Search results for "McLafferty rearrangement"
showing 4 items of 4 documents
Mass spectra of chlorinated esters: 2—Methyl mono- and dichlorobutanoates
1982
The mass spectral fragmentations of methyl mono- and dichlorobutanates have been studied. Deutrium labelling and metastable ion analysis were used to elucidate the fragmentation mechanisms. The molecular ion peaks of the esters are weak and show only in the spectra of the monochloro isomers. A McLafferty rearrangement gives the base peaks in the spectra of methyl 2-chloro-, 4-chloro- and 4,4-dichlorobutanoate; α-cleavage, [COOCH3]+, in methyl 2,2- and 2,4-dichlorobutanoate; [MCl]+, in methyl 3-chlorobutanoate; [MClHCl]+, in methyl 3,4-dichlorobutanoate; [MClCH2CO]+, in methyl 3,3-dichlorobutanoate and [MClCOOCH3]+˙, in methyl erythro- and threo-2,3-dichlorobutanoate. The mass spectra of the…
Mass spectra of halogenated esters 5—Chloromethyl esters of aliphatic C2C12n-carboxylic acids and their monochlorinated derivatives
1984
A study has been made of the mass spectral fragmentation upon electron impact of aliphatic C2C12 chloromethyl esters and all their 66 monochlorinated derivatives. The fragmentation pathways of the parent chloromethyl esters were elucidated with the aid of the 1st FFR metastable ions. A McLafferty rearrangement gives the base peak in the C6C11 parent esters and in almost all the 4-chloro and ω-chloro isomers. The subsequent loss of HCl gives a very characteristic peak of the chloromethyl esters and their (3-ω)-chloro derivatives at m/z 72, [C3H4O2]+. The 2-chloro isomers have the corresponding chlorine-containing fragment ion at m/z 106/108. The mass spectra of 2-, 3-, 4-, 5- and ω-chloro is…
Mass spectra of halogenated esters. 7. Methyl esters of 2-chloro C2C20n-alkanoic acids
1988
The mass spectral fragmentation of a homologous series of methyl esters of 2-chloro n-alkanoic acids ranging from acetic (C2) to eicosanoic (C20) acid on electron impact has been investigated. The fragmentation pathways were elucidated with the aid of the first field-free region metastable ions, the results being presented with one compound, i.e. with ionized methyl 2-chloro-octauoate. Owing to the Cl/H exchanges and to the formation of the non-chlorinated parent esters prior to the fragmentations the spectra show the peak pairs with and without the chlorine atom. The effects become more evident with increasing chain length; shown most visually by the abundance ratios of the McLafferty rear…
Mass spectra of halogenated esters 6—Methyl esters of some trihalogenated propanoic and butanoic acids
1984
The mass spectral fragmentation of trihalogenated methyl esters, formed in the reactions of monochlorinated methyl propenoates and 2-butenoates with Cl2, BrCl and Br2, have been investigated. In most cases α-cleavage gives the base peak, [COOCH3]+, the peaks originating from the subsequent losses of one or two halogen atoms also being abundant. The primary loss of a halogen atom is more prominent in the C4 derivatives, Br˙ and Cl˙ being preferentially lost from the 2- and 3-positions, respectively. The McLafferty rearrangement yields in one case the base peak; the 2-halo compounds could in general be distinguished by that fragmentation. Typical for all 2-bromo-substituted methyl butanoates …