Investigation of the Bromination/Dehydrobromination of Long Chain Alkanes

Abstract

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).

Critical assessment of wet-chemical oxidation synthesis of silicon quantum dots

“…This is also the case in the absence of Mg 2 Si. Bromination of alkanes has been demonstrated before, [99][100][101][102] and results in the formation of alkyl bromides and HBr gas. 102 1 H NMR spectroscopic analysis indeed conrms the formation of octyl bromides, as evidenced by signals at 3.99, 4.04 and 4.13 ppm, which were assigned (primarily) to three isomers of secondary octyl bromides (ratios not quantied, see Fig.…”

Chemical Upcycling of Polyethylene to Value-Added α,ω-Divinyl-Functionalized Oligomers

“…The result is an improved industrial-scale process design for converting PE to α,ω-divinyl-functionalized oligomers which yields a positive NPV with revenue derived only from the sale of α,ω-divinyl-functionalized oligomers. Specifically, thermal dehydrobromination can produce the desired olefin and HBr without the need for an expensive base (e.g., t -BuOK) or generation of other coproducts (i.e., KBr and t -BuOH) . The HBr formed in dehydrobromination can be recycled oxidatively to Br 2 , as in the base case considered above.…”

“…Specifically, thermal dehydrobromination can produce the desired olefin and HBr without the need for an expensive base (e.g., t-BuOK) or generation of other coproducts (i.e., KBr and t-BuOH). 45 The HBr formed in dehydrobromination can be recycled oxidatively to Br 2 , as in the base case considered above.…”

Synthesis of Unsaturated Drying Oils from Saturated Fatty Oils Derived from Renewable Feedstocks

“…13 Nishina et al 13 studied bromination of saturated cyclic compounds using Br 2 as well as NBS with Li 2 MnO 3 as a photocatalyst. 13 Wang et al 14 studied in depth the photothermal radical bromination and dehydrobromination of saturated long-chain alkanes. Dehydrobromination was performed readily at temperatures between 175 and 190 °C without any catalyst.…”

“…In principle, if saturated oils can be halogenated and subsequently dehydrohalogenated, unsaturation can be created in the molecule. To our knowledge, there are no reports on such a protocol for functionalization of saturated lipids in any of the prior work, even though there are reports on functionalization of partially saturated oils and saturated alkanes. − We considered it as a desirable objectiveboth from the viewpoint of sustainability and use of more diverse and affordable feedstocks for alkyd preparation.…”