Pentane fragmentation ions from

The t-butyl cation was found by Olah and Lukas (1967) to be perfectly stable in FSOgH-SbFg solutions, even at 150°C, while all other carbonium ions from the protonation of butanes, pentanes and hexanes were observed to be converted into the t-butyl cation, following various fragmentation and isomerization pathways. 

Although the molecular ion of pentane have m/z value of 72, its mass spectrum shows a very small peak at m/z = 73. This is called an M+1 peak because the ion responsible for this peak is one unit heavier than the molecular ion. The M+1 peak occurs because there are two naturally occuring isotopes of carbon 98.89% of natural carbon C and 1.11% is C. The M+1 fragment results from molecular ions that contain one C instead of a C. ... 

For example, the C—C bonds in the molecular ion formed from pentane have about the same strength. However, the C-2—C-3 bond is more likely to break than the C-1—C-2 bond because C-2—C-3 fragmentation leads to a primary carbocation and a primary radical, which together are more stable than the primary carbocation and methyl radical (or primary radical and methyl cation) obtained from C-1 —C-2 fragmentation. C-2—C-3 fragmentation forms ions with mjz = 43 or 29, and C-1 —C-2 fragmentation forms ions with mjz = 57 or 15. The base peak of 43 in the mass spectmm of pentane indicates the preference for C-2—C-3 fragmentation. (See Sections 7.7 and 7.8 to review the relative stabilites of carbocations and radicals.)... 

Linear and cyclic structures of polycarbonates from bisphenol-A, from bisphenol-Z, and from 4,4 -dihydroxydiphenyl-3,3-pentane, were determined by PSD MALDI-TOF experiments. It was foimd that the fragmentation behavior of these polycarbonates depends on the substituents boimd to the central carbon atom of the bisphenol unit. The cleavage of the polymer backbone is suppressed, and the spectra are dominated by the loss of side groups. PSD MALDl spectra of these polycarbonates could be acquired only from Li adduct ions, because the sodium or potassium cationized adduct ions yield only dissociation of the cation from the polymer. ... 

---