Mass Spectra of Dodecadienic Compoundswith a Conjugated Double Bond, Lepidopterous Sex Pheromones

Size: px

Start display at page:

Download "Mass Spectra of Dodecadienic Compoundswith a Conjugated Double Bond, Lepidopterous Sex Pheromones"

Elijah Tyler
6 years ago
Views:

1 Agric. Biol. Chem., 49 (2), , Mass Spectra of Dodecadienic Compoundswith a Conjugated Double Bond, Lepidopterous Sex Pheromones Tetsu Ando, Yoshio Katagiri and Masaaki Uchiyama Department of Plant Protection, Faculty of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183, Japan Received July 17, 1984 All geometrical isomers of 5,7-, 6,8-, 7,9-, 8,10- and 9,1 1-dodecadien-l-ols, and their acetates and aldehyde derivatives were analyzed by electron impact mass spectrometry. The abundanceof molecular ion (M+) was observed in every spectrum, and the relative intensity of M+ tended to be strong if the compound possessed an (is)-double bond(s). In addition to M+, [M-H2O]+ (alcohols) and [M-CH3CO2H]+ (acetates), every dienic compound showed typical series of CwH2n_2+~CnH2M_5+with abundance maxima around C4, C5, C6 or C7. Each double bond positional isomer characteristically yielded different ion peaks in the series, which were useful for its distinction from other isomers. These results indicate that the chemical structure of a natural pheromone of Lepidoptera is easily deduced successfully by GC-MSanalysis if it is a conjugated dienic pheromone. To date, sex pheromones species in Lepidoptera secreted by about have been characterized, and some of them are dodecadien-1- ols, dodecadienyl acetates and dodecadienals with a conjugated double bond system, they were listed cates that in our preceding paper.1} This indi- dodecadienic compounds with a conjugated groups of double bond are one of the main lepidopterous sex pheromones. Recently gasliquid chromatography combined with mass spectroscopy (GC-MS)has been widely used for pheromone studies, so the functional group and the carbon chain length of a pheromonal component can be easily determined with a rather limited amount of the female extract. As to pheromonal monoene compounds, it has been reported that double bond positional isomers show mass spectra which can differentiate them from each other on careful examination.2* We are now interested in examining whether the mass spectrum of a pheromone with a conjugated dienic system provides information on the position and the geometry of the double bonds or not. This paper reports systematic analyses of synthetic dodecadienic compounds with a conjugated double bond by electron impact mass spectrometry. MATERIALS AND METHODS Every geometrical isomer of 5,7-, 6,8-, 7,9-, 8,10- and 9,1 1-dodecadien-l-ols was synthesized in our laboratory by the method described in our preceding paper.1} Their acetates and aldehyde derivatives were obtained by treatment of the alcohols with acetic anhydride in pyridine and with pyridinium chlorochromate in CH2C12, respectively. GC-MSmeasurements were carried out with a Hitachi RMU-6MGspectrometer under the following conditions; ionization method: electron impact, ionization voltage: 20 ev, ion source temperature: C, molecular separator temperature: C, H. V.: 0V, column: OV-1 1%, 3mmi.d. x cm. The flow rate of the carrier gas (He) was ml/min and the column temperature was changed to monitor the effluent for different compounds for appropriate periods as follows; 110 C for alcohols (Rt: ca. 4min), 120 C for acetates (Rt: ca. 6min) and C for aldehydes (Rt. ca. 3min). The mass spectrum for each compoundswas measured five times, and then the average intensities of a parent peak and fragment peaks werecalculated. RESULTS AND DISCUSSION All geometrical isomers of 5,7-, 6,8-, 7,9-,

2 414 T. Ando, Y. Katagiri and M. Uchiyama loo-i 67 >, 79 (a) (5,7 )-Isomer 5-93 a, 164 5ol,,... j.i.,jlil..illiihjilljiiili iii.i.,!..., JL Ju,_ 0 w/z >> (b) (6,8 )-Isomer /vwwqj 5-96 a> I 164 s0...ii,ll.i.ijin,iin,ill L I..,.i.. I. 0 ffl/z loo-i 82 >> 67 (c) (7,9 )-Isomer I * I 164,, h, J < 1.jpili).111III lll l. Ill. [i.^ å.l<..,"..., 0 m/z >, (d) (8,10 )-Isomer - /VWW qh 1 82 > I à"så J 164 " ,mL..111,, Jllll.,.Jllll., 111,.. I,,,,I...,.., Jf 0 m/z 10 l >, (e) ( )-9,ll-Isomer 5 - I 182 % I II 164 I S III ll 0,, jil,, ijin, illl l.,il llli, å llllllj lll i. In,, i.... 1, Ii 0 'm/z Fig. 1. Mass Spectra of Dodecadien-1-ols; (a) (5E, 7 )-5,7-Dodecadien-l-ol, (b) (6E, 8 )-6,8-Dodecadienl-ol, (c) (7, 9 )-7,9-Dodecadien-l-ol, (d) (8,10 )-8,10-Dodecadien-l-ol and (e) CE)-9,l l-dodecadien-l-ol. 8,10- and 9,1 1-dodecadien-l-ols, and their acetates and aldehyde derivatives were analyzed by electron impact mass spectrometry. The mass spectra of (E, )-isomers of 5,7-, 6,8-, 7,9- and 8,10-dienes and the ( >isomer of 9,1 1-diene are shown in Fig. 1 (alcohols), Fig. 2 (acetates) and Fig. 3 (aldehydes). The relative intensities of a molecular ion (M+) and some particular fragment ions are summarized in Table I (alcohols), Table II (acetates) and Table III (aldehydes). Under our instrumental conditions, the mass spectra of dodecadien-1- ols consisted of peaks of M+ (m/z 182), [M-H2O]+ (m/z 164) and a typical series of

3 Mass Spectra of Dodecadienic Compounds 415 l OO-i 79 >>.80 (a) (5,7 )-Isomer m å 5 ' QJ I "o,.,.å å.å jl., l...i.ill.jill,iii- Jll. [l..,.'i..,.,.1 0 m/, loon 67 ^ >> (b) (6,8 )-Isomer A/VWVn «io- «135 I I 164 6o -. jl.i.-jt"i1å I',-»l -.»' "-. å å.1. å å.,...i 0. -, g5 fl»/i >» (c) (7,9 )-Isomer 5- a; I 164 &o. il,å '!å.'ill-jiå ill-å lii ]å,1.,..il.,,,..i 0 m/z, 81 $ 68 (d) (8,10 )-Isomer <U i i > Jl,,li,å,1111.à"å å HI-.,-ll fjll Jl.. [I.å, ''I I 0 m/z >, 67 (e) (E)-9,ll-Isomer I I <^>S/Av/N/S^OAC 5- I ill 164 a> > S III 224 sol... i. J-L,å "".'A-I'-..-Ill-,I li«..1'..',.ji..'.,..1-0 Fig. 2. Mass Spectra of Dodecadienyl Acetates; (a) (5, 7 )-5,7-Dodecadienyl Acetate, (b) (6E, 8 )-6,8- Dodecadienyl Acetate, (c) (IE, 9 >7,9-Dodecadienyl Acetate, (d) (8, I0. :)-8, 10-Dodecadienyl Acetate and (e) (E)-9,1 1-Dodecadienyl Acetate. CnH2n_2+~CnH2n_5+ with abundance maxima around C4, C5, C6 or C7. The mass spectra of dodecadienyl acetates were in general similar to those of the parent alcohols except that M+ appeared at m/z 224 and the ion at m/z 164 was [M-CH3CO2H]+. Dodecadienals showed M+ (m/z ) and a ^nra2w_2 CnH2n_5+ ion series of abundance like alcohols and acetates but negligibly weak [M -H2O]+ (m/z 162). Additionally we observed the ion series containing oxygen such as CMH2n_5O+ (m/z 109, 123, 137 and 151) in

4 ll., lil 416 T. Ando, Y. Katagiri and M. Uchiyama (a) 80 (5,7 )-Isomer ll.l, III (b) (6,8 )-Isomer a å i,.,ll,,illli I,å å!,.i lilip-l 1 II,.,1. 1-I-å ffi/z A^MaA (c) h I, å (7,9 )-Isomer 98,.!,,,,1. m/z kr_ijiv '-i- 68 /yvvvs/ (d) ^ (8E_,10 )-Isomer I,,..111,. JP/z i.i.ii.i,,i.i.,i..i, 67 A L hi.,111 (e) ( )-9,ll-Isomer,81 4^ ^ m/1 -i- m/z Fig. 3. Mass Spectra of Dodecadienals; (a) (5, 7 )-5,7-Dodecadienal, (b) (6, 8 )-6,8-Dodecadienal, (c) (IE, 9 )-7,9-Dodecadienal, (d) (8, 10 )-Dodecadienal and (e) CE>9, 1 1-Dodecadienal. the mass spectra of aldehydes. The mass spectra of the geometrical isomers with a conjugated diene system at the same position were very similar and it is not so easy to distinguish them from each other, however, the different intensity of M+caught our attention. Namely, the (E, ')-isomers showed the most abundant M+and the (Z, Z)-isomers the least for any double bond positional isomer (5,7-, 6,8-, 7,9- and 8,10-dienes) or any functional derivative investigated (alcohols, acetates and aldehydes). The intensity of M+of the (Z, E)- and (E, Z)-isomers was intermediate and it was not determined as to which

5 MassSpectra of DodecadienicCompounds Table I. Relative Intensity (%) of Molecular Ion (M+) and Some Fragment Ions in Mass Spectra of Dodecadien-1-ols C4H6+ C5H7+ C5H8+ C6H7+ C6H8+ C6H9+ C6H10+ C7Hn+ C7H12+ C8H13+ C8H14+ C9H15+ [M-H2O]+ M+ m/z ,7-Dodecadien-l-ol (5Z,7Z)-Isomer (5Z,7 )-Isomer (5,7Z)-Isomer (5,7 )-Isomer ,8-Dodecadien-l-ol (6Z,8Z)-Isomer (6Z,8 )-Isomer (6,8Z)-Isomer (6,8 )-Isomer ,9-Dodecadien-l-ol (7Z,9Z)-Isomer (7Z,9 )-Isomer (7,9Z)-Isomer (7,9 )-Isomer ,10-Dodecadien-1-ol (8Z,10Z)-Isomer (8Z,10 )-Isomer (8, 10Z)-Isomer (8, 10 )-Isomer ,ll-Dodecadien-l-ol (Z)-Isomer ( )-Isomer

6 T. Ando, Y. Katagiri and M. Uchiyama 418 Table II. Relative Intensity (%) of Molecular Ion (m+) and Some Fragment Ions in Mass Spectra of Dodecadienyl Acetates C4H6+ C5H7+ C5H8+ C6H7+ C6H8+ C6H9+ C6H10+ C7Hn+ C7H12+ C8H13+ C8H14+ H9H15+ [M-AcOH]+ M+ m/z ,7-Dodecadienyl Acetate (5Z,7Z)-Isomer (5Z,7 )-Isomer (5,7Z)-Isomer (5,7 )-Isomer ,8-Dodecadienyl Acetate (6Z,8Z)-Isomer (6Z,8 )-Isomer (6,8Z)-Isomer (6,8 )-Isomer ,9-Dodecadienyl Acetate (7Z,9Z)-Isomer (7Z,9 )-Isomer (7,9Z)-Isomer (7,9 )-Isomer , 10-Dodecadienyl Acetate (8Z, 10Z)-Isomer (8Z,10 )-Isomer (8, 10Z)-Isomer (8, 10 )-Isomer , 1 1-Dodecadienyl Acetate (Z)-Isomer ( )-Isomer

7 Mass Spectraof DodecadienicCompounds Table. III. Relative Intensity.(%) of Molecular Ion (M+) and Some Fragment Ions in Mass Spectra of Dodecadienals C4H6 C5H7 C5H8 C6H7 C6H8 C6H9 C6H10 C7Hn+ C7H12+ C8H13+ CgH^ C9H15+ M+ m/z ,7-Dodecadienal (5Z,7Z)-Isomer (5Z,7 )-Isomer (5,7Z)-Isomer (5,7 )-Isomer ,8-Dodecadienal (6Z,8Z)-Isomer (6Z,8 )-Isomer (6,8Z)-Isomer (6,8 )-Isomer ,9-Dodecadienal (7Z,9Z)-Isomer (7Z,9 )-Isomer (7,9Z)-Isomer (7,9 )-Isomer ,10-Dodecadienal (8Z, 10Z)-Isomer (8Z,10 )-Isomer (8, 10Z)-Isomer (8, 10 )-Isomer ,ll-Dodecadienal (Z)-Isomer ( )-Isomer

420 T. Ando, Y. Katagiri and M. Uchiyama isomer exhibited abundant M+. For a 9,lldiene with any functional group, the (E)- isomer showed more abundant M+ than the (Z)-isomer.

8 420 T. Ando, Y. Katagiri and M. Uchiyama isomer exhibited abundant M+. For a 9,lldiene with any functional group, the (E)- isomer showed more abundant M+ than the (Z)-isomer. In the mass spectra of monoene alcohols with straight chains M+ is rarely observed, and M+ of conjugated diene alcohols is moreabundant than that of isolated dienes.3) These results indicate that some part of the initial ionization of a conjugated diene occurs at one of two C=Cdouble bonds and the positive charge formed on electron impact is stabilized by resonance of n electrons of the other C=Cbond, which may remain at the original position even after the ionization caused by the drastic reaction. Migration of the C=Cbond may be not the dominant reaction in the GC-MSchamber and some portion of the remaining C=C bond may retain the original geometry. For the stabilization of M+the CE)-double bond might work more effectively than the (Z)-double bond. The characteristic fragment ions (CBH2 I_2+ ~CIIH2 _5+) of significant abundance around C4~C7 are as follows; dodecadien-1-ols, 5,7-diene: m/z 67 (base peak), 79, 93, 6,8-diene: m/z 67 (base peak), 81, 96, 7,9-diene: m/z 67, 82 (base peak), 95, 8,10- diene: m/z 68 (base peak), 81, 9,ll-diene: m/z 54, 67, 68 (base peak), 81, dodecadienyl acetates, 5,7-diene: m/z 67, 79 (base peak), 80, 93, 6,8-diene: m/z 67 (base peak), 79, 93, 7,9- diene: m/z 67 or 82 (base peak), 79, 95, 8,10- diene: m/z 68 or 81 (base peak), 9,ll-diene: m/z 54, 67, 80 (base peak), dodecadienals, 5,7-diene: m/z 67, 79 or 80 (base peak), 93, 6,8-diene: m/z 67 (base peak), 81, 7,9-diene: m/z 67 or 95 (base peak), 81, 82, 8,10-diene: m/z 68, 81 (base peak), 9,ll-diene: m/z 54 (base peak), 67, 68, 81. It has been generally accepted that alkene ions showa strong tendency to isomerize through migration of the double bond and the mass spectra of alkenes tend to be independent of the double bond position.4) As to conjugated dienic compounds, however, we were able to distinguish each double bond positional isomer investigated by the fragmentation pattern, and especially the above diagnostic abundant peaks. The relative intensity of fragment ions varies with the instrumental conditions. But it should be possible to identify directly the position of the conjugated diene system in a natural pheromone by comparing its mass spectrum with that of an authentic sample, without any prior chemical modifications of the pheromone. If the pheromone includes a conjugated diene system, its chemical structure may be easily deduced successfully by GC-MS analysis. The variations of the above diagnostic fragment ions must be caused by the difference in the double bond position and we can speculate the process of formation of some of them. Namely, 8,10-dienic compounds with any functional group showed only two remarkable fragment ions, C6H9+ (m/z 81) and C5H8+ (m/z 68). The former ion can be produced by the initial ionization at the C8= C9 double bond and a-cleavage of the C6-C7 bond (allylic cleavage) before the isomerization, and the latter ion by the initial ionization at the C10=Cn double bond followed by hydrogen rearrangement from C6 and a- cleavage of the C7-C8 bond. Both ions are stabilized by the remaining C=C double bond and exhibit abundant peaks. Same fragmentation is expected of the compoundswith a conjugated diene system at other positions to yield C5H7+ (m/z 67) and C4H6+ (m/z 54) for 9,ll-diene, C7Hn+ (m/z 95) and C6H10+ (m/z 82) for 7,9-diene, C8H13+ (m/z 109) and C7H12+ (m/z 96) for 6,8-diene, and C9H15+ (m/z 123) and C8H14+ (m/z 110) for 5,7- diene. Tables I~III reveal that these ions are remarkable except for C8H14+ of 5,7-diene and C7H12+ of 6,8-diene. A compound the diene system of which is located toward the end of the carbon chain shows the characteristic ions with more noticeable intensity. Some tetradecadienic and hexadecadienic compounds with a conjugated diene system have been identified as lepidopterous sex pheromones. They are related to dodecadienic compoundswhich possess the diene system at the same position numberedfrom a functional group or an opposite terminal. Weare now

9 Mass Spectra of Dodecadienic Compounds 421 investigating the mass spectra of longer chain compounds in comparison with the corresponding dodecadienic compounds. Acknowledgments. We are grateful to professor N. Takahashi and Dr. S. Yoshida of the University oftokyo for their invaluable advice, and Dr. A. Sakurai and Dr. Y. Kamiya of the Institute of Physical and Chemical Research for their help in the GC-MS.This work was supported in part by Grants-in-Aid for Scientific Research from the Agricultural Chemical Society of Japan, the graduates' association of Tokyo University of Agriculture and Technology, and the Ministry of Education, Science and Culture of Japan (No ). REFERENCES 1) T. Ando, Y. Kurotsu, M. Kaiya and M. Uchiyama, Agric. Biol. Chem., 49, 141 (1985). 2) M. Horiike and C. Hirano, Biomed. Mass Spectrom., ll, 145 (1984). 3) T. Ando, M. H. Vu, S. Yoshida, N. Takahashi, S. Tatsuki, K. Katagiri, A. Yamane, T. Ikeda and S. Yamazaki, Agric. Biol. Chem., 46, 709 (1982). 4) F. W. McLafferty, "Interpretation of Mass Spectra," Third ed., University Science Books, Mill Valley, U.S.A., 1980, p. 179.

Part 2. Monoenoic Fatty Acids

MASS SPECTRA OF 3-PYRIDYLCARBIOL ESTERS Part 2. Monoenoic Fatty Acids Straight-Chain Monoenoic Fatty Acids The mass spectra of 3-pyridylcarbinol esters of monoenoic fatty acids are distinctive and permit