quantitatively on a cation resin, and partially retained on an anion resin; the acidic form was easily removed from the cation exchanger by use of dilute sodium hydroxide; the material on the anion column was slowly eluted with 1 to 1 hydrochloric acid. Isolation of Product. By use of much more concentrated solutions of reactants, a t p H about 3, heating the mixture for 30 minutes just below the boiling point produced a yellow-brown precipitate. The mixture was made alkaline (pH 10.5) with potassium hydroxide; the precipitate dissolved and the solution turned an intense blue. Cooling in an ice bath and addition of isopropyl alcohol to decrease the solubility resulted in formation of a precipitate (probably the potassium salt of the anionic complex). The precipitate was filtered, washed, and dried. The product was usually very dark blue (almost black), although occasionally a bright purple solid was obtained. Elemental analysis for carbon, hydrogen, and nitrogen varied considerably from batch to batch. Portions of the salts were titrated with hydrochloric acid, with potentiometric and conductometric detection of the end point;
although sharp breaks were obtained in the titration curves, results were variable from batch to batch. The yellow-brown precipitate originally formed in acidic solution likewise gave variable analyses for carbon, hydrogen, and nitrogen for different preparations. LITERATURE CITED
(1) Ayres, G. H., McCrory, R. W., ANAL. CHEM.36, 133 (1964). (2) Ayres, G. H., Meyer, A. S., Jr., Ibid., 23, 299 (1951); J. Am. Chem. SOC.77, 2671 (1955). (3) Beamish, F. E., Talanta 12,743 (1965). (4) Beamish, F. E., McBryde, W. A. E., Anal. Chim. Acta 9,349 (1953); 18,551 (1958). (5) Busev, A. I., Kiselva, L. V., Vestnik Moskov. Univ.,Ser. Mat., Mekh., Astron., Fiz.. Khim. 13. No.4.179 (1958): Chem. Absir., 53, 11105f (1959). (6) Chechneva, A. N., Podchainova, V. N., Izv. Bysshikh Uchebn. Zavedenii, Khim. i Khim. Tekhnol. 7 (5), 731 (1964); Chem. Abstr. 62, 9760c (1965). (7) Fischer, O., Hepp, E., Ber. 22, 356 (1889). (8) Greiss, P., J. Prakt. Chem. 3, 143 (1871). (9) Janota, H. F., Ph.D. dissertation, University of Texas, 1963. (10) Job, P., Ann. Chim. 9 (lo), 113 (1928); 6 ( l l ) , 97 (1936). (11) Karpova, L. V., Alyanchikova, V. N., Simirnov, P. P., Gut’ho, A. D., Ryserva, I
,
G. V., Morozova, N. F., Labkovskaya, D. B., Vopr. Analiza Blogorodn. Metal., Akad. Nauk SSSR.,Sibirsh. Otd., Tr.6go (Pyatago) Vses. Soveshch. 1963, 30; Chem. Abstr. 61, 10038b (1964). (12) Katzin, L. I., Gebert, E., J . Am. Chem. SOC.72, 5455 (1950). (13) Kirkland, J. J., Yoe, J. H., ANAL. CHEM.26, 1340 (1954). (14) Sawada, T., Kato, S., Bunseki Kagaku 11, 544 (1962); Chem. Abstr. 57, 5297h (1962). (15) Sen‘Gupia, J. G., Anal. Chim. Acla 23, 462 (19tiO). (16) Senise, P., Pitombo, L. R. M., Talanta 11, 11885 (1964). (,17) Ullmann, F., Mauthner, F., Ber. 35, 4302 (1902). (18) Ibid., 36, 4032 (1903). (19) Underwood, A. L., Toribara, T. Y., Neuman, W. F., J. Am. Chem. SOC.72, 5597 (1950). (20) Vosburgh, W. C., Cooper, G. R., Ibid., 63, 437 (1941). (21) Woldbve. F.. Acta Chem. Scand. 9, ‘ 299 (1955”). ’ ‘ RECEIVED for review May 16, 1966. Accepted June 3, 1966. Condensed from a dissertation submitted by Larry D. Johnson t o the graduate school, The University of Texas, in partial fulfillment of the reguirements for the doctor of philosophy egree, June 1966. The authors gratefully acknowledge the financial support of National Science Foundation grant G14479, and fellowships provided by Procter and Gamble, Monsrtnto Co., and the. Dow Chemical Co. \ - - - - I -
Analysis of a High-Molecular-Weight Phenolic Inhibitor H.
S. KNIGHT and HERBERT SIEGEL
Shell Development Co., Emeryville, Calif. Gas chromatography and phase solubility analysis were combined to achieve a more definitive analysis of a high-molecular-weight phenolic inhibitor than would have been possible by either technique alone. Phase solubility analysis showed that the material was about 99% pure, and about 1% of a related phenol wos found by gas chromatography. The agreement of the two techniques showed that this was the only significant impurity present.
T
H E OXIDATIOK-IKHIBITIKG PROPERTIES of certain hindered phenols
have given these materials widespread commercial interest. In the manufacture of films and fibers which may be subjected to high temperature during processing, it is desirable that the inhibitor be of high molecular weight and correspondingly low vapor pressure to avoid evaporation losses. High molecular weight also contributes to low extractability of the inhibitor from the polymer on contact, for example, by foods packaged in films.
A phenolic inhibitor having a molecular weight of 775 and a vapor pressure of 0.014 mm. at 180’ C., suitable for use in food packaging materials, is 1,3,5trimethyl - 2,4,6 - tri(3,5 - di - tertbutyl-4-hydroxybenzyl)benzene, Shell trade-named Ionox 330. The application of this inhibitor in the food and drug industry leads to the need for detailed and precise knowledge concerning its purity, which was believed to be 98% or more. Two complementary techniques were employed to obtain a more definitive analysis than would have been possible by either technique alone or by other available procedures. Phase solubility analysis, a known but little used technique, was applied to determine nonvolatile impurities but was not suitable for light materials. Gas chromatography was employed for the volatile components but could not be used to determine polymers or other nonvolatile impurities. Final agreement of the two techniques showed that only one impurity was present in significant concentration. This was identified by gas chromatography on the basis of its re-
tention volume compared with that of a known compound. I n the course of the gas chromatographic study, it was found possible to determine the Ionox 330 itself. This is believed to be the highest-molecularweight phenol to be successfully eluted from a gas chromatographic column. Analytical techniques that have been successfully used for lower-molecularweight phenols include various forms of spectrometry, determination of weak acidity, gas chromatography, and determination of physical properties such as melting point. Spectrometry and titration were not specific for Ionox 330 which might be expected to contain phenolic impurities, although nuclear magnetic resonance could detect these impurities if they were present a t a sufficiently high level. KO gas chromatographic method was available in the 775 molecular weight range. The melting point of high-molecular-weight materials is strongly influenced by traces of low-molecular-weight impurities and therefore does not provide a practical measure of purity. Phase solubility analysis consists of VOL. 38, NO. 9, AUGUST 1966
0
1221
measuring a t constant temperature the solubility of a solid sample in a relatively poor solvent as a function of sample size. From these data, interpretations with respect to punty, concentration of impurities, and even the number of impurities can frequently be made. A detailed discussion of various systems has been adequately presented by Mader (6). Much work on analysis of phenols by gas chromatography has been published, and a few selected papers will be mentioned here. The techniques employed can be divided into two categories, depending on whether the phenol is determined directly or after conversion to a less polar derivative to avoid adsorption and tailing or to reduce decomposition. Mixtures of phenols of structural complexity up to di-tert-butyl were analyzed directly by Duvall and Tully (9) who employed a packed column containing a mixture of Carbowax 4000 and DC-550 silicone. Close-boiling isomeric phenols such as 2,4- and 2,5-xylenol were resolved fairly well by Brooks ( I ) , using a packed column containing 2,4-xylenyl phosphate on acid-treated Celite. Tominaga (8) resolved di- and trinuclear phenols, the latter on a 40-cm. column packed with 10% Apiezon L on Celite. Porcaro (7) analyzed bisphenols on columns as short as 8 to 10 inches. Grant and Vaughan (5) converted 66 low-molecular-weight phenols to trimethylsilyl ethers and analyzed them on a capillary column coated with a silicone. They reported low conversion for hindered phenols. Freedman and Charlier (3) described conditions for obtaining complete conversion, and recommended a capillary column coated with 2,4-xylenyl phosphate. Gill (4) was unable to repeat Tominaga's work with di- and trinuclear phenols because of tailing. He used columns as short as 3 inches to analyze these compounds after acetylation. In techniques used in this laboratory hindered phenols have not tailed seriously and short low-loaded packed columns have given satisfactory separations of many high-boiling materials. Therefore, direct gas chromatography was explored for Ionox 330. At first, a marker technique was employed to determine the impurities and the Ionox 330 was obtained by subtracting the impurities from 100%. Later a procedure was developed in which the Ionox 330 itself emerged from the column and was measured. EXPERIMENTAL
Solubility Analysis. APREAGENTS. The apparatus included 8-dram screw-capped vials with Poly-Seal caps, and a shaker for rocking the vials horizontally. The work was performed in a constant temperature room a t 22.2' =t0.6" C. Phase
PARATUS
1222
0
AND
ANALYTICAL CHEMISTRY
Reagents were Phillips 99%m isooctane which was flashed before use, and a stock of Ionox 330 which had been recrystallized once from isooctane. PROCEDURE. Six vials were numbered 1 through 6, cleaned, dried, capped, and weighed. Recrystallized Ionox 330 was weighed into vials 1 and 2. A sample size of 1 gram was used in each case. Commercial grade Ionox 330 was weighed into vials 3, 4, 5, and 6. Sample sizes of 0.2, 1.0, 2.2, and 3.4 grams were used. Ten grams of isooctane were accurately weighed into vials 1, 3, 4, 5, and 6. These vials were then capped tightly. Approximately 10 grams of isooctane were added to vial 2, which was heated to 75" to 85' C. in an oil bath for 75 minutes with frequent shaking. This step was carried out to ensure that one of the solubility measurements for the recrystallized Ionox 330 was made using a saturated solution. Vial 2 was then capped and weighed to obtain the weight of the added isooctane. The six vials were mounted horizontally on the shaker in the constant temperature room and rocked continuously for 66.3 hours. At the end of the 66.3 hours, the vials were reweighed and showed slight losses in weight amounting to only o.5yOin the worst case. Possibly, the polyethylene cones in the PolySeal caps softened upon the prolonged exposure to the isooctane leading to a slight leaking around the seal. These losses in weight were assumed to be entil'ely isooctane; for each vial, the weight of the initial isooctane used was corrected for the measured loss. Six additional 8-dram vials were numbered 1 through 6. These vials were cleaned, dried, capped, and weighed. The contents of each vial containing the mixture of sample and isooctane were filtered into a corresponding numbered empty vial. Each vial plus filtrate was capped and weighed. The vials were uncapped and placed in a water bath a t 50' C. The filtrate in each vial was then evaporated to constant weight under a stream of nitrogen which was dried with Drierite and filtered through glass wool. From the weights of the initial sample, initial isooctane (corrected for losses by leaking of capped vials) and from the weights of the residues obtained by evaporation of the filtrates, the following calculations were made for vials 3 through 6.
w w=2 w,. 100 where
W
= composition of system, grams
of sample per 100 grams of isooctane W , = weight of sample, grams W , = weight of isooctane, grams
W,
w = - ' 100
w/
where
w
composition of solution (liquid phase), grams of solute per 100 grams of isooctane W , = weight of residue obtained by evaporating filtrate, grams W , = weight of isooctane in filtrate, grams =
For vials 1 and 2, only w was calculated and the average of these values was taken as the solubility of pure Ionox 330 in isooctane a t 22.2' =t 0.6' C. (72' A '1 F.). Vial 1 2
Solubility grams Ionox 330/100 grams isooctane 0.4142 0.4147 Av. 0.415 ~
Gas Chromatography. APPARATUS. An apparatus with hydrogen flame ionization detector was employed which made use of a Beckman Thermotrac for temperature programming. The apparatus was designed for 3/lginch columns because this size tubing provides a good match between detector and column optimum flow requirements. The column was suspended from an insulating board in the programmer. The injector and detector were mounted on top of the board and were independently heated to 300' to 325' C. Early marker analyses were carried out with a 1-foot by 3/16-in~hcolumn packed with 20% DC-710 silicone (Dow Corning) on Chromosorb W (JohnsNanville). Later direct determinations of Ionox 330 were carried out with 16gauge (heavy-walled) stainless tubing having an internal diameter less than that of 1/8-inch copper tubing, about 1/16inch. This column was packed with 2% SE-30 (General Electric) on Chromosorb W, 80 to 100 mesh. In spite of the lower polarity of the SE-30 silicone, tailing was not objectionable. The SE-30 was a faster solvent and was more stable thermally. PROCEDURE. The solid samples were dissolved in acetone or carbon disulfide, and about 1 111. of 5y0 solution was injected. The SE-30 column was then temperature programmed from 200' to 300" C. in 10 minutes. Somewhat milder conditions were used for the DC-710 column. The carrier flow was maintained at about 40 ml. per min. even in the small bore column, in a sacrifice of efficiency for speed of elution. THEORY OF PHASE SOLUBILITY ANALYSIS
Mixtures of the solid sample and solvent at concentration W (grams of sample/100 grams of solvent) are brought to equilibrium by thorough mixing at constant temperature. The liquid phase of each equilibrated mixture is analyzed for the amount of solute present at concentration w (grams of solute/100 grams of solvent). In many cases the amount of solute can be conveniently obtained by evaporating the liquid phase and weighing the non-
it z
0.2
I-
W , 8. sam~le/lOO s. solvent
Figure 1. analysis
00
Plot of data obtained by phase solubility
w = 1.w
+s
The plotted ( W ,w ) data obtained for this system follow a straight line as shown by AB in Figure 1. The slope of this line is equal to the concentration of impurities I in the sample, and the intercept of the line on the w axis is equal to the solubility S of the pure major component with the particular solvent and temperature used. If one of the impurities exceeds its solubility, then a discontinuity occurs as a t B. Beyond this point, the data follow a new line BC whose slope represents the concentration of the remaining impurities. It is, therefore, possible in some cases to detect and determine several impurities individually. When the concentrations of the major component in the solvent are below its solubility, the unsaturated region OA with a slope of unity is reached. Nonvolatile impurities that are completely insoluble can in principle be detected by examining the unsaturated region. These insoluble residues form a solid phase which is reflected in line OA having a slope less than unity. RESULTS AND DISCUSSION
Phase Solubility Analysis. The phase solubility data ( W , w) for an Ionox 330 sample are plotted in Figure 2. The solubility of recrystallized Ionox 330 is plotted as a point on the w axis. The ( W , w) data and
1.2 100
= -X
20
15
25
35
30
0
Phase solubility analysis of an Ionox 330
the solubility point on the w axis fall on an excellent straight line as shown in Figure 2. The line has the following equation :
w
10
W , s. lonox 330 samDle/100 e . Isooctane
Figure 2. sample
volatile residue. The major component of the sample dissolves in the solvent according to its solubility S (grams of component/100 grams of solvent) at the temperature of the system. For the system under consideration, it is assumed that the impurities are completely soluble in the liquid phase of each sample-solvent mixture. Accordingly, the concentration of impurities in each liquid phase is equal to their concentration I (grams of impurities/lOO grams of sample) multiplied by the sample-solvent concentration W . The Concentration w of solute in the liquid phase of each sample-solvent mixture is then as follows.
I
5
N' + 0.415
The slope corresponds to a nonvolatile impurity concentration of 1.2% w so that the concentration of Ionox 330 in the sample is accordingly 98.8'% w. The gas chromatographic method found 1.2% impurities. The dashed lines drawn in Figure 2 with slopes corresponding to 1.4 and 1.0% w impurities, respectively, indicate the current estimate of the precision of the method to be *0.2y0 w, which is three times the standard deviation. The excellent linearity of the phase solubility data depicted in Figure 2 can be appreciated by the calculations summarized in Table I. I n these calculations, a slope was computed for each hypothetical straight line drawn between a ( W , w) point and the solubility of Ionox 330 plotted as the intercept on the w axis. The procedure using recrystallized Ionox 330 gave the following solubility values: 0.4142 and 0.4147 grams Ionox 330/100 grams isooctane at 22.2' =k 0.6' C. Gas Chromatography. Ionox 330 is apparently the highest-molecularweight phenol t o be determined by gas chromatography t o date. It seems desirable to present the evidence t h a t the peak observed is actually the starting phenol. With a flame detector, oxygen in the phenol molecule does not respond. About 7.5% of the Ionox 330 is oxygen. The area-to-weight calibration factor actually measured relative to xylene was 1.05. Higher factors were occasionally observed, indicating decomposition, and were reduced by rinsing the injector with sodium bicarbonate solution or sometimes just by injecting several samples. The factor
for Ionox 330 was reasonable compared to other similar phenols, showing that a very large percentage of the injected sample is included in the peak. By analyzing a series of phenols and waxes of known structure it was shown that the material that emerges when Ionox 330 is injected is well over C,. The fairly symmetrical peak was trapped in a few inches of hypodermic tubing, dissolved, and reinjected. It emerged at the same time as before. Several peaks were then trapped together and examined by nuclear magnetic resonance, which gave a spectrum consistent with the starting material. There was not enough sample for an unequivocal identification. The sample of the inhibitor which had been subjected to phase solubility analysis was analyzed by gas chromatography. It was found that 1.2y0 of the sample appeared in a single peak a t about 250' C. and the remainder, identified as Ionox 330, emerged after about 5 minutes at 300' C. The early peak coincides with a phenolic compound similar to the Ionox 330, namely 1,3,5 - trimethyl - 2,4 - di(3,5 - di - tertbutyl-4-hydroxybenzy1)benzene. The calibration factor for this material relative to xylene was also 1.05. Small amounts of volatile impurities were found by conventional gas chromatographic techniques. The agreement
Table I.
Linearity of Phase Solubility Data
Slope ( W , w ) point 1 2 3 4
=
concentration
of nonvolatile
impurities, % w 1.19 1.22 1.12 1.20 Av. 1 . 1 8 f 0.04a
a Standard deviation based on three degrees of freedom.
VOL. 38, NO. 9, AUGUST 1966
0
1223
between gas chromatography and phase solubility analysis was considered excellent. ACKNOWLEDGMENT
Certain phenols suspected of being impurities were prepared by T. H. Colby. The gas chromatographic apparatus was designed by F. M. Nelsen.
LITERATURE CITED
(1) Brooks, V. T., Chem. Znd. (London) 105Q.o.1317. .C
(2)-DUvall, A. H., Tully, W. F., J . Chromatog. 11, 38 (1963). (3) Freedman, R. W., & Charlier, G. O., ANAL.CHEM.36, 1880 (1964). (4) Gill, H. H., Zbid., p. 1201. (5) Grant, D. W., Vaughan, G. A., in
“Gas Chromatography,” M. van Swaay, ed., p. 305. Butterworths, London, 1962.
(6) Mader, W. J., “Organic Analysis,” J. Mitchell, Jr., ed., Vol. 11, p. 253, Interscience, New York, 1954. (7) Porcaro, P. J., ANAL.CHEM.36, 1664 (1964). (8) Tominaga, Sachiyuki, Bunseki Ka aku 12, 137 (1963); Lowry Abstract &rd 37, 6-15-63.
RECEIVEDfor review March 7, 1966. Accepted June 6, 1966.
Identification of Normal Paraffins, Olefins, Ketones, and Nitriles from Colorado Shale Oil TAKE0 IIDA, EllCHl YOSHII,’ and EITARO KlTATSUJl Faculty of Pharmaceutical Sciences, Toyama University, loyama, lapan Straight-chain components of a Colorado shale oil distillate boiling from 280” to 305’ C. were obtained through urea adduct formation, and analyzed principally b y chromatographicseparation methods. They were found to be a mixture of paraffins (C13 to CIS), olefins (c13 to CIS) with predominantly 1-alkenes, nitriles (CIZ to Cia), and ketones (C13 to GIB) in which 2-alkanones are predominant. A useful and convenient chromatographic method for the separation of hydrocarbon components uses a silica gel-silver nitrate mixture. A mixture of ketones and nitriles is most effectively separated b y sodium borohydride reduction followed b y adsorption chromatography.
I CRUDE I
SHALE OIL1
1
GAS O I L ( C u t 4 ) B . p . 2 8 O o - 3 0 5 e C.
E x t r a c t i o n w i t h 5% KOH I
I
TAR BASE E x t r a c t i o n w i t h 60% H 2 g 0 4 I
r
60%
NEUTRAL O I L
91% of o r i g i n a l gas o i l
oil is a complex mixture of saturated, olefinic, and aromatic hydrocarbons, as well as nitrogen-, oxygen-, and sulfur-containing compounds. The nonhydrocarbon constituents that make up approximately half of the shale oil are an outstanding characteristic of shale oil as compared to petroleum. It is important to know the types of these compounds and desirable to determine the structures of individual components, not only in connection with processing techniques for fuel oil production but also the use of byproducts with industrial raw materials. U. S. Bureau of Mines workers (14) and others (6, 6, 9-12) have made valuable contributions to the identification of the shale oil naphtha components consisting of tar bases, tar acids, neutral nitrogen and oxygen compounds, and hydrocarbons. However, high boiling fractions which constitute a major portion
D i l u t i o n w i t h H2g
HALE
address, Department of Chem2yPresent, Columbia University, New York, 1
1224
ANALYTICAL CHEMISTRY
SOLUBLE
I
Urea Adduct Formation
S
n2s04
COMPOUND
I
BRANCHED-CHAIN NEUTRAL OIL
STRAIGHT-CHAIN NEUTRAL O I L
80% Adsorption Using S i l i c a Gel
T PARAFFIN-QLEFIN MIXTURE, C12-C19
9%
I P r e p a r a t i v e S c a l e GLC
MIXTURE, 2%
I NaBH Reduction -4
I
A d s o r p t i o n U s i n g Silica G e l
Cr03 O x i d a t i o n
Figure 1.
Separation of groups of compounds from shale oil
of shale oil distillate have not been so extensively investigated. The type analyses of individual concentrates separated according to physical prop-
erties have been principally carried out (2-4). In 1956, one of the present authors (T. I.) began to study the components
