J. Am. Chem. Soc.

1969

DOI: 10.1021/ja01052a046

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Mass spectrometry in structural and stereochemical problems. CLXXXIII. A study of the electron impact induced fragmentation of aliphatic aldehydes

Carl Djerassi²

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Cited by 44 publications

(14 citation statements)

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“…Electron ionization-mass spectrometry (EI-MS) produced the signature fragmentation pattern for the aldehyde and alcohol products, yielding ions that result from dehydration [m-18], elimination of ethylene [m-28] and dehydration with terminal demethylation [m-33]. 36 …”

Section: Resultsmentioning

confidence: 99%

Cyanobacterial Aldehyde Deformylase Oxygenation of Aldehydes Yields n – 1 Aldehydes and Alcohols in Addition to Alkanes

¹

,

²

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³

et al. 2013

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Aldehyde-deformylating oxygenase (ADO) catalyzes O2-dependent release of the terminal carbon of a biological substrate, octadecanal, to yield formate and heptadecane in a reaction that requires external reducing equivalents. We show here that ADO also catalyzes incorporation of an oxygen atom from O2 into the alkane product to yield alcohol and aldehyde products. Oxygenation of the alkane product is much more pronounced with C9-10 aldehyde substrates, so that use of nonanal as the substrate yields similar amounts of octane, octanal, and octanol products. When using doubly-labeled [1,2-13C]-octanal as the substrate, the heptane, heptanal and heptanol products each contained a single 13C-label in the C-1 carbons atoms. The only one-carbon product identified was formate. [18O]-O2 incorporation studies demonstrated formation of [18O]-alcohol product, but rapid solvent exchange prevented similar determination for the aldehyde product. Addition of [1-13C]-nonanol with decanal as the substrate at the outset of the reaction resulted in formation of [1-13C]-nonanal. No 13C-product was formed in the absence of decanal. ADO contains an oxygen-bridged dinuclear iron cluster. The observation of alcohol and aldehyde products derived from the initially formed alkane product suggests a reactive species similar to that formed by methane monooxygenase (MMO) and other members of the bacterial multicomponent monooxygenase family. Accordingly, characterization by EPR and Mössbauer spectroscopies shows that the electronic structure of the ADO cluster is similar, but not identical, to that of MMO hydroxylase component. In particular, the two irons of ADO reside in nearly identical environments in both the oxidized and fully reduced states, whereas those of MMOH show distinct differences. These favorable characteristics of the iron sites allow a comprehensive determination of the spin Hamiltonian parameters describing the electronic state of the diferrous cluster for the first time for any biological system. The nature of the diiron cluster and the newly recognized products from ADO catalysis hold implications for the mechanism of C-C bond cleavage.

“…Electron ionization-mass spectrometry (EI-MS) produced the signature fragmentation pattern for the aldehyde and alcohol products, yielding ions that result from dehydration [m-18], elimination of ethylene [m-28] and dehydration with terminal demethylation [m-33]. 36 …”

Section: Resultsmentioning

confidence: 99%

Cyanobacterial Aldehyde Deformylase Oxygenation of Aldehydes Yields n – 1 Aldehydes and Alcohols in Addition to Alkanes

¹

,

²

,

³

et al. 2013

View full text Add to dashboard Cite

Aldehyde-deformylating oxygenase (ADO) catalyzes O2-dependent release of the terminal carbon of a biological substrate, octadecanal, to yield formate and heptadecane in a reaction that requires external reducing equivalents. We show here that ADO also catalyzes incorporation of an oxygen atom from O2 into the alkane product to yield alcohol and aldehyde products. Oxygenation of the alkane product is much more pronounced with C9-10 aldehyde substrates, so that use of nonanal as the substrate yields similar amounts of octane, octanal, and octanol products. When using doubly-labeled [1,2-13C]-octanal as the substrate, the heptane, heptanal and heptanol products each contained a single 13C-label in the C-1 carbons atoms. The only one-carbon product identified was formate. [18O]-O2 incorporation studies demonstrated formation of [18O]-alcohol product, but rapid solvent exchange prevented similar determination for the aldehyde product. Addition of [1-13C]-nonanol with decanal as the substrate at the outset of the reaction resulted in formation of [1-13C]-nonanal. No 13C-product was formed in the absence of decanal. ADO contains an oxygen-bridged dinuclear iron cluster. The observation of alcohol and aldehyde products derived from the initially formed alkane product suggests a reactive species similar to that formed by methane monooxygenase (MMO) and other members of the bacterial multicomponent monooxygenase family. Accordingly, characterization by EPR and Mössbauer spectroscopies shows that the electronic structure of the ADO cluster is similar, but not identical, to that of MMO hydroxylase component. In particular, the two irons of ADO reside in nearly identical environments in both the oxidized and fully reduced states, whereas those of MMOH show distinct differences. These favorable characteristics of the iron sites allow a comprehensive determination of the spin Hamiltonian parameters describing the electronic state of the diferrous cluster for the first time for any biological system. The nature of the diiron cluster and the newly recognized products from ADO catalysis hold implications for the mechanism of C-C bond cleavage.

“…The predominent transfer occurs from the y and positions (Figures 3 and 4), as in electron impact. 5 The kinetics (figures) suggest a fairly direct process possibly with an activation energy less than that for formation of m/e 44, since the rates do cross over with m/e 45 being favored at long times.…”

Section: Discussionmentioning

confidence: 94%

“…The formation of m/e 56 from hexanal involving transfer of the hydrogen may proceed according to reaction 6, (6) which is directly analogous to reaction 2 but involving a seven-rather than a six-membered cyclic transition state in the initial step. 5 m/e 45. The formation of this (C2H50)+ ion involves the transfer of two hydrogens from the alkyl chain to the oxygen end of the molecule.…”

Section: Discussionmentioning

confidence: 99%

Field ionization kinetics. Unimolecular decomposition of the hexanal radical cation over the time range from 10 ps to 10 .mu.s

et al. 1979

J. Phys. Chem.

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Rates of formation of the major product ions from decomposition of hexanal, [3,3-2H2]hexanal, [4,4-2H2]hexanal, and [5,5-2H2]hexanal following field ionization have been determined over the time range 10 ps to several microseconds. These ions can be attributed to decomposition processes initiated by ß-, -, -, or e-hydrogen transfer to the oxygen via five-, six-, seven-, or eight-membered cyclic transition states. It is suggested that the McLafferty rearrangement at short times (<10-10 s) forms a vinyl alcohol ion and but-l-ene, and at longer times (10-10 to 10-6 s) a but-2-ene ion and vinyl alcohol. The observations at times <1 ns of m/e 57, m/e 73, and m/e 82 with [3,3-2H2]hexanal and m/e 73 with [4,4-2H2]hexanal are explained by decompositions initiated by /3-hydrogen transfer. The intermediate so formed rearranges by a 1,2-hydrogen shift to (CH= 0+,iHCH2C,sH1'HCTHCH2CH3), which then decomposes along its usual pathways (i.e., as if it were formed directly by -hydrogen transfer).

“…Break of the C-H and C-C bonds next to the oxygen atom renders an MÀ1 peak and an M-R peak (m/z 29, CHO + ). The MÀ1 peak is characteristic even for long-chain aldehydes, but the m/z 29 peak in > C 4 aldehydes may also result from the C 2 H 5 + hydrocarbon ion [1,3,72].…”

Section: Hydroxy Compoundsmentioning

confidence: 99%

Interpretation of Mass Spectra

1992

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The chapter includes an introduction to the main ionisation techniques in mass spectrometry and the way the resulting fragments can be analysed. First, the fundamental notions of mass spectrometry are explained, so that the reader can easily cover this chapter (graphs, main pick, molecular ion, illogical pick, nitrogen rule, etc.). Isotopic percentage and nominal mass calculation are also explained along with fragmentation mechanism. A paragraph emphasises the ionisation energy issues, the basics of ionisation voltage, the developing potential and the energy balance. A frame time of the main theoretical milestones in both theory and experimental mass spectrometry is highlighted here. In the second part of the chapter, the molecular fragmentation for alkanes, iso-alkanes, cycloalkanes, halogen, alcohols, phenols, ethers, carbonyl compounds, carboxylic acids and functional derivatives, nitrogen compounds (amines, nitro compounds), sulphur compounds, heterocycles and biomolecules (amino acids, steroids, triglycerides) is explained. Fragmentation schemes are followed by the simplified spectra, which help the understanding of such complex phenomena. At the end of the chapter, acquisition of mass spectrum is discussed. The chapter presented here is an introduction to mass spectrometry, which, we think, helps the understanding of the mechanism of fragmentation corroborating spectral data and molecular structures.The scientific term spectrograph starts being part of the scientific vocabulary (1884) [1,3] E. Goldstein studied 'canal rays' composed of positive ions. His work opened the gate to mass spectrometry (1886) [1,3] Wilhelm Wien showed that the mass-to-charge ratio of the positive ions (canal rays) has opposite polarity that of the electron (1898) [1,3]

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