1625
Anal. Chem. 1985, 57,1625-1630
that All-120Ac and 29-120Ac coeluted on the Superox FA stationary phase. The A l l position was confirmed by reanalysis of turnip moth extracts on a nonpolar silicone-coated capillary column (SE-30) that separates these isomers. An analysis on a polar cyano-containing stationary phase (19)that resolves E and 2 isomers supported the 25-14OAc assignment. The retention time of the hexadecenyl acetate was identical with that of synthetic 211-16OAc on the polar column and on Supelcowax 10 (a poly(ethy1ene glycol) type stationary phase) column.
CONCLUSIONS We suggest that data obtained by the method described here be combined with GC retention time values to determine double bond position. Both methods require that reference compounds be analyzed concurrently with the insect-derived sample. If these reference analyses are made with coupled high-resolution GC-MS, both mass spectral ratios and retention indexes can be obtained at the same time. The mass spectral ratios do not offer any information with respect to 2 and E geometry, and no single stationary GC phase can unequivocally resolve both the double bond position and the geometry of long-chaip acetates. However, by combining these two methods, it is possible to determine the exact isomerism of monounsaturated straight-chain acetates in insect extracts where the unknowns are present only in nanogram quantities. ACKNOWLEDGMENT We wish to thank Ann-Britt Wassgren for development and preparation of the capillary columns, Berit Hamlet for help with numerical calculations, Bo G. Svensson for collection and identification of the bumble bees, Tommy Liljefors, Goran Odham, and Anders Tunlid for critical reading of the manuscript, and David Tilles for revising the language. Registry No. 22-120Ac, 84801-15-0;23-120Ac, 38363-24-5; 24-120Ac, 38363-25-6; 25-120Ac, 16676-96-3; 26-120Ac, 16974-12-2; 27-120Ac, 14959-86-5; 28-120Ac, 28079-04-1; 29120Ac, 16974-11-1;210-120Ac, 35148-20-0; A11-120Ac, 3515310-7;22-140Ac, 51309-20-7; 23-140Ac, 54897-65-3; 24-140Ac, 54897-66-4; 25-140A~,35153-13-0; 26-140Ac, 39650-11-8; 27-
140Ac, 16974-10-0;28-140Ac,35835-80-4;Z9-140Ac, 16725-53-4; 210-140Ac, 35153-16-3; 211-140Ac, 20711-10-8; 212-140Ac, 35153-20-9; A13-140Ac, 56221-91-1; 25-160Ac, 34010-18-9;E5160Ac, 56218-65-6;26-160Ac, 34010-19-0; 27-160Ac,23192-42-9; ZS-lGOAc, 56218-67-8; 29-160Ac, 34010-20-3; 210-160Ac, 56218-70-3; Zll-lGOAc, 34010-21-4; 212-160Ac, 56218-73-6; E12-160Ac, 64789-90-8; 213-160Ac, 56218-74-7.
LITERATURE CITED (1) Beroza, Mortof~; Blerl, Barbara A. Anal. Chem. 1987, 39, 1131-1135. (2) Kenner, George W.; Stenhagen, Elnar. Acta Chem. Scand. 1984, 18, 1551-1552. (3) Odham, Goran; Stenhagen, Elnar. "Biochemical Applications of Mass Spectrometry"; Waller, George R.. Ed.; Wlley: New York, 1972; Chapter 8. (4) Buser, Hans-Rudolf; Arn, Heinrlch; Guerin, Patrick; Rauscher, Stefan Anal. Chem. 1983, 55, 818-822. (5) Budzikiewicz, H.; Busker, E. Tetrahedron 1980, 36, 255-266. (6) Lester, R. J. Chromatogr. 1978, 156, 55-62. (7) Teal, P. E. A.; Hepth, R. R.; Tumlinson, J. H.; McLaughlin, J. R. J. Chem. Ecol. 1981, 7 , 1011-1022. (8) Horiike, M.; Mlyata, N.; Hkano, C. Biomed. Mass Spectrom. 1981. 8 , 41-42. (9) Horlike, M.; Hirano, C. Agric. Blol. Chem. 1982, 46, 2667-2672. (10) Horlike, Michlo; Hlrano, Chisato Biomed. Mass Spectrom. 1984, 1 1 , 145-148. (11) Leonhardt, B. A,; De Vllbiss, E. D.; Klun, J. A. Org. Mass Spectrom. 1983, 18, 9-11. (12) Lofstedt, C.; Van der Pers, J. N. C.; Lofqvist, J.; Lanne, B. S.; Appelgren, M.; Bergstrom, G.; Thelin, B. J. Cbem. Ecol. 1982, 8 , 1305-132 1. (13) Bergstrom, 0.; Appelgren, M.; Svensson, 8. G.; Agren, L.; Descolns, C.; Frerot, B.; Gallios, M.; Lettere, M. Apidologie, in press. (14) Mathews, R. J.; Morrison, J. D. Aust. J . Chem. 1974, 27, 2167-2173. (15) Buser, Hans-Rudolf; Arn, Heinrlch J. Chromatogr. 1975, 106, 83-95. (16) Rasmussen, G. T.; Isenhour, T. L. J. Chem. Inf. Comput. Sci. 1979, 19, 179-186. (17) Beynon, J. H.; Saunders, R. A.; Williams, A. E. Anal. Chem. 1981, 33, 221-225. (18) Bergstrom, G.; Lanne, B. S.; Pimlott, W., unpublished results, Department of Chemical Ecology, Unlverslty of Goteborg, Sweden, 1984. (19) Markides, K.; Blomberg, L.; Buijten, J.; Wannman, T. J. Chromatogr. 1983, 267, 29-38.
RECEIVED for review October 10,1984. Accepted January 30, 1985. This work was supported by the Swedish Natural Science Research Council and Kungliga Fysiografiska sallskapet, Lund.
Determination of Double Bond Position in Conjugated Dienes by Chemical Ionization Mass Spectrometry with Isobutane R. E. Doolittle,* J. H. Tumlinson, and A. Proveaux Insect Attractants, Behavior, and Basic Biology Research Laboratory, Agricultural Research Service, US.Department of Agriculture, Gainesville, Florida 32604
The chemical ionization (CI)mass spectra of a series of functionaiized conjugated dienes, lnciudlng aldehydes, alcohols, formates, acetates, and hydrocarhons were Investigated to determine whether fragmentations occur that are characterlstlc of the posltion of the conjugated system within the hydrocarbon chain. CI with isobutane as ionlzlng gas produces structure-speclflc fragment Ions with m /I ratlos that can be used to locate the positions of the double bonds In most of the cases studied. When the conjugated system is proximal to the functional group or conjugated with the functlonal group, other fragmentation processes take precedence. These patterns of fragmentations constitute a very useful analytlcaitool for the location of conjugated double bonds in a variety of natural products.
The determination of the position of the double bond in a linear alkene by mass spectrometry has been under intense investigation for several years. Many of these studies have employed chemical ionization with a variety of reagent gases including methane, isobutane, oxides of nitrogen, amines, ethers, and tetramethylsilane (Id). Chemical ionization (CI) studies have also incIuded the reaction of transition-metal ions (6, 7)with olefins, and the use of Fe+ with tandem mass spectrometry shows great promise for double bond location (8). Methods for double bond localization have been developed wherein alkenes are microchemically modified before introduction into the ion source, and the mass spectra of the reaction products produce fragmentation patterns characteristic
Thls article not subject to U S . Copyright. Published 1985 by the American Chemical Society
1626
ANALYTICAL CHEMISTRY, VOL. 57, NO. 8, JULY 1985
Table I. Functionalized Conjugated Dienes Studied by CIMS
CH~(CH~)XCH=CHCH=CH(CH~) rR
R
x,y 0,6 098
1,5 1,7 119 2,s
399
498
-CH202CCH3 +a
-
++ ++ + + +
-CH20H
-CH=O
+ + +-+ ++ + + +
+ +
-
-
+ ++ + -+
-CHZOCHO -b
-
+
-
+
-CH3
double bond position 8,10-C12 lO,l2-CI4 7,g-Ciz 9,11-c14 11,13-C16 10,12-Cl8 11,13-C18 10,12-c18 2,4-C12 3,5-c14
I
-
-
+
6,O + + 7s "Plus indicates compound was prepared and spectrum recorded. *Minus indicates compound was not prepared.
of the double bond position (9-18). Collisional activated decomposition (CAD)spectra of [M - HI-ions from fatty acids are useful for double bond location (19). Electron impact (EI) mass spectra of straight chain monounsaturated C12to C18 acetates and alcohols have been shown to be useful for the localization of double bond position (20). Some success has been recorded (2,8,14,15,19,21) in the determination of bond position in multiple unsaturated systems. Structwe-sPecific fragments have been reported (22) from the E1 mass spectra of the l,n,(n+ 2)dkatrienes (such as 1,7,9), which are useful for the determination of the position of the conjugated double bonds in the alkyl chain, but the relative intensities for some of the characteristic ions are rather low and may be difficult to detect in some cases. A major disadvantage of present methods is that no single reagent ion or chemical derivitization is satisfactory for all types of olefinic samples and consequently Current ~ s e a r c h continues to be focused on this problem (4). In view of the frequent occurrence of the functionalized conjugated diene in the chemical structure of insect pheromones, semiochemicals, and attractants (23-27)) and as part of an ongoing research effort (28) into the development of microanalytical methods for determination of the chemical structure Of products?we investigated the mass I) bearing a dienes spectra Of a series Of variety of functional groups. We report here Preliminary results of a new mas5 spectrometric method for localization of double bonds in conjugated dienes. This simple new technique, based upon isobutane chemical ionization, provides unambiguous identification of double bond position for a wide variety of compounds containing the conjugated diene system.
EXPERIMENTAL SECTION Spectrometry. fvfass Spectrometry. Finnigan 1015c. CI isobutane, pressure adjusted to maximize the reagent ion C4H9+ (m/z 57) ion, approximateb Oa4 torr. cr methane pressure adjusted to maximize the reagent ion C2HS+( m / z 29). Source temperature 95-100 "C, 70 eV electron energy. GC, HewlettPackmd 5710A equipped with split/splitless injection and either a 50 m 01 a 15 m x 0.32 mm i.d, DB-1 (J&W Scientific,Inc.) fused silica capillary column using He as carrier gas at a linear flow velocity of 18 cm/s. Samples of 1 pL were introduced in the splitless mode as solutions (100 ng/pL) in hexane at an injector temperature of 250 "c. The oven temperature Was held at 80 "c for 2 min, then programmed at 32 OC/min to 250 "C. The gas chromatograph was interfaced to the mass spectrometer with an open-split interface (ScientificGlass Engineering, Inc.) operated at 250 oc. The gas, methane or isobube, was introduced at the end of the capillary column via the inlet side of the open-split interface. D a b were acquired and reduced with a PDP 8/m computer (Digital Equipment CO.)with Nermag SADAR software.
NMR. Nicolet 300 MHz, CDCl,, Me4Si, 6 ppm. The NMR spectra of the synthesized compounds were in complete agreement with the assigned structures. IR. Perkin-Elmer 1420,2% w/v solutions in CCl,. IR spectra ofthe synthesized compound5 were in complete agreement with the assigned structures. The purities of synthesized compounds were determined by capillary gas chromatography on a Varian Aerograph 2100 gas chromatograph equipped with user-designed all-glass capillary split inlet system equipped with a 15 m x 0.25 mm i.d. fused silica DB-1 (J&W Scientific, Inc.) capillary column operating at a linear flow velocity of He carrier gas of 18 cm/s. Syntheses. The E,E-8,10-C12alcohol and the E,Z-10,12-C14 and E,Z-7,9-Cizacetates were used to prepare the corresponding acetates, alcohols, and/or aldehydes by acetylation, saponification, or oxidation (29), respectively. The 9,11-Cl4 compounds were obtained from a commercial source Laboratories, Willoughby, OH) as the acetates and were subsequently saponified and formylated. The remaining functionalized dienes were prepared as follows. The Z,E and E,Z isomers were synthesized from simple alkyl and functionalized alkynes by the method of Zweifel (30). The Z,Z isomers were prepared from simple alkyl and functionalized alkynes via the Chodkiewicz (31) coupling reaction and subsequent dicyclohexylborane reduction (32). The E,E isomers were Prepared by isomerization of the other three isomers as the alcohol with tfiophenol (33)followedby simple low-temperature from hydrocarbon solvent. All the isomers in each case were purified as the alcohols by low-temperature recrystallization from hydrocarbon solvents to a purity >95% as determined by capillary gas chromatographic analysis. The alcohols were subsequently acetylated, formylated, and oxidized (29)to the acetates, formates, and aldehydes, respectively. RESULTS AND DISCUSSION The conjugated, functionalized dienes investigated are listed in Table I. The CI mass spectra with isobutane as the ionizing gas of these dienes are presented in Tables I1 and 111. In some cases, all four geometric isomers of the functionalized diene were examined, whereas in other cases only one or two such isomers were available. The CI spectra showed routinely Observed ions such as [M IM - 60(H0Ac)1+' (M 4- 1 - 18(H@)l+ 85 well as those ions produced via allylic cleavage of the [M + 11' ion as described by Budzikiewciz ( 1 ) for monounsaturated compounds. In addition, two other characteristic ions, [a]+ and [b]+,were recorded that arise from apparent cleavage a t the double bonds and concomitant addition of three hydrogens, as depicted in Figure 1. No mechanistic implications are intended in Figure 1,and The it is only a formal presentation of the exact mechanism and the source of [a]+ and [bl+ (whether Other from fragmentation Of IM + 'I+, LM + 'I+, Or ion) is under investigation. The mass to charge ratios (and abundances) of d the principal ions for at least One geometric isomer of each substitution pattern are included in Table 11. +
+
ANALYTICAL CHEMISTRY, VOL. 57, NO. 8,JULY 1985
1627
Table 11. Mass to Charge Ratios and (Percent Relative Abundances) of Principal Ions Produced by Isobutane CI of Conjugated Dienesa c~I+= CH,(CH~),CH=CHCH=CH(CH&R i Cbl'
R = CHO
X,Y
[MI'
0,6;E,Eb O,& E,Z 1,9;z,z 2,8;z,z 3,9;z , z 4,8;Z,Z 6,O;Z,Z
180 (33) 208 (46) 236 (48) 236 (42) 264 (13) 264 (13) 180 (5)
[M+ 1'
+
[M 1 - 181'
[M+ 391'
[M+ 571'
219 (22) 247 (13) 275 (10) 275 (12) 303 (6) 303 (3) 219 (1)
237 (30) 265 (39) 293 (35) 293 (26) 321 (14) 321 (8) 237 (1)
57 (c) 57 (c) 71 (83) 85 (98) 99 (100) 113 (90) 141 (0)
155 (90) 183 (66) 197 (100) 183 (100) 197 (54) 183 (100) 71 (2)
[a]+
[bl'
163 (28) 191 (35) 219 (18) 219 (15) 247 (9) 247 (7) 163 (1)
181 (100) 209 (99) 237 (88) 237 (77) 265 (29) 265 (41) 181 (100)
[a]'
[bl'
R = CHzOH
x,y
[MI'
0,6;E P O,& E,Z 1,5;E,Z 1,7;Z,Z 2,8;z,z 3,9;z,z 4,8;z,z 6,QZ,Z 7,l;Z,Z
182 (21) 210 (17) 182 (26) 210 (27) 238 (26) 266 (11) 266 (46) 182 (8) 210 (22)
[M + 1'
[M+ 1 - 181'
[M + 391'
[M + 571'
165 (100) 193 (79) 165 (100) 193 (68) 221 (51) 249 (11) 249 (35) 165 (100) 193 (33)
221 (3) 249 (5) 221 (4) 249 (3) 277 (5) 305 (1) 305 (5) 221 (3) 249 (4)
239 (11) 267 (13) 239 (7) 267 (8) 295 (8) 323 (0) 323 (9) 239 (0) 267 (6)
183 (97) 211 (100) 183 (94) 211 (100) 239 (100) 267 (23) 267 (100) 183 (2) 211 (100)
R
x,y
[MI'
0,6;E , E 0,8;E,Z 1,5;E,Z 1,7;Z,Z 3,9;z,z 4,8;Z,Z 6,QZ,Z 7,l;Z,Z
224 (4) 252 (5) 224 (12) 252 (17) 308 (17) 308 (42) 224 (42) 252 (14)
[ M + 1'
157 (28) 185 (14) 143 (25) 171 (25) 185 (31) 199 (39) 185 (38) 73 (0) 87 (2)
[a]'
[bl+
CHZOZCCH,
[M + 1 - 601'
[M + 391'
[M + 571'
165 (100) 193 (100) 165 (100) 193 (90) 249 (38) 249 (80) 165 (100) 193 (100)
263 (0) 291 (3) 263 (2) 291 (3) 347 (6) 347 (7) 263 (6) 291 (0)
281 (0) 309 (2) 281 (1) 309 (0) 365 (3) 365 (0) 281 (0) 309 (0)
225 (45) 253 (45) 225 (84) 253 (100) 309 (100) 309 (100) 225 (9) 253 (52)
57 (c) 57 (4 71 (2) 71 (15) 85 (28) 99 (100) 113 (21) 141 (0) 155 (11)
57 (c) 57 (4 71 (25) 71 (98) 99 (3) 113 (2) 141 (0) 155 (0)
199 (1) 227 (2) 185 (2) 213 (6) 241 (8) 227 (0) 115 (1) 129 (0)
R = CHzOCHO
X,Y
[MI'
1,7;Z,Z 4,8;Z,Z 6,O;Z,Z 7,l;Z,Z
238 (40) 294 (68) 210 (36) 238 (1)
[M+ 1'
[M+ 1 - 461'
[M + 391'
[M + 571'
193 (33) 249 (13) 165 (100) 193 (100)
277 (5) 333 (3) 249 (0) 277 (0)
295 (17) 351 (20) 267 (0) 295 (4)
239 (100) 295 (44) 211 (5) 239 (11)
[a1'
PI+
71 (49) 113 (75) 141 (1) 155 (20)
199 (80) 213 (100) 101 (0) 155 (3)
R = CH,
x,y
[MI'
4,8;Z,Z
250 (52)
[M + 11' 251 (39)
[M + 391'
[M+ 571'
289 (5)
307 (5)
[a]'
[bl'
113 (80)
169 (100) The abundances of several of the principal ions of the remaining isomers are in Table 111. *Configuration of conjugated double bonds. By convention, the configuration of the double bond nearest the functional group is given first; Le., where X = 2,Y = 8,the Z,E isomer is Z,E-10,12-hexadecadienal,-01, -yl acetate, -yl formate, or -e, respectively. Abundances cannot be measured at this m/z because of isobutane background.
Table I11 contains the mass to charge ratios (and abundances) of only two principal ions plus ions [a]+ and [b]+ for the remaining geometric isomers studied. The ion from cleavage a (Figure 1)is observable when X (Table I) is >O but is hidden in the isobutane plasma background when X = 0. An unsaturated neutral molecule is produced from each cleavage, but its structure is unknown and it is not possible to make structural assignments to the neutral fragment or the ions [a]+ and [b]+ with the available data. The spectra of the aldehydes and alcohols of Tables I1 and I11 display similar cleavage patterns, but the [a]+and [b]+ ions are generally 2-4 times more abundant in the case of the
aldehydes. However, despite the lower abundances, the ions for the alcohols are characteristic of the diene position. The abundances for the [a]' and [b]+ ions are especially low for the 2,4-dodecadienol (X= 6, Y = 0) and for the 3,5-tetradecadienols ( X = 7, Y = 1). The data for the aldehyde 2,4dodecadienal (X= 6, Y = 0) show that systems in which the double bonds are also conjugated with a carbonyl oxygen do not undergo the a and b cleavages. Inspection of the acetate data (Tables I1 and 111) reveal that the abundances of [a]' and [b]+ are generally low. Only in the a cleavages for X = 1, Y = 7 (9,11-tetradecadienylacetates) and X = 1, Y = 5 (7,9-dodecadienyl acetate) are the abun-
1628
ANALYTICAL CHEMISTRY, VOL. 57, NO. 8, JULY
1985
R = CHO, 0 2 C C H 3 , CHzOCHO, CH20H. CH3
Figure 1. Formal representation of the fragmentation of functionallzed dienes by isobutane CI.
dances greater than 10%. The spectra of the acetates are dominated by those ions generated by the loss of acetic acid (mol wt 60) from the protonated molecular ion. In contrast to the acetates, the formates gave high abundances for ions [a]+ and [b]+ when X = 1, Y = 7 (9,ll-tetradecadienyl formates), and X = 4, Y = 8 (lOJ2-octadienyl formates). However, when X = 6, Y = 0 (2,4-dodecadienyl formate) and X = 7, Y = 1 (3,ij-tetradecadienyl formate), the abundances were low for ions [a]+ and [b]+ as was the case with the aldehydes and alcohols, and the ion resulting from loss of formic acid was dominant. The resulta from those cases where X = 6, Y = 0 and X = 7, Y = 1 may be due to some interaction of a charged adduct with the functional group. This effect is under investigation. In the case of the one hydrocarbon studied, X = 4, Y = 8 (10,12-octadecadiene)the cleavages a and b are the dominant features of the spectra. Comparison of the aldehyde, alcohol, acetate, formate, and hydrocarbon data indicates that the cleavages to produce [a]+ and [b]+ are competitive with those processes that lead to the well-known ions such as [M 1]+, [M 1- 60]+, [M 1 HzO]+and with those processes that lead to allylic cleavage (1). Those reactions leading to ions [a]' and [b]+ are more favored in hydrocarbons, aldehydes, and formates than in alcohols and acetates. In those cases where several geometric isomers of the conjugated system were available (Table 111),the abundances of [a]+and [b]+form a pattern which has a reasonably consistent isomer dependence although there are some exceptions. For example, the Z,Z and E,E isomrs of 10,12-hexadecadienal ( X = 2, Y = 8), 10,12-0ctadecadienal ( X = 4, Y = 81, and 11,13-octadecadienal ( X = 3, Y = 9) gave similarly high abundances for [a]+ and [b]+ in four out of the six cases. On the other hand the Z,E and E,Z isomers showed preferred cleavage of the E bond; the Z,E isomers gave a high abundance of [b]+ and the E,Z isomers gave a high abundance of [a]'. Figure 2 and 3 show the spectra of the four geometric isomers of 10712-hexadecadienal. Ions [a]+ and [b]+ are of high abundance whereas those ions from allylic cleavage (m/z,195, 209, 111, 97) are much less abundant. These patterns are repeated in the spectra of the alcohol analogues of these compounds but are less consistent for the X = 1, Y = 9 ( 11713-hexadecadienal)compounds. The reproducibility of spectra was examined by running a standard [(E,Z)-10,12hexadecadienal] each time spectra were run. The relative abundance of the principal ions including [a]+and [b]+was reproducible within &5%. Unfortunately, the inconsistencies in the abundance patterns for isomers detracts from the usefulness of these data for the assignment of isomeric configuration to an unknown. However, when taken in context with other spectral information, it could prove to be valuable. In consideration of the well-known tendency of double bonds to migrate within a hydrocarbon chain upon ionization,
+
+
2 I
7
fMCd
'
lnll
Flgure 2. Isobutane C I mass spectra of (Z,Z)and (Z,E)-10,12-
hexadecadlenals using isobutane as the ionlzlng gas. IU
+
1
5
a
u
2
z n 3
Y
k
100
E.E
4
c I!
50
21
Flgure 3. Isobutane C I mass spectra of (E,Z)- and (€,€)-10,12-
hexadecadienals using isobutane as the lonlzing gas. the isobutane CI mass spectra of two isolated diene aldehydes were examined for fragmentation patterns similar to those produced by the conjugated dienes. (Z,E)-9,12-Tetradeca-
ANALYTICAL CHEMISTRY, VOL. 57, NO. 8,JULY 1985
Table 111. Mass to Charge Ratios (Percent Abundanoes) of Several of the Principal Ions Produced by Isobutane C1 of the Remaining Isomeric Conjugated Dienes' [a]+, CH,(CH,),CH=CHCH=CH(CH&R
E Cbl' [MI+
[M + 1]+
236 (8) 236 (52) 236 (38) 236 (19) 236 (25) 236 (38) 264 (24) 264 (18) 264 (16) 264 (14) 264 (9) 264 (11)
237 (18) 237 (100) 237 (83) 237 (34) 237 (57) 237 (81) 265 (54) 265 (25) 265 (40) 265 (23) 265 (IO) 265 (28)
[a]+
[bl+
71 (100) 71 (91) 71 (63) 85 (32) 85 (100) 85 (96) 99 (44) 99 (100) 99 (100) 113 (98) 113 (100) 113 (100)
197 (29) 197 (56) 197 (100) 183 (100) 183 (41) 183 (100) 197 (100) 197 (31) 197 (85) 183 (100) 183 (40) 183 (58)
85 (15) 239 (100) 239 (100) 85 (45) 239 (100) 85 (39) 267 (39) 99 (43) 267 (39) 99 (100) 267 (100) 99 (58) 267 (100) 113 (22) 267 (100) 113 (30) 267 (100) 113 (33) 211 (100) 155 (4) 211 (100) 155 (33) 211 (100) 155 (6)
185 (47) 185 (22) 185 (36) 199 (100) 199 (35) 199 (58) 185 (31) 185 (24) 185 (44) 87 (2) 87 (1) 87 (0)
R = CHO
R = CHzOH 238 (25) 238 (29) 238 (29) 266 (19) 266 (5) 266 (14) 266 (30) 266 (43) 266 (49) 210 (24) 210 (37) 210 (23)
R = CH202CCH3 252 (14) 252 (16) 308 (16) 308 (18) 308 (14) 308 (21) 308 (37) 308 (34) 252 (11) 252 (2) 252 (17)
253 (96) 253 (98) 309 (100) 309 (100) 309 (100) 309 (100) 309 (100) 309 (100) 253 (46) 253 (47) 253 (43)
71 (33) 71 (71) 99 (3) 99 (7) 99 (2) 113 (1) 113 (2) 113 (0) 155 (0) 155 (2) 155 (0)
213 (9) 213 (6) 241 (7) 241 (3) 241 (4) 227 (10) 227 (5) 227 (9) 129 (0) 129 (0) 129 (0)
R = CHzOCHO 238 (34) 238 (39) 294 (50) 294 (51) 294 (61) 238 (1) 238 (1) 238 (1)
239 (82) 239 (100) 295 (85) 295 (78) 296 (68) 239 (8) 239 (6) 239 (3)
R
71 (35) 71 (26) 113 (72) 113 (100) 113 (69) 155 (6) 155 (62) 155 (13)
199 (100) 199 (61) 213 (100) 213 (60) 213 (100) 115 (4) 115 (3) 115 (3)
CH,
250 (13) 251 (12) 113 (89) 169 (100) 250 (42) 251 (38) 113 (100) 169 (47) 250 (33) 251 (33) 113 (90) 169 (100) Abundance5 of and the principal ions for the remaining isomers are in Table 11. Configuration of conjugated double bonds. By convention, the configuration of the double bond nearest the functional group is given first; i.e., where X = 2,Y = 8,the Z,E isomer is Z,E-10,12-hexadecadienal,-01, -yl acetate, -yl formate or -e, respectively.
dienal would be expected to produce a fragmentation pattern similar to either the 10,12-tetradecadienal or 9,11-tetradecadienal or a combination of both if significant double bond
1629
migration into conjugation were occurring. The isobutane CI spectrum of (Z,E)-9,12-tetradecadienal had ions at m/z 183 (possibly from 10,12-tetradecadienal) and m/z 169 (possibly from 9,ll-tetradecadienal) at abundances of 3.8 and 2.8%, respectively. It was not possible to detect the other two ions that would be expected (mlz 57 from the 10,12-CIdaldehyde and mlz 71 from the 9,11-Cl4 aldehyde) due to background interference. The CI mass spectrum of (2,2)-9,12-octadecadienal was examined for ions that could have arisen from fragmentations produced by 9,ll- and 10,12-octadecadienal, the two conjugated aldehydes that would be produced upon double bond migration into conjugation. The spectrum had ions a t mlz 113,127,168 and 183 with abundances of 12.4, 34, 7.9, and 7 % , respectively. The abundances in the case of the (Z,E)-9,12-tetradecadienal are too small to be significant in light of the abundances from ion [b]+ for (E,Z)-10,12-tetradecadienal(see Table 11, X = 0, Y = 8). In the case of (Z,Z)-9,12-octadecadienalthe abundances of ions [a]' and [b]+ that could have come from the ionization produced 10,12-octadecadienal (mlz 113 and 183, respectively) were much smaller than those abundances produced by the 10,12-octadecadienals examined (Tables I and 11; X = 4, Y = 8) and not likely to cause misidentification even in the case of the alcohols where the abundances of ions [a]+ and [b]+ are reasonably high. Unfortunately the 9,11octadecadienal was not examined, therefore, no comparison is available for those ions at m/z 127 and 169. The possibility of misidentification would seem to be remote except in the case of acetates and could best be avoided by examination of other spectral and chromatographic data or conversion of the acetates under investigation into formates (where the abundances for [a]+ and [b]+ are high) by simple chemical manipulation and examination of those isobutane CI spectra. The isobutane CI spectra of conjugated diynes structurally related to the dienes listed in the tables consist of only the normally expected ions such as [MI+, [M + l]+, [M + 1HzO]+, etc.; no ions due to cleavage of the triple bonds are observed. When methane was used as the ionizing gas, the conjugated functionalized dienes produce the usual [MI+, [M + 1]+, [M + 1- HzOJ+,[M + 1- 60]+, [M + 1- 46]+,etc. ions, but not ions [a]' or [b]+.
CONCLUSIONS The chemical ionization mass spectrometry with isobutane of conjugated diene aldehydes, alcohols, formates, and hydrocarbons produces two ions, and the mlz ratios of these ions are characteristic of the positions of the conjugated bonds in the hydrocarbon chains. Thus, isobutane CI mass spectrometry of these molecules should prove a very useful analytical technique for structure elucidation. Conjugated acetates also produce these characteristic ions, but the abundances are very small rendering these ions less useful. The pattern of abundances produced by the Z,Z, Z,E, E,Z, and E,E isomers is of limited diagnostic value for the determination of the configuration of the conjugated diene systems. The extension of this new analytical procedure is under investigation, as is the mechanism for the formation of the characteristic ions. It came to our attention while in the final preparation of the manuscript, that Jacques Einhorn of the Laboratoire des Mediateurs Chimiques, Domaine de Brouessy, France, has observed results similar to those herein recorded (34). ACKNOWLEDGMENT We acknowledge L. McDonough of ARS, USDA, Yakima, WA, for the generous gift of the E,E-8,10-CI2alcohol and the E,Z-lO,l8-C14 acetate, and W. Roelofs, Department of Entomology, New York State Agricultural Experiment Station, Geneva, NY, for the generous gift of the E,Z-7,9-CI2 acetate. We wish to thank R. A. Yost and C. S. Roan of the Chemistry Department, University of Florida, Gainesville, for many
1830
Anal. Chem. 1985, 57, 1630-1636
helpful discussions and for preliminary review of the manu(9) Arlga, T.; Arakl, E.; Murata, T. Chem. Phys. Llplds 1977, 19, 14-19. (IO) Abley. P.; McQulllln, F. J.; Mlnnlkln, D. E.; Kusamran, K.; Maskens, K.; script. Polgar, N. Chem. Common. 1970, 348-349. Registry No. (E,E)-CH3CH=CHCH=CH(CH2)&H0, (11) Tumlinson, J. H.; Heath, R. R.; Doollttle, R. E. Anal. Cbem. 1974, 46, 1309-1312. 69775-58-2; (E,Z)-CH&H=CHCH=CH(CH2)&HO,96362-35-5; (12) Vostrowsky, 0 . ;Mlchaells, K.; Bestmann, H. J. Jusfus Lleblgs Ann. (Z,Z)-CH3CH2CH=CHCH=CH(CH&CHO,71317-73-2;(2,Chem. 1981, 1721-1724.
Z)-CH3(CH2)2CH=CHCH=CH(CH2)&HO,96348-46-8; (2,Z)CHS(CH~)~CH=CHCH=CH(CH~)&HO, 96348-47-9;(2,Z)CH,(CH2)4CH=CHCH=CH(CH2)8CHO, 96348-48-0;(2,Z)CHs(CH2)6CH=CHCH=CHCHO, 96348-49-1; (E,EE)-CH,CH= CHCH=CH(CH~)BCH~OH, 33956-49-9; (E,Z)-CH,CH= CHCH=CH(CH2)&H20H, 80625-59-8;(E,Z)-CH&H2CH= CHCH=CH(CH2)6CH20H, 54364-60-2;(Z,Z)-CH3CH2CH= CHCH=CH(CH2),CH20H, 72553-59-4; (Z,Z)-CH3(CH2)2CH= CHCH=CH(CH2)&H20H, 765-18-4;(Z,Z)-CHS(CH2),CH= CHCH=CH(CH2)9CH20H, 96348-50-4; (Z,Z)-CH3(CH2)4CH= CHCH=CH(CHZ)&H20H, 96348-51-5; (Z,Z)-CH3(CH2)&H= CHCH=CHCHZOH, 96348-52-6;(Z,Z)-CH3(CH2),CH= CHCH=CHCHZCH20H, 79532-13-1;(E,E)-CH,CH=CHCH= CH(CH~)BCH~O~CCH~, 53880-51-6;(E,Z)-CH,CH=CHCH= CH(CH,)SCH202CCH3, 69775-62-8;(E,Z)-CHSCHzCH= C H C H = C H ( CH2)5 C HzOzCCH3, 54364-62-4; (2,Z) CH&H2CH=CHCH=CH(CH2)7CH202CCHs154664-97-0;(2,Z)-CH3(CH2)3CH=CHCHUH(CH~)&H20&CH3,96348-53-7; (Z,Z)-CH3(CH2)4CH=CHCH=CH(CH2)sCHzOzCCH3, 96348-
(13) Wolff, R. E.; Wolff, G.; McCloskey, J. A. Tefrahedron 1988, 22, 3093-3101. (14) Dommes, V.; Wlrtz-Peltz, F.; Kunau, W. H. J. Cbromafogr. Sci. 1978, 14, 360-366. (15) Suzuki, M.; Arlga, T.;Sekine, M.; Arakl, E.; Mlyatake, T. Anal. Chem. 1981, 53,985-988. (16) Kldwell, D. A.; Blemann, K. Anal. Chem. 1982, 54,2462-2465. (17) Buser, H. R.; Arn, H.; Guerln, P.; Rauscher, S. Anal. Chem. 1983, 55, 818-822. (18) Leonhardt. B. A. In "Semlochemlcals: Flavors and Pheromones"; Acree, T. E., Soderlund, D. M., Eds., Walter de Gruyter and Co.: Berlin, Federal Republlc of Germany, In press.
(19) Tomer, K. B.; Crow, F. W.; Gross, M. L. J. Am. Chem. SOC. 1983, 105,5487-5488. (20) Leonhardt, B. A.; DeVllblss, E. D.; Klun, J. A. Org. Mass Specfrom. 1983, 18,9-11. (21) Brauner, A.; Budzlkiewicz, H.; Boland, W. Org. Mass Specfrom. 1982, 17, 161-164. (22) Vostrowskv. 0.: Michaelis. K.: Bestmann. H. J. Jusfus Lleblas Ann. Chem. 1962, 1001-1005. I
54-8; (Z,Z)-CH&CH&CHUHCH=CHCH,02CCH202CCH3,9634&55-9;
(Z,Z)-CH3(CH2)&H=CHCHUHCH2CH202CCH3,60754-63-4; (Z,Z)-CH3CH2CH=CHCH=CH(CH2),CHzOCHO, 82623-59-4; (Z,Z)Z)-CHS(CH~)~CH=CHCH=C"~)~CH~)&H~OCHO, 96348-56-0; (Z,Z)-CH3(CH2)eCH=CHCH=CHCH2OCHO,96348-57-1; (2,Z)-CH3(CH2)7CH=CHCH=CHCH&H2OCHO, 96348-58-2; (Z,Z)-CH3(CH2)4CH=CHCH=CH(CH2)SCHS, 96394-00-2. LITERATURE CITED (1) Budzlklewlcz, H.; Busker, E. Tetrahedron 1980, 36, 255-266. (2) Greathead, R. J.; Jennlngs, K. R. Organic Mass Specfrom. 1980, 15. 431-434. (3) Chal, R.; Harrlson, A. G. Anal. Chem. 1981, 53,34-37. (4) FerrerCorrela, A. J. V. K.; Jennlngs, K. R.; Sen Sharma, D. K. A&. Mass Specfrom. 1978, 7A, 287-294. (5) Hunt, D. F.; Harvey, T. M. Anal. Chem. 1975, 47, 2136-2141. (6) Burnier, R. C.; Byrd, G. 0.; Freiser, B. S. Anal. Chem. 1980, 52, 1641- 1650. (7) Peake, D. A.; Gross, M. L.; Ridge, D. P. J. Am. Cbem. SOC. 1984, 106, 4307-4316. (8) Peake, D. A.; Gross, M. L., unpubllshed results.
Doollttle, R. E.; Roelofs, W. L.; Solomon, J. D.; Card6, R. T.;Beroza, M. J. Chem. fcol. 1978, 2 , 399-410. Henrick, C. A. Tetrahedron 1978, 33, 1-45. Coffelt, J. A.; Vlck, K. W.; Sonnet, P. E.; Doollttle, R. E. J. Chem. fCOl. 1979, 5 ,955-966. Hall, D. R.; Beevor, P. S.; Lester, R.; Nesbitt, B. F. Experienfia 1980, 36, 152-154. Davis, H. G.; McDonough, L. M.; Burdltt, A. K., Jr.; Bierl-Leonhardt, B. A. J. Chem. Ecol. 1984, 10, 53-61. Heath, R. R.; Tumllnson, J. H. I n "Insect Pheromones"; Hummel, H. H., Eds.; Sprlnger-Verlag: New York, 1984. Corey, E. J.; Suggs, J. W. Tefrahedron Left. 1975, 2647-2650. Zwelfel, G.; Backlund, S. J. J. Organomef. Chem. 1978, 156,
159-170. Chodklewlcz, W. Y.; Cadlot, P. C . R . Hebd. Seances Acad. Sci. 1955, 247, 1055-1057. Zweifel, G.; Polston, N. L. J. Am. Chem. SOC. 1970, 92, 4068-4071. Henrlck, C. A.; Wllly, W. E.;Baum, J. W.; Baer, T. A.; Garcia, B. A,; Mastre, T. A.; Chang, G. M. J. Org. Chem. 1975, 40, 1-7. Elnhorn, J.; Vlrellzler, H.; Gemal, A. L.; Tabet, J. C. Tefrahedron Left. 1985, 1445-1448.
RECEIVED for review December 20,1984.Accepted March 19, 1985. Mention of a commerical or proprietary product does not constitute an endorsement by the USDA.
Smoke Aerosol Analysis by Pyrolysis-Mass Spectrometry/Pattern Recognition for Assessment of Fuels Involved in Flaming Combustion Kent J. Voorhees* and Rushung Tsao Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, Colorado 80401
Pyrolysis-mass spectrometry with pattern recognltlon has been used to analyze smoke aerosols to determine contrlbuting fuels involved in fires. Aerosols generated in a flaming mode in a laboratory calorimeter from mixtures formulated from 10 polymeric substances were collected on glass filters. The nonvolatile materials associated with the aerosols were pyrolyzed to provide mass spectral flngerprints of the mixtures. Factor analysis with graphical rotation generated factor spectra whlch were compared to reference pyroiysls spectra of aerosols from the pure polymers. An overall IdentHlcatlon rate of 78% was achleved.
The legal actions associated with catastrophies like the Las
Vegas, NV, MGM Hotel fire have demonstrated the need for an analytical technique for the assessment of the fuels involved in smoke aerosol formation at a particular site. Smoke aerosols are usually composed of a highly condensed carbon material, an amorphous polymeric substance, and various volatile compounds adsorbed on the other materials. The amorphous polymeric substance produced from nonoxidative conditions has been shown to have similar structure to that of the original polymeric source (1,2).Although some structural modification and molecular weight degradation had occurred to this material, enough of the original polymer structure was present to allow for the identification of the original polymer source. Pyrolysis-mass spectrometry has been extensively used for fingerprinting a number of materials (3-5). Recently, we reported on the application of Py-MS with pattern recognition 0 1985 American Chemlcal Society
