Investigation of the Bromination/Dehydrobromination of Long Chain Alkanes

The partial oxidation of dodecane and paraffin wax with bromine at relatively low temperatures (≤120 °C) and the dehydrobromination of the subsequent alkyl bromide intermediates at higher temperatures (>175 °C) to form higher alkenes were investigated. Products were analyzed using nuclear magnetic resonance spectroscopy, gas chromatography, and mass spectrometry. Bromination favored the formation of alkyl bromides on internal carbons of the model long chain alkanes over terminal sites. At lower temperatures (∼90 °C), ultraviolet photochemical initiation of bromination was necessary, while above 105 °C, thermally initiated bromination was observed. Photochemical bromination was found to be inhibited by water and oxygen. The formation of alkenes by the dehydrobromination of the alkyl bromides was observed by temperature-programmed reaction to occur at higher temperatures for n-dodecane (∼190 °C) than for the mixed alkanes in paraffin wax (∼175 °C).