Mass spectrometry of nitroazoles 1–The mass spectra of methyl substituted nitropyrazoles

Abstract

The mass spectra of aU isomers of methylnibopyrazoles are reported. Generally, the spectra are charactenstic of nitropyrazoles. In some cases however, o d o eñects occur, recognizable by primary losses of, for example,

Selective Preparation of 3,4,5‐Trinitro‐1H‐Pyrazole: A Stable All‐Carbon‐Nitrated Arene

“…The pK a of TNP was determined by potentiometry to be 2.35, which is worth comparing to those reported in the literature for pyrazole and partially nitrated pyrazoles: [5a, 19,20] 1H-pyrazole: pK a = 14.2; 3(5)-nitropyrazole: pK a = 9.81; 4nitropyrazole: pK a = 9.67; 3(5),4-dinitropyrazole: pK a = 5.14; 3,5-dinitropyrazole: pK a = 3.14. The effect of the introduction of a nitro group in position four of the pyrazole ring is strongly dependent upon the presence of flanking nitro groups in the 3-or 3,5-positions.…”

Selective Preparation of 3,4,5‐Trinitro‐1H‐Pyrazole: A Stable All‐Carbon‐Nitrated Arene

“…The p K a of TNP was determined by potentiometry to be 2.35, which is worth comparing to those reported in the literature for pyrazole and partially nitrated pyrazoles:5a, 19, 20 1 H ‐pyrazole: p K a =14.2; 3(5)‐nitropyrazole: p K a =9.81; 4‐nitropyrazole: p K a =9.67; 3(5),4‐dinitropyrazole: p K a =5.14; 3,5‐dinitropyrazole: p K a =3.14. The effect of the introduction of a nitro group in position four of the pyrazole ring is strongly dependent upon the presence of flanking nitro groups in the 3‐ or 3,5‐positions.…”

Facile Synthesis and Structural Characterization by NMR, ESI–MS/MS and DFT Calculations of New (E)‐6‐[2‐Ferrocenylalkylidenehydrazino]nicotinic Hydrazides and Their (E)‐Ferrocenyl‐pyrazolyl‐pyridine Heterocyclic System

“…. The analysis of these compounds was not possible employing GC-MS [Electron Impact (EI) or CI] techniques.The positive ion ESI mass spectra of the ferrocenecarboxaldehyde derivatives (5aaÀ5ac), in the scan mode, confirmed the formation of pyrazolinic ring through the presence of fragment ion at m/z 440, which is characteristic fragmentation of pyrazoles, where the fragment R 1 CN is eliminated as [M-R 1 CN][18]. The sp 2 -carbons bonding, the hydrazinylpyridine, and ferrocenyl groups show signals, as singlets, in the average of 139 ppm.…”