摘要:

1766 J.C.S. Perkin I1Kinetics of Oxidative Condensation of p-Phenylenediamines with Mono-and poly-substituted BenzoylacetanilidesBy Ezio Pelizzetti, Laboratori di Ricerca 3M ltalia S.p.A., Ferrania, Savona, ItalyGuido Saini," lstituto di Chimica Analitica, Universith di Torino, ItalyThe kinetics of the oxidative condensation of NN-dialkyl-p-phenylenediamines and mono- and poly-substitutedbenzoylacetanilides in aqueous alkaline solution, in the pH range 7.5-1 0.8, have been investigated by the stopped-flow technique. In this pH range the rate i s proportional to the concentration of the positively charged p-benzo-quinone di-imine and of the anion corresponding to the benzoylacetanilide. It is suggested that the rate-determin-ing step is the formation of the leuco-dye.The reactivity of the benzoylacetanilide anions increases with increasingbasicity. A linear relationship between log (kc-/koc-) (where koc- i s the specific rate constant of the unsubstitutedbenzoylacetanilide) and theo values of the substituents was obtained for both mono- and poly-substituted benzoyl-acetanilides.IN the colour photographic process yellow dyes areobtained by oxidative coupling reactions of NN-dialkyl-9-phenylenediamines (PPD) and benzoylacetanilides(B) Though the kinetics of the oxidative coupling of(1) X = Y = H(2) X = H, Y = 0-C1(3) X = H, Y = o-Br(4) X = H, Y = m-C0,Me(6) X = H, Y = m-Ac(5) X = H, Y = WZ-NO,(7) X = H, Y = WZ-CN(8) X = H, Y = p-AC(9) X = H, Y = p-NEt,(10) X = H, Y = 9-OH dR3 N(11) X = H, Y = P-CO,H(13) X = 2,4,6-Me3, Y = H(15) X = 0-C1, Y = o-OMe(16) X = p-OMe, Y = m-NO,(17) X = p-OMe, Y = m-CN(18) X = Y = p-OMe(19) X = p-OMe, Y = o-NEt,(12) X = H, Y = P-SOZNH,(14) X = Y = o-ClN H+N/ \R' R2a ; R1 = Et, RZ = C,H,NHSO,Me, R3 = Mec ; R1 = R2 = Et, R3 = Meb; R1 = R2 = Et, R3 = Hdiamines and phenols have been extensively investi-gated,2*3 little work has been devoted to the dye form-ation from benz~ylacetanilides.~~~Van Brandt and Bruylants6 investigated the con-densation of a group of benzoylacetanilides with NN-dialkyl-@-nitrosoaniline in ethanol and a relationshipbetween reactivity and the substituent effect c wasobtained.This paper reports the kinetics of the reaction inaqueous alkaline solution (pH 7-5-10-8), in order toascertain how the reactivity is affected by substituentson the aromatic ring.C.E. K. Mees, ' The Theory of the Photographic Process,'Macmillan, New York, 1969.L. K. J. Tong and M. C. Glesmann, J . Amer. CJaem. SOC.{a) 1957, 79, 583; (b) 1968, 90, 5154.(u) J. F. Corbett, J . Chem. Soc. ( B ) , 1970, 1418; (b) E. Peliz-zetti and G. Saini, J . Photogyaphic Sci., in the press.B. P. Brand, J . PJzotogyaphicSci., 1965, 13, 248; 1968, 16, 1.P. W. Vittum and A. Weissberger, J . Photographic Sci.,1957, 5, 157.The preparation and the acid dissociation constants ofthe benzoylacetanilides have been described.'Ki9zetics.-Literature data and the present experi-ments show that the benzoylacetanilides in aqueoussolution and in the pH range investigated are mainly inthe ketonic form and that the oxidative coupling needs,a t first, two equivalents of oxidant per mole of PPD toform 9-benzoquinone di-imine (QDI) [reaction (l)].h 1 P-phenylenediamine - 9-di-imine (1)oxTwo further equivalents of oxidant are then required t ooxidize the leuco-dye (L) to the final dye2 (Scheme 1,which takes account of the structure of the dye 6~10).G+ + N R z/0 = c,/ C H 2 o = c\Ik 2 * A -H+f a s t / - 2 H+- 2 eC C'\0 \ c / LoN R 2SCHEME 1The reaction was carried out in aqueous alkalinesolution (pH 76-10.8) at 25 -& 1" with potassiumP. Van Brandt and A. Bruylants, Bull. SOC. chim. Belges,E. Pelizzetti and C. Verdi, J.C.S. Peykin IT, 1973, 808.L.Hevesi, P. Van Brandt, and -4. Eruylants, Bull. SOL.J. F. Corbett, J . Chenz. Soc. ( B ) , 1969, 207.lo G. H. Brown, J . Figueras, R. J . Gledhill, C. J. Icibler, F. C.McCrosscn, S. M. Parmenter, P. 147. Vittum, and A. Weissberger,J . Amer. Chem. SOG., 1957, 79, 2919.1964, 73, 843.chim. Fvance, 1970, 11, 39711973 1767ferricyanicle as oxidant. Under these conditions therate-determining step is the formation of the le~co-dye.~Taking into account the hydrolysis of QDI,ll Tongzafound that equation (2) was obeyed where m = 1 +( k d ) [ € € i ] / { (K,)[E+l[B]o), [B], is the initial concentration of2.303benzoylacetanilide, irrespective of its ionic form, [QDI],is the initial concentration of di-imine, irrespective of itsionic form, [D] is the concentration of dye at time t,obtained from [D] = At/&D, where At and ED are re-spectively the absorbance (at time t) and molar ab-sorptivity at a given wavelength, and (kd)[H+] is theoverall hydrolysis rate constant for QDI at a given pH.Equation (2) and the expression for m were derived byassuming that four equivalents or more of oxidantare added per mole of PPD.Equation (2) holds for theearly part of the reaction or in the presence of a largeexcess of coupler. Most reactions were carried out withdi-imine (Zla), for which the C,H,NHSO,Me group candissociate (Scheme 2).N H N HiN\ - + N/ \.E t C,H,N H S02M e E t C2HLN S 0,M e(ills) ( 2 2 )SCHEME 2Previous studies 2 9 3 of reactions of phenolsH+with di-imines suggest that even benzoylacetanilides shouldreact in their dissociated forms in the pH range in-vestigated; therefore the kinetic expression (3) is ob-tained where k’c- and k”,- are respectively the specificrate constants of the reactions of the benzoylacetanilideanion with the two forms of di-imine [(ela) and (22)l.With (k2)LR+] as the observed rate constant at constantpH (Scheme 1) equation (4) holds where K , is the aciddissociation constant of the benzoylacetanilide, Kt theacid dissociation constant of the sulphonamido-group[see Scheme 2; Kt = 3 x (ref. l l ) ] and p =k”,-/k‘,-.For the other di-imines the kinetics are described byequation (5), hence equation (6) applies.d[DJ/dt = kc-[B-][QDI+]RESULTSThe ( k , ) ~ ~ + , values were evaluated by means of a com-puter; the calculated absorbances were compared with theexperimental ones and (h,) [H+l was optimized by successiveiterations.According to Tongzb ( h , ) [ ~ + ] increases t o a limit as theratio [B],/[QDI], decreases (with [QDI], constant). Thevariations are related to the initial concentration of benzoyl-acetanilide and only indirectly to pH (see Table 1).TheTABLE 1Rate data for the reaction of (1) with (2la) a t 25”PH9.09.09.09.69.69.69.610.010.010.010.010.010.010.010.410.410.410.810.8lO5[(l)]/~5 105[(21a)]/~ 10-4(K,)IH+1/l mol-l s-l4.0 4.0 2-88.0 4.0 2.416.0 4.0 1.9(2.8)4-0 4.0 5.28.0 4.0 4.712.0 4.0 4.416.0 4.0 3.84.0 2.0 5.68.0 2.0 4.912.0 2.0 3.616.0 2.0 3.24-0 4.0 5.88.0 4.0 5.216.0 4.0 3.98.0 4.0 5.312.0 4.0 5.016.0 4.0 4.78.0 4.0 4.816.0 4.0 5.0(5.0)(5-2) a(5.8) a(5.5) a= 1.6 x lo5 1 mol-l s-1, t,r = 0.28Estimated upper limit for the ( k p ) [ ~ + ] value.values of k,- [for (21b and c) from equation (S)] and A’,- [for(2la) from equation (a)] were calculated from the limitingvalues of ( h z ) [ ~ t 1 .The assumption of a single p value for reaction of (2la)with the benzoylacetanilides is unsatisfactory.Thereforean estimate of k’,- and p was made for every benzoyl-acetanilide by trial and error at various pH values. Theestimated VC- and p values were fed into a computer toobtain the best fit with the experimental (k,)[=+] values.The optimized values of p ranged from 0.22 to 0.44.Table 1 collects the (K,)[H.+~ values for the reaction of (1)with (21a); values of k’c- = 1-6 x lo5 1 mol-l s-1 and p =0.28 were obtained from the limiting value of (k,)[g+] atevery pH.Table 2 lists the specific rate constants (k’,- and hc-) forthe reactions of the benzoylacetanilides with (21a-c).DISCUSSIONFigure 1 shows a plot of log k,- vs.pK, for the benzoyl-acetanilides and di-imines. The experimental data lieon a straight line corresponding to equation (7) where,log kc- = log a + PpKa (7)for (zla), log a = 0.11 and P = 0.55 were calculated byleast square method with correlation coefficient Y 0.986[compound (13) was excluded; the large deviation mayl1 L. K. J. Tong, J . Phys. Chern., 19S4, 58, 10901768 J.C.S.Perkin I1be due to the steric effect of the two ortho-methyl groups). The effect of the substituents on reactivity is shownThis relationship is valid also for (21b and c) with the by Figure 2 which is a plot of log (Kc-/,VOc-) [where Poc-same value of p and log a = 0.43 for (21b) and -0.36 is the specific rate constant of the unsubstituted benzoyl-for (21c). acetanilide (l)] against CT values, for monosubstitutedCorrelations of this type are quite common for re- benzoylacetanilides (Y # H, X = H); the experimentalactions with nucleophiles; l2 in the present case the data lie on a straight line where py = -0.48 (Y 0.987).PKa a9.48.98.79.28-99.28-99.19.810.29.48.88.37.47.89.69.810.410.3TABLE 2Specific rate constants for the reaction of benzoyl acetanilides with various di-iminesk,/l mol-l s-l kjC- (2 1 a) /(21c) PH 105[QD1]/~ c 105[B]/~ 1 mol-l s-l p log ( / ~ ' ~ - / k ' , , ~ - ) (21b)9.0-10.8 2.0-4.0 44--16-0 1.6 X lo5 0.28 3.2 x 105 5.0 x 1048.0-10.0 4.0 8.0-20.0 9.1 X lo4 0.44 - 0.26 2.0 x 105 3.8 x 1048.0-10*0 4.0 4.0-20.0 7.8 X lo4 0.37 - 0.318.5-1 0.4 4.0 4.0-20.0 1-2 X lo5 0.37 - 0.138.0- 10.0 4.0 4.0-16.0 8.2 X lo4 0.43 - 0.298.0--10.0 4.0 4.0-16.0 1-1 X lo5 0.41 -0.168.5-10.4 4.0 4.0-20.0 9.0 x lo4 0.39 - 0.258.5-10.4 4.0 4.0-16.0 1.0 X lo5 0-40 -0.219.6-10.4 3.0-4.0 4.0 3.2 x lo5 0.37 + 0.309.0-10.4 4.0 4.0-20.0 1.6 X lo5 0.31 0.008.5-1 0.4 4.0 4.0-10-0 7.3 x lo4 0.35 - 0.348-5-10.4 4.0 4.0-20*0 4.0 X lo3 0.23 - 1.867.5-9.6 2.5 4-0-10.0 2.1 X lo4 0.30 - 0.887.5-9.6 2-5 4.0-10.0 2.5 X lo4 0.22 - 0.80 8.3 x 104 9.0 x 1039.6-1 0.4 2.0 2.0--8.0 2.1 x 105 0.24 +0.128.5-10.4 4.0 4.0-20.0 5.5 x lo5 0.24 + 0-54 1.0 x 106 1.8 x 1059.0-10-4 2.0 2*0-8*0 2.8 X lo5 0.22 + 0.248.5-1 0.4 2.0 2.0 8.0 x 105 0.31 + 0.708*5-10*4 2.0 2.0 7.2 x lo5 0.35 $0.64* See ref.7. b Experimental range of pH. c Columns 4 and 5 give the experimental range of di-imine and benzoylacetanilideconcentrations respectively.from the relationl3 between the charge density on thecarbon atom of the methylene group and the pK, value.FIGURE I Diagram of log (k,/koe-) as a function of pKa of thebenzoylacetanilides for various di-imines: A, (21b) ; B, (21a) ;c, (21c)FIGURE 2 Diagram of log (h',JVOc-) as a function of thesubstituent effect for the monosubstituted (Y # H, X = H)benzoylacetanilidesFIGURE 3 Combined effect of the substituents on the reactivityof benzoylacetanilides.The points are the experimental dataand the straight line, according to equation (8), has a slopepxpy = 0-64 (in order to calculate the abscissa values p y= -0.48 and p x = -1.3 were adopted)For polysubstituted compounds (Y # H, X $. H)equation (8) holds, as shown in Figure 3 where thecalculated line gave a good fit for px = -1.3 (r 0.986).l2 J. F. Bunnett, Aim. Rev. Phys. Chem., 1963, 60, 271; K. M.l3 H. 1. Hofmann. hl. Scholtz, and C . Weiss, 2. Chem., 1971,Ibne Rasa, J. Chem. Educ., 1967, 44, 8911, 181. .,l4 J. Hine, ' Physical Organic Chemistry,' Holt, New York,19591973 1769The monosubstituted compounds are reported forcomparison.The results show that electron-releasing substituentsincrease the reactivity of the benzoylacetanilides.Table 2 shows decreasing reactivity of the di-imines inthe order (21b) > (21a) > (21c).This result wasfound previously for the reaction of these di-imines withphenols ; 36 electron-releasing groups decrease the re-activity of the di-imines, while the opposite holds forfor coupler.TABLE 3Visible spectra of dyes in aqueous alkaline buffer (pH ca. 9)Dye obtained fromEXPERIMENTALBenzoy1acetanilides.-TheAmas./nm46046046 1461462464462462458458464466474472462456457453447456456468450456456470456preparation1 0-4~max./1 mol-1 cm-l1.301.421-401.381.361.451-201.401-151.001.401.501.001-151.201.801.700.850.851.521-701.221.651.201.600-821.20and the dissoci-ation constants of the benzoylacetanilides have been givenpreviously.' Solutions were prepared in organic solvents(acetone or methanol) and alkaline buffer. The reactingmixture did not contain > 1% organic solvent.p-PhenyZenediamines.-Reagent grade products weredissolved immediately before use in distilled and deaeratedwater.Oxidant.-Reagent grade potassium ferricyanide wasadded in the amount of four equiv. per mole of PPD.Buffeer Solutions.-Solutions were prepared by nixing0.0125~1-borax with O-~M-HC~ or -NaOH.l5 The pH of thereacting mixture was constant within 0.05 pH unit.Apparatus.-The absorption spectra of the dyes wererecorded with a Hitachi-Perkin-Elmer EPS 3T spectro-photometer. Kinetic measurements were made with astopped flow Durrum-Gibson apparatus.Molar A bsorptivities.-The molar absorptivities of thedyes a t the absorption maxima were evaluated by mixinga constant amount of PPD with a large excess of benzoyl-acetanilide.The measured absorbance increased till to alimiting value which allowed to estimate E ~ . The measure-ments were carried out a t pH 9, with the stoicheiometricamount of oxidant. The molar absorptivity is given byED = absorbance/[PPD]. Table 3 collects the A,. and EDdata for the investigated dyes.Hydrolysis Rate Constants (Kd)p+].-These have beenpreviously evaluated and reported.3bKinetic Experiments.-A mixture of benzoylacetanilideand oxidant in buffer solution was mixed in the stopped-flow apparatus with a buffered solution of PPD and thevariation of absorbance with time was taken at the wave-length of maximum absorption of the dye. Since thebenzoylacetanilides were previously dissolved into thealkaline buffered solution, no induction periods, as observedfrom Vittum and Wei~sberger,~ were found. The experi-ments were carried out at 25 & 1".[3/077 Received, 12th Januavy, 1973115 L. Meites, ' Handbook of Analytical Chemistry,' JIcGraw-Hill, London, 1963, sect. 11-7

ISSN:1472-779X    

DOI:10.1039/P29730001766

出版商:RSC    

年代:1973

数据来源: RSC