Mass spectrometry fragmentation behavior

Understanding how molecules fragment upon electron impact pennits a mass spectrum to be analyzed in sufficient detail to deduce the structure of an unknown compound. Thousands of compounds of known structure have been examined by mass spectrometry, and the fragmentation patterns that characterize different classes are well documented. As various groups are covered in subsequent chapters, aspects of their fragmentation behavior under conditions of electron impact will be described. 

A comparison of the electron impact (El) and chemical ionization (Cl-methane) mass spectra of 1//-azepine-1-carboxylates and l-(arylsulfonyl)-l//-azepines reveals that in the El spectra at low temperature the azepines retain their 8 -electron ring structure prior to fragmentation, whereas the Cl spectra are complicated by high temperature thermal decompositions.90 It has been concluded that Cl mass spectrometry is not an efficient technique for studying azepines, and that there is no apparent correlation between the thermal and photo-induced rearrangements of 1//-azepines and their mass spectral behavior. 

The proposed subsequent reaction fits the fragmentation patterns observed in mass spectrometry where, even at 20 eV, group 14 centered radicals form in increasing order Sibasic data of this kind can provide estimates of kinetic behavior of such reactions, where M—M bonds are cleaved by electrophiles and which depend on the ionization potentials of the former as well as the electron affinity of the latter. 

By analogy with their behavior in mass spectrometry, branched hydrocarbons are cleaved when oxidized in CH3 CN/TEABF4 at —45 °C. The resulting acetamides of the fragments (Table 6) are formed by cleavage of the initial radical cation at the C,C bond between the secondary and tertiary C atom, to afford after a second electron transfer, carbocations, which react in a Ritter reaction with acetonitrile [29]. 

Djerassi, C. Tokes, L. Mass Spectrometry in Stractural and Stereochemical Problems. XCIII. Further Observations on the Importance of Interatomic Distance in the McLafferty Rearrangement. Synthesis and Fragmentation Behavior of Deuterium-Labeled 12-Oxo Steroids. J. Am. Chem. Soc. 1966,88,536-544. 

Aubagnac, J.L. Campion, p. Mass Spectrometry of Nitrogen Heterocycles. X. Contribution to the Behavior of the Aniline Ion and TVminopyridine Ions Prior to Fragmentation by Loss of Hydrogen Cyanide. Org. Mass Spectrom. 1979, 14, 425-429. 

FAB mass spectrometry of cluster-opened 3 and the isomeric mixture of n-butyl-amine adducts 4 revealed an unprecedented fragmentation behavior [12]. Whereas the usual exohedral adducts of Cjq exhibit typical characteristics, namely relatively... 

Since dithio- and selenocarbamates and their derivatives are used so widely in the deposition of thin films and nanoparticles that a mechanistic study of their decomposition behavior was carried out by O Brien et al. [ 107]. Wold et al. [78] studied the decomposition products of Zn(S2CNEt2)2 using gas-chromatography mass spectrometry (GC-MS) and their reported deposition path shows clean ehmination of ZnS from the precursor (Eqs. 1 and 2 below). However, the proposed decomposition route is somewhat different to the step-by-step fragmentation observed in the electron-ionization mass spectrometry (EI-MS) of the compoimd, (Eq. 3). This difference can be attributed to inherent differences between the two techniques. 

Recently, the electrochemical behavior saturated alcohols, that is, propargyl alcohol (HCSCCH2OH, PA) [145], benzyl alcohol (C6H5CH2OH, BA) [146] andallylalcohol [147], has been studied at Pd electrodes in an acid medium by cyclic voltammetry, chronoamperometry, and on-line mass spectrometry. For BA, it was observed that the fragmentation of the molecules occurs at potentials in the hydrogen ad-sorption/absorption region of palladium, whereas for PA the adsorbates maintain the C3-chain. On the other hand, the yields of the electroreduction and electrooxidation products for both PA and BA differ from those obtained at Pt [146,148,149]. 

M. T. Cancilla, S. G. Penn, J. A. Carroll, and C. B. Lebrilla, Coordination of alkali metals to oligosaccharides dictates fragmentation behavior in matrix assisted laser desorption ionization/ Fourier transform mass spectrometry, J. Am. Chem. Soc., 118 (1996) 6736-6745. 

Mass spectrometry of organic molecules has become well established in recent years and both the recording of spectra and the fragmentation patterns of functional groups have been comprehensively discussed (14, 19, 33, 126, 142). In the last 2 3 years the study of the behavior of organometallic compounds in the mass spectrometer, previously a neglected... 

As part of a study to identify the degradation products of sulfur mustard, bis(2-chloroethyl) sulfide, the behavior of various sulfonium salts towards electrospray ionization mass spectrometry has been investigated. Among the compounds studied was 3 -(2-chloroethyl)pentamethylene sulfonium tetrafluoroborate. The ion was readily detected at the 0.01 M level with no ion fragmentation <1997JMP1247>. 

As described in the previous section, a powerful technique to probe most of the chemical or physical properties of molecular clusters is mass spectrometry after ionization of these clusters. Generally, an excess of energy is given by this ionization process and can lead to various dynamical behaviors from the simplest one—fragmentations of the clusters (evaporation)—to intracluster chemical reactions. This means that the observed distribution of the ionic clusters often does... 

Metal-ethoxo cations derived from solutions of B(C6F5)3 and M2(OEt)10 were observed in the gas phase by electrospray mass spectrometry.293 They included [M(OEt)4]+, [M2(OEt)9]+, and [M20(0Et)7]+ as well as heterometallic analogs when both metals were present in the sprayed solutions. Their fragmentation behavior under collision-induced dissociation was examined. 

Inman, R. C., and M. P. Serve. 1982. The fragmentation behavior of the endo-and exo-octahydro-4,7-methano-lH-indene systems. Organic Mass Spectrometry 17 220. 

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