The electron impact ionization of some mono-and dinitropyridylphenylsulfiede, ether, amine and sulfone derivatives were studied at 70 eV energy. All the 8 compounds studied underwent ring closure during the formation of a carbazole radical cation as a general feature in their mass spectra. The basic differences in the mass spectral behaviour are mainly attributed to the position of the nitro group in the pyridyl ring and the fragmentation pathway is directed by the sulfur, oxygen or nitrogen moiety. The base peak in the mass spectra is determined by such differences.
The structures of some new carboxamide, thiocarboxamide, nicotinoyl and isonicotinoyl pyrazoline derivatives have been related to their mass spectral data. The ions produced under electron impact showed both the characteristic pyrazoline ion and unusual azete fragmentation patterns. These results suggest that the mass spectra of these pyrazoline derivatives are both position and substituent dependent. Fragmentations of the ions are discussed in view of their metastable transitions. # 1998 John Wiley & Sons, Ltd. Received 22 September 1997; Revised 31 March 1998; Accepted 26 April 1998 It has been reported that substituted pyrazoline derivatives possess a wide spectrum of biological activities and are crucial intermediates in the synthesis of substituted cyclopropane derivatives.1 Their mass spectra have been studied in some detail, and proven to be of use in structure determination.2 As a continuation of our work on the structure-reactivity of some erythro2,3-dibromo ketones with different nucleophiles that produce pyrazoline, 3 we investigate here electron impact induced fragmentation of some newly prepared compounds:
DISCUSSIONThe characteristic peaks observed in the spectra of carboxamide and thiocarboxamide pyrazoline derivatives 1-3 are summarized in Scheme 1. Their spectra except for 1 exhibit molecular ion peaks and contain fragments that confirm the pyrazoline ring structure. 4 The most prominent ions in the spectrum of 1 show a depleted [M À 15] ion at m/z 284, this trisubstituted pyrazoline ion then eliminates carbonyl chloride to produce a diphenyl pyrazoline ion (base peak) at m/z 221, and subsequently produces phenyl pyrazoline ion at m/z 145 via loss of a phenyl radical. Ring fragmentation of the diphenyl pyrazoline ion gives two azirinium ions at m/z 119 and 118, or a tropylium ion at m/z 91. Peaks at m/z 77 and 65 are routinely observed in the degradation of the tropylium ion. The corresponding metastable ion peaks (Table 1) confirm these fragmentations.The degradation pattern of 2, as shown in Scheme 1, demonstrates a relatively low intensity molecular ion peak but a rather intense [M À H] ion. Formation of a diaryl substituted pyrazoline ion at m/z 267(base peak) involved a two-step elimination of an amide group from the pyrazoline ring. This substituted pyrazoline ion then dissociates further, producing the characteristic phenyl pyrazoline ion at m/z 145. In addition, as for 1, low-intensity azirinium ions and abundant tropylium and phenyl ions are formed following ring fragmentation of the phenyl pyrazoline ion. Interpretation of some of these processes is substantiated by observation of the appropriate metastable ion peak and tandem mass spectrometry (Fig. 1).The structure of the thiocarboxamide-2-pyrazoline derivative 3 is established from its mass spectral fragments, and in addition two metastable ion peaks are detected. The spectrum shows an [M À SH] ion at m/z 282. This is followed by elimination of HCN to produce a disubstituted pyrazoline ion at m/z 255 (base peak). Its ring ...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.