Editing Alkane (section)

====Mass spectrometry====
Since alkanes have high [[ionization energy|ionization energies]], their [[Electron ionization|electron impact mass spectra]] show weak currents for their molecular ions. The fragmentation pattern can be difficult to interpret, but in the case of branched chain alkanes, the carbon chain is preferentially cleaved at tertiary or quaternary carbons due to the relative stability of the resulting [[free radical]]s. The mass spectra for straight-chain alkanes is illustrated by that for [[dodecane]]: the fragment resulting from the loss of a single methyl group (''M''&nbsp;−&nbsp;15) is absent, fragments are more intense than the molecular ion and are spaced by intervals of 14 mass units, corresponding to loss of CH<sub>2</sub> groups.<ref>{{cite web |title=Dodecane |url=https://webbook.nist.gov/cgi/cbook.cgi?ID=C112403&Mask=200 |work=NIST Chemistry WebBook |id=SRD 69 }}</ref>