Characterization of 4,4’-Dichlorodiphenyl Sulfone Impurities by Gas Chromatography and Mass Spectrometry 0. M. Garty, J. W. Lewis, and L. E. Brydia Union Carbide Corporation, Chemicals and Plastics, Bound Brook, N.J. 08805
Gas chrumatography and mass spectrometry were employed to characterize and analyze 4,4’-dichlorodiphenyI sulfone, one of the starting materials used in the production of polysulfone. A gas chromatographic method was developed which is capable of resolving six dichlorodiphenyl sulfone isomers. Separation is achieved via a cyanosilicone (OV-225) column on which it is possible to detect 0.02% and 0.03%, respectively, of the 3,4‘ and the 2,4’ isomers, the major impurities in monomer grade 4,4’-dichlorodiphenyl sulfone. The same chromatographic system was used to isolate nonisomeric compounds from crude dichlorodiphenyl sulfone for subsequent identification by mass spectrometry. This GC-MS study has identified the major nonisomeric impurities in 4,4’-dichlorodiphenyl sulfone as p-dichlorobenzene, o-dichlorobenzene, dichlorodiphenyl sulfide, trichlorodiphenyl sulfide, and tetrachlorodiphenyl sulfide. Mass spectra of the chloroaryl sulfides are presented and their major assignments are discussed.
Polysulfones ( 1 , 2 ) are a family of thermoplastics which are used in a wide variety of applications because of their excellent mechanical and electrical properties a t high temperatures. These high molecular weight polyaryl ethers are derived from 4,4’-isopropylidine diphenol (bisphenol A) and 4,4’-dichlorodiphenyl sulfone (4,4’-DCDPS) and are prepared according to the following scheme:
DISODIUM SALT OF BISPHENOL A
I
4, 4’-OCDPS
mass spectrometric ( 7 ) , and nuclear magnetic resonance (8) spectra of aryl sulfones have been published, but these techniques are not generally applicable to the determination of low level isomer impurities in the presence of a major (>99%) isomer. Thin-layer chromatography was employed by Fishbein and Fawkes to separate mixtures of sulfones, sulfoxides, and sulfides (9), by Peters, Lin, and Levy for the separation of 4,4’-diaminodiphenyl sulfone (DDS) and its acetylated derivatives ( I O ) , and by Lerman et al. for the determination of isomers in 3,3’-diaminodiphenyl sulfone ( 11 ) . However, quantitative results are difficult to obtain with this technique. This shortcoming of TLC prompted Gordon and Peters to use microbore column chromatography to determine DDS, 4-amino-4’-acetamidodiphenylsulfone (MADDS), and 4,4’-diacetamidodiphenyl sulfone (DADDS) in urine (12). Burchfield and coworkers extended the analysis of DDS and MADDS by converting these aminosulfones and their respective meta isomers (added as internal standards) to the corresponding iodo derivatives and determining them by gas chromatography ( 1 3 ) . Gas chromatography has also been used by Cates and Meloan to resolve nonisomeric sulfoxides and sulfones (14, 15) and by Wallace and Mahon to separate nonisomeric sulfoxides, sulfones, and sulfides (16). Despite wide applicability of GC for the analysis of sulfur-containing compounds, little has been reported on the analysis of sulfone isomers. In fact, a recent review by Ashworth on the use of gas chromatography for the analysis of sulfones (17) does not include a single reference to the separation of aryl sulfone isomers. This paper describes a GC method which resolves six dichlorodiphenyl sulfone isomers. This method was used in conjunction with mass spectrometry to characterize 4,4’-DCDPS.
OMSO/C~HSCI
EXPERIMENTAL
POLY SULFONE
Knowledge of the purity of the starting materials is important. Bisphenol A has been well characterized and a gas chromatographic method has been published for determination of the major, high boiling impurities in this product (3). No similar method for the analysis of 4,4’DCDPS has been reported. The predominant impurities in 4,4’-DCDPS are dichlorodiphenyl sulfone isomers. The literature, however, contains few references pertinent to the analysis of mixtures of isomeric aryl sulfones. Ultraviolet (4, 5 ) , infrared (6), R N Johnson A G Farnham R A Clendinning W F Hale and C N Merriam J PolymerScf PartA 5, 2375 (1967) W F Hale A G Farnham R N Johnson and R A Clendinning J Polymer Sci PartA 5, 2399 (1967) L E Brydia Ana/ Chem 40,2212 (1968) G Leandri A Mangini and R Passerini Gazz Chfm Ita/ 84, 73 (1954) V Balick and V Ramakrishnan, J Indian Chem Soc 35, 151 (1958) Infrared Spectra of Organosulfur Compounds Between 2000 and 250 c m Technical Documentary Report RTD-TDR-63-4016 Air
’
A p p a r a t u s . A H e w l e t t - P a c k a r d 5750 d u a l c o l u m n gas c h r o m a t o g r a p h e q u i p p e d w i t h b o t h f l a m e i o n i z a t i o n a n d t h e r m a l cond u c t i v i t y detectors was used. T h e c h r o m a t o g r a p h i c c o l u m n s were 2.5-m stainless steel (3.2-mm 0.d. X 2.6-mm i.d.), S i l i c l a d t r e a t ed, a n d p a c k e d w i t h 10% O V - 2 2 5 o n 80- t o 100-mesh a c i d washed, d i m e t h y l d i c h l o r o s i l a n e t r e a t e d C h r o m o s o r b P. T h e i n j e c t i o n p o r t was m a i n t a i n e d a t 310 “C a n d t h e f l a m e detector a t 325 “C. Gas flows were: h e l i u m , 28 ml/min; hydrogen, 50 ml/min; a n d air, 425 Force Materials Laboratory, Wright-Patterson Air Force Base, Ohio, December 1963. S Meyerson, H. Drews, and E. Fields, Anal Chem.. 36, 1294 (1964). J B. Hyne and J. W Greidanus. Can J . Chern.. 47, 803 (1969). L. Fishbein and J. Fawkes, J. Chrornatogr.. 22, 323 (1966) J. H. Peters, S. C. Lin, and L. Levy, I n t . J . Lepr , 37, 46 (1969) 2 . A Lerman, A. V . Ivanov, A. G Popua, and S. S. Gitis, Zh Ana/ K h m . . 27, 403 (1972);Chem. Abstr. 79, 132796 (1973) G. R . Gordon and J . H. Peters, J Chromatogr 47, 269 (1970) H. P Burchfield, E E. Storrs. R . J. Wheeler, V K . Bhat, and L L. Green, Ana/. Chem.. 45, 916 (1973) V. E. Cates and C E. Meloan, J. Chrornatogr.. 11, 472 (1963) V . E. Cates and C. E. Meloan, Ana/. Chem.. 35, 658 (1963). T.J. Wallace and J. J . Mahon. Nature f i o n d o n l . 201, 817 (1964) M R F. Ashworth, “The Determination of Sulphur-Containing I , The Analysis of Sulphones. Sulphoxides. SulGroups-Volume phony1 Halides, Thiocyanates, Isothiocyanates, and Isocyanates,” Academic Press, New York. N.Y.. 1972, pp 24-26.
A N A L Y T I C A L CHEMISTRY, VOL. 46, NO. 7 , JUNE 1974
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Table I. Elemental Analyses of Synthesized DCDPS Isomers
C H 0 S C1
Found
Calculated for CnHsO?SClz
4,4'-
2,4/-
3,4'-
DCDPS
DCDPS
DCDPS
3,3'DCDPS
50.19 2.81 11.14 11.17 24.69
50.19 2.79 11.13 11.17 24.71
50.38 2.80 10.98 11.31 24.71
50.29 2.71 11.11 11.28 24.67
49.77 2.86 11.80 11.21 24.48
ml/min. The column temperature was 265 "C isothermal. This column had an H E T P of 0.485 m m or 630 theoretical plates/foot for diphenyl sulfone (uncorrected retention time of 26 min). All samples were analyzed as 15% (w/w) solutions in acetone. Mass spectra were obtained using a Varian Cycloidal Mass Spectrometer M-66, equipped with variable source and collector slits. Instrument Conditions: electron energy 70 eV, electron current 40 gA, analyzer temperature 150 "C, source temperature 225 "C, and source pressure should be 10- Torr. GC-MS Procedure. Compounds were collected from the gas chromatograph in 1.0-mm diameter glass capillary tubes which were inserted into rubber septa and immersed in Dry Ice. Individual constituents were trapped by holding t h e septa firmly against the exit port of the chromatograph so that flow from the thermal conductivity detector passed through the cooled collection tubes. The capillary tubes containing condensate were placed into the solids probe assembly of the mass spectrometer. The probe was then heated to 100 "C t o permit facile vaporization of the collected compounds directly into the mass spectrometer source. Mass spectra of t h e sulfides were obtained by sweeping from 10 amu to 500 amu using slow sweep rates of 2.5-5.0 min. T h e spectrometer was calibrated using perfluorokerosene. An IBM 1130 computer system equipped with a plotter was used to normalize the ion intensities and plot the corrected spectra in standard form (relative abundance us. mass/charge ratio). Synthesis of Isomers. 2,4'-Dichlorodipheny1 Sulfone. A solution of 31.9 grams (0.125 mole) o-chloroaniline and 62.5 grams (0.625 mole) of concentrated hydrochloric acid was warmed to 75 "C, and 200 ml of water were added. T h e mixture was cooled to 0-10 "C by addition of 100 grams of ice, and the diazonium chloride of o-chloroaniline was prepared by the dropwise addition of a 36% solution of sodium nitrite. The cold diazonium salt solution was then added dropwise, with stirring, a t 65-75 "C over 1 hour t o a solution of 36.4 grams (0.252 mole) p-chlorobenzenethiol, 17 grams sodium hydroxide, and 150 ml distilled water prepared and kept under nitrogen. The reaction mixture was held a t this temperature for a n additional hour, during which time nitrogen was slowly evolved. The mixture was cooled and extracted with ethyl ether. The ether layer was separated and washed successively with 10% sodium hydroxide, dilute hydrochloric acid, and water. The ether solution was dried with anhydrous calcium chloride, and the ether distilled under vacuum to 100 "C to give 58.6 grams of crude 2,4'-dichlorodiphenyl sulfide which was purified as follows. The sulfide was dissolved in 500 ml of ethanol, and 100 ml of a 40% ethanolic solution of stannous chloride dihydrate were added. Dry hydrogen chloride was bubbled into the mixture which was then refluxed for 3 hours. This treatment lightened the color of the product considerably. T h e solution was diluted with water and the purified sulfide extracted with ethyl ether. The ether solution was washed successively with 10% sodium hydroxide, dilute hydrochloric acid, and dried with potassium carbonate. The ether was removed and the 2,4'-dichlorodiphenyl sulfide distilled under high vacuum to give 31.2 grams of intermediate product. The 2,4'-dichlorodiphenyl sulfide was dissolved in 300 ml of glacial acetic acid. T h e solution was heated to 55-60 "C and 33.3 grams (0.294 mole) of 30% hydrogen peroxide were added dropwise with stirring. After approximately half the peroxide was added, the temperature was raised to 60-65 "C, and finally heated to 90-100 "C and held for 90 minutes. The reaction mixture was diluted with 100 ml of water and cooled in a refrigerator t o crystallize. The crystals were filtered to give 25.2 grams of 2,4'-dichlorodiphenyl sulfone, m p 101-103 "C. The sulfone was further purified by recrystallization from 10/1 (v/vj ethanol/water to give white needles, m p 103-104 "C [lit. (18) 101 "C]. Ele(18)
Johann Huismann, German Patent 701,954 (1941)
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A N A L Y T I C A L CHEMISTRY, VOL. 46,
NO. 7 , JUNE 1974
mental analyses for 2,4'- and the other synthesized DCDPS isomers are shown in Table I. 3,4'-Dichlorodiphenyl Sulfone. This isomer was prepared by a route similar to t h a t used to synthesize 2,4'-dichlorodiphenyl sulfone except that m-chloroaniline was substituted for o-chloroaniline. M p of the purified product was 109-110 "C. 4,4'-Dichlorodiphenyl Sulfone. This isomer can be prepared by a route similar t o that used t o synthesize 2,4'-dichlorodiphenyl sulfone except t h a t p-chloroaniline is substituted for o-chloroaniline. T h e 4,4'-DCDPS used in this work was prepared by the procedure described under Results and Discussion. The product was recrystallized from chlorobenzene before use, m p 148.4 "C [lit. (18) 147.5 "C]. 3,3'Dichlorodiphenyl Sulfone. A mixture of 105 grams (0.441 mole) rn-iodo chlorobenzene, 23 grams "K2S" (powdered, 0.21 mole; Mallinckrodt-13% polysulfides) and 250 ml tetramethylene sulfoxide was refluxed for 18 hours. The reaction mixture was poured into 1.5 liters of water and extracted with carbon tetrachloride. The organic layer was evaporated t o dryness. T h e result a n t brown oil was oxidized with 75 ml of 30% hydrogen peroxide in 250 ml acetic acid a t 60 "C for 5 hours. The volatiles were evaported on a steam bath and the residue was crystallized three times from ethanol. Colorless crystals of m p 110-110.5 "C [lit. (4) 109-110 "C] were obtained.
RESULTS AND DISCUSSION One of the routes by which 4,4'-dichlorodiphenyl sulfone can be prepared involves two steps: (1) the reaction of chlorobenzene, sulfur trioxide, and thionyl chloride to form a mixture of p-chlorobenzenesulfonyl chloride and 4,4'-DCDPS, and (2) subsequent reaction of the sulfonyl chloride with chlorobenzene in the presence of ferric chloride to give additional product (19).
CI
sopci
CI
CI
O + b ;.;-Q
+HC'
CI
6' CI
Monomer grade 4,4'-DCDPS prepared by this procedure is of high purity (>99%) and contains isomeric dichlorodiphenyl sulfones as major impurities. The goal of this study was to develop a method for the analysis of 4,4'DCDPS samples and to identify nonisomeric impurities indigenous to crude material prepared by the above route. Isomeric Impurities. The chemical similarity of the major impurities to 4,4'-DCDPS and to each other, and their low concentration in the samples of primary interest, suggested gas chromatography as possibly the technique with the greatest potential for achieving these objectives. Although there are six isomeric dichlorodiphenyl sulfones, the 2,4' and 3,4' isomers predominate over 2,2', 2,3', and 3,3' in 4,4'-DCDPS produced by the procedure outlined above. Consequently, a study of GC liquid phases was conducted in which evaluation was based solely on their ability to resolve the 2,4', 3,4', and 4,4' isomers. The low volatility of these sulfones limited the study to liquid phases which possess good thermal stability. Nonpolar silicone rubber columns, even capillary columns with high theoretical plates, resolve 2,4'-DCDPS before 4,4' but do not separate the 3,4' and 4,4' isomers. Therefore, the eval(19) M J Keogh and A K Ingberman, U S Patent 3,701,806 (1972)
Figure 1. Resolution of
synthesized D C D P S isomers
Separation with a 2 5-m (3 2-mm o d X 2 6-mm I d ) 10% OV-225 column at 265 “C
1
( I O J X 4)
(IO 3 x, 44)’
0
Figure 2.
4
Gas chromatogram of
8
12
4,4‘-DCDPS
16
20
24 28 32 36 40 RETENTION TIME (MINUTES)
containing 0 . 4 7 %
3,4’
44
48
:I
4’4’
2 , 4’ (10x4)
iI 52
56
60
and 0 . 4 7 % 2 , 4 ‘ isomers
Conditions were the same as for Figure 1
uation was subsequently narrowed to polar phases possessing high thermal stability. Most polar phases elute the 3,4‘ isomer before the 4,4’ isomer but give no separation of 2,4’-DCDPS from 4,4’-DCDPS. This behavior is typified by polymetaphenoxylene. Carbowax 20M can resolve the 2,4’-, 3,4‘-, and 4,4’-DCDPS isomers, but its poor thermal stability requires very low liquid loadings to elute the high-boiling sulfones at usable column temperatures. These low loadings do not provide the capacity required for trace analyses nor do Carbowax columns operated at their maximum temperature have a reasonable lifetime. The polar silicones best satisfy the criterion of stability and polarity in sulfone isomer resolution. Of these phases, QF-1 and OV-225 provide efficient and thermally durable columns for sulfone isomer analyses. Figure 1 is a chromatogram of a quaternary mixture of the four individually synthesized isomers on an OV225 column. At this balanced concentration level, base-
line separation among the 3.3’-, 3,4’-, 4,4’-, and 2,4’DCDPS isomers is achieved. Figure 2 shows a chromatogram of a 99% 4,4’-DCDPS sample under the same conditions. Despite incomplete resolution of 3,4’- from 44‘DCDPS. precise analyses can be obtained. At the 0.47% isomeric impurity levels shown in this chromatogram, precision data from five successive analyses indicate an absolute standard deviation of 0.014 (3.7% relative) for the 3,4‘ isomer and of 0.004 (17’0 relative) for the 2,4’ isomer. The limit of detection for all three isomers in high purity 4,4’-DCDPS using 2-microliter injections of a 15% solution is 0.02% for 3-3’ and 3,4’ isomers and 0.03% for the 2,4’ isomer. Nonisomeric Impurities. While this GC method can provide analyses of low level isomeric impurities in >99% 4,4’-DCDPS, it also has applicability for the analysis of crude intermediate mixtures. Figure 3 shows the chromatogram of such a crude mixture. Peaks for all six A N A L Y T I C A L C H E M I S T R Y , VOL. 46, N O . 7 , J U N E 1 9 7 4
817
I
,
Figure 3.
~
,
4
0
~
1
~
8
1
~
,
1
12
1
~
,
~
1
~
20
16
,
1
1
24
1
,
1
28
1
~
,
1
1
1
/
1
1
1
1
1
1
1
32 36 40 44 RETENTION TIME IMINUTESI
,
1
48
1
1
1
1
52
,
~
1
56
~
,
~
1
60
1
1
~
64
1
1
68
1
1
1
1
1
1
1
1
,
1
1
~
1
~
1
~
72
Isomeric and nonisomeric impurities in crude 4 , 4 ' - D C D P S
Conditions were the same as for Figure 1. Peak identification and attenuation follow: (1) Dichlorodiphenyl sulfide, 10 X 4; ( 2 ) Trichlorodiphenyl sulfide, 10 X 4: (3) Tetrachlorodiphenyl sulfide, 10 X 4: ( 4 ) 3,3'-DCDPS, 10 X 4; (5) 3,4'-DCDPS. 10 X 32; (6) 4,4'-DCDPS, l o 3 X 8 ; (7) 2,3'-DCDPS, 10 X 32; (8) 2,4'-DCDPS. 10 X 32; (9) 2,2'-DCDPS, 10 X 2: (10) Unidentified, 10 X 2
100
z
80
a
0
f
60
a w 40 a
-1
w
20
0 20 Figure 4.
40
60
80
100
120
160
180
200
220
240
Mass spectrum of dichlorodiphenyl sulfide (Fraction I I I )
DCDPS isomers are observed in Figure 3 as well as peaks for nonisomeric impurities which are seen in the early portion of the chromatogram. Assignments for the 2,3' and 2,2' isomers are postulated on the basis of the meta, para, and ortho elution order observed for the authentic isomers. A simple temperature program which includes maintaining the column a t 150 "C for 7 min and then heating a t 60 "C/min to 265 "C permits the determination of monochlorobenzene and dichlorobenzenes in the same crude product. The major nonisomeric compounds normally present in crude 4,4'-DCDPS were identified via mass spectrometry as dichlorobenzene, dichlorodiphenyl sulfide, trichlorodiphenyl sulfide, and tetrachlorodiphenyl sulfide. These impurities were isolated by trapping the individual gas chromatographic peaks in cooled glass capillary tubes. The capillaries containing the trapped constituents were cut to fit the recess in the solids probe assembly of the mass spectrometer. The probe tip is equipped with a variable heater. Fractions I and I1 were inserted into the ion source 818
140 M/E
ANALYTICAL
C H E M I S T R Y , VOL. 46, N O . 7 , JUNE 1974
assembly Torr and 225 "C) where facile vaporization occurred without additional heat. Fractions 111, IV, and V were white solids and were inserted into the ion source and heated to approximately 100 "C. Fractions I and I1 were identified as dichlorobenzenes on the basis of a molecular ion a t m l e 146 and a two-chlorine isotopic distribution. The mass spectra of these fractions are in good agreement with spectra reported in the literature for dichlorobenzene (20). Identification of the individual dichlorobenzene isomers was made on the basis of GC retention times and enrichment experiments. Fraction 111, a white solid, sublimed readily from the probe at 100 "C. The mass spectrum of Fraction 111 is shown in Figure 4, and was identified as that of 4,4'-dichlorodiphenyl sulfide. It is known that molecular ions of diphenyl sulfide and ditolyl sulfide are the most abundant
(20) Index of Mass Spectral Data, AMD 11, American Society for Testing and Materials, Philadelphia, Pa., 1969.
1
~
I00
W
40 J 4 [L W
20
0 M/E
Figure 5. Mass spectrum of trichlorodiphenyl sulfide (Fraction IV)
20
40
100
80
60
120
160 180 W E
140
200
220
180
200
240
260
280
JOO
320
Figure 6. Mass spectrum of tetrachlorodiphenyl sulfide (F,ractionV )
100
y z 2 f
m
80
60
a W
2
t
40
-I W [L
20
20
40
60
80
I00
120
140
160 M/E
220
240
260
280
Figure 7. Mass spectrum of 4,4'-dichlorodiphenyl sulfone
ions in their mass spectra (21). Aryl disulfides (22) and aryl sulfones (7, 23) exhibit molecular ions which are less than 100% relative abundance. A molecular ion a t m / e 254 is observed with a relative abundance of 100% for dichlorodiphenyl sulfide. Appropriate mass defects a t m / e 254, 256, and 258 are consistent with a two-chlorine isotopic distribution. Loss of a chlorine molecule from the molecular ion gives rise to the very stable dibenzothiophene, even mass-odd electron ion a t m / e 184. The strong pro(211 P. C . Wszolek, F. w. McLafferty. and J . H. Brewster, Org Mass Spectrom.. 1, 127 (1968) (22) S. Kozuka. H Takahashi, and S . Oae, Bull. Chem SOC. Jap.. 43, 129 (1970) ( 2 3 ) T Nagai, T. Maeno, and N. Tokura, Bull. Chem. SOC.Jap., 43, 462 (1970)
pensity to form this parent minus Clz ion (relative abundance 66%) is consistent with the skeletal rearrangements observed by Wszolek, McLafferty, and Brewster (21). The predominance of m / e 184 over m l e 186 lends additional support to halogen substitution on the ring rather than on sulfur since the molecular ion would have to be two amu's greater if >SC12 were the bridging group. One could envisage 1,l'-dichlorodibenzothiophene as the precursor to m l e 184; however, this is unlikely since supportive ions for >SC12 and the biphenylene ion are either weak or absent ( 2 4 ) .
(24) 0.N. Porter and J. Baldas, "Mass Spectrometry of Heterocyclic Compounds," Wiley-lnterscience. New York, N.Y , 1971, p 269.
ANALYTICAL C H E M I S T R Y , VOL. 46, NO. 7, JUNE 1974
819
Table 11. Relative A b u n d a n c e us. Mass-to-Charge Ratio ( m / e ) f o r Aryl Sulfides and Aryl Sulfone Relative abundance m, e
50 51 63 69 73 74 75 76 91 92 99 108 109 110 111 139 142 143 144 145 146 159 160 161 162 182 183 184 185 186 187 217
DCDP sulfide"
TCDP sulfide
23.0 15.2 21.0 23.0 12.1 14.8 36.0 10.6 27.0 9.9 12.1 31.0 30.0 14.6 12.1 10.2 2.7 13.9 4.1 5.5 1.2
1.5 0.5
TECDP sulfide
Kelative abundance 4,4'-DCDPS
2.0 0.7 3.3
10.9 10.0
3.0 4.9 4.9
10.8 6.0 9.0 30.0 10.7 3.9
3.1 1.5 2.1 5.6 0.8 2.8 0.7 1.7 7.9 6.3 3.0 2.7
6.9 8.8 2.5 3.1
6.5 4.1 3.4 2.4 1.1
25.0 11.1 19.7 5.9 1.8
9.8
43.0
100.0 23.0 75.0 8.3 2.9 18.8 65.0 15.9 2.9 3.3 2.9
3.5 3.0 6.7 1.6 1.8 0.5 6.4
3.6 0.9 0.6 5.8 2.1 5.3
m/e
218 219 220 221 222 251 252 253 254 255 256 257 258 259 260 286 287 288 289 290 291 292 293 294 295 322 323 324 325 326 327 328
DCDP sulfidea
TCDP sulfide
TECDP sulfide
31.0 21.0 13.5 8.2 9.4
67.0 13.2 24.0 5.0 3.5
4.4 3.5 2.6 1.9
3.3 100.0 35.0 83.0 24.0 32.0 4.5 1.6
13.4 5.4 36.0 8.0 24.0 4.5 6.2 2.7
98.0 16.1 100.0 16.1 37.0 6.2 6.2 1.8
4,4'-DCDPS
3.9 54.0 12.7 45.0 7.8 10.1 2.1
5.0 1.7 2.8 1.0 1.1 0.6
81.0 15.1 67.0 8.8 12.8 1.6 0.8
72.0 10.6 100.0 13.8 49.8 6.9 12.2
DC = dicldoro. TC = trichloro. TEC = tetrachloro. DP = diphenyl. S = sulfone.
Fraction IV was identified as trichlorodiphenyl sulfide. The mass spectrum is shown in Figure 5. An intense molecular ion a t m / e 288 (the base peak) is observed with a corresponding three-chlorine isotopic distribution. The mass spectrum of Fraction V, tetrachlorodiphenyl sulfide, appears in Figure 6. This compound exhibits a molecular ion a t m / e 322 and an isotopic distribution consistent with a four-chlorine isotope abundance ratio. Trichlorodiphenyl sulfide and tetrachlorodiphenyl sulfide fragment in a manner analogous to dichlorodiphenyl sulfide. The mass spectrum of 4,4'-DCDPS is depicted in Figure 7 . The relative intensities us. mass/charge ratio of dichlorodiphenyl sulfide (Fraction 111), trichlorodiphenyl sulfide (Fraction IV), tetrachlorodiphenyl sulfide (Fraction V ) , and 4,4'-DCDPS are presented in Table 11. Crude sulfone can also contain traces of relatively nonvolatile impurities not detected by the usual gas chromatographic method because of the thermal limit and polarity of OV-225.However, utilization of a 2-m (3.2-mm 0.d. x 2.6-mm i.d.) column of 3% polymetaphenoxylene programmed to 330 "C disclosed the presence of several additional low level impurities in crude samples of 4,4'DCDPS. Two of these peaks were concentrated sufficiently to enable them to be trapped from the gas chromatograph. These impurities were subsequently identified by
820
A N A L Y T I C A L CHEMISTRY, VOL. 46, N O . 7, J U N E 1974
mass spectrometry as 2-(4-chlorophenylsulfonyl)-4,4'-dichlorodiphenyl sulfide (I) and 2-(4-~hlorophenylsulfonyl)2',4,4'-trichlorodiphenyl sulfide (11). CI
d"
CI
(11
d"
CI
(II)
Assignment of the above structures was made on the basis of molecular ions (obtained a t 70 and 5 eV), chlorine isotope distributions, and fragmentation data. These sulfidesulfone compounds are logical impurities resulting from sulfur dichloride impurity in thionyl chloride.
ACKNOWLEDGMENT The authors express their appreciation t o A. G. Farnham and W. T. Reichle for the synthesized DCDPS isomers. Received for review October 29, 1973. Accepted February 15, 1974.
