1424
I n d . Eng. Chem. Res. 1989, 28, 1424-1431
Rao, Y. K. Stoichiometry and Thermodynamics of Metallurgical Processes; Cambridge University Press: Cambridge, 1985. Sain, D. R.; Belton, G. R. Interfacial Reaction Kinetics in the Decarburization of Liquid Iron by Carbon Dioxide. Met. Trans. B 1976, 7B, 235-243. Sigal, C., Vayenas, C. G. Ammonia Oxidation to Nitric Oxide in a Solid Electrolyte Fuel Cell. Solid State Ionics 1981,5, 567-570. Sigworth, G. K.; Elliott, J. F. The Thermodynamics of Liquid Dilute Iron Alloys. M e t . Sci. 1974, 8 , 298-310. Smith, J. M. Chemical Engineering Kinetics, 2nd ed.; McGraw-Hill: New York, 1970. Solar, M. Y.; Guthrie, R. I. L. Kinetics of the Carbon-Oxygen Reaction in Molten Iron. Met. Trans. 1972, 3, 713-722. Stoukides, M.; Vayenas, C. G. Kinetics and Rate Oscillations of the Oxidation of Propylene Oxide on Polycrystalline Silver. J . Catal. 1982a, 74, 266-274. Stoukides, M.; Vayenas, C. G. Transient and Steady-State Vapor Phase Electrocatalytic Ethylene Epoxidation. Voltage, Electrode Surface Area, and Temperature Effects. In Catalysis under Transient Conditions; ACS Symposium Series 178; American Chemical Society: Washington, DC, 1982b; pp 181-208. Stoukides, M.; Vayenas, C. G. Solid Electrolyte-Aided Study of Propylene Oxidation on Polycrystalline Silver. J . Catal. 1983,82, 45-55. Subbarao, E. C.; Maiti, H. S. Solid Electrolytes with Oxygen Ion Conduction. Solid State Ionics 1984, 11(4),317-338. Suzuki, K.; Mori, K. Rate of Desorption of CO from Liquid Iron. Trans. I S I J 1977, 17, 136-142. Teague, C. E. The High Temperature Ammonia Fuel Cell: Production of Nitric Oxide with Cogeneration of Electricity. MSc. Thesis, Massachusetts Institute of Technology, Cambridge, 1981. Takeda, Y.; Kanno, R.; Noda, M.; Tomida, Y.; Yamamoto, 0. Cathodic Polarization Phenomena of Perovskite Oxide Electrodes with Stabilized Zirconia. J . Electrochem. SOC.1987, 134(11), 2656-2661. Vayenas, C. G. Comment on “Interpretation of the Electromotive
Forces of Solid Electrolyte Concentration Cells during CO Oxidation on Platinum and on Electromotive Force Studies of CO Oxidation on Platinum”. J . Catal. 1984, 90, 371-373. Vayenas, C. G. Catalytic and Electrocatalytic Reactions in Solid Oxide Fuel Cells. Solid State Ionics 1988, 28-30, 1521-1539. Vayenas, C. G.; Farr, R. D. Cogeneration of Electric Energy and Nitric Oxide. Science 1980, 208, 593-594. Vayenas, C. G.; Lee, B.; Michaels, J. N. Kinetics, Limit Cycles, and Mechanism of the Ethylene Oxidation on Platinum J. Catal. 1980, 66, 36-48. Vayenas, C. G.; Debenedetti, P. G.; Yentekakis, I.; Hegedus, L. L. Cross-Flow, Solid-State Electrochemical Reactors: A Steady-State Analysis. Ind. Eng. Chem. Fundam. 1985,24, 316-324. Vayenas, C. G.; Bebelis, S.; Neophytides, S. Non-Faradaic Electrochemical Modification to Catalytic Activity. J . Phys. Chem. 1988, 92, 5083-5085. Wagner, C. Adsorbed Atomic Species as Intermediates in Heterogeneous Catalysis. Adv. Catal. 1970, 21, 323-381. Weissbart, J.; Ruka, R. A Solid Electrolyte Fuel Cell. J . Electrochem. SOC.1962, 109(8), 723-726. Winkler, 0.;Bakish, R. Vacuum Metallurgy; Elsevier: Amsterdam, 1971. Yentekakis, I. V.; Vayenas, C. G. The Effect of Electrochemical Oxygen Pumping on the Steady-State and Oscillatory Behavior of CO Oxidation on Polycrystalline Pt. J. Catal. 1988, 111, 170- 187. Yentekakis, I. V.; Vayenas, C. G. Chemical Cogeneration in Solid Electrolyte Cells: The Oxidation of H2S to SO2. J . Electrochem. SOC.1989, 136,996-1002. Yentekakis, I. V.; Neophytides, S.; Vayenas, C. G. Solid Electrolyte Aided Study of the Mechanism of CO Oxidation on Polycrystalline Platinum. J . Catal. 1988, 111, 152-169.
Received for review September 23, 1988 Revised manuscript received May 30, 1989 Accepted June 13, 1989
Common Mass Spectrometric Characteristics of Durable Press Reactants Based on Cyclic Ureas Brenda J. Trask-Morrell,* Bethlehem A. Kottes Andrews, and William E. Franklin S o u t h e r n Regional Research Center, M i d South Area, Agricultural Research Service, U S D A , N e w Orleans, Louisiana 70179
Solid probe mass spectrometric analyses were performed on 16 compounds based on cyclic ethyleneurea or cyclic propyleneurea. These compounds are used in durable press finishing of cotton textiles. T h e mass spectral ion profiles were examined t o reveal common characteristics that are related t o compound structure. Possible fragmentation routes were suggested to account for the majority of ions produced by these agents. The N-methylol-substituted agents are ones that easily release formaldehyde, which is a problem for the textile industry. The mass spectral technique provided a new means of identifying such agents and may find applications in the textile industry as a means of monitoring the ability of etherifying agents to suppress formaldehyde release of finishing agents. Durable press (DP) reactants used in the textile finishing industry are often based on derivatives of cyclic ureas. Ethyleneurea (EU) and propyleneurea (PU) are the structural skeletons upon which many agents are built. The ones most commercially successful in the past were adducts of cyclic ureas and formaldehyde, that is, methylol derivatives of the cyclic ureas. We recently began research to achieve a basic understanding of the thermal stability of these reactants (Trask-Morrell and Kottes Andrews, 1988). By use of thermal analyses, a variety of common structural characteristics were recognized. The most important finding was a means to identify some agents capable of releasing formaldehyde. A number of these same cyclic compounds were examined by solid probe mass spectrometric (MS) analyses. With this technique, we were able to support our thermal
marker for formaldehyde release with a mass spectrometric marker (Trask-Morrellet al., 1987,1988). Some concurrent research has been reported on a group of durable press agents in the GC/mass spectrometer (Beck et al., 1988). The research reported here is a presentation of the results of MS solid probe analyses of 16 compounds based on ethylene- and propyleneureas. The aim is to elucidate some features common to these compounds through mass spectrometric analyses.
Materials and Methods The reagents analyzed were urea, unsubstituted cyclic ethyleneurea, and propyleneurea, as well as compounds that contained groups symmetrically substituted, unless stated otherwise. Substituents on the ring nitrogens included CH,OH, CH3, and CH20CH3 Substituents on the
This article not subject to U.S. Copyright. Published 1989 by the American Chemical Society
Ind. Eng. Chem. Res., Vol. 28, No. 9, 1989 1425 Table I. ComDounds Examined in Mass Spectrometric base base compound MW peak peak“ 60 44 urea 30 86 86 EUb 114 114 N,N’-dimethyl-EU N,N’-dimethyl-4,5-dihydroxy-EU 146 60 132 42/46 N-methyl-4,5-dihydroxy-EU 118 46 4,5-dihydroxy-EU 146 4,5-dimethoxy-EU 60 174 4,5-diethoxy-EU 46 146 N,”-dimethylol-EU 31 42 N,N’-dimethylol-4,5-dihydroxy-EU 178 30131 46 206 N,N’-dimethylol-4,5-dimethoxy-EU 60 174 N,N’-(dimethoxymethy1)-EU 45 234 N,N’-(dimethoxymethy1)45 4,5-dimethoxy-EU PU‘ 100 30 100 N,”-dimethylol-PU 31 44 160 N,N’-(dimethoxymethy1)-PU 45 188
Study
figure la lb, 7a 2C
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I,j,j
,
,
,
,
,
a
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This peak is the second most intense peak when scanned from 29 to 450 amu. * Ethyleneurea. Propyleneurea. 60-
ring carbons included OH, OCH,, and OC2H5. These reactants are described in detail in our earlier publication (Trask-Morrell and Kottes Andrews, 1988), and their structures are drawn on the figures within the text. The compounds are named in the manner common to textile chemists. The IUPAC nomenclature would identify the ethyleneureas and propyleneureas as derivatives of 2imidazolidinone and tetrahydro-2(1H)-pyrimidinone, respectively. A Finnigan 4500 mass spectrometer equipped with a solid probe analyzer and an Incos data system containing the National Bureau of Standards’ library of compounds was used for our samples. In most cases, 5 pL of an approximately 50 pg/pL water solution was placed in a direct probe sample vial and dried in a vacuum desiccator. Occasionally, a minute speck of solid agent was placed in a sample vial and run as is. This latter technique was needed for some samples whose substituents were easily hydrolyzed in solution. The sample probe was heated ballistically from ambient temperature to 300 “C over a time period of 3-5 min. An electron impact ionization of 70 eV was used. The instrument scanned from 33 to 450 or 29 to 450 amu using a scan time of 1.00 s. The mass spectra were generally summed over the first major peak of the reconstructed ion current (RIC) chromatogram, and backgrounds were substracted.
Results and Discussion In table I are the names of the compounds tested along with their molecular weights, and their base peaks when scanned from 29 to 450 amu and when scanned from 33 to 450 amu, if the base is different. Certain spectra chosen for illustration contained scans from only 33 to 450 amu because the detection of higher mass ions was improved when oxygen was not part of the scan. In some instances, this resulted in the second most intense ion appearing as the base peak. In addition, the last column indicates in which figure(s) the mass spectral data and structures appear. In Figure 1are the data for urea (a), cyclic ethyleneurea (b), and cyclic propyleneurea (c). Of the cyclic compounds, only ethyleneurea was found in our instrument library as 2-imidazolidinone. None of the other cyclic compounds was listed. These spectra were relatively simple when compared to those of the more substituted compounds examined later. All the compounds in Figure 1 have molecular ions in their mass spectra. The base peak for urea
T b
100 1.4
300 6.0
6008CAN 6.2 TIME
C
Figure 1. Mass spectra and reconstructed ion current (RIC) chromatograms for urea (a), ethyleneurea (b), and propyleneurea (c).
was m / z 44, [H,NC=O]+, and represented loss of NH,. Ions m / z 43, [HN=C=O]+, and m/z 42, [N=C=O]+, are also present and will be commonly seen throughout this study. Under these analytical conditions, urea produced a strong [M 1]+ ion. Had we chosen a spectrum very early in the reaction, only the molecular ion would have been present. The reconstructed ion current chromatograms also are shown in this figure. Throughout this paper, the RIC’s are plotted on the same scan number/time scale. Only ethyleneurea reacted slowly under these heating conditions. Data for N,N’-dimethyl-4,5-dihydroxyethyleneurea (a), N-methyl-4,5-dihydroxyethyleneurea (b), and N,N‘-dimethylethyleneurea (c) are presented in Figure 2. The spectra are more complicated than those shown in Figure 1. Molecular ions are present in all three spectra. In spectrum a, we saw the first occurrence of an [M + 1]+ ion among the cyclic compounds, indicating some unexplained form of chemical ionization. Like the results with urea above, examination of specific mass ion chromatograms showed the presence of m / z 147 was limited to the most intense spectra, while m / z 146 was found throughout the heating period. When a spectrum was obtained early in the experiment in order to eliminate the m/z 147 ion (not shown), the only other difference in the ion profiles was the the next ion represented loss of water at m / z 128. The
+
1426 Ind. Eng. Chem. Res., Vol. 28, No. 9, 1989 lool
00: r
roo
’I
I
h
100 1.4
lo0i
481
8CAN TINE
. a
501
I too 1.4
WAN TIME
Figure 3. Mass spectra and reconstructed ion current (RIC)chromatograms for 4,5-diethoxyethyleneurea(a) and N,”-(dimethoxymethyl)-4,5-dimethoxyethyleneurea(b).
--
160
Figure 2. Maas spectra and reconstructed ion current (RIC)chromatograms for N,”-dimethyl-4,5-dihydroxyethyleneurea (a), NmethyL4,5dihydroxyethyleneurea(b), and N&’-dimethylethyleneurea (c).
spectrum chosen shows the presence of both the [MI+ and [M + 1]+ions and the loas of water as the first peak at m / z 129. In spectrum b, the next two peaks after the mdecular ion were ions caused by loss of water and two OH radicals, respectively. The monomethyl compaund also showed ion peaks that were higher than the mass of the mo1eq.h ion. This MS analysis was accomplished using the solid compound; therefore, ion/molecule reactions were possible. Howeverf this phenomenon was found in several of our compounds where sample size was not a factor and will be the subject of a future paper discussing the production of residues in thermal analyses and mBs8 spectral analyses. N,”-Dhthylethy€eneurea (c) is a liquid that proved difficult to analyze. The compound peaked in the RIC in a matter of seconds. Its spectrum showed an M - CH, ion. The m / z 85 ion could represent the loss of NCH, as a consequence of fragmentation path 1, CH2NHa~ described in path la, or the loss of C2H5 as in 2, all of which will be discussed later in Figure 6. In Figure 3 are shown the mass spectra and RIC’s of 4,5-diethoxyethyleneurea (a) and N,N‘-(dimethoxymethyl)-4,5-dhethoxyethyleneurea(b). The diethoxy “ p o u n d also showed an [M + 1]+ ion; the next major ion in the spectrum was at m / z 145, which probably represented the ion [M - C&]+. The base peak for this compound was at m / z 46, which probably represented [C2HsOH]+.
Compound 3b is the largest compound included in this study. This compound is also a liquid, but it was much less volatile than N,”-dimethylethyleneurea (24. The molecular weight is 234 and was only recorded in minute quantity (0.1%base peak). The first major ion, m/z 203, probably results from the loss of OCH, and the next peak from the loss of a second such radical. The base peak for this compound was 45 and represented [CH20CH3]+. We were interested in whether MS analyses would enable us to show loss of the methyl group in compounds that had been methylated. In our previous report, we compared MS results of samples containing NCH20H and NCH20CH, groups (Trask-Morrell et al., 1987,1988). However, it was suspected that the mass spectral results were actually of hydrolyzed samples because the spectra were so similar. Two pairs of compounds were reanalyzed using solid compound specimens, and the newer results, which confirmed our suspicions, are contained in Figures 4 and 5. In Figure 4 are the MS results for the N,”-dimethyl01 and N,N’-dimethoxymethyl derivatives of ethyleneurea. The molecular ion was present in the N-methylol compound ( m / z 146)and was missing in the methylated sample ( m / z 174);water loss was the first major ion present for the former, while loss of OCHBwas the first major ion for the latter. The loss of CH, was barely registered at m / z 159 (0.2% base peak). Figure 5 presents the corresponding data for the propyleneureas. Neither molecular ion ( m / z 160 or 188) was detected. Again, the first major ions measured represented water and OCH, losses, respectively. As in the previous methylated sample, loss of the methyl group registered at m / z 173 in very small abundance (0.4% base peak). Two more points need to be made for Figures 4 and 5. The base peaks in the spectra for the N-methylol compounds are m / z 31 and for the N-methoxymethyl com-
Ind. Eng. Chem. Res., Vol. 28, No. 9, 1989 1427 e-
100
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+
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-
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60 -
Figure 6. Schematic representation of three multicenter fragmentation pathways commonly found among this series of compounds: fragmentation after ring opening (1,laJb); fragmentation as ring carbon/nitrogen bonds cleave (2); and loss of formaldehyde (3a,3b).
4r ,100
j
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Figure 5. Mass spectra and reconstructed ion current (RIC) chromatograms for N,N"-dimethylolpropyleneurea (a) and N,"-(dimethoxymethy1)propyleneurea (b).
pounds are m J z 45. This is evidence that these nitrogen substituents are lost intact in great abundances. The textile industry is sensitive to the issue of formaldehyde release from treated fabrics. The portion of this research that most closely relates to that subject involves those compounds that contain N-methylol groups. Those
substituents are known to release formaldehyde more easily than others. In the initial examination of mass spectrometric results, we found a marker for agents capable of releasing formaldehyde, first by inference and then by the presence of a specific ion present in the ion profiles (Trask-Morrell et al., 1987, 1988). The ion was the [CH,OH]+ ( m / z 31) mentioned above. These early conclusions were strengthened by the study of fragmentation patterns discussed below. Three possible fragmentation routes have been found useful in explaining a majority of the mass spectral ion profiles of these cyclic compounds. They are shown in Figure 6. The first (1) involves ring opening and the formation of an ion radical and is illustrated for ethyleneurea. This step involves the breaking of a single bond. Numerous fragmentation possibilities are available after this first step, frequently involving the C-C bond (la) and most often a shifting hydrogen (lb). The second fragmentation (2) that we have found common among these compounds involves breaking of both carbonlnitrogen ring bonds. This pathway yields two segments in ethyleneurea as shown in the figure. While the CH2=CH2 species, mass 28, was not an ion and was beneath our detection limits, the corresponding segment from compounds with ring carbon, alkoxy substituents was always detected. This detection was probably facilitated by the presence of unshared electrons on the oxygens. An [M - 281' ion that might represent loss of CO as a possible first step fragmentation route was not routinely found among our compounds. The third common fragmentation path occurred with N-methylol compounds. While it is known that N methylol compounds lose formaldehyde easily under
1428 Ind. Eng. Chem. Res., Vol. 28, No. 9, 1989 100
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Figure 7. Comparison of mass spectra of compounds with and without N-methylol substituents: (a) ethyleneurea and (b) N,N'dimethylolethyleneurea. Formula of possible neutral radical ion species (n) or fragment (f).
Figure 8. Comparison of mass spectra of compounds with and without N-methylol substituents: (a) 4,5-dihydroxyethyleneureaand (b) N,"-dimethylol-4,5-dihydroxyethyleneurea. Formula of possible neutral radical ion species (n) or fragment (f).
room-temperature equilibrium conditions, it was important to find an ionic explanation for such a loss because [M HCHO]+ ions were collected. An electron impact induced hydrogen migration (a McLafferty rearrangement) was one possibility (Shrader, 1971; McLafferty, 1980). This reaction can occur when a carbonyl oxygen is present and hydrogen is in a position y to the carbonyl. In our compounds, a McLafferty rearrangement (3a) results in the loss of CH20. The loss of a second formaldehyde theoretically can occur after the hydrogen migrates from the oxygen to the nitrogen. In addition, simple proton transfers to the unshared pairs of nitrogen electrons (3b) would also result in formaldehyde loss. These three multicenter fragmentation pathways apparently occur frequently in this series of compounds. With these three speculative pathways in mind, four sets of compounds with and without the N-methylol groups can be examined more closely. Figure 7 shows the spectra of ethyleneurea (a) and N,"-dimethylolethyleneurea (b) for comparison. The ion profile of EU included the molecular ion m / z 86. This could occur by the simple abstraction of an electron or by the breaking of a single bond which opens the ring as described in pathway 1 (Figure 6). Ion m / t 58 could be formed by a common fragmentation of these compounds, Le., breaking of two ring bonds as shown in pathway 2 (Figure 6). This same route, differing by a shifting hy-
drogen, would yield the fragment mlz 57, and this ion was present in nearly as great abundance as 58. The ion at mass 42 was found commonly in our compounds, and although species with the formula C2Hz0or C2H4Nsatisfy the weight criteria, we think the ion was probably more often represented by the fragment [ N=C=O]+. The mass spectrum of the companion N-methylol compound was much more complex. We saw the molecular ion at 146, the loss of an OH radical at 129, and loss of water at 128. The ion at 116 could be formed through a McLafferty rearrangement with the loss of HCHO. Ion 115 represented loss of the CHzOH substituent, and the [CHzOH]+ion itself was found at m / z 31. The ion at m / z 99 could arise through loss of CHzOplus the loss of an OH radical. A loss of two formaldehydes, [Figure 6 (3a or 3b)], could yield an EU fragment m / z 86. This would then explain all the lower weight ion fragments found in both spectra (Trask-Morrell et al., 1987, 1988). Note the m / z 42 ion, [O=C=N]+, was again present. Figure 8 shows the spectra of 4,5-dihydroxyethyleneurea (DHEU) (a) and N,"-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) (b). DHEU showed a small [M + 1]+ ion possibly from chemical ionization. The ion at mass 100 was M - HzO. The complementary ion pairs 72/46 and 73/45 were probable after ring opening, as in pathways la and 1b (Figure 6), yielding fragments differing by a single shifting hydrogen. Ion m / z 60 was presumably formed
Ind. Eng. Chem. Res., Vol. 28, No. 9, 1989 1429 100
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F i g u r e 9. Comparison of mass spectra of compounds with and without N-methylol substituents: (a) 4,5-dimethoxyethyleneurea and (b) N,N'-dimethylol-4,5-dimethoxyethyleneurea. Formula of possible neutral radical ion species (n) or fragment (0.
when the carbonlnitrogen ring bonds were broken, as described in pathway 2 in Figure 6. The spectrum of DMDHEU is again more complex than its parent compound. Small abundances of high mass ions represented loss of OH, H20, CH20Halone and in various combinations. There was evidence of an ion at m / z 118 that could be formed by the loss of two formaldehydes, which yielded a DHEU fragment. This would explain the similarities of the lower weight portions of the ion profiles. There was an indication of ion pairs 118160 and 102176 as shown on the structural diagram itself. Both compounds in this figure had a base peak at m/z 46 (when collecting was from 33 to 450 m u ) . This ion was probably [HOCHNH2]+(Beck et al., 1988). When DMDHEU was analyzed from 29 to 450 amu, m/z 30 and 31 were the two most intense peaks (not shown). The [CH,OH]+ fragment was clearly present. The spectrum, as illustrated, however, showed the higher weight ions in greater abundances. A third pair of compounds, 4,5-dimethoxyethyleneurea (a) and its N,"-dimethyl01 analogue (b), is shown in Figure 9. The former compound showed an [M + 1]+ ion. The next major ion arose at m / z 131 and was due to the loss of a methyl radical. The ion at m/z 115 possibly indicated loss of the OCH, radical. Ion pairs were found, i.e., 58/88 and 86/60, and both presumably occurred as described in the figure, with the latter pair in greater abundance.
100
160
200
Figure 10. Comparison of mass spectra of compounds with and without N-methylol substituents: (a) propyleneurea and (b) N,N'dimethylolpropyleneurea. Formula of possible neutral radical ion species (n) or fragment (0.
In the more complex spectrum, b, there was an indication of the molecular ion at 206 and low intensity ions that demonstrated loss of OH, CH,, CH,OH, or HCHO. In Figure 9, the most important feature was the ion at m / z 131 common to both spectra. This can be formed by loss of two formaldehyde molecules plus the loss of a CH, radical. After the m/z 131 ion was formed, the remainder of the spectrum was similar to that of the unmethylolated compound. The last pair of compounds, propyleneurea and N,N'dimethylolpropyleneuea, is illustrated in Figure 10. Ring opening and simple bond cleavage between carbons 4 and 5 plus a shifting hydrogen could result in ion pairs of 56/44 and 51/43. The base peak was at m/z 30, as seen previously. The methylolated compound showed no molecular ion but showed a M - H20 ion as the first significant peak at m/z 142. Loss of two OH radicals could produce the 126 ion. The most intense peak above m / z 33 was the ion m / z 44. The ion produced by formaldehyde loss at m / z 130 was present. The ion at m/z 113 could arise from a McLaffertylHCHO loss and the loss of an OH radical. Finally, this compound clearly exhibited the N-methylol marker at m / z 31. The mass spectra for this series of compounds based on cyclic ureas showed some general similarities. These similarities most often occurred in the production of lower mass ions. Ion rragments were commonly present in the
1430 Ind. Eng. Chem. Res., Vol. 28, No. 9, 1989
ranges 42-46, 56-60, and 70-74 amu. More variety was present in ion fragments a t higher masses. Three different ethyleneurea derivatives with the molecular weight 146 (Figures 2a, 4a, and 9a) could be distinguished by their mass spectra. Although two had the same base peaks, the ion profiles were recognizably different. Among the compounds, there were four that produced an [M + 11’ ion. They were 4,5-dihydroxyethyleneurea, N,Nf-dimethyl-4,5-dihydroxyethyleneurea, 4,5-dimethoxyethyleneurea, and 4,5-diethoxyethyleneurea. The concurrent researchers (Beck et al., 1988) also examined the first and third compound; they found the [M + 1]+ ion for 4,5-dimethoxyethyleneurea, only. All four of our compounds that produced such an ion were structurally similar; they had ring carbons substituted with OH or OR groups. Examination of the specific mass ion chromatograms and the RIC’s yielded a variety of results. 4,5-Dihydroxyethyleneurea actually produced trivial amounts of both [MI+ and [M + 1]+ions. Water loss was essentially the first ion in this spectrum. Specific mass ion chromatograms of 4,5-dimethoxyethyleneureashowed no molecular ion at all, only the [M + 11’ ion. 4,5-Diethoxyethyleneurea produced both ions. The three 4,5-dialkoxyethyleneureas produced an exotherm during thermal analyses (Trask-Morrell and Kottes Andrews, 1988), and this exothermic activity may have increased the rate of vaporization, leading to higher pressures in the source region of the instrument. This explanation does not hold for the N,N’-dimethyl-4,5-dihydroxyethyleneureacompound which does not produce an exotherm in TA but does produce both [MI+ and [M + 11’ ions. Specific mass ion chromatograms of this compound showed the [M + 1]+ curve to have a narrower peak that was most intense at the peak of the RIC. Very early or very late spectra showed no ions resulting from chemical ionization. These are speculations and relate to our inability to attribute any ion production to thermal effects (Trask-Morrell et al., 1987, 1988) at this time. A base peak of 60 was produced by three compounds N,N’-dimethyl-4,5-dihydroxyethyleneurea, 4,5-dimethoxyethyleneurea, and N,N’-dimethylol-4,5-dimethoxyethyleneurea. An ion with the composition C2H6N0can be achieved for all three compounds as in example l b in Figure 6. However, the N-methylol compound must lose formaldehyde first. An ion of C2H402composition also could account for the peak a t mlz 60. In this group of three compounds, only the one containing the 4,5-dihydroxy substituents would be likely to produce such a fragment. Three other compounds produced a base peak a t mlz 46. They were 4,5-dihydroxyethyleneurea,4,5-diethoxyethyleneurea, and N-methyl-4,5-dihydroxyethyleneurea. Fragments of composition CHINO are possible with two of these compounds by the same route as described in pathway l b (Figure 6). The only restriction would be that the single methyl group remain with the carbonyl fragment. DMDHEU (Figure 8b) produced this strong peak also. This ion could be produced after a McLafferty rearrangement in the same manner. Lastly, the diethoxy compound probably produced a different mlz 46 base ion represented by a C2H60formula with the [C2H50H]+ion structure. If this compound followed the fragmentation route outlined in Figure 6 (lb), the ion at mlz 74, while present, would be in greater abundance. Three compounds had mlz 30 as the base peak. Ethyleneurea and propyleneurea could both produce a CH3NH fragment after ring opening according to example l b in
a
b
C
d
200 32
260
SCAN
3 2
TIME
Figure 11. Comparison of specific mass ion chromatogram (ion m / z 31) with reconstructed ion current (RIC) chromatogram for four N-methylol cyclic ureas: (a) N,N’-dimethylolethyleneurea; (b) N,N’-dimethylolpropyleneurea; (c) N,N’-dimethylol-4,5-dimethoxyethyleneurea; (d) N,N’-dimethylol-4,5-dihydroxyethyleneurea.
Figure 6 if the 4-5 carbon bond breaks and a hydrogen migrates to the carbon 5 segment. DMDHEU and the other N-methylol compounds also produced a strong mlz 30 peak. In those cases, we may be measuring the formaldehyde released. Three compounds with N-methoxymethyl substituents shared a common base peak a t mlz 45. That finding indicated that the methoxymethyl fragment was apparently removed intact as a primary ion. The presence of the base peak at mlz 31 ion for all compounds containing N-methylol substituents indicated that the hydroxyrnethyl group also may be lost intact. This feature represented the MS marker for compounds with formaldehyde release capability. In figure 11 are plotted the RIC’s and the specific mass ion chromatograms of the [CH20H]+ion at mlz 31, for each of the four N-methylol compounds investigated. This figure indicated that, in general, the mlz 31 ion was being produced throughout the experiment when tested under these heating conditions. Only N,N’-dimethylolethyleneurea (a) and DMDHEU (d) clearly appeared to produce less mlz 31 near the end of the experiment. The formaldehyde release marker should be simple to recognize in mass spectrometric analyses.
Summary and Conclusions The mass spectrometer was used successfully to analyze a series of cyclic ureas based on ethyleneurea and propyleneurea. There were many similarities in the spectra, in general, and distinctive differences in fragmentation patterns. Three related compounds with the same molecular weight were distinguishable. The fragmentation patterns of these compounds were products of common paths that often included loss of OH, HOH, OCH3,and CH, groups. Three major fragmentation pathways were proposed to explain the majority of all
Ind. E n g . C h e m . R e s . 1989,28, 1431-1437
major ions seen in these spectra as well as their various base peaks. There may be some way to distinguish between thermal and electron impact effects. However, additional information is required before any such distinction can be made. The chemical ionization of certain structurally related compounds provokes speculation that thermal effects are present. The presence of a marker for compounds capable of releasing formaldehyde was identified previously by thermal analyses and speculatively in mass spectrometry. The analyses of the fragmentation patterns reported here supported the assumption that the mlz 31 ion seen with N-methylol compounds was a reliable marker for use with mass spectrometric data. The full potential of the thermal and mass spectral markers to the textile industry remains to be explored. An unknown agent can be examined for the capacity to release formaldehyde, and the techniques could offer a means to monitor etherification reactions that are often used to reduce formaldehyde release in textile finishing formulations.
Acknowledgment The authors thank Elena Graves for performing a portion of the mass spectrometric analyses and Mary Patterson for lettering drawings for the figures. Presented in part in the Symposium on Textile Finishing at the 194th National Meeting, American Chemical Society New Orleans, Aug 1987, and the 39th Pittsburgh Conference and Exposition, New Orleans, Feb 1988. Names of companies or commercial products are given solely for providing scientific information and do not imply endorsement by the US.Department of Agriculture over others not mentioned.
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Nomenclature amu = atomic mass unit DHEU = 4,5-dihydroxyethyleneurea DMDHEU = N,N’-dimethylol-4,5-dihydroxyethyleneurea EU = ethyleneurea = 2-imidazolidinone M = molecular ion m / z = mass-to-charge ratio PU = propyleneurea = tetrahydro-2-(1H)-pyrimidinone RIC = reconstructed ion current chromatogram Registry No. EU, 120-93-4; PU, 1852-17-1;N,”-dimethyl-EU, 80-73-9; N,Nf-dimethyl-4,5-dihydroxy-EU, 3923-79-3; Nmethyl-4,5-dihydroxy-EU, 22322-62-9; 4,5-dihydroxy-EU,372097-6; 4,5-dimethoxy-EU,3891-44-9;4,5-diethoxy-EU,24044-29-9; N,”-dimethylol-EU, 136-84-5;N,”-dimethylol-4,5-dhydroxy-EU, 1854-26-8; N,N’-dimethylol-4,5-dimethoxy-EU, 4211-44-3; N,N’-(dimethoxymethy1)-EU, 2669-72-9; N,N’-(dimethoxymethyl)-4,5-dimethoxy-EU, 4356-60-9; N,N’-dimethylol-PU, 3270-74-4; N,”-(dimethoxymethy1)-PU, 13747-15-4;urea, 57-13-6.
Literature Cited Beck, K. R.; Springer, K.; Wood, K.; Wusik, M. GC/MS Analysis of Durable Press Agents. Text. Chem. Color. 1988, 20(3), 35. McLafferty, F. W. Interpretation of Mass Spectra, 3rd ed.; Turro, N. J., Ed.; University Science Books: Mill Valley, CA, 1980; Chapters 3, 4, and 8. Shrader, S. R. Introductory Mass Spectrometry; Allyn and Bacon: Boston, 1971, Chapter 3. Trask-Morrell, B. J.; Franklin, W. E.; Liu, R. H. Thermoanalytical and Mass Spectrometric Search for Formaldehyde Release Markers in DP Reagents. Book of Papers 1987 AATCC Internatl. Conf. & Exhibition, 1987, p 72. Trask-Morrell, B. J.; Franklin, W. E.; Liu, R. H. Thermoanalytical and Mass Spectrometric Search for Formaldehyde Release Markers in DP Reagents. Text. Chem. Color. 1988, 20(3),21. Trask-Morrell,B. J.; Kottes Andrews, B. A. Common Thermoanalytical Characteristics of Durable Press Reactants Based on Cyclic Ureas. J. Appl. Polym. Sci. 1988, 35(1), 229.
Received f o r review September 26, 1988 Accepted June 5 , 1989
Absorption Kinetics and Mixing Studies in Pressure Response Cells Richard G. Rice,* John A. King, and Xiang Y. Wangt Department of Chemical Engineering, Louisiana State University, Baton Rouge, Louisiana 70803
The recently popularized pressure response cell (PRC) allows direct physical measurements to deduce chemical rate parameters. Because of its batch nature, the PRC method is subject to serious problems owing to possible interfacial temperature rise following initial gas-liquid contact. Furthermore, if a PRC is not properly mixed, the effects of physical mass transfer can become significant. Conditions under which these two effects can be neglected are determined for the PRC. In addition, an improved cell design that can be used a t elevated gas pressures is described. The new cell is applied to the industrially important dissolution of carbon dioxide in carbonate-bicarbonate solution. Rate parameters are determined to be in good agreement with the literature values obtained with widely different methods. New results are also obtained which extend the rate parameters to elevated carbon dioxide partial pressures exceeding 3 atm, and it is shown the reaction order is unchanged a t these conditions. Recently, Rice and Benoit (1986) demonstrated how the pressure response cell (PRC) could be used to obtain not only reaction rate constants but also the reaction order. Several researchers have independently developed pressure response methods (Laddha and Danckwerts, 1981,1982; Blauwhoff et al., 1984) to find linear rate constants only. Owing to its physical simplicity, this method is becoming *To whom all correspondence should be sent.
‘Present address: Research Institute of Nanjing Chemical Industry Company, Nanjing, People’s Republic of China.
quite popular (Chakraborty et al., 1986; Versteeg et al., 1987, 1988; Kim et al., 1988). Because the method is a batch process, questions have arisen regarding the possibility of a local temperature rise at the gas-liquid interface. Since the pressure is measured only in the early time period (initial 15 min), it is important to determine if these primary data are in any way contaminated owing to the unwanted local temperature excess. In the present work, we use the PRC method to study C02reaction-absorption in carbonate-bicarbonate buffer solutions at higher pressures than heretofore obtained.
0888-5885/89/2628-1431~01.50/0 0 1989 American Chemical Society
