98 SOPER THE HYDROLYSIS OF ACYLCHLOROAMINES IN WATER. XVII.-The Hydrolysis of Acylchloroamines in Water. By FREDERICK GEORGE SOPER. THE slight extent of the reversible hydrolysis of chloroamines in water (Orton and Gray Brit. Assoc. Rep. 1913 135) :NCI + H,O + :NH + HCIO renders its quantitative study difficult, since it necessitates direct estimation of the concentrations of the hydrolysis products (as opposed to their estimation by difference), and further neither of the hydrolysis products is a sufficient'ly good electrolyte to allow of the application of sensitive electrical methods. Moreover the one partition method available that of estimation of the hypochlorous acid by distillation (Orton and Gray Zoc. cit.) is as will be shown later complicated by the fact that the chloroamine is itself volatile.I n order to increase the hydrolysis of a chloroamine and thu SOPER THE HYDROLYSIS OF ACYLCHLOROAMINES I N WATER. 99 allow of the general application of methods available for the examination of homogeneous equilibrium the concentration of one of the products of the hydrolysis may be still further reduced by its reversible combination with some other substance the conditions of equilibrium with which are known. Substances considered for this purpose were hydrochloric acid interacting with the hypo-chlorous acid to form chlorine or an alkali forming hypochlorite. Both these substances however may cause secondary reactions, the chlorine forming C-chlorinated products whilst the alkali may cause hydrolysis of and to a certain extent may form complexes with the acylamine present.The use of another amine which forms reversibly a chloroamine with the hypochlorous acid present, is free from the objections associated with the use of hydrochloric acid or an allrali but it demands a knowledge of the hydrolysis equilibrium of one chloroamine beforc calculation of other hydrolysis constants becomes possible. p-Toluenesulphondichloroamide was selected as this standard chloroamine for reasons that have already been given (J. 1924 125 1899). When the hydrolysis of the chloroamine under investigation has been displaced the method of examination employed is of a solu-bility type and depends on the following considerations. p-Toluene-sulphondichloroamide dissolves in solutions of anilides with the formation of the corresponding chloroamines : C ,H 7.S O,*NHCl C,H,*SO,*NCI + II@' BrAcKH 1 + HCIO -7 L4rllcKC1.1. C,H *S O,*NH, Hypochlorous acid is removed by combination with the added anilide and causes further solution and hydrolysis of the sulphondi-chloroamide. From the increase in the solubility of the sulphon-dichloroamide as measured by the thiosulphate titre of the saturated solution the concentrations of the chloroamines formed in solution can be calculated. This " solubility " of the sulphondichloroamide n a solution of an anilide is made up of the concentrations of the dichloroamide the monochloroamide the chloroamine formed from the anilide and the hypochlorous acid. If a is the equilibrium concentration of the dichloroamide in millimols.in solution T the t,hiosulphate titre expressed as milliequivalents per litre then [C,H,-SO,*NHCI] + [ArAcNCl] + [HCIO] = (T - 4a)/2, or neglecting the [HClO] for reasons discussed below and denoting the concentration of the chloroamine ArAcNCl formed from d millimols. of anilide by x and that of the sulphonmonochloroamide by b, ( 1 ) .c -/- I = ( T - 4CL)/2 - x . . . . E 100 SOPER THE HYDROLYSIS OB ACYLCHLOROAMINES M WATER. It is known that (J. 1924,125 1906) at 25", [C7H7*S02*NHCl][HC10] = 8.0 x 10-4 [C,H,*S02*NCl,] = 6-27 x 10-5 . . . . . (2) and [C7H7*S0,*NH2][HCIO] = 4-9 x 10-5 [C,H,-S02*NHCl] (3) while from the general conditions of equilibrium [C,H,*SO2*NH2] = x - 6 . . . . (4) Combining (3) and (4), eliminating HClO from (Z), and eliminating x from (l), [HClO](x - b)/b = 4.9 x 10-5; (X - b)/b2 = 0.781 ; 0*781b2+ 2b - S = O .. . . . (5) This equation allows of the calculation in millimols. of b of the concentration of hypochlorous acid from (2) and of that of the chloroamine formed from (1). The hydrolysis constant is given by the expression [HClO][anilide]/[chloroamine] = [HClO]x/(d - x). The omission of the hypochlorous acid concentration from equa-tion (1) is permissible because the progressive hydrolysis of the dichloroamide caused by combination between the anilide and hypochlorous acid results in an increase in the concentration of its hydrolysis product C,H,*SO,*NHCl and hence in a diminution of the concentration of the hypochlorous acid initially only 0.0079 millimols.since in presence of one solid phase wix. the sulphondi-chloroamide the expression [HC10][C,H,*S02*NHC1] is constant. It is this reduction in the concentration of the hypochlorous acid that makes the method of extensive use. For since the equilibrium concentration of the amine is measured by a difference d - x it is necessary that x(= [ArAcNCl]) should not approach d (the concentration of the anilide initially present) too closely in value, i.e. the hydrolysis of the chloroamine should always be extensive. This is effected by the automatic diminution of the concentration of the hypochlorous acid for the smaller the hydrolysis constant of the chloroamine (and therefore the greater the need for the dis-placement of its hydrolysis equilibrium) the smaller does the concentration of hypochlorous acid become due to the accumulation of the sulphonmonochloroamide in the system.The hydrolysis constants of the chloroamines of acetanilide, formanilide aceto-o- and -p-toluidides and 0- and p-chloroacet-anilides have been determined. The details of one determinat'ion and the mean values of Kh in the other cases are given in Table I SOPER THE IfYDROLYSIS O F ACYLCHLOROAMINES M WATER. 101 TABLE I. N-Chloroacetanilide. Conc. of Thio. titro anilide of sat. soh. b in ~t in HClO x 103. x lo?. M x 10-3. 171 x 10-3. x x 10-7. ILX 107. 0-511.1 O*ODGN 0.161 0.152 3.89 6.80 1.0 1.322 0.232 0.274 2.70 7-15 2.0 1.784 0.317 0.420 1.8s 7-44 5.0 2.734 0.506 0.706 1.24 7.53 &an 7.27 K ~ X 107. I < ~ x 107. N-Cliloroformanilide .........2.4 No-Dichloroacetanilide ...... 6.0 X-Chloroaceto-o-toluidide ... 3.3 ~p-Dichloroacetanilide ...... 150 AN-Chloroaceto-p-toluidido ... 22.0 I n Table 11 the hydrolysis constants of the chloroamines exatmined are compared with the ionisation constants of similarly substituted compounds and with the equilibrium constants of the hydrolysis of anilides into amine and acid (MacBain and Davies 2. p!~yskd. Cliem. 1911 78 369). TABLE IJ. 1 /IL. I</& (c:lloro- 1 (benzoic Group. aniinc). I< (anilide). h'b (amine). (phcnol). acid). €I ............ 0 . 7 3 ~ 4.1 4 4 x 10-10 7 . 3 x 105 113.7 x 103 o-CH ......... 0.33 1.7 3.3 - 8.3 p-CII ......... 2.8 6.4 20.0 - 19.4 c-C1 ............ 0.69 0.14 - 1.3 0.76 pC1 ............ 1.5 2-2 1-3 2.5 10.7 The relative effects of the o-methyl and the p-methyl goups 011 the hydrolysis of the chloroamines and the ionisation of the amines aro almost identical as are also the relative effects of the o-chlorine and the p-chlorine atoms on the chloroamines and the phenols.The iiifluciice of the chlorine atom compared with that of the hydrogen atQru on the hydrolysis of the chloroamines does not however, appear to be similar to its influence on the ionisation of other SlZl)EIcZi?CCS. Thc volatility cf the chloroamine when its aqueous solutions are subjected to distillation at 25" causes the estimate of the percentago of free hypochlorous acid in an aqueous solution of N-chloroacet -anilide (Orton and Gray loc. cit.) to be high. Thus on addition of successive quantities of acetanilide to the aqueous chloroamine solution the ratio of the thiosulphate titre of the distillate to that of the original solution decreases to a minimum value of 0.20, independent of the coiicentration of the chloroamine solution.This behaviour is unlike that observed in the distillation of soclium hypochlorite in presence of excess of sodium hydroxide the titre oi the distillate then falling to zero. The thiosulphate titre of the distillate obtained from a 0.1 yo solution of N-chloroacetanilidc was found (Orton and Gray Zoc. cit.) to be O-O0368N which afte 102 SOPER THE HYDROLYSIS OF ACYLCHLOROAMINES IN WATER. allowing for the volatility of the chloroamine corresponds to a concentration of 0-00016 mol. of hypochlorous acid in the distillate or 5.94 x 10-5 mol.of hypochlorous acid in the chloroamine solution. The calculated hydrolysis constant of N-chloroacetanilide is then 6.0 x 10-7 a satisfactory confirmation of the value obtained by the solubility method (7.3 x 10-7). The limited solubility of anilides in water has prevented extensive examination in this medium. The primary object has been the determination of a few hydrolysis constants as a basis for testing theories of the mechanism of the chloroamine-chloroanilide trans-formation. The effect of substituents on the hydrolysis is being examined in other media. E x P E R I M E N T A L. Betermination of the Solubility .-The determination of the solu-bility of p-toluenesulphondichloroamide in solutions of anilides was carried out in the same way as that in aqueous solutions of p-toluene-sulphonamide (Soper loc.cit.). The sohtion attained a practically constant titre after 3-6 hours. Since the chloroamines of anilides decompose slowly in water owing to hydrolysis of the anilides to anilines (Orton and Gray loc. cit.) one molecule of which removes a number of molecules of hypochlorous acid the concentration of hypochlorous acid falls and since the expression [HC10][C7H7*S0,*NHCI] is constant in presence of the solid dichloroamide the concentration of the monochloroamide increases. The net result is that the titre of the solution slowly increases on standing (i.e. after 24 hours). The following figures obtained during the solution of the dichloroamide in a solution'of acetanilide (2M x lO-3) are typical.Time ..................... 2 4 6 12 24 hours Titre of 20 C.C. in N/500-thio. ......... 13-71 17.80 17-86 17-92 18.05 C.C. D,istillat.ion of Aqueous Chloroamine Solutions.-The diagram of the apparatus used has been given elsewhere (Soper J. 1924,125,2230). The thiosulphate titre of the solutions was taken before and after the distillation. There was no appreciable change during this process. No further decrease in the ratio of the titre of the dis-tillate to that of the solution was obtained on increasing the acet-anilide concentration from 0*02M to 0.05M. I n conclusion I wish to express my thanks UNIVERSITY COLLEGE OF NORTH WALES, Orton F.R.S. for his interest in this work. BANGOR. [Received, to Professor K. J. P. September 27th 1924. 98 SOPER THE HYDROLYSIS OF ACYLCHLOROAMINES IN WATER.XVII.-The Hydrolysis of Acylchloroamines in Water. By FREDERICK GEORGE SOPER. THE slight extent of the reversible hydrolysis of chloroamines in water (Orton and Gray Brit. Assoc. Rep. 1913 135) :NCI + H,O + :NH + HCIO renders its quantitative study difficult, since it necessitates direct estimation of the concentrations of the hydrolysis products (as opposed to their estimation by difference), and further neither of the hydrolysis products is a sufficient'ly good electrolyte to allow of the application of sensitive electrical methods. Moreover the one partition method available that of estimation of the hypochlorous acid by distillation (Orton and Gray Zoc. cit.) is as will be shown later complicated by the fact that the chloroamine is itself volatile.I n order to increase the hydrolysis of a chloroamine and thu SOPER THE HYDROLYSIS OF ACYLCHLOROAMINES I N WATER. 99 allow of the general application of methods available for the examination of homogeneous equilibrium the concentration of one of the products of the hydrolysis may be still further reduced by its reversible combination with some other substance the conditions of equilibrium with which are known. Substances considered for this purpose were hydrochloric acid interacting with the hypo-chlorous acid to form chlorine or an alkali forming hypochlorite. Both these substances however may cause secondary reactions, the chlorine forming C-chlorinated products whilst the alkali may cause hydrolysis of and to a certain extent may form complexes with the acylamine present.The use of another amine which forms reversibly a chloroamine with the hypochlorous acid present, is free from the objections associated with the use of hydrochloric acid or an allrali but it demands a knowledge of the hydrolysis equilibrium of one chloroamine beforc calculation of other hydrolysis constants becomes possible. p-Toluenesulphondichloroamide was selected as this standard chloroamine for reasons that have already been given (J. 1924 125 1899). When the hydrolysis of the chloroamine under investigation has been displaced the method of examination employed is of a solu-bility type and depends on the following considerations. p-Toluene-sulphondichloroamide dissolves in solutions of anilides with the formation of the corresponding chloroamines : C ,H 7.S O,*NHCl C,H,*SO,*NCI + II@' BrAcKH 1 + HCIO -7 L4rllcKC1.1. C,H *S O,*NH, Hypochlorous acid is removed by combination with the added anilide and causes further solution and hydrolysis of the sulphondi-chloroamide. From the increase in the solubility of the sulphon-dichloroamide as measured by the thiosulphate titre of the saturated solution the concentrations of the chloroamines formed in solution can be calculated. This " solubility " of the sulphondichloroamide n a solution of an anilide is made up of the concentrations of the dichloroamide the monochloroamide the chloroamine formed from the anilide and the hypochlorous acid. If a is the equilibrium concentration of the dichloroamide in millimols.in solution T the t,hiosulphate titre expressed as milliequivalents per litre then [C,H,-SO,*NHCI] + [ArAcNCl] + [HCIO] = (T - 4a)/2, or neglecting the [HClO] for reasons discussed below and denoting the concentration of the chloroamine ArAcNCl formed from d millimols. of anilide by x and that of the sulphonmonochloroamide by b, ( 1 ) .c -/- I = ( T - 4CL)/2 - x . . . . E 100 SOPER THE HYDROLYSIS OB ACYLCHLOROAMINES M WATER. It is known that (J. 1924,125 1906) at 25", [C7H7*S02*NHCl][HC10] = 8.0 x 10-4 [C,H,*S02*NCl,] = 6-27 x 10-5 . . . . . (2) and [C7H7*S0,*NH2][HCIO] = 4-9 x 10-5 [C,H,-S02*NHCl] (3) while from the general conditions of equilibrium [C,H,*SO2*NH2] = x - 6 . . . . (4) Combining (3) and (4), eliminating HClO from (Z), and eliminating x from (l), [HClO](x - b)/b = 4.9 x 10-5; (X - b)/b2 = 0.781 ; 0*781b2+ 2b - S = O .. . . . (5) This equation allows of the calculation in millimols. of b of the concentration of hypochlorous acid from (2) and of that of the chloroamine formed from (1). The hydrolysis constant is given by the expression [HClO][anilide]/[chloroamine] = [HClO]x/(d - x). The omission of the hypochlorous acid concentration from equa-tion (1) is permissible because the progressive hydrolysis of the dichloroamide caused by combination between the anilide and hypochlorous acid results in an increase in the concentration of its hydrolysis product C,H,*SO,*NHCl and hence in a diminution of the concentration of the hypochlorous acid initially only 0.0079 millimols.since in presence of one solid phase wix. the sulphondi-chloroamide the expression [HC10][C,H,*S02*NHC1] is constant. It is this reduction in the concentration of the hypochlorous acid that makes the method of extensive use. For since the equilibrium concentration of the amine is measured by a difference d - x it is necessary that x(= [ArAcNCl]) should not approach d (the concentration of the anilide initially present) too closely in value, i.e. the hydrolysis of the chloroamine should always be extensive. This is effected by the automatic diminution of the concentration of the hypochlorous acid for the smaller the hydrolysis constant of the chloroamine (and therefore the greater the need for the dis-placement of its hydrolysis equilibrium) the smaller does the concentration of hypochlorous acid become due to the accumulation of the sulphonmonochloroamide in the system.The hydrolysis constants of the chloroamines of acetanilide, formanilide aceto-o- and -p-toluidides and 0- and p-chloroacet-anilides have been determined. The details of one determinat'ion and the mean values of Kh in the other cases are given in Table I SOPER THE IfYDROLYSIS O F ACYLCHLOROAMINES M WATER. 101 TABLE I. N-Chloroacetanilide. Conc. of Thio. titro anilide of sat. soh. b in ~t in HClO x 103. x lo?. M x 10-3. 171 x 10-3. x x 10-7. ILX 107. 0-511.1 O*ODGN 0.161 0.152 3.89 6.80 1.0 1.322 0.232 0.274 2.70 7-15 2.0 1.784 0.317 0.420 1.8s 7-44 5.0 2.734 0.506 0.706 1.24 7.53 &an 7.27 K ~ X 107. I < ~ x 107. N-Cliloroformanilide .........2.4 No-Dichloroacetanilide ...... 6.0 X-Chloroaceto-o-toluidide ... 3.3 ~p-Dichloroacetanilide ...... 150 AN-Chloroaceto-p-toluidido ... 22.0 I n Table 11 the hydrolysis constants of the chloroamines exatmined are compared with the ionisation constants of similarly substituted compounds and with the equilibrium constants of the hydrolysis of anilides into amine and acid (MacBain and Davies 2. p!~yskd. Cliem. 1911 78 369). TABLE IJ. 1 /IL. I</& (c:lloro- 1 (benzoic Group. aniinc). I< (anilide). h'b (amine). (phcnol). acid). €I ............ 0 . 7 3 ~ 4.1 4 4 x 10-10 7 . 3 x 105 113.7 x 103 o-CH ......... 0.33 1.7 3.3 - 8.3 p-CII ......... 2.8 6.4 20.0 - 19.4 c-C1 ............ 0.69 0.14 - 1.3 0.76 pC1 ............ 1.5 2-2 1-3 2.5 10.7 The relative effects of the o-methyl and the p-methyl goups 011 the hydrolysis of the chloroamines and the ionisation of the amines aro almost identical as are also the relative effects of the o-chlorine and the p-chlorine atoms on the chloroamines and the phenols.The iiifluciice of the chlorine atom compared with that of the hydrogen atQru on the hydrolysis of the chloroamines does not however, appear to be similar to its influence on the ionisation of other SlZl)EIcZi?CCS. Thc volatility cf the chloroamine when its aqueous solutions are subjected to distillation at 25" causes the estimate of the percentago of free hypochlorous acid in an aqueous solution of N-chloroacet -anilide (Orton and Gray loc. cit.) to be high. Thus on addition of successive quantities of acetanilide to the aqueous chloroamine solution the ratio of the thiosulphate titre of the distillate to that of the original solution decreases to a minimum value of 0.20, independent of the coiicentration of the chloroamine solution.This behaviour is unlike that observed in the distillation of soclium hypochlorite in presence of excess of sodium hydroxide the titre oi the distillate then falling to zero. The thiosulphate titre of the distillate obtained from a 0.1 yo solution of N-chloroacetanilidc was found (Orton and Gray Zoc. cit.) to be O-O0368N which afte 102 SOPER THE HYDROLYSIS OF ACYLCHLOROAMINES IN WATER. allowing for the volatility of the chloroamine corresponds to a concentration of 0-00016 mol. of hypochlorous acid in the distillate or 5.94 x 10-5 mol.of hypochlorous acid in the chloroamine solution. The calculated hydrolysis constant of N-chloroacetanilide is then 6.0 x 10-7 a satisfactory confirmation of the value obtained by the solubility method (7.3 x 10-7). The limited solubility of anilides in water has prevented extensive examination in this medium. The primary object has been the determination of a few hydrolysis constants as a basis for testing theories of the mechanism of the chloroamine-chloroanilide trans-formation. The effect of substituents on the hydrolysis is being examined in other media. E x P E R I M E N T A L. Betermination of the Solubility .-The determination of the solu-bility of p-toluenesulphondichloroamide in solutions of anilides was carried out in the same way as that in aqueous solutions of p-toluene-sulphonamide (Soper loc.cit.). The sohtion attained a practically constant titre after 3-6 hours. Since the chloroamines of anilides decompose slowly in water owing to hydrolysis of the anilides to anilines (Orton and Gray loc. cit.) one molecule of which removes a number of molecules of hypochlorous acid the concentration of hypochlorous acid falls and since the expression [HC10][C7H7*S0,*NHCI] is constant in presence of the solid dichloroamide the concentration of the monochloroamide increases. The net result is that the titre of the solution slowly increases on standing (i.e. after 24 hours). The following figures obtained during the solution of the dichloroamide in a solution'of acetanilide (2M x lO-3) are typical. Time ..................... 2 4 6 12 24 hours Titre of 20 C.C. in N/500-thio. ......... 13-71 17.80 17-86 17-92 18.05 C.C. D,istillat.ion of Aqueous Chloroamine Solutions.-The diagram of the apparatus used has been given elsewhere (Soper J. 1924,125,2230). The thiosulphate titre of the solutions was taken before and after the distillation. There was no appreciable change during this process. No further decrease in the ratio of the titre of the dis-tillate to that of the solution was obtained on increasing the acet-anilide concentration from 0*02M to 0.05M. I n conclusion I wish to express my thanks UNIVERSITY COLLEGE OF NORTH WALES, Orton F.R.S. for his interest in this work. BANGOR. [Received, to Professor K. J. P. September 27th 1924.