McLafferty studies

Various substituted 1,3-cyclohexadienes and their open-chain isomers, the respective 1,3,5-hexatrienes, have been studied by El mass spectrometry with special regard to the stereospecificity of the mutual pericyclic interconversion. A brief discussion including the parent systems, ionized 1,3-cyclohexadiene and 1,3,5-hexatriene has been provided by Dass in his review on pericyclic reactions of radical cations4. McLafferty and coworkers119 have shown that the two parent isomers are (almost) indistinguishable... 

The loss of alkenes from molecular ions of carbonyl compounds has early been noted. [23,82] Soon, a mechanism involving y-H shift and P-cleavage has been proposed and studied in detail. [24-26,83,84] Strictly speaking, the term McLafferty rearrangement only describes an alkene loss from molecular ions of satu-... 

Studying the competition of McLafferty rearrangement either with charge retention or charge migration and double hydrogen transfer has revealed that ion-neutral complex intermediates (Chap. 6.12) can also play a role for the latter two processes. [102]... 

The influence of substituents upon the mass spectral collapse of furoate esters can be correlated according to McLafferty, and the kinetics show that the first scission gives the furoyl ion (79MI31011). A study of 5-substituted 2-furoic acids (Me, Cl, Br, I) including... 

The roots of tandem mass spectrometry can be traced back to fundamental studies conducted by McLafferty and coworkers in the late 1960 s on metastable ion analysis (19-21). Metastable ions are ions which undergo decompositions in the field free regions of mass spectrometers giving rise to unusual diffuse peaks in the resulting... 

Although collision induced dissociation (CID) is a well-known method for investigating the structures of cations in the gas phase (McLafferty, 1983), it has been applied much less to anions (Bowie, 1986). Actually, in some cases CID has been used to study the fragmentation mechanisms of anions, such as the elimination of molecular hydrogen from alkoxide ions (Hayes el al., 1984) or the primary fragmentation routes of ester enolate ions (Froelicher et al., 1985). 

McLafferty et al. (37) studied the collisionally activated dissociation (CAD) of the ions resulting from the fast-atom bombardment ionization of cyano- and methylcobalamins, using a tandem mass spectrometer. They showed that mlz 1329 is produced only from the quasi-molecular ion. Similar CAD spectra are produced by both the quasi-molecular ions and the 1329 peak, indicating that essentially all fragmentation arises from this latter ion. CAD spectra produced for the 1329 ion derived from methylcobalamin or vitamin B12 coenzyme are also similar. This is consistent with the work of Taylor (10), who used linked-scan metastable ion techniques in a conventional double-focusing mass spectrometer to show the same thing. The sequential... 

Background. As an analytical technique, tandem mass spectrometry is just entering its second decade of development. The variety of reported applications belies its relative youth. Tandem mass spectrometry (MS/MS) grew out of early work which used metastable ion transitions in order to establish ion structures and interrelationships. After extensive applications to ion structural studies, its usefulness in direct catplex mixture analysis became apparent with the early work of Cooks (1-3). Its successes in problem solving are summarized in a recent book edited by McLafferty (4). New, with several ccnmercial instruments available, MS/MS is being evaluated for application in several new areas, including biochemical analysis, forensic chemistry, and food and flavor analyses. The principles of MS/MS will be surmarized in the first part of this chapter. The second part of the chapter will deal with the reported applications of MS/MS to flavor analysis. 

The McLafferty rearrangements is the mass spectrometric analog of the Norrish type II photochemical cleavage of ketones. The relationship between these two processes is easily the most extensively studied of aU mass spectral photochemical correlations. In addition to the well known reaction of aldehydes, ketones, and esters, Eq. (62), many analogous y-hydrogen... 

Strauss E, Zhai H, Brand LA, McLafferty FW, Begley TP. Mechanistic studies on phosphopantothenoylcysteine decarboxylase trapping of an enethiolate intermediate with a mechanism-based 33. inactivating agent. Biochemistry 2004 43 15520-15533. 

The types of ion fragments produced by the decomposition of organic halogen compounds in the mass spectrometer have been summarised by McLafferty - . Brief reviews have also been given by Beynon and by Budzikiewicz et al . These authors have also summarised the results of other workers, such as the early studies on the monohalides by Stevenson and Hippie and by Dibeler and Reese (ref. 146) and on the polyhalides by Bernstein et by McDowell et al and by Dibeler et Electron impact studies on aromatic halogen compounds have been reported by Majer and Patrick . The interpretations of the mass spectra of halogen compounds have been provided in some detail by McLaffierty , and the main features only of these spectra are discussed very briefly here. 

A further study aimed to distinguish isomeric C3H3 ions was reported by Koppel and McLafferty ". Using appropriately labelled precursors and analysing the collision induced dissociation pattern the authors present evidence for the existence of several noninterconverting C3H3 species, including 204 and 207. 

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