nificantly by heating. These results can be seen in Table 11. Repeated readings on a series of different samples indicated good color stability for periods up to one week. Solutions of 9-chloroacridine must be prepared immediately before use because the acridine undergoes rapid ethanolysis in ethanol (5). Velocity constants of the nucleophilic replacement of the chlorine atom by ethoxide ion in 9-chloroacridine and other chloroheterocycles have been studied by Chapman and Russell-Hill (6). These solutions are permissible to use for approximately one-half hour after preparation. Decomposition can be seen by the appearance of a brownish-colored precipitate. Two batches of powdered reagent, both obtained (5) A. Albert, “The Acridines,” 2nd ed., St. Martin’s Press, New York, 1966, p 254. (6) N. B. Chapman and D. Q. Russell-Hill, J . Chem. Soc., 1956, 1563.
from Eastman Kodak, were utilized during the course of the research and behaved the same in their reactions with primary aromatic amines. No special precautions had to be taken in the storage of 9-chloroacridine powder even though the literature states that decomposition will occur unless stored over potassium hydroxide at 4 “C (5). In summation, spectrophotometric measurements with 9-chloroacridine provide a relatively simple and rapid means of determining primary aromatic amines in the presence of aliphatic amines and secondary and tertiary aromatic amines. It is comparable in its sensitivity to diazotization-coupling techniques and possesses the advantage of simplified reagent preparation. RECEIVED for review September 23, 1968. Accepted November 18, 1968. Investigation supported in part by the Office of General Research, University of Georgia.
Identification of Alkyl Aryl Sulfides in Wasson, Texas, Crude Oil R. L. Hopkins, R. F. Kendall, C. J. Thompson, and H. J. Coleman Bartlesville Petroleum Research Center, Bureau of Mines, U.S. Department of the Interior, Bartlesville, Okla. THERE is ample evidence that thiols (1-3), sulfides (1, 4 4 9 , thiophenes ( I , 9-12), benzothiophenes (13,14), and thiaindans (15) are present in crude oils. However, prior to this investigation no alkyl aryl sulfide had been identified in any crude oil. This paper describes the isolation and the positive identification of (2-methyl-1-thiabutyl)benzene (phenyl sec-butyl sulfide), the tentative identification of three other alkyl aryl sulfides, and establishes for the first time the presence of this class of sulfur compounds in petroleum.
(1) S. F. Birch, J. Ins!. Petrol., 39, 185-205 (1953). (2) H. J. Coleman, C. J. Thompson, R. L. Hopkins, and H. T. Rall, J . Chem. Eng. Data, 10,80-4 (1965). (3) D. Haresnape, F. A. Fidler, and T. A. Lowry, Ind. Eng. Chem., 41, 2691-7 (1949). (4) J. S. Ball and H. T. Rall, Proc. Am. Petrol. Inst., Sect. III, 42, 128-45 (1962). (5) H. J. Coleman, N. G. Adams, B. H. Eccleston, R. L. Hopkins,
Louis Mikkelsen, H. T. Rall, Dorothy Richardson, C. J. Thompson, and H. M. Smith, ANAL.CHEM., 28, 1380-4 (1956) (6) C. F. Mabery and W. 0. Quayle, J . SOC. Chem. Ind., 19, 505-6 (1900); Am. Chem. J., 35,404-32 (1906). (7) C. J. Thompson, H. J. Coleman, R. L. Hopkins, and H. T. Rall, J . Chem. Eng. Data, 9, 473-9 (1965). (8) Ibid., 10, 279-82 (1965). (9) S. F. Birch, T. V. Cullum, R. A. Dean, and R. L. Denyer, Ind. Eng. Chem., 47,240-9 (1955). (10) C. J. Thompson, H. J. Coleman, Louis Mikkelsen, Don Yee, C. C. Ward, and H. T. Rall, ANAL.CHEM., 28, 1384-7 (1956). (11) C. J. Thompson, H. J. Coleman, C. C. Ward, and H. T. Rall, J . Chem. Eng. Data, 4, 347-8 (1959). (12) H. J. Coleman, C. J. Thompson, R. L. Hopkins, and H. T. Rall, J . Chromatog., 20, 240-9 (1965). (13) H. J. Coleman, C. J. Thompson, R. L. Hopkins, N. G. Foster, M. L. Whisman, and D. M. Richardson, J . Chem. Eng. Data, 6,464-8 (1961). (14) F. P. Richter, A. L. Williams, and S. E. Meisel, J. Am. Chem. Soc., 78, 2166-7 (1956). (15) C. J. Thompson, H. J. Coleman, R. L. Hopkins, and H. T. Rall, ANAL.CHEM., 38,1562-6 (1966).
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ANALYTICAL CHEMISTRY
EXPERIMENTAL PROCEDURES Preparation of Concentrate. The origin of the 200 to 250 “C distillate and of the thiaindan concentrate, in which the alkyl aryl sulfides were found, has been described in a previous publication (15). Referring to the chromatogram of Figure 4 of that publication (15), material producing the chromatographic peak at about 28 minutes retention time was the object of this investigation. Identification of Alkyl Aryl Sulfides. Most of the material producing the peak at 28 minutes was identified using data from mass and infrared spectrometry, gas-liquid chromatography (GLC), and microdesulfurization. The mass spectrum of the material under investigation indicated an intense molecular ion at m/e 166, two units higher than the 164 ion for the 2,2-dimethyI-l-thiaindan, which had been identified (15) as the principal component of the material emerging from the GLC column at 36 minutes. A parent mass of 166 could result from several classes of sulfur compounds-namely, cycloalkylthiophenes, dithienyls, alkyltetrahydrobenzothiophenes, alkylbenzenethiols, and alkyl aryl sulfides. The cycloalkylthiophenes were eliminated by GLC retention time data and/or spectral evidence. The 2- and 3-cyclohexylthiophenes have retention times 4 to 10 minutes beyond the trapped area on both the polar and nonpolar columns. The disubstituted thiophenes (methyl cyclopentyl) of molecular weight 166 were eliminated by infrared spectral data. 2,5-Disubstituted thiophenes have a very strong band at 12.6 p (16). All other disubstituted thiophenes have a medium to strong band between 11 and 12 p (17). Absorp(16) Dorothy M. Richardson, Norman G . Foster, Barton H. Eccleston, and Cecil C. Ward, U. S. Bur. Mihes Rept. Imest. 5816,22 pp (1961). (17) John F. Zack, Jr., I. Synthesis of Compounds Containing
Condensed Thiophene and Pyrrole Rings. 11. Spectra Studies of Thiophene Derivatives. Ph.D. Thesis, Univ. of Illinois, Champaign-Urbana, Ill., 1956.
tion bands of medium to strong intensity were not present in the spectrum of the isolated material at these positions. Further, the cycloalkylthiophenes would not produce the propane, n-butzne, cyclohexane, and methylcyclohexane observed in the products of desulfurization to be discussed later. The dithienyls and alkyltetrahydrobenzothiophenes were excluded by GLC retention time data. For example, the three possible dithienyls have retention times on the nonpolar column of approximately 30 minutes beyond the trapped area and 100 to 190 minutes beyond the trapped area on the polar column. The tetrahydrobenzothiophenes have retenlion times well past the trapped area on both polar and nonpolar columns. The alkylbenzenethiols, if present in the original material, would have been removed from the sample by the extraction with sodium hydroxide and sodium aminoethoxide. These circumstances leave only the Cioalkyl aryl sulfides contributing to the intense mje 166 ion. Mass spectral data are reported in Table I. The data of column 3, pertaining to the material isolated from the crude oil, show intense ions at rnje 110, 124, and 166. The mass spectra of ten of the Cloalkyl aryl sulfides show intense fragment ions either at m/e 110 or 124, resulting from cleavage of the bond beta to the aromatic ring (18, 19) and rearrangement of one hydrogen atom. These compounds are listed in Table 11. Only four of these 10 sulfides have retention times compatible with the trapped area on both nonpolar and polar columns (see Tables I11 and IV), thereby eliminating the other SIX as components of the peak material. Both mass and infrared data (discussed later) suggest that all four sulfides, namely (2-methyl-l-thiabutyl)benzene,2-methyl-l-(2-methyl1-thiapropy1)benzene. 3-methyl-l-(2-methyl-l-thiapropyl)benzene, and 4-methyl-l-(2-methyl-l-thiapropyl)benzene are present in the sample. Based on the quantitative evidence from the infrared spectral data, experimental blends of these four alkyl aryl sulfides were prepared. Table I, column 4, shows the mass spectrum of the blend in closest agreement with that of the sample spectrum. Very small quantities of Cgalkyl aryl sulfides are indicated by the residual ion in the sample spectrum at rnje 152. Two C9 sulfides-2-methyl-1(I-thiapropy1)benzene and 1-thiabutyl-benzene-fall within the trapped area and may be present in concentrations less than 2%. Small quantities of aromatic hydrocarbon impurities are suggested by the residual ions at mje 105 and 106. The minor peak at mje 138, which is somewhat larger in the spectrum of the blend than in the spectrum of the sample, may result from desorption in the mass spectrometer-a phenomenon commonly reported in the literature (20). The infrared spectra of the suspected four principal components, together with a comparison of the spectrum of the sample and the four-component blend, are reproduced in Figure 1. The wavelengths of correlatable infrared absorption bands of isomeric benzenes have been established in the literature ( 2 / ) . Thus, the two absorption bands at 12.4 and 12.9 p, observed in the spectra of 4-methyl-1-(2-methyl-lthiapropy1)benzene and 3-methyl-l-(2-methyl-l-thiapropyl)benzene (see two upper panels, Figure 1) are associated with
(18) Glenn L. Cook and G. U. Dinneen, U.S. Bur. Mines Rept. Inrest. 6698, 86 pp (1965). (19) Henry M. Grubb and Seymour Meyerson, in “Mass Spectrometry of Organic Ions,” 453-527, F. W. McLafferty, Ed., Academic Press, New York, N. Y . , 1963. (20) J. H. Beynon, “Mass Spectrometry and Its Applications to Organic Chemistry,” Elsevier, New York, N. Y.,1960, p 67. (21) L. J. Bellamy, “The Infra-red Spectra of Complex Molecules,’’ 2nd ed., Wiley, New York, N. Y . , 1958, pp 6491.
Table I. Partial Mass Spectra of Blend of Selected Sulfides and of Material Isolated from Wasson Crude Oil Sample isolated Four from Wasson component m/e Probable fragment crude oil blenda 89 90 91
O c -
92 105 106 109 110
0
s
-
123 124 137 138 151 152 165
4.33 3.78
3.94 3.92
50.85
49.82
4.47 4.35 1.52 16.92
4.50 1.41 0.49 19.23
97.46
99.14
14.24
15.05
c o s -
87.95
89.33
C”
14.35 3.75 8.70 5.60 1.54
13.82 7.06 6.23 2.28 0.66
100.00
100.00 ___
166
( m = 1 to4 n = 4-m) a
Composition of blend: C 49%
*s-c-c-c
c,
I
C
c
I
Table 11. Clo Alkyl Aryl Sulfides with Intense Mass Ions at m/e 110 or 124 Following Cleavage of Bond p to Aromatic Ring Monosubstituted alkyl Disubstituted alkyl aryl sulfides producing large aryl sulfides producing large peaks at mje 124 peaks at m/e 110 0s-c-c-c-c
c
c
1,4- and 1,3-disubstituted aromatics, respectively. These two bands are prominent in the spectra of the blend and of the isolated sample. The two bands at 13.5 and 14.5 1 (the latter band a doublet) are attributed to mono-substituted aromatics. As such they are present in the spectrum of (2-methyl1-thiabuty1)benzene (4th panel from top, Figure 1). As this VOL. 41, NO. 2, FEBRUARY 1969
363
r
I
2
I
4
9
0 WAVELENGTH, microns
I
IO
12
14
Figure 1. Infrared spectra establishing the presence of alkyl aryl sulfides in Wasson, Texas, crude oil
364
ANALYTICAL CHEMISTRY
Table 111. GLC Retention Times of Alkyl Aryl Sulfides Identified in Wasson, Texas, Crude Oil GLC retention time on: Nonpolar column, Polar column, Silicone rubber Reoplex SE-30 400 (min) (rnin)
Material C
I
Os-c-c-c
Table IV.
GLC Retention Times of Other Alkyl Aryl Sulfides of Molecular Weight 166 and Also Yielding Observed Hydrocarbons on Desulfurization GLC retention time on: Nonpolar column, Polar column, Silicone rubber Reoplex SE-30 400 (min) (min)
Compound
41.1
28.0
Os-c-c-c-c
50.8
40.7
39.9
25.3
ds-c-c-c
49.6
38.3
s -c- c-c
50.4
41 .O
cos-c-c-c
51.4
37.8
YI 0s-c-c I
34.0
18.1
43.5
31.8
C
6 s - L c
cb C
c o s - c - Ic Or Trapped area, Figures 3 and 4 of Ref. (14)
41.2
21.9
38.5-43.8
25.5-29.5
C
compound constitutes almost half of the blend, absorption bands at these wavelengths are strong in the spectrum of the blend. The presence of these bands in the spectrum of the sample attests to the presence of this compound in relatively high concentration, 1,2-Disubstituted aromatics have a strong absorption band at 13.5 microns and this band is characteristic of the spectrum of 2-methyl-l-(2-methyl-lthiapropy1)benzene. Unfortunately this band coincides with the strong absorption band of (2-methyl-1-thiabuty1)benzene discussed above and thus cannot be used for identification in this instance. In fact, the spectrum of 2-methyl-l-(2-methyl1-thiapropyl)benzene, present in the blend in only 8 concentration, adds little conspicuous character to the spectrum of the blend or of the sample. A small enhancement of the peaks at 9.35 and 9.50 1 is produced by the characteristic doublet in the spectrum of the compound centered at about 9.48 1and by the enhancement of the 13.5-p band as observed in making the experimental blends mentioned earlier. A comparison of the spectra of the sample and the blend shows that the absorption bands discussed above match favorably in both wavelength and intensity. A careful study of the spectra of Figure 1 indicates additional similarities. Thus, despite the presence of small quantities of materials other than the alkyl aryl sulfides, the composition of the blend is a reasonable, though not exact, representation of the sample composition. A small amount of the material isolated from the crude oil was desulfurized (22) and the resulting products qualitatively support the sulfide identifications by revealing the generation of the compounds expected from their desulfurization--i.e., propane, n-butane, cyclohexane, and methylcyclohexane. The combination of infrared and mass spectra, GLC, and desulfurization data confirm the presence of the four alkyl aryl sulfides in the fraction isolated from Wasson, Texas, crude oil. This evidence was further substantiated by making and ana(22) C. J. Thompson, H. J. Coleman, C. C. Ward, and H. T. Rall, ANAL.CHEM., 32,424-30 (1960).
C
0 s - c - c - cI
lyzing a blend of the identified compounds in the approximate percentages indicated. The possibility of combining compounds, other than the four sulfides suggested, to meet all of the following requirements is most limited : 1. GLC retention times for each compound in agreement with retention times of the isolated material on both polar and nonpolar columns. 2. Compounds restricted to a molecular weight of 166 as established by mass spectrometry. Intense ions in the mass spectrum at m/e 110, 124, and 166 as found in the spectrum of both isolated material and the reference blend. 3. Agreement of infrared spectrum of proposed combination with the infrared spectrum of the isolated material. 4. Qualitative agreement of major hydrocarbon fragments upon desulfurization. Agreement as shown between the reference blend and the material isolated from the crude oil in such diverse disciplines as GLC, mass, and infrared spectra, and desulfurization leaves little doubt as to the qualitative composition of the isolated material. ACKNOWLEDGMENT
The authors are indebted to J. E. Dooley and B. H. Eccleston of the Bureau of Mines, Bartlesville Petroleum Research Center for the mass spectral assistance rendered in the course of this investigation. The sample of 3-methyl-l-(l-thiabutyl)benzeneused in this investigation was generously provided by the late R. W. Higgins of Texas Woman’s University, working under a Welch Foundation grant.
RECEIVED for review August 1, 1966. Resubmitted October 7, 1968. Accepted October 28, 1968. VOL. 41, NO. 2, FEBRUARY 1969
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