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Energy & Fuels 1990, 4 , 518-524
Aqueous High-Temperature Chemistry of Carbo- and Heterocycles. 6.' Monosubstituted Benzenes with Two Carbon Atom Side Chains Unsubstituted or Oxygenated at the a-Position Alan R. Katritzky* and Franz J. Luxem Department of Chemistry, University o f Florida, Gainesville, Florida 32611-2046
Michael Siskin* Corporate Research Science Laboratory, Exxon Research and Engineering Company, Annandale, New Jersey 08801 Received December 4, 1989. Revised Manuscript Received April 30, 1990
Ethylbenzene reacts very slowly, but perceptibly, via the formation of PhCH2' radicals in both water and cyclohexane. By contrast, styrene rapidly polymerizes in aqueous solution but leads to dimers, trimers, and tetramers in cyclohexane. Phenylacetylene reacts at an intermediate rate, mainly by thermal dimerization and trimerization reactions. 1-Phenylethanol decomposes quite rapidly; the major pathways are cationic, via the a-phenethyl cation, through which acetophenone and ethylbenzene are formed. Styrene is also formed, but in aqueous solution rather than by polymerizing; it is captured by a phenethyl cation to give dimers and trimers. Acetophenone reacts slowly, even with added acid.
Introduction The preceding paper in this series dealt with monosubstituted benzenes carrying two carbon atom side chains that were oxygenated in the P-position. We now report on the analogous compounds oxygenated at the a-position (i.e., 1-phenylethanol and acetophenone) and also ethylbenzene and the corresponding unsaturated compounds styrene and phenylacetylene. As in previous parts of this series, Table I lists all the compounds encountered in the present work as reactants or as products. Table I1 records the authentic compounds that we used as starting materials or for the identification of products. Table I11 gives MS fragments for products identified by comparison of their spectra with literature data. Table IV records the MS fragmentation patterns for compounds of which the structures were deduced from their mass spectraa2 In most cases, peaks of low intensities with long retention times that could not be positively identified are grouped together as unresolved peaks. Tables I1 and I11 are deposited as supplementary material (see paragraph at end of paper regarding supplementary material).
Mass Spectral Assignments of Structures The structures of the products 15,16, 18-21,23-28,31, 34, 36, 37, 39, 41, and 42 were deduced from their mass spectra. (2-Phenylethy1)cyclohexane(15) displays the expected fragment ions at m / z 105 (15% relative intensity (r.i.)) (loss of C6Hll), m/z 91 (10070) (PhCH,+), and m/z 77 (20%) (Ph+)together with an important peak at m / z 92 (98%) which is formed by proton transfer to give (1) For part 5 in this series see: Katritzky, A. R.; Luxem, F. J.; Siskin, M. Energy Fuels, preceding paper in this issue. (2) Katritzky, A. R.; Lapucha, A. R.; Murugan, R.; Luxem, F. J.; Siskin, M.; Brons, G.Energy Fuels, part 1, in this issue. (3) Budzikiewicz, H.; Djerassi, C.; Williams, D. H. Mass Spectrometry of Organic Compounds; Holden-Day: San Francisco, 1967; p 83. (4) MacLeod, J. K.; Djerassi, C. Tetrahedron Lett. 1966, 2183.
0887-0624/90/2504-0518$02.50/0
1-Cyclohexyl-3-phenylprop-1-ene (16) displays a molecular ion peak at m/z 200 (37% r.i.) and a base peak at m/z 118 (C9H10),which results from the loss of cyclohexene. Compound 18 is probably 1-phenyl-1-@-ethylpheny1)ethane and exhibits a base peak at m/z 105 (C,H,+), formed through cleavage of a p-ethylbenzyl radical. The molecular ion peak expected a t m/z 210 was too weak to be observed. 1-Phenyl-1-cyclohexylethene(19) shows its molecular ion at m/z 186 (90% r.i.) and a loss of CGH10 (cyclohexene) to give a styrene radical cation a t m/z 104, which is also the base peak.5 The loss of C4H, gives a fragment a t m/z 129 (37%). Compound 20 is probably 2,3-diphenylbutane and shows a base peak a t m/z 105 (PhCH+CH3). In addition a fragment a t m/z 104 (20%) is observed, formed through the loss of phenylethane. The molecular ion peak m/z 210 was again too weak to be observed. l-Ethyl-2-(1-phenylethy1)benzene (21) gives fragment ions at m/z 195 (78% r.i.) (loss of CHJ, m / z 181 (40%) (loss of C2H5), m/z 105 (75%) (PhCzH5+),and m/z 91 (84%) (C7H7+).The base peak is the fragment at m/z 117 (CgHg+). 1,3-Diphenylbutane (23) shows the expected fragments m / z 91 (90% r.i.) (PhCH,') and m/z 105 (100%) (PhC,H,+). Important peaks a t m/z 92 (20%) (C7H8'+) and m/z 106 (30%) (C8Hlo'+)arise from proton transfers via McLafferty type rearrangements.6 l-(Z-Ethylpheny1)-2-phenylethane (24) displays the fragment ion m/z 195 (M - CH3),which is also the base peak. The fragment at m/z 181 (50% r i ) results from the loss of C2H5, and fragment m / z 105 (81%) is PhC2H5+. The fragment m / z 165 (61%) probably arises via a rearrangement of m / z 181 to a dihydrophenanthrene m/z 180 (5) Heller, S. R.; Milne, G. W. EPAJNIH Mass Spectral Data Base; NBS: Washington, DC, 1978-80; p 88. (6) Johnstone, R. A. W.; Millard, B. J. J . Chem. SOC.C 1966, 1955.
0 1990 American Chemical Society
Energy & Fuels, Vol. 4,No. 5, 1990 519
Aquathermolysis of Carbo- and Heterocycles. 6
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
min 0.62 1.04 1.22 1.28 1.53 1.81 1.83 1.97 2.09 2.97 3.23 7.16 7.76 8.52 8.99 9.62 9.75 9.90 9.94 10.08 10.43 10.45 10.83 10.84 10.84 11.25 11.31 11.32 11.49 11.84 12.09 12.56 13.62 17.47 17.55 18.00 18.93 19.80 20.80 21.58 23.51 23.68
tR,
structure PhCH3 PhCHZCH3 PhC=CH PhCHECHp 2-MeC6H4Et PhCHZCHO PhCH(CHJ2 PhCHO PhCHzCH=CH2 PhCOMe PhCH(OH)CH3 PhCOzH PhCH2Ph C6H4(Me)Ph PhCHZCHzC6H11 1-cyclohexyl-3-phenylprop1-ene PhCHzCH(CH3)Ph 1-phenyl-1-(pethylpheny1)ethane Ph(C6Hl1)C=CH2 2,3-diphenylbutane o-P~CH(CH~)C~H~E~ Ph(CHJ3Ph PhCH(CH3)CHzCHzPh O-E~C~H~CHZCH~P~ PhCOCHzCH(CH3)Ph (E)-PhCH&H=C(CHJPh PhC=CCHzCH2Ph 1,3-diphenylpropene 2-phenyl-1,2,3,4-tetrahydronaphthalene PhCH=CHCH(CH3)Ph (Z)-PhCHZCH=C(CH,)Ph 1-phenylnaphthalene 2-phenylnaphthalene styrene trimer 1,2,3-triphenylbenzene styrene trimer styrene trimer 1,2,4-triphenylbenzene PhCOCHZCHzCOPh 1,3,5-triphenylbenzene styrene tetramer styrene tetramer
mol wt 92 106 102 104 120 120 120 106 118 120 122 122 168 168 188 200 196 210 186 210 210 196 210 210 224 208 206 194 208 208 208 204 204 312 306 312 312 306 238 306 416 416
equiv wt 106 102 104 120 120 120 106 118 120 122 122 84 84 188 200 98 105 186 105 105 98 105 105 112 104 103 97 104 104 104 102 102 104 102 104 104 102 117 102 104 104
identification basis Table 111 Table I1 Table I1 Table I1 Table I11 Table I11 Table I11 Table I11 Table I11 Table I1 Table I1 Table I1 Table I11 Table I11 Table IV Table IV Table I11 Table IV Table IV Table IV Table IV Table I11 Table IV Table IV Table IV Table IV Table IV Table IV Table I11 Table I11 Table IV Table I11 Table 111 Table IV Table I11 Table IV Table IV Table I11 Table IV Table I11 Table IV Table IV
response factor 1.12 0.96 0.95 0.96 0.95 0.62 0.95 0.64 0.95 0.75 0.78 0.51 0.85 0.93 0.93 0.91 0.92 0.92 0.93 0.92 0.92 0.92 0.92 0.92 0.74 0.92 0.91 0.91 0.92 0.92 0.92 0.92 0.92 0.88 0.88 0.88 0.88 0.88 0.57 0.88 0.85 0.85
37
Table IV. Identification of Products from Mass Spectral Fragmentation Patterns MW fragmentation pattern, m / z ( % relative intensity, structure of fragment ion) 188 188 (30, M'); 105 (15, c6Hg+);92 (98, c7H6+);91 (100, PhCHz+);77 (20, Ph+); 65 (50, C5H5'); 55 (52. \ - - , C.Hn+) -*--, , 200 200 (37, M+); 118 (100, M - C6Hlr));115 (35, CgH7'); 55 (44, C4Hg'); 39 (40, C3H3') PhCHZCH=CHC6Hl1 210 1 2 1 (19, M - C5H5.); 106 (16, M - CBH10); 105 (100, CsH9'); 77 (24, Ph') EtC6HdCH(CHJPh 186 186 (90, M'); 129 (37, M - CdHg'); 128 (44, M - C4H10); 115 (55, CgH7'); 104 (100, CBHB') Ph(C6H11)C=CH2 210 105 (100, c~H9'); 104 (20, C&3+);79 (16, C6H7'); 77 (20, Ph') PhCH(CH,)CH(CH,)Ph 210 (53, M'); 195 (78, M - CH3); 181 (40, M - Et); 117 (100, CgHg+);105 (75, CBHg'); 91 (84, o - P ~ C H ( C H ~ ) C ~ H ~ E 210 ~ PhCH.+) - _____ 210 210 (42, "M;); 106 (30, CBHlot);105 (100, C!&+); 92 (20, C7HS'); 91 (90, PhCHZt);79 (40, C & , + ) ; PhCH(CHS)CZH,Ph 77 (53. Ph') 210 210 (82, M+);'195 (100, M - CH3); 181 (50, M - Et); 178 (51, C14H10); 165 (61, C13Hg+); 105 (81, o-PhCHzCHzC6H4Et C&') 224 224 (13, M'); 119 (21, M - PhCO); 106 (100, PhCHO); 105 (98, PhCO'); 91 (62, PhCH2') PhCOCHzCH(CH3)Ph (E)-PhCHzCH=C(CHs)Ph 208 208 (21, M'); 193 (10, M - CH3); 130 (28, M - C&3); 115 (30, CgH7'); 91 (100, PhCHZ'); 65 (55, C5H5') 206 206 (18, M+); 116 (54, CgHJ; 115 (100, CgH7+);91 (48, PhCHz'); 65 (69, C5HS') PhCzCCHZCHzPh 194 194 (57, M'); 179 (17, M - CH3); 178 (25, C,,H,o); 116 (50, CgH,); 115 (100, C9H7'); 91 (50, PhCHzCH=CHPh PhCH,+I - ..___ (Z)-PhCHzCH=C(CH,)Ph 208 208 (58, $); 193 (28, M - CH,); 130 (29, M - PhH); 115 (100, CgH7'); 91 (53, PhCHZ') 312 312 (14, M); 207 (66, M - PhCZH,); 129 (55, CloHg'); 117 (66, PhCH=CHCHz'); 91 (100, (see Scheme I) PhCH.'): 77 (17. Ph') (see Scheme I) 312 312 (13, Mi; 207 (21, M'- PhCzH4);129 (5, CloH9+);117 (66, PhCH=CHCH,+); 103 (11, PhC2H2+);91 (100, PhCHzt) (see Scheme I) 312 312 (30, M); 207 (67, M - PhCzH4); 129 (79, CIoHg'); 117 (28, PhCH=CHCHZ'); 91 (100,
39 41 42
PhCOCHzCHzCOPh (see Scheme I) (see Scheme I)
no.
compound 15 PhCHZCH&H,,
16 18 19 20 21 23 24 25 26 27 28 31 34 36
PhCH,+)
238 238
