Document 44LQQMMaw0znRg8w201Jjx1ex

, NOVRMDKIt 10G1 CIILOJiINATIOiv u" TJIrHEjvyti Journal of Organic Chemistry * added to ft solution of potassium cyanide (0.380 g.), niolcel chloride (0,300 g,), and anliydroua sodium carbonate (0.1 g.) in water (10 ml.) at 15 with Blirring. The mixture allowed to stand for 2 hr. and then heated at 70 for 0..r> hr. The cooled reaction solution was extracted with other (4 X 25 ml.); tho combined other extract dried over an hydrous sodium sulfate and ether removed by distillation to give a gum. Tho gum was refluxed with aqueotm caustic potash (20 ml.; 10%) for 5 hr., cooled, and acidified with concentrated hydrochloric acid (Congo red). The neidified solution was filtered from insoluble mnttor and repeatedly extracted with chloroform; the combined extracts were dried over anhydrous sodium suifuto. Evaporation of the solvent gave a gum which slowly solidified in an ice chest, m.p. 65-66. Vacuum sublimation at I10-115/0,05 mm. yielded a white solid, m.p. 86-88. It was crystallized from petroleum ether (b.p. 40-00) with a few drops of chloro form (ice chest) when S,/,-d.ihydro-7,8-dime.thoiyisocoumarin (V) was obtained as rectangular prisms (0.130 g.; 60,0%), m.p. 02. Aval. Cnled. for CnlbaO,: G, 03,4; IT, 5.8, Found; G, 08.2; H, 5.8, Tho infrared spectrum (chloroform solvent) had a band at 5.88 v (conjugated S-luctonc.). Acknowledgment. Wo are grateful to Dr. Tapan. K. Mukherjeo, Retina Foundation, Boston 14, Mass., for tho infrared data of tho dihydroisoeoumarin (V). Muzaffarpur, India ICnNTniuuTiON FnoM Tiin Research and Engineering Division, Monsanto Chemical Co,| Chlorination of Biphenyl EXHIBIT . HAROLD WEINGARTEN . ' Received May 16, 1061 ' Diphenyl was ohlorinntod under a wide range of conditions. Tho ortho-para ratios were observed to rise sharply with increas ing meta-para ratio, Explanations are discussed. Although the halogcnation of biphenyl has re This system has been reported to involve a positive ceived only moderate attention in the past thirty specie as chlorinating agent8 and seems to be simi years,1-' we felt it would be a convenient system lar, at least in 1/2m/p ratio, to acid-catalyzed halo- with which to study tho chlorination process. In genation by hypohalous acids.2'9 Since the '/ m/p this paper we report the results of a detailed exam ratios in Table I continue to increase, it is unlikely ination of the chlorination of biphenyl, 2-ehIoro- that ehloronium ion is involved in this system or in biphenyl, and 4-chlorobiphenyI. Those results have any of the examples. Some form of complexing be permitted us further insights into the electrophilic tween chlorine molecule and acid is probably in aromatic substitution process. volved in each ease. Changes in '/2 m/p ratio nan bo correlated with RESULTS AND DISCUSSION Vi o/p ratio changes. As the */2 m/p ratio increases, Biphenyl, 2-ehIorobiphenyI, and 4-chIorobiphcnyl were chlorinated under a wide range of conditions and the results arc recorded in Tables I, II, and III, respectively. Table I is arranged in descending order of '/2 m/p ratios and represents, therefore, a scale of chlorinating agent reactivity14 *2a63n7d Lewis acid strength. The order of Lewis acid strength is in good agreement with previous reports,6-7 Attention should be called to the sulfuric neid-silver sulfate system which falls in the middle portion of the scale. the */2 o/p ratio increases precipitously, then levels out just below unity (Fig. I). This relationship can be rationalized in several ways. One explanation is based on the arguments of Ingold,10 Waters,11 Remick,15 and DeLaMare,13 suggesting that the transition state for substitution para to an orlhopara-directing conjugativo substituent is more stable than the ortho transition state as a result of eonjugative effects. Tho magnitude of this para preference would be approximated by the examples at the bottom of Table I whore conjugativo effects are expected to be large. If the above assumption is (1) R. I,. Jenkins, R. McCullough and C, F. Booth, Ind. Eng.Chm., 22, 31 (1930). (2) I*. B. D. DoLftMarc and M. Hassnn, J. Chem. Soc., correct the '/2 o/p ratio should gradually rise with increasingly reactive chlorinating agents, and this 3004 (1057). (3) I', A, Vimna amt M, ICrlHliiiaimntli J. Indian Chem, Soc,, 14, 160(1037). (4) H. C. Brown and IC. L. Nelson, J. Am. Chem. Sac., 75, 6292 (1953). (6) D, L. Hawke and J. Stcignian, Awif, Chem., 26, 1089 (1954), . (6) O. C. Dormer, D, M. Wilson, F. M, Johnson, and V. H. Dormer, J, Am, Chem. Soc., 63, 2881 (1941). (7) J. L. Cotter and A. Q. Evans, J. Chem. Soc., 2088 (1989), (8) J, H. Cion-In, Ohm, <6 /ml., 910 (1951), (9) P. B. D. De La Mare and J, H. Itldd, Aromatic Sub stitution, Academic Press, New York, 1959, Chap. 9. (19) O. K. Ingold, Structure and Mechanism in Organic Chemistry, Cornell Univ. Press, Ithaca, New York, 1953, pp, 267-269. (11) W, A, Waters, J. Chem. Soc., 727 (1948). (12) A. E. Remick, Electronic Interpretations of Organic Chemistry, Wile)-, Now York, 2nd od,, 1949,.pp. 300-309. (13) Ref. 0, pp. 145 and 107. STLCOPCB0003576 WATER PCB-SD0000054550 4348 WETNOARTEN VOE. 2(5' TABLE I CHLORINATION OP Bll'HENVL Chlorinating System % o % m %p AlCli, Ch, 40, in benzone GuCi,, Ci,, 0, in ODCB AlDri, Cl,, 0, in ODCB FoCh, Cl,r 40, in benzene SbCl, Cl,, 40, in benzene BnCh, Cl,, 40, in-benzene Htilth, AgtSO,, Ch, 0, in CCh 11F,0(C,H,),, Cl,, R.T., in CCh HOAc, Ch, II.T. llOAoiCCh (1:3), Cl,, R.T. 65.7 62.5 01.1 56.5 60.7 62.1 59.1 42,0 34.0 28.1 G.O 4.3 4.5 Jx 1.5 1.0 0.8 1.0 0.0 1.0 38.4 33.4 34,5 41.0 35.8 37.0 40,2 57.0 64.8 70.3 - Tho ortho and para values are generally within 3% while the mela ore within 0.5%. . V o/p 0.73 0.93 0.89 0.69 0.88 0,83 0.73 0.37 0.26 0.2 - .. ' '' ' Vs m/p 0.08 0.065 0.065 0.03 . 0:02' 0.015 0.01 0.009 0.005 0.007 - ' r- '- .` 1 .. . fa: , TABLE II 2-CttLORODiPiiENyt, Chlorination Chlorinating System 2,2'- 2,6- 2,5- 2,4- 2,3'- 2,3- 2,4'- V, o/p AlClj, Cl,, 40, in benzene FeClj, Cl,, 40, in benzene SnCL, Cl,, 40, in benzene . IIOActOCh, Ch, R.T. 35.8 3.4 7.6 2.5 38.4 2.5 0.1 2.0 44.2 0.6 2.1 0.0 20.5 1.3 2.6 1.5 18.6 3.8 28.4 0.63 15.3 2.9 32.7 0.58 9.7 0.8 42,0 0.53 C.l 1.1 66.8 0.16 0 The larger values are generally within 3%, the smaller within 0.4%, Chlorinating system Aid,, Ch, 40, in benzene Fed,, OI,, 40, in benzene SnCh, Cl,, 40, in henzeno HOAoiCCI,, Ch, R.T. See onto in Table 11. TABLE III 4-CiiLonoBipnENYi. Chlorination 2,4- 1.3 0.85 1.5 <0.73 2,4'- 34.3 40.4 56.0 29.5 3,4- Trace Trace Trace Trane 3,4'- 1.5 0.50 0,66 0.59 4,4'- 62.9 52.1 41,5 09.2 7. o/p 0.28 0.45 0,08 0.21 V. m/p 0.33 0.23 0.11 0.015 V* m/p 0.012 0.006 0.007 0.004 \S. \' *l ' ,1 - is expressed graphically by the dotted line in Tig. 1. The dotted line is a plot of '/: o/p vs. 5/s m/p ratios calculated from the equation. H*|S [log kptm)/kp " /L'(^e(nO"" Aj,)/ItT Experimentally, however, the */* o/p ratio dons not gradually rise; it rises sharply ns shown by the solid line in Fig. 1. Another piece of evidence contrary to the hypothesis of eonjugative para preference is the similarity of the.1/} o/p ratio for chlorination in carbon tetrachloridc-acetic acid of biphenyl (Table I) and 2-chlorobiphcnyl (Table II). The substitution of a chlorine atom in the 2-position of biphenyl should significantly enlarge the angle between the rings, decreasing the activity of ortho and para relative to meta positions and the para relative to ortho positions.11 Tho former dona occur, Iho '/14 * 16 (14) M. J. B. Dewar, T. Molo, end E. W. T. Warlord, J. Chem.Sne., 3581 (1050), (16) The (No(m) -- Np) values were computed using a p,1 of -- 13 teal, (ref. 14) and tlio */* o/p and '/% m/p ratios obtained experimentally for tho chlorination in carbon tetrachiorido-acetio acid, The '/* o(m)/p ratios "vee thon calculated by substituting other appropriate values for /9'. <10) It, 1). Brown, J. Am. Chum. Sot., 7S, 4077 (1053). Figure 1 m/p ratio jumps nearly an order of magnitude, but the latter does not, In other words, chlorination under conditions extremely sensitive to eonjugative 1 STLCOPCB0003577 WATER PCB-SD0000054551 NOVEMBER 19G1 CHLORINATION OF BIPHENYL 4349 changes in a system known to have undergone sig nificant conjugativo change (biphenyl to 2-chlorobiphenyl) nets no */ o/p ratio increase. It scorns doubtful that conjugativo effects are responsible for tho observed '/* /P ratios. We propose an alternative explanation based on the suggestion of Dewar17 that the `/j o/p ratio should be nearly unity for anionoid electromcric (+E)18 s1u9bstituents having a small electron affinity (--I).18 If this assumption is correct, the most im portant faotor determining '/ o/p ratios in bi phenyl substitution is steric.14 The transition state formed by reaction with the more selective chlori nating agents will be similar to the Wholand inter mediate. As the reagent becomes more reactive the forming carbon-chlorino bond becomes longer and its direction becomes more orthogonal to the plane of tho phenyl ring18'20 in the transition state, and the hybridization around tho carbon being sub stituted14 becomes less sp` and more spi (see Fig. 2). tion as well as the proceeding one. Table II offers some support for this hypothesis as the 2,6/2,4 ratios for the more reactive chlorinating systems are greater than unity, Presumably the larger angle between the rings provides further relief of steric interactions. One advantage of this third explana tion is that it allows a more satisfactory unification of electrophilic and homolitic substitution mecha nisms. The latter, carried out with extremely reac tive, relatively nonpolar species such as phenyl radicals, tends to give a preponderance of ortho substitution.55 Thus far we have not discussed inductive effects which we expect to be relatively small in biphenyl. The results recorded in Tabic III allow a clear-cut example of inductive influence to be examined. The substitution of a chlorine atom in the 4-position has no effect on the '/t o/p ratio for the low reac tivity reagents but has a marked lowering effect on the `/2 o/p ratios for the more reactive species. This probably means as the reagent increases in activity and the positive charge in the transition state is distributed less in the rings and localized more on the incoming chlorine atom, inductive effects become dominant,5,-5< Inductive effects in the chlorination of biphenyl by highly reactive agents may account, in part, for the leveling of the curve below unity in Fig. i. EXPERIMENTAL This change in bond length and direction should decrease steric interactions very rapidly causing a sharp rise in V o/p ratios with increasing chlori nating agent activity, which is what we observe.21 A third possible explanation based on tho con clusion of R. D. Brown14 must also bo considered, Brown suggests the '/* o/p ratio should be greater than unity in the absence of steric effects. Our ex perimental results and rational will fit this nssump- (17) M. J~ 8. Dowar, J. Chem. Boo., 403 (1049). (18) The sign convention is that of Ingolil, Chem, /levs., IS, 226 (1034). (19) J. H. Binks, J. Greaser and M. Szwuro, J, Chem. Soe,, 3044 (1000). (20) II. Woingarten, J. Org. Ohm., 20, 730 (1001). (21) Tho npparont deviation of tho forl'io chloride sml aluminum chloride systems may bo dun tn tho relative Insolubility of those reagents, permitting reaction to tako place on the surface of iindlssolvcd catalyst or on the sur face of colloidal aggregates thus'changing tho storlc require ments. Tho solvents, catalysts and other reagents were the best commercial grades available. The gallium trichloride was kindly supplied by Robert I. Stearns, Monsanto Chemical Co,, Dayton, Ohio. The 2- and 4-chlorobiphenyls were pre pared ota the Gomberg route. Chlorination method A. Biphenyl or nnonoehlorobiphenyl 0.01 to 0.02 mole, was placed in a 10-ml, amber volumetric flask and dissolved in about 6 ml. of solvent (carbon tetra chloride: acetic acid, 3:1; acetic acid or carbon tetrachloride). A solution of 0.001 to 0.005 mole of chlorine in 4 ml. of cold solvent was then added. (To the reaction in carbon tetra chloride 20 drops of boron trifluoride ethernte was also added,) The volume was brought to the calibration line, the flask shaken and stored in the dark at room temperature. After an appropriate amount of time an aliquot was removed and from it most of tho solvent was evaporated. The residuo was used directly for gas chromatographic, analysis. Chlorination method B, To a cold solution of 0.6 g. of silver sulfate in 30 ml. of sulfuric, acid and 3 ml. of water was added 0.02 mole of biphenyl. To this cold solution was added a solution of 0.003 mole of chlorine in 20 ml. of earbon tetra chloride, The reaction mixture was shaken vigorously in an ico bath for 5 min. then poured into ice. Tho aqueoiiB layer was dooanlod and tho organic layer was Allured to remove silver chloride. The organic layer was then washed with bi carbonate solution, water, dried ovor magnesium sulfate, filtered, and most of tho solvent removed. The concentrate was used directly for gas chromatographic analysis. Chlorination mollmt C, Biphenyl, 0,02 mnls, was dissolved In 10 ml. of o-dlohlorobonzono and cooled In an ice bath. To (22) D, R. Angood and G. II, Williams, Chem, Rem,, 57, 172 (1067). . . (23) J, R, ICnowles, R. O. C. Norman, and Q, K, Rudda, C/iem. .See,, 4885 (19(1(1), (24) Rof. 0, p. 158. Ipli STLCOPCB0003578 WATER PCB-SD0000054552 4350 HANCOCK AND PAVIA VOL. 20 thin whs added ft solution of 0.003 molo of chlorine In 10 ml, o-ilichlorr>iieozum'. A third anlulion of 0.1 to 0.3 g. of outalysl (ulimiimini bromide or gnllium chloride) in 6 ml. of cold o* ilichlorohenzono wan milled raptiJly with stirring. A 5-ml. nlii|Uot was then removed, washed with wator, dried over magnesium sidfftle, littered, and used directly for gas chromutogruphie noftlyala, Chlorination method D. Chlorine wns bubble! through a solution of 0.01 mole of biphenyl or moiioclilorobiphonyl uml 0.1 g. of cntnlyHt (SnCI., nnliinnny pcnlachloride, ferric chloride, nr aluminum chloride) in 12 ml. of hnnzeno at a rate which maintained the tempernluro at 40 I . Two-milliliter aliquots were taken at fi, 10 and 16 min, Tho aliquots worn washed with water, dried over magnesium sulfate, fdterod and most of the solvent removed. Tho concontrato was imed directly for gas ohromntogrnphic analysis. Analytical procedure.*1 The nnalyses were performed on a Burber-Colmnn Model 20 gas ohromatogrnphctniippcd with ft 200-ft, apiozon "L" capillary column and an argon ionlzntiou detector. Although ureas worn found generally to ho pro portional to molo percent any deviation from linearity woe corrected for by use of calibrated standard samples. St, Louis, Mo. (26) Details of tho analytical procedure for biphony!, the three monochlorobiphenyta and tho twelve dichlorobiphonyla nre reported olsowhoro, H. Weingarten et at., Anal. Chim. Acla, in prut. [Contiudution rnoM the Chemistry Department, Heed Colleob] The Nature of Lagidze's Hydrocarbons. III.1 The 217 Hydrocarbon Produced by Dehydrogenation of S,5,10,10-Tetramethyl-4b,5,9b,10-tctrahydroindcno- [2,1,a] indene J. E. II. HANCOCK and D. L. PAVIA Iteceivcd May SO, 1081 Dehydrogenation of Ifn over pulladiumsjn-chnrcoal at 300-360 yields III. Previous studies'-4 in this field have been con cerned with tho structures of hydrocarbons formed by the following general sequence: Rf AcO-C--C=C--C--OAc products all other diacetatea apparently give rise to sub stituted tetrahydroindenoindenes (II), ",ly\ + la. R - R/ - H lb. R - E' - CH, lo. R-CH,; R'U' (CH,). aici3 Recently Lagidze has carried out4 many different condensations of this type, using both different acetylenic diacetates, and also somo substituted benzenes; as a result of this work it would appear that there are in general two types of products-- diacetate la produces 2-phenylimphthalene, and (1) Part IX, J. E. H. Hancock and D. R, Scheuchanpflug, J. Am. Chem. Sac., 80, 3021 (1958); the title of the sorics has been changed, since Lugidzo's original proposals' involving cyclobuladlene-like structures have been with drawn.' (2) R. M. Lagidzo and A. D, Petrov, Doklady Akad. Nauk, S.S.S.R., 83, 235 (1952). (3) R. M, Lagidze, N. R. Loladze, and A. D. Petrov, Soobshchenya Akad. Nauk, Gruzin. S.S.R., 19, 270 (1067); G, Maier, Chem. Ber., 90, 2940 (1067); J, E, H. Hancock nnd H. W. Tnbor, Tetrahedron, 3, 132 (1058); S. W. Fenton et of., J. Org. Chem., 23, 904 (10S8). (4) C/,, inter alia, (a) R. M. Lagidze and Bb. D. Knprava, Doklady Akad. Nauk, S.S.S.R. 110, 705 (1050); (b) R, M. Lagidze, N. If. Iromadzo, and Sh. D. Kuprava, Doklady Akad. Nauk, S.S.3.R., 121, 470 (1058); (o) R. M. Lagidze et at., Soobshchenya Akad. Nauk, Gruzin. SJS.R., 25, 19 (1000). We have studied the mechanisms of these reac tions, and it was hoped that Part III of this series would consist of a detailed discussion of tho mech anism of formation of 2-phenylnaphthalene; how ever, no clear-cut evidence in favor of our hypothe sis of ring-expansion of indoneB1 has us yet been accumulated, since experiments with these sub stances hawsaEg far only yielded polymeric mate rials. It is the purpose of this paper to report on the dehydrogenation of Ha, m.p. 84. Lagidze has stated4* that treatment, of Ila with palladium-oncharcoal catalyst at 300 in a carbon dioxide atmos phere gave a hydrocarbon, m.p. 216-217; he has further claimed that dehydrogenation of Hb yields the same hydrocarbon. This interesting report has caused us to examine the dehydrogenation of Ila, but we find it difficult to reconcile our results with the preceding italicized statement, for all the evi dence herein presented points to the conclusion that the 217 hydrocarbon has the constitution III. Thus no methane was detected (mass spectrometer) during the dehydrogenation, the infrared absorption mm ET- Is&r"1 mm '"i'SassMKfai' SSSPil s STLCOPCB0003579 WATER PCB-SD0000054553