Mass Spectroscopy, Example #3

Analysis: C9H10O MW = 134.18 Help with Analysis
Mass Spectrum

Mass Spectrum

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C9H10O MW = 134.18

From the molecular formula, the compound has "5 degrees of unsaturation" (five double bonds, carbonyls, rings or any combination thereof). The large number of degrees of unsaturation strongly suggests an aromatic molecule (DU = 4).

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The spectrum shows a moderate molecular ion peak, and a peak at m-15, strongly suggesting the presence of a labile methyl group. The base peak occurs at m/e = 91, which is highly suggestive of a benzyl fragment. The presence of an intense peak at m/e = 43 is also suggestive of the presence of a methyl ketone, which can fragment to form the acylium ion.

Fragmentation of Common Functional Groups
Common Ions and Fragments

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Structure: structure

IUPAC Name: 3-pentanone (diethyl ketone)

MS Fragments:
fragments

The spectrum shows a moderate molecular ion peak, and a peak at m-15, strongly suggesting the presence of a labile methyl group. The base peak occurs at m/e = 91, which is highly suggestive of a benzyl fragment, which rearranges to form the tropylium cation. The presence of an intense peak at m/e = 43 is also suggestive of the presence of a methyl ketone which can fragment to form the acylium ion.

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Copyright 1996, Paul R. Young, University of Illinois at Chicago, All Rights Reserved