Fragmentation of trimethylsilyl derivatives of 2‐alkoxyphenols: A further violation of the ‘even‐electron rule’

This review describes the mass spectral fragmentation of trimethylsilyl (TMS) and related alkylsilyl derivatives used for preparing samples for analysis, mainly by combined gas chromatography and mass spectrometry (GC/MS). The review is divided into three sections. The first section is concerned with the TMS derivatives themselves and describes fragmentation of derivatized alcohols, thiols, amines, ketones, carboxylic acids and bifunctional compounds such as hydroxy‐ and amino‐acids, halo acids and hydroxy ethers. More complex compounds such as glycerides, sphingolipids, carbohydrates, organic phosphates, phosphonates, steroids, vitamin D, cannabinoids, and prostaglandins are discussed next. The second section describes intermolecular reactions of siliconium ions such as the TMS cation and the third section discusses other alkylsilyl derivatives. Among these latter compounds are di‐ and trialkyl‐silyl derivatives, various substituted‐alkyldimethylsilyl derivatives such as the tert‐butyldimethylsilyl ethers, cyclic silyl derivatives, alkoxysilyl derivatives, and 3‐pyridylmethyldimethylsilyl esters used for double bond location in fatty acid spectra. © 2019 Wiley Periodicals, Inc. Mass Spec Rev 0000:1–107, 2019

show abstract

“…Fragmentation involving successive losses of methyl radicals and cyclization from methyl/TMS derivatives of o ‐diphenols (Krauss et al., ).…”

Section: Trimethylsilyl Derivativesmentioning

confidence: 99%

Mass Spectrometric Fragmentation of Trimethylsilyl and Related Alkylsilyl Derivatives

Harvey

Vouros

2019

Mass Spectrometry Reviews

View full text Add to dashboard Cite

show abstract

“…28 On the other hand, numerous violations of this rule have been documented. 29,30 A comparison of energy required for the fragmentation of the m/z 121 ion derived from ethoxybenzoic acids showed that less laboratory-frame collisional energy is required for the ion derived from the ortho isomer to fragment than those needed for the onset of the homolytic fragmentation observed for meta and para isomers (Fig. 3).…”

Section: [M H] ) Ion Derived From Ortho-(a) Meta-(b) and Para-ethoxymentioning

confidence: 99%

Loss of benzene to generate an enolate anion by a site‐specific double‐hydrogen transfer during CID fragmentation of o‐alkyl ethers of ortho‐hydroxybenzoic acids

et al. 2008

View full text Add to dashboard Cite

Collision-induced dissociation of anions derived from ortho-alkyloxybenzoic acids provides a facile way of producing gaseous enolate anions. The alkyloxyphenyl anion produced after an initial loss of CO(2) undergoes elimination of a benzene molecule by a double-hydrogen transfer mechanism, unique to the ortho isomer, to form an enolate anion. Deuterium labeling studies confirmed that the two hydrogen atoms transferred in the benzene loss originate from positions 1 and 2 of the alkyl chain. An initial transfer of a hydrogen atom from the C-1 position forms a phenyl anion and a carbonyl compound, both of which remain closely associated as an ion/neutral complex. The complex breaks either directly to give the phenyl anion by eliminating the neutral carbonyl compound, or to form an enolate anion by transferring a hydrogen atom from the C-2 position and eliminating a benzene molecule in the process. The pronounced primary kinetic isotope effect observed when a deuterium atom is transferred from the C-1 position, compared to the weak effect seen for the transfer from the C-2 position, indicates that the first transfer is the rate determining step. Quantum mechanical calculations showed that the neutral loss of benzene is a thermodynamically favorable process. Under the conditions used, only the spectra from ortho isomers showed peaks at m/z 77 for the phenyl anion and m/z 93 for the phenoxyl anion, in addition to that for the ortho-specific enolate anion. Under high collision energy, the ortho isomers also produce a peak at m/z 137 for an alkene loss. The spectra of meta and para compounds show a peak at m/z 92 for the distonic anion produced by the homolysis of the O-C bond. Moreover, a small peak at m/z 136 for a distonic anion originating from an alkyl radical loss allows the differentiation of para compounds from meta isomers.

show abstract

“…The Interpretation of the mass spectra was based on the data published for the TMS derivatives of hydroxy monocarboxylic acids (Petersson 1970;Mamer et al 1971;Markey et al 1974;MacLeod 1975;Thompson et al 1975;Petersson and Samuelson 1976;Niwa et ai 1982;Sjöström 1985b, 1986b), dicarboxylic acids (Mamer et al 1971;Petersson 1972Petersson , 1975Large and Saunders 1973;Markey et al 1974;Przyrembel et al 1975;Löwendahl et al 1976b;Greter et al 1980;Truscott et al 1981;Sjöström 1985c, 1986a), tricarboxylic acids (Dalgliesh et al 1966;Niemelä and Sjöström 1985c), fatty acids (Markey etal 1974;Kuksis et al 1976), aromatic compounds (Horman and Viani 1971;Lhugenot etal 1971;Mamer et al 1971;Higuchi et al 1972;Kornreich and Issenberg 1972;Morita 1972;Markey et al 1974;Riley and Kolattukudy 1975;Hattox and Murphy 1978;Löwendahl et al 1978;Wittkowski et al 1981;Concin et al 1983;Lapierre et al 1983;Odier et al 1983;Gellerstedt et al 1984;Krauss et al 1985;Niemelä and Sjöstr...…”

Section: Mass Spectrometrymentioning

confidence: 99%

Simultaneous Identification of Aromatic and Aliphatic Low Molecular Weight Compounds from Alkaline Pulping Liquor by Capillary Gas-Liquid Chromatography — Mass Spectrometry

Niemelä¹,

Sjöström²

1986

Holzforschung

View full text Add to dashboard Cite

Fragmentation of trimethylsilyl derivatives of 2‐alkoxyphenols: A further violation of the ‘even‐electron rule’

Cited by 21 publications

References 16 publications

Mass Spectrometric Fragmentation of Trimethylsilyl and Related Alkylsilyl Derivatives

Mass Spectrometric Fragmentation of Trimethylsilyl and Related Alkylsilyl Derivatives

Loss of benzene to generate an enolate anion by a site‐specific double‐hydrogen transfer during CID fragmentation of o‐alkyl ethers of ortho‐hydroxybenzoic acids

Simultaneous Identification of Aromatic and Aliphatic Low Molecular Weight Compounds from Alkaline Pulping Liquor by Capillary Gas-Liquid Chromatography — Mass Spectrometry

Contact Info

Product

Resources

About