Environ. Sci. Technol. 1983, 17, 256-261
Chan, M. W.; Smith, M. I. “Tracer Study at the Federal Prototype Oil Shale Lease Tract C-b in Rio Blanco, Colorado”; report by AeroVironment, Inc., 1978. Klusman, R. W. personal observation, Colorado School of Mines, 1975. Marlatt, W. C., personal communication, Colorado State University, 1982. Klusman R. W.; Matoske, C. P.; Brown, D. G.; Rice, J. A. In “Trace Elements in Oil Shale”; Chappell, W. R., Ed.; Report to Department of Energy, Contract EV-10298, in press. National Research Council “Geochemistry and the Environment”;National Academy Press: Washington, D.C., 1978, Vol. 111. Fang, S. C. Environ. Sci. Technol. 1978, 12, 285-288. Landa, E. R. J. Environ. Qual. 1978, 7, 84-86. Landa, E. R. Geochim. Cosmochim. Acta 1978, 42, 1407-1411. Hogg, T. J.; Stewart, J. W. B.; Bettany, J. R. J. Environ. Qual. 1978, 7, 440-445. Ropers, R. D. Soil Sci. Am. J . 1979, 43, 289-291. Lindberg, S. E.; Jackson, D. R.; Huckabee, J. W.; Janzen, S. A.; Levin, M. J.; Lund, J. R. J . Environ. Qual. 1979,8, 572-578.
Soil ConservationService, “General Soil Map,” Rio Blanco County, CO, three sheets; Garfield County, CO, four sheets, 1972. “Methods of Soil Analysis” American Society Agronomy: Madison, WI; Part 11, 891-901, 914-926, 1372-1376. Ifatch, R. W.; Ott, W. L. Anal. Chem. 1968,40,2085-2087. “Handbook of Chemistry and Physics”,58th ed.; Chemical Rubber: West Palm Beach, FL, 1977-78; D-182. Grade, M.; Hirschwald, W. 2.Anorg. Allg. Chem. 1980,460, 106-114. Dean W. L.; Ringrose, C.D.; Klusman, R. W. Geol. Surv. Bull. (U.S.) 1979, 1479. Barth, R. C. Soil Sci. SOC.Am. J. 1980, 44, 112-114. Jenne, E. A. In “Trace Inorganics in Water”; American Chemical Society: Washington, D.C., 1968; Adv. Chem. Ser., NO. 73, 337-387. Chappell, W. R., Petersen, K. K., Eds. In “Molybdenum in the Environment”;Marcel Dekker: New York, 1977; Vol. 2, pp 425-553.
Received for review April 12,1982. Accepted December 16,1982. Financial support was provided by Department of Energy Contract E V -10298-2.
Physical Properties of Some Synthetic TrialkyVAryl Phosphates Commonly Found in Environmental Samples Robert H. Wlghtman
Department of Chemistry, Carleton University, Ottawa, Canada K1S 5B6 Murugan Malalyandl”
Environmental Health Centre, Health and Welfare Canada, Ottawa, Canada K1A OL2
rn The synthesis of regioisomerically pure samples of 21 triaryl or trialkyl/aryl phosphates commonly encountered in environmental samples is described, using either a mild, clean condensation procedure involving triethylaminepromoted substitution of alcohols/phenols on various chlorophosphatesor a variation involving the more reactive phosphorus trichloride and subsequent oxidation to the phosphate. Physical and spectral data are presented that for the first time completely characterize many of these compounds.
Introduction Esterification of phosphoric acid with various combinations of alcohols, phenols, and alkyl-substituted phenols produces a large number of compounds known collectively as trialkyl/aryl phosphates. Because of their viscosity, relative stability, phosphorus content, etc., such compounds find a myriad commercial applications as fire retardants, plasticizers (especially for PVC), lubricating oil additives, and hydraulic fluids. The production, chemistry, toxicology, analysis, and regulation of this class of materials have already been reviewed (1). A considerable amount of physiological/toxicological testing has been performed on some of these compounds (2,3).Although no severe problems have been associated with commercial handling of these types of products in the last 10-15 years, it is becoming imperative to monitor these compounds in the work environment and the ecosystem since significant amounts may have been inadvertently released into the environment. Techniques for detection of these compounds have covered the usual gamut of chromatography, e.g., TLC or GC, and spectroscopy, e.g., UV, IR, 31PNMR, and mass 258
Environ. Scl. Technol., Vol. 17, No. 5, 1983
spectrometry, the most successful probably being the GC/MS combination (4). Isolation techniques vary depending on the sources to be checked, e.g., air, water, soil, fish, etc., but the most successful approaches have been variations of those methods developed for monitoring phosphorus-containing pesticides (5). One of the drawbacks to development of successful analytical techniques involves the complexity of many of the commercial products (6). Most manufacturing processes involve heating at elevated temperatures phosphoric acid or phosphorus oxychloride with varying amounts of phenols, alcohols, or alkylated phenols (often as a mixture of regioisomers, e.g., ortho, meta, or para, or structural isomers, e.g., n-, iso, tert-, etc. Consequently, the resulting trialkyl/aryl phosphate can be composed of a variety of compositional, i.e., triaryl, monoalkyl diaryl, etc., and positional, i.e., 3,4-xylyl and 3,5-xylyl isomers, in varying ratios depending on the source of phenols and method of manufacture (7). This report describes the gynthesis and complete characterization of analytically pure samples of many of the suspected components of the more common commercial trialkyl/aryl phosphates. Many of these compounds have never been reported; those that have are frequently poorly characterized.
Discussion Preparation of Phosphates. Of the many possible syntheses of symmetrical and unsymmetrical triaryl and trialkyl/aryl phosphates (8) the procedures utilized in this paper were adopted for two basic reasons: (i) the commercial availability of diphenyl chlorophosphate, the obvious starting material for all unsymmetrical compounds
0013-936X/83/09 17-0256$01.50/0
0 1983 American Chemlcal Society
Scheme 11. Preparative Sequence for Phenols
Scheme I. Preparative Sequences for Triaryl/Alkyl Phosphates
for compounds 1,2,3,4,5,6,7,8,9,1O,ll,l2,l3,l4 FOCI3
RoH
E13N
compounds
’
(RO
f
P=O
3
220pp
230,b,c
“’A
>
& 6 ,CH3
or
F
or
nC9H9
CH3
260
to be prepared; (ii) a desire to use the mildest conditions so that possible rearrangements, etc., could be avoided. The reactions are outlined in Scheme I. Purity of products was of prime importance rather than maximization of yield. Two exceptions to the general procedure arose involving the preparation of o-tert-butylphenyl diphenyl phosphate, 7, and tris(2,6-xylyl) phosphate, 21. Synthesis of both compounds involved the condensation of sterically hindered phenols, and both were essentially unreactive under standard conditions. In the case of o-tert-butylphenol a successful condensation was achieved by simply performing the reaction at reflux in benzene, Le., 80 “C, rather than diethyl ether, i.e., 35 OC. However, reaction of 2,6-dimethylphenol (3 equiv) with POC13 (1 equiv) and triethylamine (3 equiv) in refluxing benzene, toluene, or xylene for extended periods of time produced only bis(2,6-xylyl) chlorophosphate, that is, the product of disubstitution. Accordingly, trisubstitution with the more reactive phosphorus trichloride (PC13)was achieved as described in the literature (9) and the resulting tris(2,6-xylyl) phosphite was oxidized with 12/H20 (10)to the corresponding phosphate. Commercially available, rn-isopropylphenol (26a) could not be adequately purified; commercial p-nonylphenol (26c) after distillation was a complex mixture of p-alkyl(presumably C,) phenols as judged by 13C NMR analysis, and rn-nonylphenol(26b) was unobtainable. As outlined in Scheme 11,syntheses of all these compounds was hence accomplished by a sequence that is a composite of similar work (see ref 11-15). This approach was appealing because the starting materials 22a-c (i) are commercially available and (ii) could be used to establish isomeric purity, while (iii) the conditions are reasonably mild and not likely to induce rearrangements. Neither purification and complete characterization of intermediates nor maximization of yields was attempted. Rather, a final product of demonstrably high purity was sought. In retrospect, two points in the sequence could be significantly improved. The Grignard products 23a-c vary significantlyin ease of dehydration; a milder, more general procedure might involve distillation from KHSOl (16,17). Second, purification by chromatography or distillation should be performed at the penultimate stage of the sequence, Le., the substituted anisoles 25a-c. Purity of the requisite phenols was based mainly on spectroscopic evidence. In this respect it should be emphasized that 13C NMR is particularly helpful: (i) The number of carbons in the alkyl side chains can be readily discerned (6 35-14) as well as (ii) meta substitution (C-1 at 6 155, C-3 at 145 or 151, C-5 at 129, C-4 at 121 and
4
a) m r l a , R = CH3 ,R=H; b) melo, R =H,R’=nC7HBQ c b a r o . R=H,R’=nC,H15
15,16,17,18,19,20
comDound 21
25o,b,c
24O,b,C
/
nC9H9
26b
26s
C-2/C-6 at 115/113) or para substitution (C-1 at 6 153, C-4 at 135, C-3/C-5 at 129 and C-2/C-6 at 115). The malonic ester approach for the synthesis of 2ethyloctanol is considerably simplified by the commercial availability of diethyl ethylmalonate and is a modification of a reported procedure (18). Direct decarbethoxylation of the dialkylated malonate ester using wet dimethyl sulfoxide (19) is another possible variation for this route. Triphosphates: Purity and Spectral Analysis. No single spectroscopicmethod seems to offer an unequivocal structure proof or show potential for unambiguous proof of isomeric purity. Taken in total, however, the data summarized in Table I and I1 present a unique picture of the individual triphosphate and represent the most complete set of data assembled for such a range of compounds. Some comments follow. Boiling Point/Melting Point. As expected there appears to be no possibility to effect isomer separations by simple distillation. It should be noted that differences exist between our results and published data, e.g., ref 20 vs. original literature or ref 21, concerning melting points of compounds 17, 19, and 20. Gas Chromatography. The analyses of the phosphates have been carried out using OV-101 and OV-17 columns and a flame ionization detection system under identical conditions. The regioisomers 1-3 and 7-9 may not be completely resolvable as noted from their retention times on OV-101 packing, whereas they would be well resolved on the OV-17 column. Both columns would resolve isomeric mixtures of 4-6 and rn- 10 and p - 11 n-nonylphenyl diphenyl phosphates. In the case of regioisomers 17-21, the resolution would be good on both columns although the isomeric phenols would be very difficult to resolve. However, a small note of caution! In the course of this project, we prepared a “p-nonylphenyl diphenyl phosphate” that exhibited one peak on GC investigation. However, this material was prepared from a commerical sample of p-nonylphenol that had been shown to be a complex mixture of p-alkyl- (probably C,) phenols. Thus, although GC analysis can distinguish between rn- and p-tert-butylphenyl diphenyl phosphates, the method might not be capable of distinguishing p-tert-butylphenol diphenyl phosphate from p-iso- (or n-)butylphenyl diphenyl phosphate. Capillary GC might resolve this problem. Mass Spectrometry. As might be expected, each triphosphate ester exhibits a unique mass spectrum, although sometimes differences between isomers are minimal, e.g., rn-cresyl (2) and p-cresyl (3) or rn-isopropyl (5) and pisopropyl (6). Whenever an ortho substituent is present, the mass spectrum is much changed from the meta or para isomer, e.g., 1 compared to 2 or 3; however, the tert-butyl compounds 7-9 are the exceptions here. For detection purposes the molecular ion (M+) is often very weak comEnvlron. Scl. Technol., Vol. 17, No. 5, 1983
257
Table I. Physical Properties
phosphate 1. o-cresyl diphenyl
bp/mmHg, (lit. value) [mp, "C]
2. rn-cresyl diphenyl
185/0.60 (260/12) 190/0.60
3. p-cresyl diphenyl
200/0.70 [ 371
4. o-isopropylphenyl diphenyl
175/0.05
5. rn-isopropylphenyl diphenyl
180/0.20
6. p-isopropylphenyl diphenyl
185/0.05
7. o-tert-butylphenyl diphenyl
19510.20
8. m-tert-butylphenyl diphenyl
200/0.20
9. p-tert-butylphenyl diphenyl
190/0.20
10. rn-n-nonylphenyl diphenyl
220-225/0.07
11. p-n-nonylphenyl diphenyl
21 5-2 2 010.07
12. 4-cumylphenyl diphenyl
230-235/O.15
13. 2-ethylhexyl diphenyl
181/0.60 (232/6)
14. 2-ethyloctyl diphenyl
178-8210.07
15. tris(n-pentyl) 16. tris(3-methylbutyl)
13610.06 (158-16316) 130/0.15
17. tris( 2,3-dimethylphenyl)
200-205/0.20 [ 6 1 ]
18. tris(2,5-dimethylphenyl)
80-82 (79-81)
19. tris(3,4-dimethylphenyl)
65-67 (72 or oil)
20. tris( 3,5-dimethylphenyl)
195-200/0.2 (236/2) [ 33; 461 137-139 (136-138)
21. tris(2,6-dimethylphenyl)
micro analysis (C, H) calcd (found) 67.06, 5.04 (67.27, 5.05) 67.06, 5.04 (67.15, 5.22) 67.06, 5.04 (66.58, 5.68) 68.47, 5.75 (68.05, 5.68) 68.47, 5.75 (68.10, 5.85) 68.47, 5.75 (68.68, 5.83) 69.10, 6.06 (69.50, 5.95) 69.10, 6.06 (69.18, 5.87) 69.10, 6.06 (69.28, 6.27) 71.66, 7.35 (71.61, 7.46) 71.66. 7.35 (71.12, 7.71) 72.96, 5.67 (72.88, 5.70) 66.28, 7.51 (66.58, 7.40) 67.67. 8.00 (67.57, 8.06) 58.42, 10.79 (58.98, 11.24) 58.42, 10.79 (58.65, 11.07) 70.23, 6.63 (70.19, 6.78) 70.23, 6.63 (70.05, 6.65) 70.23, 6.63 (70.29, 6.82) 70.23, 6.63 (69.79, 6.84) 70.23, 6.82 (69.9, 6.8)
pared to some base peak, e.g., the tert-butyl compounds 7-9, where the M+ - CH3 peak predominates or the 2ethylalkyl derivatives 13 and 14, where the base peak occurs at m/z 251. Such preliminary data, of course, argue strongly for GC/MS combinations as the most promising, unambiguous, and sensitive method of analysis, provided data on the pure compounds are available. Only those peaks representing >20% of the base peak are listed in Table 11. Complete spectra are available from the authors. Proton Magnetic Resonance Spectroscopy. In general the lH NMR spectra are not distinguishable from the corresponding phenols. Minor differences in chemical shift for the benzylic protons depending on ortho, meta or para substitution, e.g., compounds 4-6, can sometimes be discerned, but this is not a general phenomenon. Only in the case of alkyl esters can one differentiate by chemical shift between CHOH and CHOP(0). Experimental Section General Details. Infrared spectra in CCll (v, in cm-') were recorded on a Perkin-Elmer 237B spectrophotometer. Ultraviolet spectra [A- in nm ( E ) ] were obtained in EtOH on either a Perkin-Elmer/Coleman 124 or a Cary 14 spectrophotometer. Proton magnetic resonance (lH NMR) 258
Environ. Sci. Technol., Vol. 17, No. 5, 1983
GC ret time, min temp, "C
OV 101
OV
1.5638 (24)
240
9.6
13.6
1.5624 (24)
240
9.9
15.0
1.5618 (24)
240
1.5622 (23)
250
6.6
10.9
2
1.5548 (22)
250
7.8
13.6
30
1.5532 (24)
250
8.7
16.0
30
1.5569 (23)
255
8.4
11.5
1.5568 (23)
255
8.8 12.6
1.5510 (24)
255
10.5
15.4
1.5346 (22)
300
7.8
9.7
1.5350 (22)
300
9.4
12.1
31,2
1.5845 (22)
300
10.1
16.0
31,2
1.5189 (23) [1.510 (25)] 1.5076 (24)
240
10.05
9.7
250
11.0
11.0
1.4315 (22) [ 1.4319 (20)I 1.4274 (23)
180
14.5 12.6
1.5632 (20)
275
n~ (temp) [lit.]
1.5513 (23)
180
17
ref 29
10.3 16.2
8.8
21,2
32
33,34
6.9
10.1 15.5
21
275
8.3
8.0
27 5
12.2
21.2
36,20
27 5
7.5
11.2
35,20
275
6.2
7.2
9,20
35
spectra were recorded on Varian HA-100 (100 MHz) or Varian T-60 (60 MHz) instruments. 13C NMR spectra were recorded on Varian XL-100 (25 MHz) or Varian FT-80 (20 MHz) instruments. All spectra were taken in CDC1, and values recorded in 6 with reference to tetramethylsilane. lH NMR spectra band shapes are indicated by s (singlet), t (triplet), q (quartet), m (multiplet), and br (broad). Thin-layer chromatography (TLC) was performed by using silica gel G or aluminum oxide E as 0.25-mm layers on glass plates (Merck). Analytical gas chromatography (GC) data were obtained on a PerkinElmer 990 instrument using 2 mm (i.d.) X 2 m glass columns packed with 3% OV 101 and 3% OV 17 on Chromosorb W 80-100 mesh. The flow rate of argon was 25 mL/min. Low-resolution mass spectra were obtained on an AI31 MS12 instrument using a direct probe, inlet/source temperatures of 60-120 "C (depending on the volatility of the compound), and an ionizing electron energy of 70 eV. Refractive indices were taken on an Abbe refractometer manufactured by Officine Galileo di Milano. Micro analyses were performed by Guelph Chemical Laboratories, Guelph, Ontario. Anhydrous ether was commerically available from Mallinckrodt Chemical Co. Anhydrous triethylamine was
Table 11. Spectral Data formula (mol wt) C19H1704P
(340.32) 2. C,,H,,OP (340.32) 3* C19H1704P (340.32). 4.' C,,H,,O,P (368.37) 5. C,lH,,O,P (368.37) 6. CZIH,,O,P (368.37) f . C,,H,',O,P (382.39) 8.
C22HZ304P
(382.39)
C22H2304P
1382.39) 10. C,,H3:0,P (452.54) 11. C,,H,,O,P (452.54) 12. C,,H,,O,P (444.47) 13. C,,H,,O,P (362.41) 14. C,,H,,O,P (390.44) 15. C,,H,,O,P (308.40) 16. C,,H,,O,P (308.40) 17. C,,H,,O,P (410.54) 18. C,,H,,O,P (410.54) 19. C,,H,,O,P (410.54) 20. C,,H,,04P (410.54) 21. C,,H,,O,P (410.54)
uv Amax, nm (€1 261 (1850) sh at 256, 268 262 (1080) sh a t 257, 267 261 (1150) sh at 257 261 (1060) sh at 256, 268 261 (1080) sh at 256, 268 267 (1850) sh at 262, 273 262 (1320) sh at 257, 268 262 (1290) sh at 257, 268 262 (1640) sh at 257, 267 263 (1250) sh at 257, 269 261 (1140) sh at 266 262 (1670) sh at 256, 267 261 (470) sh a t 256, 267 262 (880) sh at 256, 268
259 (730) sh at 265 273 (2150) sh at 267 267 (1840) sh at 273 263 (800) sh at 268 259 (533) sh at 267
'H NMR, 6 (band shape, integration)
mass spectrum, m / z (% of base peak)
7.28 (m, 1 4 H), 2.31 (s, 3 H)
340 (30), 167 (55), 1 6 6 (loo), 94 (38), 9 1 (31), 90 (31), 77 (71), 65 (44) 340 (loo), 339 (53), 77 (29)
7.26 (m, 1 4 H), 2.30 (s, 3 H)
341 (32), 340
7.26 (m, 1 4 H), 3.18 (m, 1 H), 1.12 (d, 6 H ) 7.20 (m, 1 4 H), 2.85 (sept, 1 H), 1.22 (d, 6 H) 7.20 (m, 1 4 H), 2.88 (sept, 1 H), 1.19 (d, 6 H ) 7.23 (m, 1 4 H), 1.30 (s, 9 H )
368 (100).354 136). 353 (91), . , 251 (33), 118 (33j, 77 (43j ' 368 (53), 354 (36), 353 (loo), 77 (29)
7.29 (m, 1 4 H), 2.20 (s, 3 H)
7.25 (m, 1 4 H), 1.24 (s, 9 H ) 7.28 (m, 1 4 H), 1.30 (s, 9 H ) 7.2 (m, 1 4 H), 2.56 (t, 2 H), 1.25 (m, 1 4 H), 0.85 (t, 3 H ) 7.2 (m, 1 4 H), 2.58 (t, 2 H), 1.30 (m, 1 4 H), 0.89 (t, 3 H ) 7.18 (m, 1 9 H), 1.62 (s, 6 H) 7.28 (m, 10 H), 4.20 (t, 2 H), 1.30 (m, 9 H), 0.90 (t, 6 H ) 7.3 (m, 1 0 H), 4.2 (quin, 2 H), 1.26 (m, 1 3 H), 0.90 (2t, 6 H) 4.03 (9, 6 H), 1.69 (m, 6 H), 1.40 (m, 1 2 H), 0.94 (t, 9 H ) 4.05 (9, 6 H), 1.59 (m, 9 H), 0.93 (d, 1 8 H) 7.07 (m, 9 H), 2.28 (s, 9 H), 2.10 (s, 9 H ) 7.02 (m, 9 H), 2.30 (s, 9 H), 2.18 (s, 9 H ) 7.03 (m, 9 H), 2.21 (br, 1 8 H)
(loo), 339 (42), 77 (36) 368 (62), 251 (52), 118 (loo), 77 (30)
382 (63), 367 (100)
(loo), 115 (40), 91 (40), (loo), 57 (54) 452 (42), 451 (loo), 353 (39), 340 (loo), 251 (29), 165 (39), 28 (89) 452 (38), 451 (84), 340 (38), 339 (loo), 77 (46) 444 (55), 430 (56), 429 (loo), 178 (20) 362 (27), 251 (loo), 250 (38), 94 (29) 382 (41), 367 77 (51) 382 (50); 367
390 (18),259 (50), 252 (32), 251 (100) 308 (5), 239 (42), 139 (36), 99 (loo), 4 3 (34) 308 (5), 239 ( 8 8 ) , 169 (65), 99 (loo), 71 (51), 55 (55), 43 (52) 410 (go), 305 (65), 209 (38), 193 (65), 1 2 1 (35), 105 (50), 77 (40), 28 (100) 410 (95), 305 (91), 209 (59), 193 (loo), 1 2 1 (44), 105 (52), 104 (42), 77 (47) 411 (48), 410 (loo), 1 2 1 (29)
6.64 (s, 9 H), 2.18 (s, 18 H )
410 (85), 32 (43), 28 (100)
7.01 (s, 9 H), 2.34 (s, 18 H )
410 (86), 305 (loo), 209 (67), 193 (68), 1 2 1 (45), 105 (52), 77 (37)
prepared by distillation and stored over KOH pellets. All starting materials (i.e., phenols, alcohols, or chlorophosphates were purified (distillation/crystallization),and all solvents used in workups, chromatography, etc., were previously distilled. General Procedure for the Preparation of Unsymmetrical Trisubstituted Phosphates (1-14). Diphenyl chlorophosphate (Aldrich, 97%, redistilled, X mol) and the necessary phenol or alcohol (99% pure, X mol) were dissolved in anhydrous ether (-300 mLlO.1 mol of reactants) in a three-necked round-bottomed flask equipped with magnetic stirrer, reflux condenser plus drying tube, and dropping funnel. Triethylamine (anhydrous, X mol), diluted with an equal volume of anhydrous ether, was added slowly with stirring and cooling (external ice bath) over a period of 15 min. A white precipitate, presumably triethylamine hydrochloride, began to form almost immediately. After addition of the triethylamine, the coolant was removed and the mixture refluxed overnight. Heating was discontinued after 18-24 h, and the contents of the reaction flask were rinsed into a separatory funnel. The ether solution was washed successively with equal volumes of 5% aqueous HC1 (2X), 5% aqueous NaOH (2x1, and saturated aqueous NaCl (lx), before drying (K2C03)and removing solvent via a rotary evaporator a t water aspirator pressure. The crude product (50-75% yield) was then distilled by using a short (3 in.) Vigreux
column or a bulb-to-bulb (Kugelrohr) apparatus. In this manner compounds 1-14 were obtained and characterized (see Tables I and 11). For the preparation of compound 7 normal yields (50-75%) were achieved only by substituting refluxing benzene for the reaction solvent rather than ether (5-10% yield). This method was generally used for 0.14.3-mol quantities. General Procedure for the Preparation of Symmetrical Triphosphates (15-20). Phosphorus oxychloride (POCl,, X mol) and the necessary phenol or alcohol (3X mol) were allowed to react in anhydrous ether with triethylamnine exactly as described above for the unsymmetrical triphosphates. Workup was also as previously described. Crystallization where applicable was achieved from petroleum ether. In this manner compounds 15-20 were obtained and characterized (see Tables I and 11). Preparation of Tris(2,6-dimethylphenyl)Phosphate (21). When the above procedure was attempted with 2,6-dimethylphenol,a crystalline compound was obtained: mp 49-51 "C (from petroleum ether); IR (nothing at 3400, 1305, 1150 cm-l); UV 260 nm (e 470); lH NMR 7.00 (s, 6 H), 2.36 (s, 12 H). These data were not unambiguously diagnostic; however, the mass spectrum showing the molecular ion as mlz 3241326 suggested this compound to be the bis(2,6-xylyl) chlorophosphate. Repeating the reaction in refluxing benzene (2 days), refluxing toluene (5 days), or refluxing xylene (8 days) gave the same product. Environ.'Sci. Technol., Vol. 17, No. 5, 1983
259
Accordingly an indirect preparation of 21 was undertaken (9,20) (see Scheme I). Reaction of 2,6-dimethylphenol (3.1X mol) and phosphorus trichloride (Xmol) at 100 "C for 24 h produced, after workup and crystallization from petroleum ether, tris(2,6-xylyl) phosphite, mp 85-88 "C [lit. mp 83-84 "C (913. Decomposition occurred on prolonged exposure to air so that the crude phosphite was immediately oxidized with Izin tetrahydrofuran/water (10, 23) to the corresponding tris(2,6-xylyl) phosphate (21), mp 137-139 "C [lit. mp 138 "C (9)]. Physical and spectral data for all the triphosphates are presented in Tables I and 11. In addition to these data it should be noted that all compounds exhibited IR bands at -1300 ( P a ) and 1100-1200 cm-l (P-OC, alkyl or aryl) (24). Preparation of Starting Hydroxy Compounds. (A) Phenols 26a-c (Scheme 11). The starting materials, Le., m-methoxyacetophenone(22a),rn-anisaldehyde (22b),and p-anisaldehyde (22c) were redistilled and checked for isomeric purity by lH and 13C NMR. No attempt was made to purify and completely characterize intermediates in these sequences; rather, structures were inferred from spectroscopic data, and final purification was performed only on the desired phenol. The alcohols 23a-c were prepared by Grignard reactions in the usual fashion (25), and products (-70%) were characterized by IR and 'H NMR. Dehydration to the olefins 24a-c was accomplished by reflux in acetic anhydride (13,15)for the tertiary alcohol 23a and by pyrolysis (350 "C) of the corresponding acetates of the secondary alcohols 23b,c. 'H NMR readily confirmed the presence of olefinic protons. Hydrogenation to the corresponding alkylated anisoles %Sa-cwas achieved with 10% Pd/C charcoal in ethyl acetate at room temperature and pressure in 2-5 h. The crude anisoles were refluxed with concentrated HI for 12 h to achieve demethylation to the phenols: (i) m -1sopropylphenol (26a): bp 190-195 "C (760 mmHg) [Lit. (15) bp 109 "C (11mmHg), lit. (15) mp 26 "C]; IR (neat liquid) 3320 cm-'; lH NMR 6 7.2-6.5 (m, 4 H), 5.95 (br, 1H), 2.78 (sept, 1H), 1.15 (d, 6 H); 13CNMR 6 155.3, 151.0, 129.5, 119.1, 113.5, 112.8, 34.0, 23.8. (ii) p-n-Nonylphenol(26c): mp 41-43 "C [lit. (26) mp 42 "C] from petroleum ether; IR (CC14) 3600 (sharp, H bonded), 3350 cm-'; lH NMR 6 7.1 (d, 2H), 6.8 (d, 2 H), 5.3 (br, 1 H), 2.5 (t, 2 H), 1.3 (m, 14 H), 0.9 (t, 3 H); 13C NMR 6 153.2, 135.3, 129.5 (2), 115.1. (2), 35.1, 31.9, 31.8, 29.6 (2), 29.3 (2), 22.7, 14.1. (iii) m -n-Nonylphenol (26b): bp 185-190 "C (20 mmHg) [lit. (27) bp 155 "C (25 mmHg)]; IR (neat liquid) 3300 cm-l; lH NMR 6 7.2-6.5 (m, 4 H), 5.4 (8, 1H), 2.55 (t,2 H), 1.3 (m, 14 H), 0.9 (t,3 H); 13CNMR 6 155.3,145.0, 129.4, 121.1, 115.4, 112.6, 35.9, 31.9,31.3, 29.6 (2), 29.4 (2), 22.7, 14.1; mass spectrum, M+ 220 (Cl6HZ40).Note: the original preparation is almost certainly a mixture of isomers. (B) 2-Ethyloctanol. A malonic ester type synthesis was used (18) to prepare 2-ethyloctanoic acid from diethyl ethylmalonate and 1-bromohexane. After hydrolysis and decarboxylation at 150-200 "C a clear liquid (bp 130-133 OC (15 mmHg) [lit. (18) bp 145-150 "C (12 mmHg)], nzzD 1.4340) was obtained. Treatment of 2-ethyloctanoic acid with LiA1H4 in refluxing diethyl ether gave, after workup and distillation, a colorless liquid bp 207-213 "C (760 mmHg); nMD1.4393 [lit. (18)bp 104-105 "C (10 mmHg), nmD 1.43791; IR (neat) 3350 cm-l; lH NMR 6 3.54 (d, 2 H), 1.65 (br, 1 H, disappears with DzO), 1.3 (m, 13 H), 0.9 (m, 6 HI; 13C NMR 6 260
Environ. Sci. Technol., Vol. 17, No. 5, 1983
64.8,42.1, 32.0, 30.6, 29.9, 27.0, 23.4, 22.7, 14.0, 11.0; mass spectrum, M+ 158 (for CloHzzO). Acknowledgments We thank Dan Miller and Jennifer Selwyn for technical assistance and Karl Diedrich for provision of support services. lH NMR spectra were obtained courtesy of the Chemistry Department, University of Ottawa, and 13C NMR courtesy of G . W. Buchanan, Carleton University. Mass spectra were obtained at Trent University. Registry No. 1, 5254-12-6; 2, 69500-28-3; 3, 78-31-9; 4, 64532-94-1; 5, 69515-46-4; 6, 55864-04-5; 7, 83242-23-3; 8, 83242-22-2; 9, 981-40-8; 10, 84602-55-1; 11, 64532-97-4; 12, 84602-56-2; 13, 1241-94-7; 14, 84602-57-3; 15, 2528-38-3; 16, 919-62-0; 17, 65695-97-8; 18, 19074-59-0; 19, 3862-11-1; 20, 2365-16-4;21,121-06-2;22a, 586-37-8;22b, 591-31-1;22c, 123-11-5; 23a, 55311-42-7;23b, 84623-09-6;23c, 84602-58-4;24a, 25108-57-0; 24b, 84602-59-5;24c, 84602-60-8; 25a, 6380-20-7;25b, 84602-61-9; 25c, 32588-84-4; 26a, 618-45-1; 26b, 139-84-4;26c, 104-40-5;diphenyl chlorophosphate, 2524-64-3; phosphorus oxychloride, 10025-87-3; phosphorus trichloride, 7719-12-2; 2-ethyloctanol, 20592-10-3; 2-ethyloctanoic acid, 25234-25-7; diethyl ethylmalonate, 133-13-1;1-bromohexane, 111-25-1;0-cresol, 95-48-7; m-cresol, 108-39-4;p-cresol, 106-44-5;o-isopropylphenol, 88-69-7; p-isopropylphenol, 99-89-8; o-tert-butylphenol, 88-18-6; m-tertbutylphenol, 585-34-2;p-tert-butylphenol,98-54-4; 4-cumylphenol, 599-64-4; 2-ethylhexanol, 104-76-7; 1-pentanol, 71-41-0; 3methylbutanol, 123-51-3; 2,3-dimethylphenol, 526-75-0; 2,5-dimethylphenol, 95-87-4; 3,4-dimethylphenol, 95-65-8; 3,5-dimethylphenol, 108-68-9; 2,6-dimethylphenol, 576-26-1.
Literature Cited Midwest Research Institute, draft final report for the U.S. Environmental Protection Agency, May 1979, Contract 68-01-4313. Johnson, M. Arch. Toxicol. 1975, 34, 259. Johannsen, F.; Wright, P.; Gordon, D.; Levinskas, G.; Radue, R.; Graham, P. Toxicol. Appl. Pharmacol. 1977,41, 291. Lombardo, P.; Egry, I. J. Assoc. Off. Anal. Chem. 1979,62, 47. LeBel, G.; Williams, D. T.; Benoit, F. M. J. Assoc. Off. Anal. Chem. 1981,64,991. Deo, P.; Howard, P. J. Assoc. Off. Anal. Chem. 1978,61, 910. Chadwick, D.; Watt, R. "Phosphorus and Its Compounds"; van Wazer, J. R., Ed.; Interscience: New York, 1961; Vol. 2, Chapter 19. Sasse, K. "Houben-Weyl/Methoden der Organischen Chemie"; Muller, E., Ed.; G. Thieme: Stuttgart, 1964, Vol. 12, part 2 (Organische Phosphor-Verbindungen), pp 299-377. Rydon, H.; Tonge, B. J. Chem. SOC.1956,3043. Ogilvie, K.; Beaucage, S.; Schifman, A.; Theriault, N.; Sadana, K. Can. J. chem. 1978,56,2768. Easson, L.; Stedman, E. J. Chem. SOC. 1933, 1094. Behal, A.; Tiffeneau, M. Bull. Chim. SOC.Fr. 1908,3,314; see also C. R. Hebd. Acad. Sci. 1906,141, 596. Bergmann, E.; Weizmann, A. Trans. Faraday SOC.1936, 32, 1327. Backer, H.; Haack, N. Red. Trau. Chim. Pays-Bas 1941, 60, 661. Gilman, H.; Avakian, F.; Benkeser, R. A.; Broadbent, H. S.; Clark, R. M.; Karmas,G.; Marshall, F. J.; Massie, S. M.; Shirley, D. A.; Woods, L. A. J. Org. Chem. 1954,19,1067. Tyman, J. H. P. Chem. SOC.Rev. 1979,8,499. Loev, B.; Dawson, C. J. Am. Chem. SOC.1956, 78, 4083. Kajiwara, T.; Hatanaka, A.; Inouye, Y.; Ohno, M. Agric. Biol. Chem. (Tokyo) 1969,33,409. Krapcho, A.; Lovey, A. Tetrahedron Lett. 1973, 957. Grasselli, J. G., Ed. "Atlas of Spectral Data and Physical Constants for Organic Compounds", CRC Press: Cleveland, OH, 1973. Duke, A. J. Chimia 1978, 32, 457. Reference 8, p 60.
Environ. Sci. Technol. 1983, 17, 261-267
(31) Duffy, J. German Patent 2 162 286; Chem. Abstr. 1972,77, 12621f. (32) Gamrath, H.; Craver, J. U.S. Patent 2 557 089; Chem. Abstr. 1951,45, 10668e. (33) Noller, C.; Dutton, G. J. Am. Chem. SOC.1933, 55, 424. (34) Foxton, A.; Jeffrey, G.; Vogel, A. J. Chem. SOC.A 1966,249. (35) Vilyanskaya,E.; Kirichenko, I.; Raxarenova, M. Zh. Obshch. Khim. 1969, 39, 2262; Chem. Abstr. 1970, 72, 43018r. (36) Kreysler, F. Chem. Ber. 1885,18, 1700. See ref 29 (lst), 1933, 6, 482.
Reference 8, pp 343-347. Nakanishi, K. “Infrared Absorption SpectroscopyPractical”; Holden-Day: San Francisco, 1962; p 56. Fieser, L.; Fieser, M. “Reagents for Organic Synthesis”; Wiley: New York, 1967; Vol. 1, p 415. Sandulesco, G.; Girard, A. Bull. SOC.Chim. Fr. 1930,47, 1300.
Fadia, M.; Shukla. V.;h’rivedi, J. J . Ind. Chem. SOC.1955, 32, 117.
Hoaglin, R.; Kubler, D.; Leech, R. J. Am. Chem. SOC.1958, 80, 3069.
Beilstein’s “Handbuchder Organischen Chemie”,4th ed.; Boit, H. G., Ed.; Springer Verlag: New York, 1966; Vol. 6, p 1261.
Garrett, K. French Patent 1 502 426; Chem. Abstr. 1968, 69, 87744s.
Received for review October 13, 1981. Revised manuscript received September 27,1982. Accepted January 3,1983. Financial support for this work was realized from Health and Welfare Canada, through Contract 683-1980181.
Ozonation of Bromide-Containing Waters: Kinetics of Formation of Hypobromous Acid and Bromate Werner R. Haag and Jurg HolgnQ” Swiss Federal Institute for Water Resources and Water Pollution Control, EAWAG, 8600 Dubendorf, Switzerland
Ozone oxidizes Br- under water treatment conditions to form HOBr. HOBr reacts further with 03,but only in its ionized form, OBr-. OBr- is oxidized not only to Br03but also to a species that regenerates Br-. The results are consistent with the following scheme of reactions: 0,iBr-
+ OBr203 + OBrO3
-+ - + - + ki
O2
OBr-
(1)
202
Br-
(2)
202
Br03-
(3)
k2
ka
where k, = 160 f 20 M-l s-l, k2 = 330 f 60 M-l s-l, and k3 = 100 f 20 M-l s-l at 20 OC. Thus, a catalytic decomposition of 0,via reactions 1 and 2 is observed. The maximum intermediate HOBr concentration is greater the lower the pH. In the presence of organic matter, HOBr reacts to form bromo organics. Thus,more bromoform was produced with humic acid at pH 6.1 than at pH 8.8. The range of conditions conducive to haloform formation is narrower than during chlorination. Many types of water that are subject to ozonation contain some bromide. For example, 0,is presently being applied to seawater for shellfish depuration in France and Spain (1)and is being considered for use as an alternative to chlorine at coastal power plants for cooling-system biofouling control in the US. (2, 3). In these waters the chemistry of O3is dominated by its reaction with Br-, due to bromide’s relatively high concentration (65 mg/L) and reactivity compared to other seawater components (4,5). Although typical Br- concentrations for drinking waters are considerably less (0-2 mg/L for groundwaters (6, 7) and 0 . 0 . 8 mg/L for surface waters (8-11)), reaction with Br- during O3 treatment must often still be considered. Previous authors have shown that O3 behaves similarly to chlorine in that it reacts with Br- to produce hypobromous acid (4,12-14). However, unlike chlorine (15,16) O3 can oxidize HOBr further to produce bromate at a significant rate even in dilute aqueous solution (4, 14). Still, the kinetics and mechanism of the latter reaction have never been studied in detail. Since HOBr can partake in bromine substitution reactions with organic solutes to produce potentially toxic brominated organics (e.g., bro0013-936X/83/0917-0261$01.50/0
mophenols and bromoform (6, 17-19)) and since HOBr may interfere with the analysis of residual Os, it is of interest to know how long and in what concentrations HOBr may exist as an intermediate in ozonated, bromide-containing waters. Moreover, it is desirable to know to what extent these reactions influence the stability of 03.
In order to answer these questions, we have determined the rate constants for the reactions of 0,with Br- and with HOBr, along with their dependence on pH. In the process, we have discovered a third significant phenomenon, namely, the reduction of active bromine (HOBr/OBr-) to Br- as a result of ozonation. Experimental Section
Reagents, Bromide-free HOBr solutions were prepared daily by vacuum distillation of aqueous Br2/AgN03mixtures at room temperature into a flask containing a few milliliters of ice-cooled 0.5 M phosphoric acid (20). Ozone water was prepared by passing 0,-containing oxygen through redistilled, ice-cooled water as described previously (21). All other reagents were analytical grade; the humic acid was a Fluka AG product. Titrisol buffers (Merck) were used to calibrate the pH electrode. All aqueous solutions were prepared with redistilled, deionized water. Analyses. Ozone was determined in aqueous solution by its UV absorbance at 258 nm ( E 2900 M-l cm-l) (21). Bromide concentrations were measured by using a bromide selective electrode (Ag/AgBr, Metrohm AG). Active bromine (HOBr,) and bromate were determined by successive iodometric titration at pH 4 and then at pH 1 (25). The measured HOBr concentrations were verified in one experiment by the UV absorbance of the dimethylamine derivative (N-bromodimethylamine, E , , , ~ ~ nm 490 M-l s-l (20)). In another experiment, the BrO,- concentrations were verified by differential pulse polarography (4) -1.56 V in 3 M NaCl at pH >7). Prior to the analysis of these bromine species, any remaining O3was either removed by a 30-s air purge or selectively destroyed by the addition of 1 mL of 8 mM dimethylamine per 20 mL of sample. Both methods required a pH above 6, to prevent purging of Br2 or slowing of the 0,-dimethylamine reaction, respectively. Bromoform was determined by GC/
0 1983 American Chemical Society
Environ. Sci. Technol., Vol. 17,No. 5, 1983 281
