2854
Anal. Chem. 1985, 57, 2854-2858
increases to the point where less than 2% error is achieved when chlorine is present in nearly a 20-fold excess. In conclusion, the first system described is capable of measuring chlorine dioxide with a small amount of interference from high concentrations of chlorine. The second system described goes cne step further and is capable of measuring chlorine dioxide selectively even in the presence of high concentrations of chlorine. Both systems have excellent selectivity for chlorine dioxide over all other commonly encountered interferenb in the measurement of chlorine dioxide. Registry No. CIOz, 10049-04-4.
LITERATURE CITED Masscheleln, W. J. “CHLORINE DIOXIDE: Chemistry and Envlronmental Impact of Oxychlorlne Compounds”; Ann Arbor Science: Ann Arbor, MI, 1979; Chapter 14. Miller, G. W.; et ai. ”An Assessment of Ozone and Chlorine Dioxide Technologies for Treatment of Municipal Water Supplies”; Municipal Environmental Research Laboratory, USEPA: Cincinnati, OH, 1978; EPA Report EPA-800/2-78-147. Sontheimer, H. “European Experince with Problems of Drlnking Water Quallty. Safe Drinking Water: Current and Future Water Problems”;
Russell, C. S., Ed.; Resources for the Future: Washington, DC, 1978. (4) “Drinking Water and Health”; Natl. Res. Council; Natlonai Academy Press: Washlngton, DC, 1980. 1982; Vol. 3, 4. (5) Hodgden, H. W.; Ingots, R. S.Anal. Chem. 1954, 26, 1224. (6) Masscheleln, W. Anal. Chem. 1986, 38, 1839. (7) Paiin, A. T. J.-Am. Water Works Assoc. 1975, 6 7 , 32. (8) Post, M. A.; Moore, W. A. Anal. Chem. 1959, 3 1 , 1872. (9) Smart, Ronald B.; Freese, J. W. J.-Am. Water Works Assoc. 1982, 74, 530. (10) Haller, J. F.; Lister, S. S.Anal. Chem. 1948, 20, 839. (11) Isacsson, Ulf; Wettermark, Gunnar Anal. Chim. Acta 1976, 83, 227. (12) Isacsson, Uif; Wettermark, Gunnar Anal. Lett. 1978, 7 1 (I), 13. (13) Smart, Ronald B. Anal. Lett. 1981, 14 (3), 189. (14) W. E. van der Llnden Anal. Chim. Acta 1983, 157, 359. (15) Masschelein, W. J. “CHLORINE DIOXIDE: Chemlstry and Environmental ImDact of Oxvchlorine Comoounds”: Ann Arbor Science: Ann ’ Arbor, MI,’ 1979; Chapter 12. (18) Rosenbiatt, Davld H.; Hayes, Albert J., Jr.; Harrison, Bernice L.; Streaty, Richard A.; Moore, Kenneth A. J . Org. Chem. 1983, 2 8 , 2790. (17) Kieffer, R. G.; Gordon, G. Inorg. Chem. 1988, 7 , 235. (18) “Standard Methods for the Examination of Water and Wastewater”, 15th ed.; American Public Health Association: Washington, DC, 1980; pp 304.
for review February 12, lgg5* Resubmitted 19, 1985. Accepted July 19, 1985.
Characterization of Phenols from Coal Liquefaction Products by l1’Sn Nuclear Magnetic Resonance Spectrometry Esfandiar Rafii,* Robert Faure, Louis Lena, Emile-J. Vincent, and Jacques Metzger Institut de Pe‘trole‘ochimie et de SynthZse Organique Industrielle, Laboratoire Associe‘ au CNRS No. 126, Universite‘ d’Aix-Marseille III,Rue Henri Poinear&,13397 Marseille Cedex 13,France
The ”‘Sn NMR chemlcai shlfts for trl-n-butyltln derlvatlves of 33 phenols commonly found in coal-derived llqulds are reported. Analysis of coal-derlved phenol fractions by this method Is comparatively straightforward and quantitatlve. Chemlcai shlft ranges of phenol derlvatlves by various NMR methods and the present one uslng ”‘Sn NMR are compared.
The phenolic group is one of the more abundant oxygencontaining functional groups present in coal liquids. Information on the distribution of these oxygen-containing compounds is important when attempting to better understand the reactions that occur during coal conversion processes. Further, because of their polarity and reactivity phenols are important ingredients in determining the quality of coal liquefaction recycle solvents (l), since aromatic and hydroaromatic hydrocarbons are relatively poor solvents for the polar solvent-refined coals generated during the early stages of the conversion process (2).Finally, substantial evidence exists that phenols, even in low concentrations, are involved during aging reactions of coal liquefaction products (3). For these reasons, detailed characterization of phenols in coal liquids has led to numerous investigations using a wide variety of analytical techniques. The gas chromatography of underivatized phenols for the determination of the relative retention times (4)and combined gas chromatography/mass spectrometry for reliable characterizationof phenolic materials have been reported (2,5). The liquid chromatography (6), high-performance liquid chromatography (HPLC) (7), and HPLC and spectrometric methods (8)have been also used for separation and identification of phenolic compounds.
Derivatization is the general method for the analysis of phenols in coal liquids, and by far the most extensively used method is silylation by various reagents (9,lO).NMR spectrometry methods have been used for estimation of hydroxyl groups present in coal extracts (11).The ‘H NMR analyses of acetylated phenols (12)and trimethylsilyl derivatives of model phenols (13)have also been used for isomer analysis of phenols and characterization of hydroxyl groups in coal liquefaction oils. The I9F NMR analyses of hexafluoroacetone adducts (14-16)or trifluoroacetyl derivatives (17-20) and %Si NMR (21)have been described for the hydroxyl content analysis in synthetic fuels and isomer analysis of phenols. This report describes a new derivatization technique which introduces a magnetic label into coal liquids. The reaction used is the well-documented reaction of readily available bis(tri-n-butyltin) oxide (TBTO) with alcohols, phenols, thiols and carboxylic acid (22,23)
2 -X-H
-
+ ( r ~ - B u ~ S n )toluene ~0
2 - x - S n ( n - B ~ ) ~+ H20 (1)
where X is either 0 or S. The advantages of this reagent are the ease of derivative preparation and the NMR sensitivity of the tin nucleus. The lI9Sn chemical shift of compounds of the type (n-Bu)$3nOR (where R is aliphatic, alicyclic, or aromatic) is sensitive to R group and covers a range of over 40 ppm. The proposed method has been applied to coal liquids. Despite the increasing number of reviews (24,s)dealing with NMR studies of organotin compound&,the l19Sn NMR of only a few phenoxytrialkyltin compounds has been reported (26).Therefore the Il9Sn chemical shifts-neat liquid-of 33 substituted phenols relative to tetramethyltin are presented.
Q 1985 American Chemical Soclety 0003-2700/85/0357-2854$01.50/0
ANALYTICAL CHEMISTRY, VOL. 57, NO. 14, DECEMBER 1985
EXPERIMENTAL S E C T I O N Reagents. Phenol and substituted phenols were reagents grade material purchased from either Fluka or Janssen Chimica. Bis(tri-n-butyltin) oxide, about 96% purity, was purchased from EGA Chemie. Toluene (more than 99.3% pure) was obtained from S.D.S, Peypin, France. Derivatization of Phenols. The phenol (20 mmol), TBTO (12 mmol), and 20 mL of toluene were placed in a 50-mL flask equipped with a condenser and a Dean Stark trap. Reflux was started and continued for 2 h, at which time a stoichiometric amount of water (0.18 g) was collected. Completion of TBTO derivative formation was confirmed by the absence of the OH absorption bands at 3200-3600 cm-l. Derivatization of resorcinol and hydroquinone was carried out with 12 mmol of TBTO and only 10 mmol of dihydric phenol by the above procedure. Except for highly hindered phenols, such as 2,6-di-tert-butylphenol the reaction is complete in less than 2 h. Toluene was removed by rotary evaporation and the liquid was distilled under high vpcuum torr) or was purified by Kugelrohr distillation! (4 X Silylation and 29SiNMR were performed following the procedure described by Coleman et al. (21),using N,O-bis(trimethylsily1)acetamide as the silylating agent. Benzene-& was used as solvent and internal lock sample. Derivatization of Coal Liquids. Coal liquids from Charbonnages de France obtained through the courtesy of the CERCHAR were used as received. Derivatization was carried out as described before, the solvent, light hydrocarbons, was removed to rotary evaporations and the residue was examined by IR for the disappearance of hydroxyl groups before analysis by l19Sn NMR spectrometry. NMR Spectrometry. l19Sn NMR spectra (positive values at high frequency) were recorded on a Bruker AM-200 spectrometer, at 74.63 MHz. For all samples benzene-d6 was placed in a concentrically capillary tube, the deuterium signal provided field/ frequency lock. Tetramethyltin (Fluka) was used as external standard and all chemical shifts are reported relative to MelSn = 0. No corrections for bulky differences were applied. The NMR samples were studied in 10-mm tubes and the probe temperature was 30 OC. Free induction decay data were accumulated over approximately 5 transients for model compounds and 16-128 transients for coal liquids. In order to suppress the reduction in signal intensity due to the negative value of the NOE (nuclear Overhauser enhancement) factor in l19Sn NMR, an inverse gated decoupling technique was used. Furthermore to obtain quantitative results, 10-4 delay times between pulses were applied. This value is much higher than the reported spin relaxation times for tri-n-butyltin compounds (27). For coal-liquid the above procedure is time-consuming; therefore other NMR techniques should be used to allow shorter delays between pulses and hence shorter recording times. The INEPT (insensitive nuclei enhanced by polarization transfer) sequence which is independent of relaxation mechanisms of the nuclear species under investigation offers considerable improvement in relative intensities over the previous conventional method (28). Furthermore the INEPT sequence enhances the signal to noise ratio (SIN)of NMR of nucleus as l19Snwhere NOE is unfavorable (29). For quantitative analysis of known composition phenols which were derivatized as a mixture of TBTO, we found that the INEPT sequence with an average 3J(119Sn-ClH,)= 55 Hz was accurate to better than 5%. Other typical INEPT parameters were as follows: 90' pulse width of tin, 20.2 ps; 90° pulse width of proton, 28 p s ; delay time between pulses, 0.045 s. In order to avoid overlapping of signals, INEPT with refocusing and decoupling was used. RESULTS AND DISCUSSION Derivatization and Chemical S h i f t Ranges. l19Sn Fourier transform NMR has been shown to be a valuable method for determining the structure of organotin compounds (25). T o illustrate the excellent resolution and sensitivity obtained with TBTO derivatives, the chemical shifts of 44 model phenols and some alcohols, thiols, and thiophenols are presented in Table I. The yields for derivative formation of alkylphenols are quantitative in every case, as can be seen by
2855
Table I. l19Sn Chemical Shifts for Bis(tri-n -butyltin) Oxide Derivatives for Several Phenols and Selected Thiols and Alcohols" compound 2-chlorophenol a-naphthol 2-phenylphenol 0-naphthol 4-chlorophenol 4-phenylphenol 2,6-dimethylphenol phenol 2-methylphenol 4-tert-butylphenol 4-methylphenol 2-ethylphenol 3-ethylphenol 2,5-dimethylphenol 4-methoxyphenol 4-ethylphenol 2,3-dimethylphenol 2,4,6-trimethylphenol 3-methylphenol 3,5-dimethylphenol 24sopropylphenol 4-isopropylphenol 3,4-dimethylphenol 2,3,5-trimethylphenol 5-isopropyl-2-methylphenol 2,4-dimethylphenol 2-isopropyl-5-methylphenol 2,4-dimethyl-6-isopropylphenol
5-indanol resorcinol 2-tert-butylphenol hydroquinone benzyl alcohol 2-tert-butyl-4-methylphenol
cyclohexanol 1-butanol 2-octano1 thiophenol 4-methylthiophenol 2-hydroxyquinoline benzylthiol 1-butanethiol 8-hydroxyquinoline 1-methylcyclohexanol
8(119Sn),b ppm 124.7
118.4 115.5 114.9 114.3 111.4
109.0 108.2 108.0 108.0 107.0 106.8 106.8 106.5 106.2 106.0 105.9 105.6 105.5
104.8 104.8 104.8 104.7
104.5 104.3 103.6 103.2 102.9 102.7 102.2 101.0 99.6 99.0 98.5 92.5 89.8 81.8 79.5 77.6
75.7 73.0 72.1
70.1 63.2
G(TBT0) = 83.0 ppm. All chemical shifts of neat liquids are reDorted as relative to tetramethvltin. (I
complete removal of phenolic OH bands by IR spectrometry of the reaction mixture. For the TBTO derivative of dihydric phenols (resorcinol and hydroquinone), we found that the hydroxyl absorption band was completely removed assuming derivatization of both OH groups. In case of the sterically encumbered phenols (e.g., 2-tert-butylphenol) the reaction is somewhat less facile and only in the extreme case of highly does the rehindered phenols (e.g., 2,6-di-tert-butylphenol) action fail to occur. The yields for the high boiling point alcohols and the more hindered alcohols (e.g., 2-methylcyclohexanol) are quantitative. This is an interesting point in comparison with other reagents (e.g., trifluoroacetyl chloride), where the reaction is not quantitative for the more hindered alcohols (20). The thiols are highly reactive even a t room temperature, further work for the derivatization of various thiols is in progress. Actual results show that there is no overlap between the three classes of compounds, this is apparent from the chemical shift ranges presented in Figure 1 which include various der ivatives . Il9Sn NMR and Comparison of Chemical Shifts. On the basis of NMR considerations alone, conversion of hydroxyl
ANALYTICAL CHEMISTRY, VOL. 57, NO. 14, DECEMBER 1985
2856
PHENOLS
-
THIOLS NAPHTOLS
-
I’ALcoHOL;
2’ALCOHOLS 3’A LCOHOLS 120
80
100
60
P P M
Flgure 1. “’Sn chemical shift ranges for tri-n-butyltin derivatives.
Table 11. Chemical Shift Ranges Observed for ‘l9Sn,%i, “F, and ‘HNMR and Their Alkylphenol Derivatives
nuclei
nuclei: ppm
llgSn 29Si 19F ‘H
600 400 375
phenol derivatives, ppm 20 3.9b 0.6‘ ( ~ 2 ) ~ 0.28E
15
107.1
105.3
103.5
A
,
i
107.3
PPM
105.9
I
.,A
104.5
PPM
Approximately. From ref 21. ‘Trifluoroacetylated phenols, obtained from ref 20. dHexafluoroacetone adducts, from ref 15 and 16. eCalculated from ref 13.
Figure 2. ’l9Sn NMR spectrum of tri-n-butyltin derivatives with some hydroxyl compounds, chemlcal shifts in parts per million downfield of TMT: (a) all six isomers of dimethylphenol; (b) quantitative analysis of phenols.
Table 111. Comparison of Chemical Shifts of Various Derivatives of Phenols in Parts per Million
Table IV. Changes in Chemical Shifts and Quantitative Determination of a Mixture of Derivatized Alkylphenols
compounds
119Snn ZsSib
a-naphthol @-naphthol 4-phenylphenol
118.4 114.9
phenol
108.2 107.0
p-cresol 5-indanol 2-phenylphenol
111.4
l9FC
‘Hd
19.7 -7.06 18.9 -7.35 18.gh -7.50 18.2 -7.55 17.7 -7.55
2.45 2.34 2.30e 2.27 2.27e
19.1h -7.67
2.03e
102.7
115.5
‘Hf
0.268 0.19 -0.01
lo molar
al kylphenol
Appma
calcdb
3,4-dimethylphenol
0.6 1.3
15.8 26.7 15.6 25.0
2,3-dimethylphenol 4-methylphenol 2-met hylphenol
2,6-dimethylphenol
1.6 1.9 1.3
16.8
foundC 15.8
25.9 16.3 24.9 17.1
21.
a A = (6(neat liquid 119Sn) - d(obsd Il9Sn)jppm. *Percent molar from weighted amount of each phenol. CPercentmolar obtained from ’I9Snauantitative NMR. Figure 2b.
groups to tinoxyl derivatives has two advantages in comparison with other derivatization technique as mentioned before. First, the extent of the Il9Sn chemical shift is greater than those of I9F, 29Si, and ‘H (Table 11). A second advantage of this derivatization tecnique is the formation of a direct bond between phenolic oxygen and the tin “probe nucl~ei”. In comparison with others reactions, except silylation (29Si),the number of intervening bonds is two for methylation (30) and three in all other cases including acetylation, silylation (‘H), trifluoroacetylation, and adduction with hexafluoroacetone. By decreasing the number of intervening bonds, the “probe nuclei” is thus more affected by the ring current or other substituent effects, as may be seen from the data in Table 11. A comparison between the chemical shifts of phenol derivatives by various NMR techniques and the present one using lI9Sn NMR is shown in Table 111. Chemical shifts of these derivatives are in the same order (increasing shielding) as the corresponding 119Snchemical shifts. An exception to this trend is 2-phenylphenol which resonates at high frequency. Schweighardt et al. (13)and Dorn et d.(20) indicated that an increase in shielding of trimethylsilyl and trifluoroacetyl derivatives of 2-phenylphenol could be explained as being the result of conformation which allows the “probe nuclei” to be directly over an aromatic ring. Because of the number of the intervening bonds between the “probe nuclei” and aromatic ring, such geometrical orientation should not be expected for tri-n-butyltin and trimethylsilyl derivatives; therefore the corresponding signals of tin- 119 and silicon-29 are not shielded (Table 111).
Isomer Analysis. The derivatives formed with fused aromatic ring phenols are highly deshielded. For example, the chemical shift of a-naphthol, due to the ring current is downfield up to 10 ppm relative to phenol. Mono- and disubstituted phenols exhibit increased shielding and with increasing size of ortho substituent (e.g., 2-isopropylphenol and 2-tert-butylphenol) the derivatives are observed at a progressively and substantially lower frequency. The chemical shift of o-alkylphenols that were not greatly hindered (e.g., methyl- and ethylphenol) is higher than the corresponding para substituent. The effects of such substituent are on the same order as those reported for trifluoroacetate derivatives (18) and hexafluoroacetone adducts (15). A spectrum showing the TBTO derivatives of all six isomers of dimethylphenol is shown in Figure 2a. This spectrum was obtained from a mixture prepared from about 5 mmol of each dimethylphenol and 15 mmol of TBTO. Except for the derivative of 3,4- and 3,5-dimethylphenol, which have the same chemical shift, each isomer in the mixture gives a sharp and characteristic resonance. A comparison between the weighted amounts of five derivatized phenols and peaks area (Figure 2b) is shown in Table IV. Molar percentages derived from this spectrum compare well with the weighted amounts; this also indicates completeness of reaction even for 2,6-dimethylphenol. Changes in Chemical Shifts. Various factors (e.g., COordination number, solvent effects, temperature, etc.) affect chemical shift of organotin compounds. However, noncoordinating solvents such as benzene act essentially as diluents and produce only slight changes in shift (26). In addition intermolecular association and tendency toward dimerization which causes dramatic changes in chemical shifts have not been reported for the phenoxides RBSnOAr (31). This is
See footnote b, Table I. bTrimethylsilylderivatives, from ref ‘Trifluoroacetyl derivatives, obtained,from ref 20. ‘H chemical shift for the methyl protons of the acetyl derivatives, from ref 20. eFrom ref 1.2,the reported value for phenol is 2.12; a correction was made by adding 0.15 ppm to these values. flH chemical shift for the trimethylsilyl derivatives, from ref 13. gFor the meta isomer. This work, see Experimental Section.
ANALYTICAL CHEMISTRY, VOL. 57, NO. 14, DECEMBER 1985
2857
i
D
,
,
106 6
.
,
.
.
1
.
.
1074
.
.
,
I
.
.
.
I
.
I
.
.
106 2
.
.
.
1050
I
I
.
I
.
.
I
103.6
.
.
102 6
PPM
Figure 3. ligSn NMR spectra of the derivatized phenolic fraction of a coal liquid: (A) 2,6-xylenol; (B) phenol: (c) 0-cresol; (D) p-cresol; (E) m-cresol; (F) ethylphenols; (G) xylenols except 2,6.
consistent with the experimental results when the chemical shifts (neat liquid) of model compounds are compared with those of a mixture of five phenol derivatives. The observed changes in chemical shifts, as may be seen from the data in Table IV were less than 2 ppm. However, it should be noted that the changes in shift are not the same for each derivatized phenol. This represents a significant limitation of this method and a drawback in comparison with other NMR methods for qualitative determination of hydroxyl groups in coal liquids. Therefore it is more difficult to extract reliable information from '19Sn NMR analysis of more' complex phenol mixtures. Analysis of Coal Liquefaction Samples. Preliminary results obtained on the phenolic fraction of a light coal liquid are shown in Figure 3. As can be seen from the spectrum, the components in highest concentration are phenol and cresols. Ethylphenols are not well resolved and xylenol peaks, except for 2,6-xylenol, appear around 103.0-103.9 ppm. For another sample of the phenolic fraction of a coal liquid derivatized by TBTO, the INEPT sequence was applied. As noted in the Experimental Section and illustrated in Figure 4, clearly the INEPT sequence provides improved SIN for Il9SnNMR. But instead of increasing sensitivity and except for the peaks of phenol and cresols, the overlap of signals in the region of ethylphenols and dimethylphenols limits the scope of this method. CONCLUSIONS The results of the present study demonstrate that l19Sn NMR is a useful method for the analysis of mixtures of phenols. The yields for derivative formaton are quantitative in every case, even for hindered phenols (e.g., 2,6-xylenol). The ease of derivative preparation and the chemical shift ranges of 44 model compounds (phenols, thiophenols, thiols, and alcohols), which cover a range of more than 60 ppm, show the potential utility of Il9Sn NMR for characterizing various functional groups. However, the analysis of mixtures of phenol isomers is somewhat thwarted by the changes of chemical shifts. But the considerable difference in chemical shifts shown by naphthols and phenols is noteworthy and indicates that there would be no significant spectral overlap for analysis of heavy
108.0
106.0
104.0
102.0
PPM Flgure 4. 'lgSn NMR of the derivatized phenolic fraction of a coal liquid, recorded by INEPT sequence after only 16 translents.
phenols. Although this method was developed for the analysis of the phenols, other applications such as analysis of carboxylic acids seem possible (32). ACKNOWLEDGMENT The authors thank P. Chiche from Centre d'Etudes et Recherches des Charbonnages de France for generously supplying samples of their coal liquid products and s. Dhainaut who performed some of the experimental work in this study. Registry No. (n-Bu),SnOR (R = 2-chlorophenyl),59431-29-7; (n-Bu),SnOR (R= a-naphthyl),23568-82-3; (n-Bu),SnOR (R = phenyl), 3587-18-6; (n-Bu),SnOR (R = @-naphthyl),98217-97-1; ( ~ - B U ) ~ S ~(R O=R4-chlorophenyl),34713-14-9; (n-Bu),SnOR (R = 4-phenylphenyl), 3644-34-6; (n-Bu),SnOR (R = 2,6-dimethylphenyl), 98217-98-2; (n-Bu),SnOR (R = 2-phenylphenyl), 3644-37-9;(n-Bu),SnOR (R = 2-methylphenyl), 95423-31-7; (nBu),SnOR (R = 4-tert-butylphenyl), 34713-17-2; (n-Bu),SnOR (R = 4-methylphenyl), 34713-16-1; (n-Bu),SnOR (R = 2-ethylphenyl), 98217-99-3;(n-Bu),SnOR (R = 3-ethylphenyl), 9821800-9; (r~-Bu)~SnoR (R = 2,5-dimethylphenyl), 98218-01-0; (nBu),SnOR (R = 4-methoxyphenyl), 3644-33-5; (n-Bu),SnOR (R = 4-ethylphenyl), 98218-02-1;(n-Bu),SnOR (R = 2,3-dimethylphenyl), 98218-03-2; (n-Bu),SnOR (R = 2,4,6-trimethylphenyl), 98218-04-3; (n-Bu),SnOR (R = 3-methylphenyl), 35794-03-7; (n-Bu),SnOR (R = 3,5-dimethylphenyl),57754-89-9;(n-Bu)$nOR (R = 2-isopropylphenyl), 98218-05-4;(n-Bu),SnOR (R = 4-isopropylphenyl), 98218-06-5; (n-Bu)3SnOR (R = 3,4-dimethylphenyl), 98218-07-6; (n-Bu),SnOR (R = 2,3,5-trimethylphenyl), 98218-08-7; (n-Bu),SnOR (R = 5-isopropyl-2-methylphenyl), 98218-09-8; (n-Bu),SnOR (R = 2,4-dimethylphenyl),34380-60-4; 98218-10-1; (n(n-Bu),SnOR (R = 2-isopropyl-5-methylphenyl), Bu),SnOR (R = 2,4-dimethyl-6-isopropylphenyl), 98218-11-2; (n-Bu),SnOR (R = 5-indanyl), 98218-12-3;[ (n-Bu),SnO],R (R = lJ-phenylene), 98218-13-4; (n-Bu),SnOR (R = 2-tert-butylphenyl), 98218-14-5; [(n-Bu),SnOI2R (R = 1,4-phenylene), 98218-15-6; (n-Bu),SnOR (R = benzyl), 33868-53-0;(n-Bu),SnOR 98218-16-7;(n-Bu),SnOR (R (R = 2-tert-butyl-4-methylphenyl), = cyclohexyl), 1749-41-3;(n-Bu),SnOR (R = butyl), 3882-70-0; (n-Bu),SnOR (R = 2-octanyl), 98218-17-8; (n-Bu),SnSR (R = phenyl), 17314-33-9; (n-Bu),SnSR (R = 4-methylphenyl),
2858
Anal. Chem. 1985, 57,2858-2864
24696-54-6; ( ~ - B U ) ~ S ~(RO R =2-quinolinyl), 98218-18-9; (nBu),SnSR (R = benzyl), 23728-85-0; ( ~ - B U ) ~ S (R ~ S=Rbutyl), 17390-72-6; (n-Bu),SnOR (R = 8-quinolinyl), 5488-45-9; (nBu),SnOR (R = 1-methylcyclohexyl),98218-19-0;l19Sn, 1431435-3; 29Si,14304-87-1;1-phenyl-2-[(trimethylsilyl)oxy]benzene, 1022-21-5; l-phenyl-4-[(trimethylsilyl)oxy]benzene,1023-13-8; 3,4-dimethylphenol, 95-65-8; 2,3-dimethylphenol, 526-75-0; 4methylphenol, 106-44-5;2-methylphenol, 95-48-7;2,6-dimethylphenol, 576-26-1; ethylphenol, 25429-37-2; phenol, 108-95-2; rn-cresol, 108-39-4.
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(15) Ho. F. F.-L. Anal. Chem. 1974. 46. 496-499. i16) Bartle, K. D.; Matthews, R. S.; Stadelhofer, J. W. Appl. Specb'OSC 1980, 34 (6), 615-617. (17) Manatt, S. L. J. Am. Chem. SOC. 1966, 88, 1323-1324. (18) Konishl, K.; Morl, Y.; Tanlguchl, N. Analyst (London) 1969, 94 1002-1005 . - - - - - -. (19) Dorn, H. C.; Sleevi, P. S.; Koller, K; Glass, T. Prepr. Pap.---Am. Chem. SOC.,Div. FuelChem. 1979, 2 4 , 301-309. (20) Sleevi, P.; Glass, T. E.; Dorn, H. C. Anal. Chem. 1979, 51, 1931-1934. (21) Coleman, W. M.; Boyd, A. R. Anal. Chem. 1982, 5 4 , 133-134. (22) Larsen, J. W.; Nadar, P. A.; Mohammadl, M.; Montano, P. A. Fuel 1962. 6 1 . 889-893. (23) Poller, R. C. "The Chemlstry of Organotln Compounds"; Logos Press: London, 1970; pp 70-136. (24) Harrls, R. K.; Kennedy, J. D.; McFarlane, W. "NMR and the Periodic Table"; Harris, R. K., Mann, B. E., Eds.; Academic Press: London, 1976; pp 342-366. (25) Davies, A. G.; Smlth, P. J. "Comprehensive Organometallic Chemlstry"; Wllklnson, G., Ed.; Pergamon Press: New York, 1982; pp
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RECEIVED for review December 28, 1984. Accepted July 10, 1985.
Crude Oil Characterization and Correlation by Principal Component Analysis of I3C Nuclear Magnetic Resonance Spectra Olav M. Kvalheim,* Dagfinn W. Aksnes, Trond Brekke, Magnus 0. Eide, and Einar Sletten Department of Chemistry, University of Bergen, N-5000 Bergen, Norway
Nils Telnaes Norsk Hydro AIS, Lars Hilles g.30,N-5000 Bergen, Norway
Prlnclpal component analysls (PCA) Is applied to I3C nuclear magnetlc resonance spectra of the naphtha fractlon of crude oil from wells located on the Norweglan shelf. Unsupervlsed PCA correlates oil samples from the same geographlcal area. The correlatlon follows from properties related to the composltlon of the oils, e.g., long-chalned vs. short-chained alkanes, branchlng, cycllzatlon, and aromatlzatlon. Several of the major constituents present In the 011s are Identifled. The link between chemical composition of the crude crlls and the geochemlcal processes of blodegradatlon, water washlng, and maturatlon suggests a slmpllfled characterlzatlon of the oil samples. Also, by use of component scores the posslblllty of communlcatlon between the wells Is uncovered. Separate modellng of replicated spectra of each sample by the use of supervlsed PCA (SIMCA) conflrmed the results of the unsupervlsed classlflcatlon.
Extensive research during the last years reflects the growing need of rapid and quantitative methods for structural characterization of crude oils. 13Cand lH NMR spectroscopy have proved especially useful for this purpose, either separately
(1-10) or in combination with other spectroscopic techniques (10-12), element analysis (13, 14), or gas chromatography/ mass spectrometry (10, 15). The advantage of NMR spec-
troscopy for the analysis of complex hydrocarbon mixtures is easily explained. Gas chromatography (GC) or mass spectroscopy (MS) gives poor resolution due to severe overlap among the numerous peaks. The NMR spectra contain comparatively fewer peaks because carbon atoms in identical structural environments within the nearest four neighbors possess the same chemical shift (16). Since the major constituents in crude oil are made up of rather few molecular fragments, 13C NMR spectroscopy produces spectra with well-resolved parts even from fractions containing a large number of constituents. The limitation imposed on the interpretation of the NMR spectra, using molecular substructures rather than individual constituents, turns out to be an advantage in the present context. Spectra of complex hydrocarbon mixtures can be interpreted in terms of average properties, i.e., average chain length, aromatic vs. aliphatic content, and so on (15). However, as pointed out recently by Ward and Burnham in their investigation on shale oil, even identification of the major individual constituents is possible (17). The functional group
0003-2700/85/0357-2858$01.50/00 1985 Amerlcan Chemical Society
