1-Pentene mass spectrum

Example For the case of 4-methyl-1-pentene, the breakdown graph, the internal energy distribution from the photoelectron spectrum, and the 70 eV El mass spectrum are compared (Fig. 2.22). [99] From the fragmentation threshold to about... 

Fig. 2.22. Relationship of breakdown graph (a), internal energy distribution from PES (b), and mass spectrum of 4-methyl-1-pentene (c). Reproduced from Ref. [99] by permission. John Wiley Sons, 1982.

Example The base peak in the El mass spectrum of (3-methylpentyl)-benzene is formed by McLafferty rearrangement of the molecular ion (Fig. 6.28). As long as pentene loss may occur, there is not much difference to spectra of other isomers such as 2-methylpentyl-, 4-methylpentyl, or n-hexyl. Reference spectra are needed to distinguish those isomers, because differences are mainly due to peak intensities, whereas only minor peaks might appear or vanish depending on the isomer. 

Show equations to account for the major fragment ions that occur at m/z 97 and mlz 57 in the mass spectrum of 2,4,4-trimethyl-1-pentene. 

Pentane, 1 -pentene, and 1 -pentyne are low-Poiling hydrocarbons that have different molecular ions in their mass spectra. Match each hydrocarbon to its mass spectrum. 

Figure 6.1.28. Mass spectrum tentatively assigned to 2,4-bis(2-methylpropyl)-8-methyl-1-nonene, the trimer of 4-methyl-1-pentene (MW = 252).

The molecular ion in the mass spectrum of 2-methyl-l-pentene appears at m z 84. Propose structural formulas for the prominent peaks at m z 69,55,41, and 29. 

When analyzing a mass spectrum, the first step is to look for the (M) " peak, because it indicates the molecular weight of the molecule. This technique can be used to distinguish compounds. For example, compare the molecular weights of pentane and of 1-pentene. 

Pentane has 5 carbon atoms (5 X 12 = 60) and 12 hydrogen atoms (12 X 1 = 12) and therefore a molecular weight of 72. In contrast, 1-pentene only has 10 hydrogen atoms and therefore has a molecular weight of 70. As a result, we expect the mass spectrum of pentane to exhibit a molecular ion peak at 72, while the mass spectrum of 1-pentene should exhibit a molecular ion peak at 70. 

XI.2.1 Gases from representative refinery streams can be run by a GLC method to obtain pentene ratios which then can be used to calculate weighted sensitivity coefficients. Alternatively, a Cj cut could be obtained from a low-temperature fractional distillation of a sample of the type to be analyzed. The mass spectrum of this cut is recorded and the contributions of the normal and isopentane and normal butane present removed from the spectrum. The residual spectrum is typical of the pentenes present in samples of this... 

Problem 12,2 Two mass spectra are shown in Figure 12.7. One spectrum is that of 2-methyl-I 2-pentene the other is of 2-hexene. Which is which Explain. 

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