2-Methylphenol, mass spectrum

The combination of chromatography/mass spectrometry with MS/MS methods can in fact markedly enhance the analytical performance of the identification of phenols. This was demonstrated in the case of hydroxy aromatic components in coal-derived liquids. The analytical performance can be further improved by using chemical derivatization, as also shown in an MS/MS study of some methylphenols and methylnaphthols. In the course of GC/MS/MS analytical studies on nonylphenol in biological tissues, derivatization proved to be favourable in an indirect way The El mass spectrum of nonylphenol... 

Phenols typically lose the elements-of carbon monoxide to give strong peaks at mie values that are 28 mass units below the value for the molecular ion. Such a peak is designated an M - 28 peak due to the relationship between its mIe value and the mIe value of the molecular ion. Phenols also lose the elements of the formyl radical (HCO-) to give strong M - 29 peaks (the fragment ion appears 29 mass units below the molecular ion). An exception appears to be the cresols, for which these fragment peaks are rather weak. Nevertheless, the M - 28 peak mJe = 80) and the M - 29 peak mie - 79) appear in the mass spectrum of 2-methylphenol (Fig. 8.26). 

Mass Spectrum for 2-tert-butyl-6-(5-chlorobenzotriazol-2-yl)-4-methylphenol - PLAS-AX-093... 

The mass spectra of phenols usually show strong molecular ion peaks. In fact, the molecular ion at miz = 94 is the base peak in the El-MS of phenol (Fig. 4.34). Favored modes of fragmentation involve loss of a hydrogen atom to create an M - 1 peak (a small peak at mIz = 93), loss of carbon monoxide (CO) to produce a peak at M -28 (m/z = 66), and loss of a formyl radical (HCO-) to give a peak at M - 29. In the case of phenol itself, this creates the aromatic cyclopentadienyl cation at m/z = 65. In some cases, the loss of 29 mass units may be sequential initial loss of carbon monoxide followed by loss of a hydrogen atom. The mass spectrum of ortho-cresol (2-methylphenol) exhibits a much larger peak at M - 1 (Fig. 4.35) than does unsubstituted phenol. Note also the peaks at miz = 80 and m/z = 79 in the o-cresol spectrum from loss of CO and formyl radical, respectively. 

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