in differentiating species and identifying hybrids (9). Oleoresin was obtained by standard turpentining methods from 18-year-old planted trees growing in the Eddy Arboretum a t the Institute of Forest Genetics, Placerville, Calif. The trees represent almost the whole range of Coulter pine. (Coulter is a rare 1 Maintained by the Forest Service, U. 8. Department of Agriculture, in cooperation with the University of California.
pine that grows singly, never forming pure stands, in the coastal ranges of California as far nor6h as the latitude of San Francisco; it also occurs sporadically in Lower California.) Fifteen trees were tapped once a week from May 20 to August 12, 1944. The total amount of oleoresin obtained was 8674 grams, about 48 grams per cup per streak. The oleoresin was of a sugary crystalline nature; after prolonged standing a more liquid part separated on the top. I t was kept in friction-top cans until analyzed in November, 1944. The oleoresin was distilled with steam a t atmospheric pressure, the temperature not being allowed to rise above 145’ C. Batches of about 1000 grams each of the oleoresin were distilled in a roundbottom 2-liter flask. A Kjeldahl connecting bulb was plaaed between the flask and the condenser to prevent particles of rosin from being carried over mechanically. Eight batches were distilled, and 1443 grams of volatile oil (turpentine) were obtained. The average yield of the eight distillations was as follows: turpentine, 16.92%: rosin, S3.O0Y0; impurities, 0.08%; total, 100.oo% From the fact that the rosin was not perfectly soluble in 95% alcohol, it appeared that partial polymerization of some ingredients of the volatile oil had taken place a t the temperatures of the steam distillation. The volatile oil was dried over calcium chloride and kept in airtight bottleg in cold storage until used. The volatile oil had the following characteristics: specific gravity dls, 0.8505; index of refraction n22, 1.4767; specific rotation [ a ] ~-,15.21. The oil tended to polymerize much more readily than commercial turpentine. A sample of 500 grams of the oil was distilled a t atmospheric pressure with a 12-inch Hempel column. The results of this distillation (Table I) show the presence of a component boiling below the turpentine range and possessing an index of refraction lower than the indices of terpenes, a decrease in the index of refraction of the last three fractions, and a relatively high percentage (15) of polymerized residue. Another 500-gram batch of Coulter pine turpentine was distilled with a 12-inch Hempel column under 20 mm. of pressure. Figure 1 shows the results of distillation under atmospheric and
.
INDUSTRIAL AND ENGINEERING CHEMISTRY
406
TEMPERATURE AT 20 MM. PRESSURE
62 !
I
72
I
1
I
1
120 I30 140 150 160 170 180 TEMPERATURE AT ATMOSPHERIC PRESSURE 110
Figure 1.
82
190
Boiling Point Curves for the Volatile Oil of Coulter Pine Oleoresin
Vol. 38, No. 4
The product was so volatile as t'o make collection and estirnation extremely difficult. I t possessed a peculiar odor characteristic of purified heptane obtained from Pinus j e f r e u i and P. sabiniana. A sample of 10 cc. of the product was redistilled over sodium. I t boiled between 98" and 99" C., and nas not, affected by the concentrated sulfuric acid. The specific gravity determined in a 5-cc. pycnometer was di: 0.690, index of refraction was 1.3871 at 23" C., and molecular aeight determined cryoscopically in benzene was 101.85. I t is concluded that the lo~-boiling fraction of the oil contains a paraffin, n-heptane (C&€118). frobably about 5% of heptane is present in the volatile oil. I-a-PIPI'ENE. Fractions 2 to 15 of Table I1 were redistilled four times under 20 mm. of pressure. Two main fractions were obtained. One fraction, amounting to 147 grams or about, 307, of the original oil, had t>hefolloIving properties: boiling range, 55' to 59" C. at 20 mm. pressure and 154' to 158" C. at atmospheric pressure; specific gravity, 0.8530 at' 15' C,; index of refraction, 1.4690. I-a-Pinene was identified in this fraction by preparation of the nitrosochloride. A copious precipitate of pinene nitrosochloride was obtained when 14 ce. of the oil were dissolved in 30 cc. of glacial acetic acid mixed with 20 cc. of ethyl nitrite, cooled with ice, and treated with a mixture of 11 cc. of hydrochloric acid and 11 cc. of glacial acetic acid (6). After five recrystallizations from chloroform by methanol, {,he nitrosochloride melted at 104" C. I-p-PHELLANDREXE.The other large fraction mentioned in the preceding paragraph, after being redistilled five times under 20 mm. of pressure, amounted to 173 granis or about 35% of the original oil. It had the following properties: boiling point, 69" to 75" C. a t 20 mm. pressure; specific gravity, 0.8400 at, 15" C.; index of refraction, 1.4701. This fraction had a tendcncy to poly-
reduced pressure, Specific gravity, index of refraction, and specific rotation were determined for each fraction of the distillation under reduced pressure; the results (Table I1 and Figure 2) show that the component having the low boiling point was partly lost when the turpentine was distilled under reduced pressure. NeverTABLE I. FRACTIONAL DISTILLATION OF COI-LTER PIKE theless the constants of fraction 1 indicated the presence of a nonTURPEXTINE AT ATMOSPHER~C PRESSURE (756.2 AIM.) terpene substance. The characteristics of the last two fractions Temp hmulative Refractive also indicated a nonterpene component. Cor., Fraction No. C. Dist., yo Index (15" C.) Only 5y0 of the residue was left in the flask after distillation 90 -110 1,4020 1 0.3 2 110 -157 1.1 1.4561 under reduced pressure, and this included some of the oil that 3.4 1 4691 3 157 -161 trickled back to the flask from the column after distillation was 4 161 -162 5.5 1.4710 5 162 -163 7.8 1.4722 completed. It is obvious that polymerization of the volatile oil 16.6 163 -164 1.4730 6 25.5 164 -164.8 1.4742 7 was greatly reduced by distillation at reduced pressure. The de36.8 164.8-1% 1.4748 8 gree of polymerization of the volatile oil is apparent in Figure l. 47.4 166 -170 1.4778 9 53.9 10 1 ,4795 170 -172 The values of the physical constants of different fractions (Table 59.9 1.4811 172 -174.5 11 64.7 174.5-177 12 1.4821 11) are, in general, decidedly lower than they should be for ter69.6 1.4841 13 177 -180 penes. Apparently the 12-inch Hempel column, which had been 14 74.7 1.4851 180 -183 79.6 1.4825 16 183 -186 used successfully by previous workers ( 2 1 , page 10) for fractional 83.1 1.4756 186 -190 16 84.9 1,4645 190 -195 distillation of terpenes, was not efficient enough in the fractionaI? Residue Above 195 100.0 1.5103 tion of Coulter pine oil, which has nonterpene fractions boiling below and above the distillation range of terpenes. I n fact, fractionation with DISTILLATIOX OF COULTER PINETI-RPFIXTINE TABLE11. FRACTIONAL this apparatus was very poor. AT 20 ?VIM.PRESSURE IDENTIFICATION OF COMPONENTS
It appears from the physical characteristics of Coulter pine turpentine that it contains a readily polymerized terpene and two nonterpene components-one with a boiling point much lower than that of or-pinene, and the other boiling above the boiling range of the terpenes. R.-HEPTANE.The specific gravity and the index of refraction of the first two fractions (Table I) suggested the presence of a paraffin hydrocarbon. These fractions, combined with fraction 1 of Table 11, were shaken once with concentrated sulfuric acid and redistilled.
Fraction NO.
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17
Residue
Boiling Point,
c.
T o 53
53-55 55-57 57-58 58-59 59-60 60-62 62-63 63-64 64-66 66-67 67-68 08-69 69-70 70-73 73-87 87-89 Above 89
-Distillate---Quantity, Obsvd., CumulaGrams Z '. tive, 94 10.3 20.3 27.5 26.9 $7.8 23.1 24.5 21.9 19.4 22.6 22.7 22.6 25.2 23.7 21.7 18.8 4.1 20.5
2.4 4.9 6.7 6.5 13.9 5.6 5.9 5.3 4.7 5.5 6 1
5.7
.2
I)
4.6 ;.0
0.0
2.4 7.3 14.0 20.5 34.4 40.0 45.9 51.2 55.9 61.4 66.9 72.4 78.: 84.2 89.4 94.0 95.0
100
Specific Refractive Gravity Index at 15' C. a t 15' C. 0.8103 1.4596 0,8480 1.4698 0.8499 1,4702 0.8487 1.4712 1.4724 0.8483 0.8453 1.4736 0,8444 1.4744 0,8414 1.4762 0.8393 1.4776 0.8367 1.4792 0.8355 1.4808 1,4824 0.8348 0.8337 1.4838 1.4842 0.8349 0 8338 1.4818 1.4541 0.8013 0.7973 1.4364 0.9341 1.4971
Specific Rotation a t 20' C.
-
8.94 -10.10 -11.01 -11.23 -11.84 -13.10 -13.54 -14.33 -15.48 -1G.51 -17.84 -18.88 -19.42 -20.12 -19.86 -11.21 - 8.70 f24.57
April, 1946
INDUSTRIAL AND ENGINEERING CHEMISTRY
407
merize when attempts were made to distill it under atmospheric pressure. This tendency to ready polymerization was noticeable in Coulter pine turpentine in every phase of the work. The incomplete solubility of the rosin in 95% alcohol, the large amount of sirupy residue left in the flask after the fractionating of the oil under atmospheric pressure, the fuming during redistillation, the rapid polymerization of the turpentine when exposed to the air, and the physical properties, all pointed to the presence of one of the -least stable terpenes, phellandrene. Phellandrene nitrosite was obtained in abundance in the fraction by the following method: 5 cc. of the oil were dissolved in 10 cc. of petroleum ether and added to a solution of 5 grams of sodium nitrite in 8 cc. of water; then 5 cc. of glacial acetic acid were added slowly while the solution was stirred constantly and cooled with ice. The nitrosite was filtered, dissolved in a small quantity of chloroform, and precipitated with cold 8.1 8.3 8.5 1.444 1.454 1.464 1.474 1.484 -10 -20 methanol. It melted a t 103' C. Further SPECIFIC GRAVITY INDEX OF REFRACTION SPEC. ROTATION purifications resulted in a product that melted Figure 2. Specific' Gravity, Index of Refraction, a n d Specific Rotation at about 90' C. (11, page 27). The instaCurves for the Volatile Oil of Coulter Pine Oleoresin bility of phcllandrene nitrosite mentioned by other work. rs (11)who prepared it from sugar - test eliminated the possibility of the presence of limonene or dipine twpentine also occurred in this experiment. pentene. A copious precipitate of phellandrene nitrosite was obtained ~-UNDECANE The . last two fractions (Table 11) combined also when 1 cc. of the crude Coulter pine turpentine was placed with all collected residues were redistilled with a 12-inch Hempel in a test tube with 2 cc. of glacial acetic acid, 5 cc. of petroleum column, and the portion boiling between 190" and 200" C. was ether, and 2 cc. of concentrated solution of sodium nitrite. repeatedly shaken with con'centrated sulfuric acid until no coloraOTHERTERPENES. The fractions bdiling between 161' and tion occurred. It was extremely difficult t o get rid of the impuri170" C. and between 170" and 180' C. (Table I) were redistilled ties (probably polymers of phellandrene). Finally about 25 cc. repeatedly. The first group of fractions was tested for the presof colorless oil were obtained. After washing with sodium carbonence of &pinene and the second group for the presence of limoate, the oil wa6 dried for 2 days over metallic sodium. A 15-cc. nene and dipentene. sample of the oil was distilled in a 30-cc. distilling flask. Ninety Ten grams of the oil were oxidized with 24 grams of potassium per cent of the hydrocarbon boiled between 194" and 194.5' C. permanganate in 600 cc. of water to which 5 grams of sodium hydroxide mere added. The mixture was shaken for 20 minutes, (corrected). Molecular weight was determined cryoscopically in benzene. Table I11 gives the physical characteristics of the hythe unreacted oil was removed by steam distillation, and the drocarbon, compared with those for n-undecane. manganese sludge was filtered off. The filtrate was evaporated to 200 cc. under reduced pressure while a continuous stream of This hydrocarbon was found to be optically inactive. Accordingly, the second paraffin hydrocarbon found in the Coulter pine carbon dioxide was passed through the solution. No sodium turpentine was identified as n-undecane. nopinate was obtained after cooling. Therefore it was concluded RESIDUE.The residues boiling above 200' C. were fractionated that P-pinene was not present in the oil. a t reduced pressure (20 mm.) with a 12-inch Hempel column. In the redistilled fraction boiling between 170' and 180' C. no crystalline tetrabromide or hydrochloride was obtained; this The results are shown in Table IV. n-Undecane was found in all fractions. About half of fraction 4 was found to consist of n-undecane. All attempts to obtain a crystalline dihydrochloride from fractions TABLE 111. PHYSICAL CHARACTERISTICS OF COULTERPINE 6 and 7 were futile. No color reactions characteristic of cadinene UNDECAXE or aromadendrene cou!d be produced. When 5 drops of oil were Hydrocarbon from Constants Coulter Pine n-Undecane (6) dissolved in 1 cc. of acetic anhydride, a pinkish-brown color deMolecular weight 155.0 156.30 veloped which gradually turned dark brown. It appears that Index of refraction 1.4200 (23.5' C.) 1.4184 (20' C.) the residues boiling above 200' C. consisted chiefly of polySpecific gravity 0.7465 (15/15O C . ) 0.741. (20/4O C.) Boiling point, ' C. 194-194.5 195.84 merized phellandrene, with a n admixture of n-undecane and possibly a small amount of some unidentified sesquiterpenes. TABLE Iv. F R A C T I O N A L DISTILLATIONOF RESIDUESUNDER Summarizing, the turpentine obtained from Coulter pine oleo'REDUCED PRESSURE (20 MM.) resin consisted of: n-heptane, about 5%; I-a-pinene 30-35%; Fraction Temp. Dist., Si.Gr. Refractive Z-p-phellandrene 35-45 %; n-undecane, about 10%; and posNO. Cor.. c. % (22' C.) Index (23O C . ) 6668 1 0.8388 ' 1.4774 sibly a small amount of sesquiterpenes.
.
2 3 4 5 6
7 Residue
68- 70 70- 73 73- 84 84-102 102-114 114-128
.....
0.8310 1.4770 0.8289 1.4742 0.8180 1.4654 0.8114 1.4472 0 9300 1.4852 0.9340 1.4930 Very viscous, dark amber colored
DISCUSSION
The volatile oil obtained from Coulter pine oleoresin has rather unusual composition. It consists mostly of two terpenes: I-a-pinene and I-8-phellandrene with a n admixture of two ali-
INDUSTRIAL A N D ENGINEERING CHEMISTRY
408
Vol. 38, No. 4
phatic hydrocarbons, n-heptane and n-undecane. ‘Il-hile athat tht: jxiraffiii Couriti by Schorgt-r iri t h i l sugar pine ol(vrcwin pinene is the most common terpene of pines, the presence of 15-as n-undecane. J,ater, n-undecane T T ~ Sloillid in turpentine+ of phellandrene in pine oleoresin is not, very common. Schorger P . mxelsa and P . nionticola (3, 1 2 ) . (10, page 756) reported it in turpentine of lodgepole pine (Pinits So far, n-undecanr hiis h e m found in four pine s p c i w , in(*Iu(liiig r o n b t a murrayann). I n both Coulter and lodgepole pine it is :i Coultvr pinc: n-heptaiit,, in tiso species. Thus, n t prcsc,nt thc: levorotntory form of p-phellandrene. Heptane has been found oleoresins of a t least six pines contain paraffins. Prohihly t’urthtlr bcforc in oleoresins of P. jeffreyi and P. sabiniuna (10, pages 739 irivestigations in this direction will ri 11thc prcwnw i)f lx+rxffitl tirid yt?2). I n both species the voiatile oil consists of 9;c: hcphydroc;rrhris in othc~i.pinc~*. tniie, the remaining 57; being st raight-chain aldchytlcs ( 1 , 3, LITEKA’TUKE CITEI) 1 3 ) . Heptane was found also in a natural hybrid betxeen Jeffrey F’oore, P. A , . .1. Am. Phurm. Assoc., 18,350-3 (1929). and ponderosa pines ( 4 , 8 ) . In this hybrid about l5C; of the volaFoote, P: A, and Mirov, N. T., Ibid., 22, 828-34 (193:j). tile oil consisted of n-heptane a,rid 8.5% consisted of terperiw. Gordon, S. M., A m . J . Ph,urm., 100, 156-61 (1928). Coulter pine is the only pine species (not hybrid) SO lar knowii Harvley, L. F., arid Beglinger, E., unpuh. rept., Forest, ~’rlJdllc6S Laboratory, Madison, \Tis., 1929. in whose olcorcsiI: heptane is found as an admixture, t o the terHeusler, F., tr. by F . J. Pond, “Chemistry of Terpenes”. 1RO2. penes. The presence 01 normal undecanc i n Coultvr pine turpcvHodgman, C . D.. Handbook of Chemistry and I’liy~im, tine is of extraordinary interest. Originiiil) thiq l!~-tlrr~c.;irl~ot~ 27th ed.. p. 808, No. 4426, CleT-eland, Cbeni. Riihher T’iib. rvas isolated from Pennsylvania petroleum ( 7 , . CO.. 1943-44. Mabery, C . F.. Proc. Am. Acad. A r t s Sei., 32, 121-76 (1897). Schorger (10, page 753) found an oil th:it ma>-h:ivc, :i parMirov, N. T., J . FoTe.strY, 27, li6-87 (1929). affin hydrocarbon in P. lumbeitiana turpcritilics. The liydrocarIbid., 40, 953-4 (1912). h n , purified by repeated shaking with sulfuric acid, boiled heSchorger, 9.W., Trans.Wiu. Acad. Sei., 19, Pi. 2 , 728-66 (19191. Scliorger, A. IT., U. S. Dept. Agr., Forest Seraice KwU. 119 tween 194’ and 200’ C. a t 742.7 nim.; the specific gravity l m s (1913). 0.7549 and thc indrx of refraction 1.4249. Schorger attributed Simonsen, J. L., and Kau, 11. G.. I n d i r m Forest Records, 9, I -12 the p r e v n w of thi hydrocarbon to the coiitaminat ion of the (1922). oIror(:siii n-ith kt~rorrnt~: aftc>rlattsr findings thew can lw n o doubt 1-111. A . IT,,. I . A m . Phnrm. _issoc..24, 380-2 (~RRS‘I t i c L c , i i
CORRELATING EQUILIBRIUM CONSTANTS Chemical Reactions and Heats of Reaction D O N i L D F. OTHMER mi) M W H U K H. LL‘LEY Polytechnic I n s t i t c t i e of B r o o k l y n , IT. Y-.
NooL
iyhich ‘has been iounti usc.ful in correlating inan!. properties of gases, of liquids, aiid of solutions is a grapli on which soiiie property is plotted on logarithmic papor against the vapor pressure of a referencc substance a t the same trinperature. Sucli a graph was first, I w t l t o correlatv vapor prcss~~rc. data ( 7 ) . The vapor pressures of soine staiidard substaiicc arc’ indicateti on the horizontal scale of an ordinary sheet of log paper, and tho corresponding points of t emperaturc are indicated. OrdinateP for these points are erected, and on these temperature ordinate.; are plotted values of the m p o r pressures of thc desired snbstanccLs to give straight liner;. The slopes of these lines are the ratios of the molar latent lieat of the substance to the molar latent hrat of the reference at every temperature. Besides vapor pressurc, many other propert,ira of gases and solutions have been found to givr straight lines on the same type of plot, such as gas soluhilities and partial pressure (12), the pressure of adsorbed materials from adsorbents ( 1 0 ) ,vapor composit,ioris and related propotc. crtics of solutions (U), viscositics (8), REiCTION CO\STAh’T
This method ot correlation, giving straight lines, allows the ready checking of experimental data and the possibility, by extrapolation or interpolation from a relatively few experimentai
points, of obtaining data tliroughout a coniplet,e range. k‘igitrc I shows the plot of t,he recent data of Kelley ( 5 ) on the Ilissociation pressures as a function of temperature for various reartions (curves 1, 3, 4, 6, 7) and the equilibrium constants against the same tempera,turc functions for ot,her reactions (oiirws 2, 5, 8). The latter three straight liiios were obtained by extt’iitiitig tlict field of application of the mct.hod of plotting; the thcmiod?.riarrii[, background will be indicattvl lattbr. Reaction rate coiista.nt,s, ionization constants, eqiiilil)riuiii const’ants, and solubility product constants may all bo im-related by the use of E’igurc I . In rach case the slopes of tho resulting straight lines are the ratios of the heats of reaction for the particular system to thc latent heat of the reference substance.. All of these plots ma,y be construct,ed in the same way as thc previous correlations on log paper. The Y axis is calibrated i n units for the appropriate rate or equilibrium constant; tile X axis is calibrated, first in units for the vapor pressure of a suitablc reference substance, and then in corresponding temperat,ures, as indicated above. On the vapor pressure scale of the X axis tho temperature lines are erect,ed a t the eorrespoiiding vapor prcssure values, and then the rate or equilibrium constants are plottorl on t,hese temperature ordinates. For equilibrium constant,s (Figures 2, 3), reaction rate constants (Figures 4, 5 , B), and solubility product constants (Figure 8),
