Studies in Organic Mass Spectrometry IV.  Fragmentation of 2‐Alkyl‐ 1, 3‐cyclohexanediones

Vandewalle, M.; Schamp, N.; Wilde, H. De

doi:10.1002/bscb.19670760113

Cited by 18 publications

(5 citation statements)

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“…In both tables, the first column refers to the designation used in the fragmentation schemes. As already mentioned by Vandewalle et al (15,16), relative abundances of the signals in the EI spectra of 2,5-dialkylcyclohexan-1,3-diones strongly depend on the substituents, and spectra may be different after excitation of either the diketo or the enol structures. According to our investigations, some signals observed in low resolution represent fragments of at least two different atomic compositions.…”

Section: Resultsmentioning

confidence: 83%

“…In these cases, relative amounts of the species as obtained upon high resolution are provided. An example is the base peak at m/z 97 in the spectrum of compound 7 that consists of 92% C 6 H 9 O represented by fragment m and 8% C 5 H 5 O 2 represented by fragment p. Another example is the signal at m/z 84 in the spectrum of chiloglottone1: the peak with a relative abundance of 30% is made up of 6% C 4 H 4 O 2 represented by 182 [14] 210 [14] 182 [19] 182 [13] 168 [16] 182 [19] 182 fragment f and 24% C 5 H 8 O represented by fragment g. Not in all cases could reasonable structures be attributed to signals: m/z 98 in compound 3 shows a relative abundance of 31%, which comprises 11% C 6 H 10 O (fragment c) and 20% of C 5 H 6 O 2 to which no structure was assigned. In such a case, the composition of the unspecified ion and its abundance are given as a footnote in Table 1 Table 1 (21).…”

Section: Resultsmentioning

confidence: 99%

“…Basic investigations have been carried out by Vandewalle et al (15,16), whereas Goto et al (17) and Maquestiau and Lejeune (18) focused on spectra of dimedone derivatives. Therefore, it appeared highly desirable to better understand the mass spectrometric fragmentation pattern of chiloglottone1 and its analogs to identify respective diagnostic ions and, thus, facilitate structure elucidation of other volatiles representing this new type of compound in nature.…”

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The discovery of 2,5-dialkylcyclohexan-1,3-diones as a new class of natural products

Franke

Ibarra

Schulz

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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Orchids employing sexual deceit attract males of their pollinator species through specific volatile signals that mimic female-released sex pheromones. One of these signals proved to be 2-ethyl-5-propylcyclohexan-1,3-dione (chiloglottone1), a new natural product that was shown to be most important in the relations between orchids of the genus Chiloglottis, native to Australia, and corresponding pollinator species. Systematic investigations on the mass spectrometric fragmentation pattern of 2,5-dialkylcyclohexan-1,3-diones identified key ions providing information about the structures of the substituents at positions 2 and 5. Results enabled us to identify 2-ethyl-5-pentylcyclohexan-1,3-dione (chiloglottone2) and 2-butyl-5-methylcyclohexan-1,3-dione (chiloglottone3) as new natural products that play a decisive role in the pollination syndrome of some Chiloglottis species. During field bioassays, pure synthetic samples of chiloglottone1-3 or mixtures thereof proved to be attractive to the corresponding orchid pollinators. Because of their likely biogenesis from ubiquitous fatty acid precursors, 2,5-dialkylcyclohexan-1,3-diones may represent a hitherto overlooked, widespread class of natural products.2-butyl-5-methylcyclohexan-1,3-dione ͉ 2-ethyl-5-pentylcyclohexan-1,3-dione ͉ Chiloglottis ͉ semiochemical ͉ mass spectrometry

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confidence: 83%

Section: Resultsmentioning

confidence: 99%

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The discovery of 2,5-dialkylcyclohexan-1,3-diones as a new class of natural products

Franke

Ibarra

Schulz

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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“…The mass spectra of other β-diketones have been studied [6][7][8][9][10][11][12][13][14] and by comparison of differently substituted compounds it has been found that the fragmentation is influenced by the keto-enol content of the compounds (this means previous to ionization). The diketo and keto-enol tautomers of aliphatic 1,3-diketones could be easily separated by gas chromatography [13], which is not the usual case for tautomers mixtures.…”

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Tautomeric Equilibria Studies by Mass Spectrometry

Allegretti¹,

Schiavonni²,

Castro

et al. 2008

Nat Prec

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Tautomerism in organic chemistry has been extensively studied in condensed phase by spectrometric methods, mainly by IR and NMR techniques. Mass spectrometry studies start 40 years ago but just recently it has been recognized the importance of the mass spectral data for the study of tautomerism in the gas phase.Mass spectrometry can provide valuable information in regard to tautomeric equilibria when studying mass spectra among the members of different families of organic compounds.The relevance of the mass spectral data resides on several facts but there are two that are of key importance:1- Mass spectral fragmentation assignments should be tautomer specific since the corresponding abundances ratios are supposed to be correlated to the keto/enol contents.2- Ionization in the ion source is supposed to have no effect on the position of the equilibrium so that the results reflect the tautomers content in the gas phase previous to ionization.Some of the carbonylic compounds do not exhibit noticeable tautomerism so the fragment abundances assigned to the enol form is very low or not measurable. Since enolization is more noticeable in the case of thio-derivatives (which correlates adequately with the oxygenated analogues), the study of their mass spectra is an interesting choice to reach some degree of generalization. In addition, experimental findings are supported by semiempirical theoretical calculations, which probed to be adequate not only for supporting tendency correlations among the members of a compound family but also to calculate heats of tautomerization in gas phase.Reports using mass spectrometry for tautomerism are becoming less common. One of the reasons is that now it would appear that the interpretation of MS results is not as straightforward as it was once believed, even though in a recent review it was written that: “Mass spectrometry is the most informative and practical method for studying and identifying tautomers in the gas phase” [1]. In fact, mass spectrometry seems to be very informative for studying and identifying tautomers, because in this case external factors like solvents, intermolecular interactions, etc., can be excluded by transferring the tautomeric system into gas phase, where the process becomes truly unimolecular [1].This review covers the study of Tautomerism by Mass Spectrometry in the last four decades.

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“…The mass spectra of other β-diketones were studied [6][7][8][9][10][11][12][13][14], and comparison of the data for differently substituted compounds showed that the fragmentation pattern depends on the ketone-enol ratio (i.e., prior to ionization). The diketone and ketone-enol tautomers of aliphatic 1,3-diketones could be easily separated by gas chromatography [13], which is not a usual case for tautomers mixtures.…”

Section: Tautomerism Before or After Ionizationmentioning

confidence: 99%

Mass spectrometry as a tool for studying tautomerism

et al. 2008

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Studies in Organic Mass Spectrometry IV. Fragmentation of 2‐Alkyl‐ 1, 3‐cyclohexanediones

Abstract: In 2-propyl-and 2-butyl-l,3-~yclohexanediones, fragmentations in the side chain carry most of the total ionisation. Exact mass measurements and deuterium labeling led to mechanistic interpretations for the formation of the principal fragment ions.

Cited by 18 publications

References 5 publications

The discovery of 2,5-dialkylcyclohexan-1,3-diones as a new class of natural products

The discovery of 2,5-dialkylcyclohexan-1,3-diones as a new class of natural products

Tautomeric Equilibria Studies by Mass Spectrometry

Mass spectrometry as a tool for studying tautomerism

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