Energy & Fuels 1990,4,547-555
547
Aqueous High-Temperature Chemistry of Carbo- and Heterocycles. 11.' Aquathermolysis of Arylamines in the Presence and Absence of Sodium Bisulfite Alan R. Katritzky,* Ramiah Murugan, and Marudai Balasubramanian Department of Chemistry, University of Florida, Gainesville, Florida 32611-2046
Michael Siskin* Corporate Research Science Laboratory, Exxon Research and Engineering Company, Annandale, New Jersey 08801 Received December 13,1989. Revised Manuscript Received May 14,1990 Thermolysis and neutral aquathermolysis of ring and N-substituted anilines showed either no reaction or little conversion. In phosphoric acid (10%) the anilines underwent denitrogenation to give phenols. Friedel-Crafts type alkylations and dealkylations were observed for alkyl-substituted anilines, together with the formation of diarylamines and carbazoles, both in runs with phosphoric acid and in runs with an aqueous sulfite/bisulfite mixture. Mechanistic pathways are suggested for the formation of all products. Introduction Aquathermolysis is a potential method for heteroatom elimination from fuel source materials such as kerogens, coals, or heavy oils. The present paper presents the results of investigations that were initiated with the aim of using the Bucherer reaction2 to effect denitrogenation. In the Bucherer reaction, heating with aqueous sodium sulfite converts naphthylamines into naphthols: although the reaction does not work with aniline at the temperatures usually used (80-200 "C), we hoped that this conversion might be brought about at elevated temperatures. In this paper, the aquathermolysis chemistry of arylamines in the presence and absence of sodium bisulfite was studied. The model compounds selected for this investigation were o-toluidine (5),p-toluidine (7),4-ethylaniline (14),4-isopropylaniline (21),N-methylaniline (4), Nethylaniline (lo),N,N-dimethylaniline (9),N,N-diethylaniline (22), tetrahydroquinoline (32), and 2,4,6-trimethylaniline (25). These compounds are typical ring unsubstituted and alkylated primary, secondary, and tertiary aromatic amines as models for the amines present in natural resources. Each of the compounds was heated with an equivalent amount of Na2S03in aqueous NaHS03. For the differentiation of thermal, aqueous, and acidcatalyzed reactions, runs were also made in cyclohexane, in water, and in phosphoric acid (lo%), respectively. Experimental Section The gas chromatographic behavior of all the compounds encountered in this work (starting materials and products) is summarized in Table I. Table I1 records the source and mass spectral fragmentation patterns of the authentic compounds used, either as starting materials or for the identification of products. Tables I11 and IV record the mass spectral fragmentation patterns of products for which authentic samples were not available and which were identified by comparison with literature MS data (Table 111) or by deduction from their mass spectra (Table IV). Tables I1 and I11 have been deposited as supplementary material (see paragraph at end of paper regarding supplementary material). The aquathermolyses and analyses of products were conducted (1) For part 10 of the series Aqueous High-Tempoerature Chemistry of Carbo and Heterocycles, see: Katritzky, A. R.; Murugan, R.; Balasubramanian, M.; Siskin, M. Energy Fuels, preceding paper in this issue. (2) For a review see: Seeboth, H. Angew. Chem., Int. Ed. Engl. 1967, 6, 307.
Chart I
1
35
28
53 Et
\
Mc
54
Mc
El
55
59
62
Qpyp aNMe Mc2
El
El
63
Et
Me
64
65
67
as previously de~cribed,~ and the results are collected in Tables V and onward. The phosphoric acid (10%)runs were neutralized with sodium hydroxide and extracted with diethyl ether. This ether layer was used for the GC and GC/MS analyses.
Mass Spectral Assignments of S t r u c t u r e s The assignment of the final structures of each of the compounds in Table IV was made after consideratioin of the fragmentation pattern, the starting material, the reaction conditions, and a reasonable mechanistic pathway for product formation from the starting material. The products listed in Table IV can mostly be classified into three types, together with a miscellaneous category. These are (i) anilines, both N-substituted 16,20,27,33, 34,37,40,42,44and 49 and N-unsubstituted 29,30,35, 36,39,41,46,and 48;(ii) diphenylamines 50,51,58,60, 61,63,64 and 66;(iii) carbazoles 53-56,59,62,65,67, and 69;(iv) the tetrahydroquinoline (43)and biquinolines 72 and 73 forming the miscellaneous set. N,N,2-Trimethylaniline (16)fragments with loss of H, CH3, and NMez to give peaks at m / z 134 [loo% relative (3) Part 1 of the series Aqueous High-Temperature Chemistry of Carbo- and Heterocycles. Katritzky, A. R.; Lapucha, A. R.; Murugan, R.; Luxem, F. J.; Siskin, M.; Brons, C.Energy Fuels, in this issue.
0 1990 American Chemical Society
548 Energy & Fuels, Vol. 4, No. 5, 1990
Kutritzky et ul.
Table I. Structure and Identification of Starting Materials and Products no. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61
62 63 64 65 66 67 68 69 70 71 72 73 a
min 1.48 1.57 1.81 2.40 2.47 2.47 2.53 2.78 2.76 3.15 3.37 3.48 3.52 3.60 3.80 3.81 4.13 4.16 4.28 4.35 4.40 4.50 4.53 4.62 4.72 5.01 5.03 5.05 5.07 5.21 5.49 5.55 5.57 5.69 5.85 6.33 6.62 6.67 6.84 7.29 7.35 7.58 7.82 8.16 8.18 8.50 8.64 9.44 9.66 11.26 11.39 11.60 11.90 12.59 13.02 13.08 13.45 13.46 14.51 14.55 14.57 14.70 15.59 15.68 15.90 15.92 16.30 16.32 16.60 17.72 18.18 18.65 20.12
tR,
structure’ thiophenol aniline phenol N-methylaniline o-toluidine o-cresol p-toluidine p-cresol N,N-dimethylaniline N-ethylaniline 2-ethylaniline 2,4-ethylaniline 2,6-ethylaniline 4-ethylaniline 4-ethylphenol N,N,2-trimethylaniline 2,4,64rimethylphenol N,N,4-trimethylaniline quinoline N,2-diethylaniline 4-isopropylaniline N,N-diethylaniline isoquinoline 4-isopropylphenol 2,4,6-trimethylaniline 2-methylbenzothiazole N,4-diethylaniline 2-(thiomethy1)aniline 4-(hydroxymethyl)-2,6-dimethylaniline 2,4-diethylaniline 2,6-diethylaniline 1,2,3,4-tetrahydroquinoline N,2,6-triethylaniline N,2,4-triethylaniline 4-methyl-2-(thiomethyl)aniline 2-ethyl-4-isopropylaniline N,N,2-triethylaniline 6-methyltetrahydroquinoline 2,4-diisopropylaniline N,N,4-triethylaniline 2,4,6-triethylaniline
mol w t 110 93 94 107 107 108 107 108 121 121 121 121 121 121 122
6,8-tetrahydroquinoline N,N,2,4-tetraethylaniline 3,4-dihydroquinolinone 2,4-diisopropyl-6-methylaniline N-methyldiphen ylamine 2,4-diisopropyl-6-ethylaniline N,N,2,4,6-pentaethylaniline 4-ethyldiphenylamine 4,4’-dimethyldiphenylamine 9-methylcarbazole 1,8-dimethylcarbazole 1-ethylcarbazole 1,8,9-trimethylcarbazole 3-ethylcarbazole 9-ethylcarbazole 4,4’-diethyldiphenylamine 1- (dimethylamino)-8-methylcarbazole 4,4’-diisopropyldiphenylamine
135 136 135 129 149 135 149 129 136 135 149 149 139 151 149 149 133 177 177 154 163 177 147 177 177 177 205 161 205 147 191 183 205 233 197 197 181 195 195 209 195 195 225 210 253
2,4,4’-trimethyldiphenylamine
211
3,9-diethylcarbazole N,2,2’-triethyldiphenylamine N,2-dimethyl-f’-(dimethylamino)diphenylamine 1,8,9-triethylcarbazole N,4,4’-triethyldiphenylamine 1,6,9-triethylcarbazole 2-(2-aminophenyl)-4-methylbenzothiazole 3,6,9-triethylcarbazole 2-(4-aminophenyl)-6-methylbenzothiazole 2,2’-biquinoline 2,4’-biquinoline 4,4’-biquinoline
223 253 240 251 253 251 240 251 240 256 256 256
N,N,2,6-tetraethylaniline
See Chart I and Schemes I-V for the structures of these compounds.
equiv w t identification basis 110 Table I1 Table I1 93 94 Table I1 107 Table 11 107 Table I1 Table I1 108 107 Table I1 108 Table I1 121 Table I1 121 Table I1 121 Table I11 121 Table I11 121 Table I11 121 Table I1 122 Table I1 135 Table IV 136 Table I1 135 Table I11 129 Table I1 149 Table IV 135 Table I1 149 Table I1 129 Table I1 136 Table I1 135 Table I1 149 Table I11 149 Table IV 139 Table I11 Table IV 151 149 Table IV Table I11 149 Table I1 133 177 Table IV Table IV 177 154 Table IV 163 Table IV 177 Table IV 147 Table I11 Table IV 177 177 Table IV Table IV 177 205 Table IV Table IV 161 205 Table IV 147 Table I11 Table IV 191 91.5 Table I11 205 Table IV 233 Table IV 98.5 Table IV 98.5 Table IV 90.5 Table I1 97.5 Table IV 97.5 Table IV 104.5 Table IV 97.5 Table IV 97.5 Table I11 112.5 Table IV 105 Table IV 126.5 Table IV Table IV 105.5 Table IV 111.5 Table IV 126.5 Table IV 120 Table IV 125.5 Table IV 126.5 Table IV 125.5 Table I11 120 Table IV 125.5 Table I11 120 Table I1 128 Table IV 128 Table IV 128
response factor 0.72 0.81 0.76 0.71 0.71 0.79 0.76 0.77 0.71 0.71 0.71 0.71 0.71 0.71 0.78 0.70 0.75 0.70 0.82 0.70 0.70 0.70 0.82 0.78 0.70 0.57 0.70 0.46 0.52 0.70 0.70 0.70 0.69 0.69 0.45 0.69 0.69 0.69 0.69 0.69 0.69 0.68 0.69 0.68 0.53 0.68 0.68 0.68 0.67 0.67 0.67 0.68 0.68 0.68 0.68 0.68 0.68 0.74 0.44 0.66 0.67 0.67 0.66 0.42 0.66 0.66 0.66 0.29 0.66 0.29 0.64 0.64 0.64
Energy & Fuels, Vol. 4, No. 5, 1990 549
Aquathermolysis of Carbo- and Heterocycles. 11
no.
Table IV. Identification of Products from Mass Spectral Fragmentation Patterns MW fragmentation pattern, mlz (% relative intensity, structure of fragment ion)
comvounda 16 N,N,2-(Me)3-eniline 20 N,2-(Et)z-aniline 27 N,4-(Et)z-aniline 29 30 33 34 35 36 37 39 40 41 42 43 44 46 48 49 50 51 53 54 55 56 58 59 60 62 63 64 65 66 67 69 72 73
135 149 149 151 4-CH,0H-2,6-(Me)z-aniline 149 2,4-(Et)z-aniline 177 N,2,6-(Et)3-aniline 177 N,2,4-(Et)3-aniline 153 2-SMe-4-Me-aniline 163 2-Et-4-i-Pr-aniline 177 N,N,2-(Et)3-aniline 177 2,4-(i-Pr)z-aniline 177 N,N,4-(Et)3-aniline 177 2,4,6-(Et)3-aniline 205 N,N,2,6-(Et),-aniline 161 6,8-(Me),-tetrahydroquinoline 205 N,iVN,2,4-(Et),-aniline 191 6-Me-2,4-(i-Pr)-aniline 6-Et-2,4-(i-Pr)z-aniline 205 233 N,N,2,4,6-(Et),-aniline 197 4-Et-diphenylamine 4,4’-(Me)z-diphenylamine 197 195 1,8-(Me)z-carbazole 195 1-Et-carbazole 209 1,8,9-(Me)3-carbazole 195 3-Et-carbazole 225 4,4’-(Et),-diphenylamine 1-N(Me)z-8-Me-carbazole 210 253 4,4+Pr),-diphenylamine 223 3,9-(Et),-carbazole N,2,2’-(EtI3-diphenylamine 253 240 N,2-(Me)z-2’-N(Me)2diphenylamine 251 1,8,9-(Et)3-carbazole N,4,4’-(Et)3-diphenylamine253 251 1,6,9-(Et)3-carbazole 251 3,6,9-(Et),-carbazole 256 2,4’-biquinoline 256 4,4’-biquinoline
135 (60, M); 134 (100, M - H); 120 (10, M - CHJ; 119 (20, 134 - CH,); 91 (50, M - NMez) 149 (35, M); 134 (50, M - CH3); 121 (40, M - CZHJ; 106 (100, PhEt); 77 (60, Ph) 149 (25, M); 134 (100, M - CH3); 106 (70, PhEt); 91 (15, C7H7); 77 (40, Ph) 151 (100, M); 150 (60, M - H); 136 (65, M - CH3); 135 (15, 150 - CH3); 91 (15, C7H7) 149 (45, M); 134 (100, M - CH,); 106 (75, PhEt); 91 (15, C7H7); 77 (50, Ph) 177 (80, M); 162 (100, M - CHJ; 148 (5, M - Et); 134 (30, 162 - Et); 106 (20, PhEt) 177 (85, M); 162 (100, M - CH3); 148 (20, M - Et); 134 (35, 162 - Et); 106 (15, PhEt) 153 (100, M); 138 (60, M - CH3); 106 (45, M - SCHJ; 91 (15, C7H7); 77 (10, Ph) 163 (35, M); 148 (100, M - CH3); 120 (40, M - C3H7); 92 (5, PhNH); 91 (25, C7H7) 177 (40, M); 162 (100, M - CHJ; 148 (15, M - Et); 134 (40, 162 - CzH4); 106 (20, PhEt) 177 (40, M); 162 (100, M - CH3); 134 (5, M - C3H7); 120 (40,134 - CHZ); 91 (10, CeHbN) 177 (50, M); 162 (100, M - CH,); 148 (25, M - Et); 134 (50, 162 - CzH4); 106 (35, PhEt) 177 (90, M); 162 (100, M - CH3); 148 (40, M - CzH4); 120 (10, 148 - CzH4); 91 (20, C7H7) 205 (60, M); 190 (100, M - CH3); 176 (35, M - Et); 133 (50, M - NEQ; 105 (15, PhCHZCHz) 161 (50, M); 160 (100, M - H); 146 (80, M - CH3); 131 (45, 146 - CH3); 91 (25, C7H7) 205 (50, M); 190 (100, M - CH3); 176 (50, M - Et); 133 (45, M - NEh); 105 (20, PhCHZCHz) 191 (20, M); 176 (100, M - CH3); 149 (25, M - Et); 135 (25,176 - C&); 91 (30, C6HJ.V) 205 (30, M); 190 (100, M - CH3); 176 (10, M - Et); 162 (25, M - C3H7); 91 (30, C~HSN) 233 (50, M); 218 (100, M - CH3); 190 (50,218 - CzH4); 105 (15, PhCHzCHJ; 91 (20, C&N) 197 (100, M); 182 (70, M - CH3); 168 (50, M - Et); 91 (10, C6HbN), 77 (35, Ph) 197 (100, M); 182 (40, M - CH3); 106 (35, M - PhCHz); 105 (10, 106 - H); 91 (60, PhCHz) 195 (100, M); 194 (30, M - H); 180 (5, M - CH3); 91 (25, C7H7); 77 (15, Ph) 195 (60, M); 180 (100, M - CH3); 166 (45, M - CZH,); 105 (25, PhCHzCHz); 77 (10, Ph) 209 (60, M); 208 (100, M - H); 193 (15, 208 - CH3); 91 (10, C7H7); 77 (15, Ph) 195 (75, M); 180 (100, M - CH3); 152 (30, 180 - CzH4); 105 (20, PhCHZCHz); 91 (25, C7H7) 255 (100, M); 210 (95, M - CH3); 195 (15, 210 - CH3); 91 (5, C7H7); 77 (25, Ph) 210 (60, M); 195 (100, M - CH3); 166 (60, M - N(Me),); 91 (15, C7H7);77 (25, Ph) 253 (95, M); 238 (100, M - CH3); 196 (20, 238 - C3HG); 168 (10,196 - CzH4); 91 (20, CeHsN) 223 (40, M); 208 (180, M - CH3); 194 (80, M - Et); 180 (10, 208 - CzH4); 106 (20, PhEt) 253 (50, M); 238 (100, M - CH3); 224 (20, M - Et); 149 (15, M - CSH,); 134 (60, 149 - CH3) 240 (100, M); 225 (40, M - CH3); 120 (90, CBHION); 106 (40, CYHTN); 77 (50, Ph) 251 (15, M); 236 (10, M - CH,); 222 (15, M - Et); 149 (20, C10H16N);134 (10, 149 - Me) 253 (60, M); 238 (100, M - CH,); 224 (10, M - Et); 149 (10, M - PhCH=CH,); 134 (50, 149 - Me) 251 (30, M); 236 (100, M - CH3); 223 (50, M - CZH4); 194 (15, 223 - CZH4); 156 (35, 194 - C3Hz) 251 (35, M); 236 (100, M - CH3); 223 (45, M - CzH4); 194 (25, 223 - CzH4); 156 (15, 194 - C3Hz) 256 (100, M); 255 (80, M - H); 128 (55, M - C9H6N); 102 (50,128 - C,Hz); 50 (40, C4HJ 256 (100, M); 255 (75, M - H); 128 (50, C9HeN); 105 (50, 128 - CzHz); 51 (50, C4H3)
See Chart I and Schemes I-V for the structures of these compounds.
intensity (r.i.)], m / z 120 (10% r.i.), and m / z 91 (50% r.i.), respectively. From the starting material, Nfl-dimethylaniline (9), the extra Me group was assigned to the ortho-position of the phenyl ring, because this can explain the formation of the products 1,8-dimethylcarbazole (53) and 1,8,9-trimethylcarbazole(55). N,2-Diethylaniline (20) shows M+ a t m / z 149 (35% r.i.1. The base peak was a t m / z 106 arising from the loss of a C2H6Nunit. From the nature of the starting material, N-ethylaniline (lo), and the presence of products 1,8,9trimethylcarbazole (55) and N,2,2’-triethyldiphenylamine (63), the ethyl group was assigned to the 2-position. N,4-Diethylaniline (27) shows M+ a t m / z 149 (25% r.i.). The base peak was a t m/z 134 arising from a CH3 loss. The starting materials, N-ethylaniline (10) and N,N-diethylaniline (22), and the similarity of the mass spectra of compounds 20 and 27 lead us to assign the structure N,Cdiethylaniline to 27. The second ethyl group was placed at the 4-position on the basis of the observation that ortho isomers tend to show shorter retention times than the corresponding para isomers on our GC c01umn.~ This structure for 27 is also consistent with the formation of the diphenylamine 66 and the carbazole 69. 4-(Hydroxymethyl)-2,6-dimethylaniline(29) shows M+ a t m / z 151, which was also the base peak. From its starting material, 2,4,6-trimethylaniline (25), and M+ a t (4) Part 8 of the series Aqueous High-Temperature Chemistry of Carbo- and Heterocycles. Katritzky, A. R.; Murugan, R.; Siskin, M.
Energy Fuels, in this issue.
m / z 135, we infer that there is an oxygen present in 29. This product was only formed in the sulfite mixture run, and our experience with this oxidative dealkylating agent4 suggested that one of the methyl groups was oxidized to the hydroxymethyl form. The 4-position was chosen because such a product would be somewhat more stable than a 24hydroxymethy1)aniline. 2,4-Diethylaniline (30) shows M+ at m/z 149 (45% r.i.). The base peak was a t m / z 134 with a loss of a CH3 unit. From its starting material, N,N-diethylaniline (221, and its similarity with 20 and 27, the 2,4-diethylaniline structure was assigned. The formation of this product in appreciable amount ( 5 % ) only in the sulfite mixture suggested that there is no ethyl group on the nitrogen as such N-ethyl groups are easily oxidatively removed by the sulfite reagent. For the two ethyl groups, the 2- and 4-positions were chosen over the 2- and 6-positions for steric reasons. N,2,6-Triethylaniline (33) and N,2,44riethylaniline (34) both show M+ at m / z 177 (80%and 85% r.i., respectively). Their base peaks are a t m / z 162, arising from the loss of a CH, unit. From the starting material and its M+ ( m / z 149), it is known that there is an additional E t group present in both 33 and 34. The presence of only one E t group on nitrogen is confirmed by the loss of a CH2=CHNH, fragment from the M+ to give a peak a t m / z 134 (30% and 35% r.i., respectively) in both cases. The remaining two E t groups are placed a t the 2,6- and 2,4positions. From our experience with ortho- and parasubstituted compounds,4 we believe the peak first appearing in the GC is N,2,6-triethylaniline (33) and that
Katritzky et al.
550 Energy & Fuels, Vol. 4 , No. 5, 1990
appearing next is N,2,4-triethylaniline (34). 2-(Methylthio)-4-methylaniline (35) shows M+at m / z 153 as the base peak. The starting material, N,N-dimethylaniline (9), and the formation of 2-methylthioaniline (28, Table 111) from the same starting material suggest the 2-(methylthio)-4-methylaniline structure for 35. 2-Ethyl-4-isopropylaniline(36) shows M + at m / z 163 (35% r.i.). The base peak at m / z 148 arises from the loss of a CH, unit. The starting material 4-isopropylaniline (21) and the difference in the molecular weights indicate the presence of an extra E t group in 36. This Et group is confidently located a t the 2-position. N,NN,2-Triethylaniline (37) and N,N,4-triethylaniline (40) both show M+ at 177 (40% and 50% r.i., respectively). The base peak, in both cases at m/z 162, arises from a CH, loss. From the starting material, Nfl-diethylaniline (22), we deduce that an extra E t group is incorporated into products 37 and 40. From our earlier experience with ortho- and para-substituted compound^,^ the compound first appearing in the GC was assigned as N,N,B-triethylaniline (37) and that next appearing as N,N,4-triethylaniline (40). 2,4-Diisopropylaniline (39) shows M+at m/z 177 (40% r i ) . The base peak, at m/z 162, comes from loss of a CH, unit. The starting material, 4-isopropylaniline (211, and its M+( m / z 135) show the presence of a second isopropyl unit and hence indicate the 2,4-diisopropylanilinestructure for 39. 2,4,6-Triethylaniline (41) shows M+ at m / z 177 (90% r i ) . The base peak at m / z 162 involves CH, loss. The fragmentation shows no loss of a CH2==CHNH2fragment, suggesting the absence of an N-Et group [this product was formed only with the sulfite mixture from N,N-diethylaniline (22)]. Hence the three E t groups are assigned to the 2-, 4-, and 6-positions. N,N,2,6-Tetraethylaniline (42) and N,NN,2,4-tetraethy1aniline (44) both show M+at m/z 205 (60% and 50% r i , respectively). The starting material, N,N-diethylaniline (22, M + 149) indicated two additional E t groups in each of the compounds 42 and 44. Hence, from the earlier discussion on ortho and para isomers, the structures for 42 and 44 were assigned. 6,8-Dimethyl-1,2,3,4-tetrahydroquinoline (43) shows M+ at m / z 161 (50% r i ) . The base peak at m / z 160 follows loss of an H radical. The observation of two successive losses of CH3 units suggests the presence of two CH, groups rather than an E t group. The 6- and 8-positions of the starting material (1,2,3,4-tetrahydroquinoline, 32) are the most reactive leading to structure 43. 2,4-Diisopropyl-6-methylaniline(46) shows M +a t m / z 191 (20% r.i.1, and 2,4-diisopropyl-6-ethylaniline (48) shows M+at m / z 205 (30% r.i.1. Both show base peaks for loss of a CH, unit from the M +at m / z 176 and 190, respectively. The starting material 4-isopropylaniline (21, M + 135) demonstrates that 46 includes an extra four-carbon unit and 48 possesses an extra five-carbon unit. It is reasonable that these would consist of an isopropyl plus a methyl group and an isopropyl plus an ethyl group, respectively. Isopropyl rather than propyl groups are suggested on the basis of the secondary carbocation being more stable than the primary. The final assignment was made keeping the i-Pr group at the 4-position (as in the starting material). Hence the structures 46 and 48 were deduced. N,N,2,4,6-Pentaethylaniline(49) shows M +at m / z 233 (50% r.i.). The base peak was at m / z 218. From its starting material N,N-diethylaniline (22, M + 149), it is clearly seen that there are three extra Et groups present
Scheme I. Products from 2-Methyl- (5), 4-Methyl- (7), 4-Ethyl- (14), a n d 4-Isopropylaniline (21) OH
h32
in the product (491, and these are logically placed at the 2-, 4-, and 6-positions. The compounds 50,51,58,60,61,63,64, and 66 are all formed from two molecules of their respective starting materials with the loss of one nitrogen unit as ammonia or amine. The positioning of the alkyl substituents was done by using the same approach as for the alkylated anilines discussed above. All the diarylamines showed loss of an arylamino group, and the fragmentations were similar to those observed for diary1 ether^.^ The compounds 53-56, 59, 62, 65, 67, and 69 are all formed from two molecules of the starting material with the loss of one nitrogen unit as ammonia or amine and a hydrogen molecule. As these have molecular weight two units less than the diarylamines, they are assigned as carbazoles. The positioning of the alkyl substituents in the carbazoles was based on the position of the alkyl groups in their starting anilines.6
Results and Discussion All the reactions discussed in this paper were run at 250 “C over 3 days. C-Monosubstituted Anilines 5,7,14, and 21 (Table V, Scheme I). Both in cyclohexane and in water, 2methyl- (5), 4-methyl- (7), and 4-isopropylaniline (21) showed no reaction. 4-Ethylaniline (12) also showed no reaction in cyclohexane, and in water there was only 0.5% conversion to aniline (2). In the H20-H3P04medium products in which the amine group is replaced by a hydroxyl group are observed. 2Methylaniline (5) yielded 23% o-cresol (6) as the only product. From 4-methylaniline (7)19% p-cresol (8) is formed, together with 10% 4,4’-dimethyldiphenylamine (51), and 1.6% trimethyldiphenylamine (61); evidently the formation of the diarylamine is easier in the absence of an o-methyl group. The 4-ethyl (14) and 4-isopropyl (21) analogues behave similarly, yielding the corresponding phenols 15 and 24 and diphenylamines 58 (19.6%) and 60 (9.3%). A little transalkylation is also detected for 4-iso(5) Budzikiewicz, H.: Dierassi, C.: Williams, D. H. Mass Snectrometrv-
of Organic Compounds; Holden-Day: San Francisco, 196f;p 324. (6) Porter, Q.N.; Baldas, J. Mass Spectrometry of Heterocyclic Com-
pounds; Wiley Interscience: New York, 1971; p 355.
Aquathermolysis of Carbo- and Heterocycles. 11
Energy & Fuels, Vol. 4 , No. 5, 1990 551
Table V. Products of o-Toluidine (5), p-Toluidine (7), 4-Ethylaniline (la), a n d 4-Isopropylaniline (21) Reactions a t 250 O C for 3 days 5" 5" 7' 7" 14* 14b 2 1" 21' solvent H3P04 H3P04 aq aq H3P04 aq HW4 aq (10%) (10%) (10%) NaHSO, (10%) NaHSO, NaHSO, NaHS03 (satd) (satd) (satd) (satd) additive (1 mol equiv) Na2S03 Na2S03 Na2S03 Na2S03 no. structure 2
3 5 6 7 8 14 15 21 24 30 31 36 39 46 48 50 51 58 60 61 68 70
aniline phenol o-toluidine o-cresol p-toluidine p-cresol 4-ethylaniline 4-ethylphenol 4-isopropylaniline 4-isopropylphenol 2,4-diethylaniline 2,6-diethylaniline 2-ethyl-4-isopropylaniline 2,4-diisopropylaniline 2,4-diisopropyl-6methylaniline 2,4-diisopropyl-6ethylaniline 4-ethyldiphenylamine 4,4'-dimethyldiphenylamine 4,4'-diethyldiphenylamine 4,4'-diisopropyldiphenylamine 2,4,4'-trimethyldiphenylamine 2-(2-aminophenyl)-4methylbenzothiazole 2-(4-aminophenyl)-6methylbenzothiazole
0.5
77.1 22.9
0.5
2.8
25.9
71.1
4.2
7.1 69.3 19.0
85.4
1.9 14.2 64.8
62.4 3.1
11.7 70.1 18.9
81.3
0.6 0.8 0.4 0.8 0.2 0.3 1.4 9.6 19.6 9.3 1.6 28.4
'These compounds showed no reaction in cyclohexane or in water showed
