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to inactive compounds. A series of phenyl derivatives con taining various electron-donating or -withdrawing substit uent* in thp 4 position was prepared to evaluate the elec tronic contribution to the sterilizing properties of the mol ecule. However, a comparison of the activities of ENT 612758 and KNT 62586 to those of ENT 62585 and ENT 62680 plainly indicated that changes in electronic effects were not related to the activity of the sulfonamides. Selected groups of compounds, designed to correlate changes in activity with changes in location of various substituents on the benzene ring, gave conflicting results. For example, in the two isomeric pairs of chloro-eubalituted derivatives (ENT 52766, ENT 62756 and ENT 62684, ENT 52714) each isomer in a pair had essentially the game sterilizing activity. However, in the nitrobenzene se ries, the ortho (ENT 62821) and meta (ENT 62822) iso mers were inactive whereas the para isomer (ENT 62689) was moderately active. The second modification of ENT 52766 concerned the naphthyl portion of the molecule. Inactive compounds re sulted from eliminating one of the two nitro groups (ENT 62664, ENT 62788), but when the entire 2,4-dinitro-lnaphthyl group was replaced with the 2,4-dinitrophenyl group (ENT 62775), moderate activity was obtained when both sexes were treated, and male sterility increased about tenfold. However, addition of another nitro substit uent to the benzene ring (ENT 62785) gave a highly toxic picryl derivative with no apparent sterilizing activity. Similar results were encountered for ENT 62786, a trifluoromclhyl analog of ENT 62785. The importance of an unsubstituted amidic nitrogen at a prerequisite for activity became apparent when methyl- ation of the nitrogen in ENT 52766 gave inactive ENT 02697 end replacement of the amidic function in ENT 62586 with oxygen gave the inactive 2,4-dmitro-V-naphthol-p-tolucnesulfonate. PHOTOCHFU1STHV OF UlOAOfVK CO,\||-ul Because of the important role that male chemnsierilants may play in the sterile-innie technique of insect con trol, further investigation of the sulfonamides related to ENT 52766 should be directed toward the naphthyl >ijb stituent, particularly tn its replacement with various sub stituted phenyl or other groupa. Supplementary Material Available. A listing of struc ture factor amplitudes will appear following these pages in the microfilm edition of this volume of (ho journal Photo copies of the supplementary material from this paper only or microfiche (105 x 148 mm, 24X reduction, negatives) containing all of the supplementary material for the pa per* in this issue may be obtained from the Journals De partment, American Chemical Society, 1155 16th St., N. W,, Washington, D. C. 20036. Remit check or money order for $3.00 for photocopy or $2.00 for microfiche, refer ring to code number JAFC-74-197. LITERATURE CITED Borkovc, A. B., Pettic. Chem., Proe. fnl. Congr. Petite ('hem 2nd, 469(1972). Ccnsden,R., Kenyon, J..J Chtm.Soc , 1591(1935). Fys. R. L.t LsBrecque, C. C., Gouck, H. K., J. Econ. EntomoL 59. 435(1966). Fye, R. L.. Woods, C- W.p Bolkovec, A. B., Terry. P H., J Econ Entomol. 66, 36 (1973). Hall, R. C., Giam, G. S.,/ Agr. Food Chem. 20,547 (1972). Hoogeven, A. P, J., Keel. 7>ou. Chim Pays-Bos59, 37 (1931). Morgan, G.T., Evens, E. Chem. Soe. IIS, 1129 (1919). Morgan.G.T., Godden. W ,/ Chem. Soe. 7(2), 1702(1910). Wilt, O. N.t Schmitt. G,, Br 27, 2370{1894). Received for review September 24, 1973. Accepted December 10. 1973. Presented at the Division of Pesticide Chemistry, 165th Na tional Meeting of the American Chemical Society. Dallas, Tex.. April 1973. The mention of a pesticide or proprietary product in this paner does not constitute a recommendation or an endorse ment of this ptoduct by the 1). S. Department of Agriculture. TST80 SNOW Photochemistry of Bioactive Compounds: Photoproducts and Kinetics of Polychlorinated Biphenyls Luis 0. Ruzo, Matthew J. Zabik,* and Robert D. Schuelz Several symmetric tetrachlorobiphenyls were synthesized by modified Ullmann coupling of the corresponding dichloroiodobenzenoa. Hexane and methanol solutions of these compounds were irra diated at 300 nm for different time periods and the phutoproducta analyzed by gas chromatogra phy and maw spectrometry. In hexane only, de chlorination products were observed, while in methanol solution additional methoxylated prod ucts were formed. Photoreaction rates have been measured and a marked difference in reactivity has been observed for tetrachlorinated biphenyls with chlorine substituents in different positions on the aromatic rings. Mechanistic pathways for this reaction consistent with our observations are discussed. Ultraviolet radiation is known to induce chemical reac tions in many chlorinated hydrocarbons under laboratory conditions (Mitchell, 1961). Some of these reactions have also been found to occur under field conditions (Crosby and Tutass, J966). Identification of the resulting photo products end investigation of their chemical, toxicological, and pharmacological properties are necessary in order to have a correct evaluation of the merits involved in their cont inued use. The Pesticide Research Center and the Departments of Chemistry and Entomology (M. Z.), Michigan State Uni* vetsily, East Lansing, Michigan 48823. Polychlorinated biphenyls (PCB) arc among those com pounds which have received considerable attention in re cent years. They have been found to occur together with chlorinated pesticides in human adipose tissue and milk (Acker and Schulte, 1970; Biros ft a/., 1970). Sever. I re views have appeared describing their chemical and li-vicological properties (Edwards, 1971; Vos, 1970). It is gener ally agreed that their presence in the environment and in foods is detrimental. Wc have undertaken the study of PCB photochemistry in order to determine the structure of the resulting photo products, the effect of solvents on product formation and rales of reaction, and any correlations between PCB struc ture and their rate of photolysis. J. Agf Food Chem., Vol 2?. No 2. 1974 199 HUM), 7.ABIK. RCHtUCTZ Table1. Retention Times of Polychlorinated Biphenyl Standards PCB Time, sec* 2,2'-L>ich!orubiphenyl 2,6-Difhlorobiphenyl 2,6-I> (chlorobiphenyl 2,4-Dichlorubipheny) 2,3-1)it'hlorobiphcnyl S.b-Dichlorobiphenyl 3,3'-l)ic)ilorobiphenyl 3,4-I)irhl<>t-obiphey) 4,4'*Dlchlnrobiphenyl 2,2',&-Trichlorobipheny) 2,3 ',5-TrichlorobiphenyJ 2,4,4 '-Trichinrobiphenyi 70 74 84 89 96 J14 128 141 146 141 166 188 Retention lime determined at 160", 6 ml/min nitrogen flow. The tctrachlorobiphenyls selected for our work are ARKmg those found to have the greatest toxicity in biologi cal systems (Fugita, 1971; Hoopingarner ft ai. 1972). At the present time little is known about the photochemical properties of substituted biphenyls. Several studies have appeared (Safe and Hutiinger, 1971; Rum> ft at., 1972) which have shown thot the main reaction at environmen tally significant wavelengths (>290 nnt) is stepwise de chlorination. However, the actual dechlorination products have seldom been identified. In the present study our aim has been the total identifi cation of products arising from PCB photolysis in differ ent solvents and the acquisition of kinetic data which will allow elucidation of mechanistic pathways involved. EXPERIMENTAL SECTION Synthetic Methods. TetrccMoroMphenyf* Several tyn thetic methods have been used in PCB syntheses (Beaven, 1956; Taylor. 1970). 2,2',5,5'-Telrach!orobiphenyl (I), 2,2\4,4'-tetrachlofobiphenyl (II). 2,2\3,3'-tetrachlorobiphenyl (111), 3,3\4,4'*tetrachlorobiphenyl (IV), and 3,3',6,5'-telrachlorobiphenyl (V) wen* prepared by treat ing the corresponding dichloroiodobeniene with magne sium metal in ether solution, and subsequent coupling of this Grignard reagent with cupric chloride yields the de sired U'trechlorobiphcnyl. This procedure is similar to that used by Tsutsui (1957). The yields obtained by this procedure were in the 20-80% range, with lower yields being characteristic of those PCB-containing chlorines in tht> ortho position, presumably due to increased steric hindrance to coupling. 2,2\6.6'-Telrachlorobiphenyl (VI) and all mono-, di-, and trichlorinated standards were ob tained commercially (Analabs Inc., North Haven, Conn.) and purified by recrystsllir.ation from ethanol until gas chromatographic purity was achieved. All tctruchlorobiphenyls prepared were analyzed by in frared (ir), nuclear magnetic resonance (nmr), and mass spectrometry (ms) for chemical authenticity. 7'richtoromcthoxybiphenyls. 2,2',4-Trichloro-4'-methoxy- and 2,4,4'-lfichloro-2,-methoxybiphenyI were prepared by Ullinann coupling of the corresponding chioroiodoamsoles (Wells & Bauer Chemicals) in dimethylformamide (DMF) (Koniblum, 1952). The resulting products, tetrachlorobiphenyl, trichloromethoxybiphenyl, and dichlorodimethoxybipheny), were separated by gas chromatography and ident ified by mass spectrometry. Upagent*. Hexane and methanol used in photochemical reactions were glass distilled and obtained from Burdick and Jackson Laboratories. Inc., Muskegon. Mich. At all other limes, analytical grade solvents (Mallinckrodt Chemical Works, St Iuis. Mo.) were used. Itnuophcnom-, 2,5-diinethy)-2.-)-hexariiene, and 1,3cyclohexadiene were obtained from Aldrich Chemical Co. and purified; benrophenone was recrystallised twice from elli/mnl, 2,f>-dmuMhy).?,4-hexscliene was sublimed at low ?P0 . Afjr Food nnrrn , Vo' 2C.No 2.1374 temperature, and 1,3-cyclohexadiene was obtained in gas chromatographic purity. All chlorinated anilines and anisidines required for the syntheses of the tetrachloro- and trichloromethoxybiphenyh> were obtained from Italic & Bauer Chemicals, Flush ing. N. Y. Photochemical Equipment. All photolyses were carried out in a Royonnette Photochemical Reactor (The South ern N.E. Ultraviolet Co.) fitted with RUL temps heving e peak energy output at 300 rnn. During irradiation the samples were contained in borosilicat* glass test tubes (13 x 126 mm, uv cutoff at 285 nm) fitted with Teflon stop pers or, if degassed, the tube was sealed under vacuum. Photolysis was carried out at temperatures ranging from 25 to 40*. A "merry-go-round" arrangement was employed to ensure equal exposure of all samples to uv radiation. Analytical Equipment. Qlc analyses were performed on a Varian Aerograph 1400 gas chromatograph equipped with a flame ionisation detector and a 60 ft stainless steel SE-30 SCOT column (Perkln-Elmer, Norwalk Conn ). The column oven was maintained isothermaUy in the 160-200* range, with a nitrogen carrier gas flow of 6 ml/ min. Detector and inlet temperatures were 300 and 250*, respectively (see Table I). Mass spectra were obtained from a DuPont 21-490 ap paratus interfaced with a Beckman CC-65 gas chromato graph equipped with a 16% QK1, 10% DC 200, 6 ft x ft in. stainless steel column. The oven tempereture was main tained at 220*, with a nitrogen carrier gas flow of 25 ml/ min. Infrared spectra were obtained with a Perkin-EImer 337 spectrophotometer. Nuclear magnetic resonance spectra were obtained in carbon tetrachloride (spectrophotometric grade) using a Varian T-G0 instrument. Ultraviolet spectra were taken in hexane and methanol with a Beckman DB G grating spectrophotometer. Photochemical Procedures. Fifty milliliters of 0.005 M tetrachlorobiphenyl 0-V1) in hexane or methanol solu tions was irradiated for 10 15 hr. During the reaction, HCl evolution was observed. After irradiation the solutions were concentrated to 5 ml and 2-p) aliquots injected in the gc-ms for product identification. Nmr evidence for product structure was obtained by allowing the reaction to proceed until only dichlorobiphenyl remained as the mom component in solution. The solvent was evaporated and the residue taken up in carbon tetrachloride. The spectra obtained matched those of dichlorinated biphenyl stan dards. Photoproducts consisted of trichlorobiphenvls with a parent peak (M) at m/e 256 and fragments at m/e 221 (M - Cl), m/e 186 (M - 2C1) and m/c 151 (M - 3CI) and dichlorobiphenyls with M at m/c 222 and fragments at m/e 187 (M - Cl) and m/c 152 (M - 20). After 10 hr of irradiation monochlorobiphenyla constituted less than 1% of the total product formation. The products obtained for each PCB (I-Vl) in hexane solution are listed in Table n. The photoproducts obtained in methanol solutions (yields of 90-95% based U|K>n reacted starting material) consisted of dechlorinated PCB; however, methanol sub stitution products were also observed. In all cases the amount of methoxylated products did nnt exceed 5% of the total amount of products formed, with trichloromelhoxybiphenyl? being the main components. Methanol substitution has been found to take place at the same site from which a chlorine is lost. In the case of 2,2,,4,4`-tetchlorobiphenyl photolysis in methanol, the main meihoxylated product was identified as 2,4,4'-trichloro-2 methoxybiphenyl by comparison of gc retention time and mass spectra with those of authentic samples prepared in our laboratory. The parent peak for this compound ap peared at m/e 286 with fragments at m/e 271 (M ~ MHm/e 255 (M - OMe), m/c 251 (M ~ Cl), and other char acteristic masses. HONS 0815 PHOTOCHEMISTRY OF HIOACTJVK COMPOUNDS Til>| II. Photoproducls (n Hnaut and in Mflhsnol PCB 1 11 111 IV* V VI Decblorinxled products 2,3',6-Trichlorohiphenyl 3,3'-Dichlorobiphenyl 3-CWorobi phenyl* 2,4,4 '-Ti ichlorobiphenyl 4,4'-Dfchlorobiphenyl 4-Chlorobiphenyl* 2,3,3'-Trichlorobiphenyl 3,3'-Dichlorobiphenyl 3,4,4'-Trichlorobiphenyl 4,4 '* DichlorobipbenyI 3,3',5-Tnchlorobiphenyl* 2,2',6-Trichlorobiphenyl 2,2'*Dichlorobi phenyl* Time, sec 167 126 190 148 182 229 192 147 181 168 69 Methoxylated products Trichloromethoxybiphenyi Dichlorodimethoxy biphenyl* Trichlovomethoxybiphenyl Dichlorodimethoxybiphsnyl* Trichloromethoxybiphenyi Diehlorodiroolhoxy biphenyl* Trichloromethoxybiphenyi Tiichloromethoxybiphenyl* Compound represented less than 1% of total product formation. * 3,3',4-TetrachJorobiphenyl was observed in <2% after 60 hr irradiation. As shown in Table II, each tetrachlotobiphenyl irradiat ed which contained chlorines in the ortho position yielded products arising from the loss of these. Similarly, those tetracMorobiphenyls containing only melt- and pars-chlo- rJne* upon irradiation lost the meta-chlorines preferential ly. This behavior can alto be observed in the formation of the secondary products, dichlorobiphenyls, which result from the loss of ortho- or meta- but not of para-chlorines. Tho tertiary products, monochlorobipbenyls, were only formed in <1% yield (I and III) or not at all. either be cause of insufficient absorption by dichlorobiphenyls at the wavelengths employed or by decreased reactivity of meta- and para-chlorines relative to those on the ortho position. Reaction Rate* (Table III). Solutions of I-V! were pre pared so that approximately 30% of the light waa ab sorbed. Greater absorption could not be achieved doe to PCli's low solubility in methanol. The reaction waa found to be zero order. Tho rates of photolysis (A) of I-VX (1-6 X IQ*3 M) were moasured by integration of their gc peaks obtained after irradiation intervals of 0.6-20 hr with photoconversions being carried out to less than 10% in order to avoid ab sorption by the products and any possible sensitisation or quenching of the reaction. Docosene was used as an inter nal standard to normalize all injections. A marked increase in rate was observed when solutions were dcgaeeed prior to Irradiation. Oxygen is known to act as a triplet quencher by accepting excess electronic energy from excited molecules Iwfore any chemical change oc curs. An increase in the rate of reaction was also observed when methanol waa used as a solvent. The increased sol vent polarity lower* the energy of the v-v* transitions (Hmunton, 1972). Ultraviolet Spcclmtcopy. The spectra of 1-V1 showed maxima at 220-230 nm (A) corresponding to the t-t* transition of benzene. Additional maxims between 240 200 (ti) and 276-265 (C) nm were also present. Presumably these correspond to the biphenyl system as a whole. The position of chlorine substituents affects bands B and C; when ortho-chlorines arc present (I, III. VI) the molar extinction coefficient (0 decreases and. conversely, when para-chlorines are present it increases (11, IV). Meta substitution apparently has no effect on band intensity and the spectrum of V closely resembles that of biphenyl, yielding tho following values fur PC8 and < (290 nm), re spectively: I, 120: II, HO; HI, 116; IV, 6740; V. 1410; and VI. 30. Reaction Mechanism. The geometry of biphenyl has been shown to be planar in the excited state (Wagner, 1967). involving a high degree of conjugation between the two phenyl rings, and reactions of several monochlorobiphenyU are believed to proceed through triplet excited statea (Wagner, private communication). In the excited Table HI. Photolysis Rates of PCB PCB 11 HI I IV VI V Ah X JO* M sec"1 (degassed)* 15.0 2.4 2.2 1.4 0.4 <0.1 Afc X 10* M sec (O.) 2.8 1.0 0.5 0.8 0.2 * X 10* M eec "1 (degassed) 18.0 4.0 48 3.5 0.5 <0 1 Am X 10* (O,) 4.2 15 07 2.2 0.2 * Rate of reaction in hexane solution. * Hate of reaction in methanol solution. state the charge distribution could be represented as ei ther 1 or 2. The ultraviolet spectra obtained support this assumption since PCB with ortho-chlorines would bo less likely to achieve this planar structure due to steric inter actions, resulting in a decreased t for the absorption band from this transition. Para substitution would bring about increased electron donation into the ring system. The ortho substitution probably contributes to the resonance effect on the same order of magnitude as the para substi tution; however, the destabilizing steric effect appears to be more important. Tetrachlorobiphenyls containing chlo rines in the meta position do not show either a stabilizing resonance effect or destabilizing steric interactions. da c,->o-c`` a-cAy-a' ci a I2 The rate of dechlorination can then be considered to de pend upon the extent to which the particular chlorine substituents enhance or decrease the likelihood of a par ticular excited state geometry, both physical snd electron ic. Table H shows that whenever present, it is the ortho chlorines that cleave. In the absence of chlorines in the ortho position, the meta-chlorines reset. Psra-chlorines have not been observed to react to any significant extent for any of the compounds studied. It is possible that for 2.2\4,4`-tetrachlorobiphcnyl the rate is enhanced by a greater intersystem crossing rate coupled with the increased reactivity of the excited state caused by the steric interactions brought about by the chlorines in the ortho position. Studies are now underway in our laboratories to determine the triplet lifetimes, isc rates, phosphorescence, and quantum yields of l- VI. Quenching studies conducted with 2.2',4,4'-tetrHchlorobiphenyl using 1,3-cyclohexadienc indicate that the cxcit ed state reacting is indeed a triplet. Deeasserl mfibnn..) `V;? m r- 35 O c/1 X. CMKlJNt;, HKiftAH solutions of tliis PC15 irradiated with varying conccntratjonH (Q) of quencher showed decreased k values: 107 M see -1 Q. 10-M 1.80 1.62 1.21 1.04 0.62 0 2.69 5.58 8.07 13.45 The fact that oxygen, also a triplet quencher, reduces the rale suggests the same conclusion. The intermediate involved in this reaction appears to be similar Vo that observed by Kharasch (1968) in the photo reaction of iodobiphenyl in benzene. The main product observed was lerphenyl, arising from free radical attack on the solvent . In other solvents biphenyl is formed by hy drogen Abstraction. In both cases a free radical type of in termediate has been invoked, although no iodine scaveng ing was observed- It is probable that PCB's yield similar "free" radical intermediates when photolyzed in hexane or methanol solutions. This would explain the occurrence of dechlorination products. Methoxylatcd products must Scheme 1 CJ Cl cr-^H0-c form through a different mechanism, probably involving nucleophilic attack by methanol and subsequent elimina tion of chlorine and/or hydrochloric acid. This mechanism would explain the hydroxyloled products obtained by Hutzinger and coworkers (1971) in the photolysis of PCH`s in aqueous dioxane solutions (see Scheme I). CONCLUSIONS The photolysis of polychlorinated biphenyls at wave lengths greater than 290 nm indicates the environmental significance of such nonbiological degradations. The de termination of photoproduct structure and reaction rates is intimately related to the mechanism of the reaction. The presence of methanol substitution products suggests the possibility of degradative "handies" which can be in troduced photochemicaily to compounds which are other wise stable to most biological metabolic pathways. The effects of different chlorine substitution patterns upon reaction rales and the resulting products are of ecological significance. At present we are investigating other photochemical properties of these compounds. LITERATURE CITED Acker, L., Schulte, R,, Nnturwissenschaften 57, *97 (1970). Heaven G. H.,J. Chem. Soc. 4637 (1956). liiros, F. J., Walker, A. C., Medbery, A., Bull. Environ. Contain. Toxicol. 5,317(1970). Hraunton, P., J. Chem. Soc. I'crkin-Trans. 213811972). Crcwby, D. G., Tolas*, H. O..J. Agr. Food Chem 14,596 (1966}. Edwards. R.. Chem. hid 1340(1971). Fugita, S., Fukuoka Igaku Zatthi 62, 30 (1971). Hoopingnrner, R., et ai, Environ. Health I'ert 1,155 (1972). Hutsinger, O.. Safe, S., Zilko, V., Hull. Environ. Contain. Toxi col 6, 160(1971). Kharasch, N., Angeu/. Chem Ini. Ed. Engl. 7,36(1968). Kornblum, N., J. Amer. Chem. Soc. 74,5782 (1952i. Mitchell, L. C., J. Am. Of/ic. Agr. Chcm. 44, 643(1961). Huso, L. O.. Zabik, M. J., Schuetz, R. D., Bull. Environ Con- tarn. Toxicol. 8,217(1972). Safe, S., Hutr.inger, O., Nature (London) 232,641 (1971). Taylor, K. C.,/ Amer. Chcm. 9oc. 92, 3520(197`J). Teutsui, M..J. Amer. Chem. Soc 79.3062(19571 Vos, J. G., 7'ojrico/. Appl. Pharmacol. 17,656(1970). Wagner, P. J., J. Amer. Chcm. Soc. 89,2020 {1967j. Received for review May 4. 1973. Accepted October 23, 1971 This research was supported in part by fund* provided by the Food and Drug Administration, DHKW, under contrart FP.4 71 285 and the Mirhfgun Agricultural Experiment Station, Article No. 6380. Solubility and Molecular Structure of 4-Amino-3,5,6-trichloropicolinic Acid in Relation to pH and Temperature Max W. Cheung and James W. Biggar* The solubility of 4-amino-3,5,6-trich]oropico)ioic acid (piclnrom) was investigated at pH 0.20, 1.10, 2.0, 2.8, 4.2, and 4.7, and et 10, 20, 30, and 40*. The pKn values at these temperatures and the molar heats of solubility, of picloram at these pH's are reported. Explanation is offered for the variation of solubility of picloram with equilibrium pH and temperature. Dominant structural species and equilibria involved at vari ous pH ranges are suggested and elucidated. In frared studies of picloram at different pH's show that the intensities of the absorption bands at 2600 and 2650 cm1, the stretching vibration of N4H, increase inversely with pH. Existence of a number of solid structures of picloram w as sug gested. The possible formation of the zwitterien and cationic Rpecies at low pH is speculated. These findings are discussed as applied to piclo ram absorption on soil and its potential as an en vironmental contaminant. Also discussed is ap plication of the values of A//%01 as a correction of solubility-temperature effect on the standard enthalpy of pesticide adsorption processes. j Picloram (4-amino-3,5,6-trichloropicoHnic acid) has been introduced a herbicide for controlling weeds in ce- Dcpnrlment. of Water Science and Engineering, UniveruityofCalifornia, Davis, California 95616. real grains including wheat, onts, rice, and corn (Cant* and Warren, I960; Hangsma and Wiffen, 1906). Brtiadcajt application of a mixture of picloram and 2,4,5-Thas b*fn very effective in controlling undesirable woody sped*** broadleaf weeds, ami brushes infesting over 88 milhoi' J 1 , I ( ?0? J. AQf- Food.Chem.. Vol 22, No ?.. 1974 HONS 001574