The Deepwater Horizon explosion in the Gulf of Mexico released oil into the ocean causing damage to many ecosystems. To help alleviate the spill, drastic measures were taken and the gulf region was treated with millions of liters of chemical dispersants, to allow for a rapid breakdown of the oil. Our objective is to synthesize original phosphorous based surfactants to help make the oil spill clean-up more environmentally friendly. The first step of our synthetic scheme is the silicon-based (tetraethyl orthosilicate (TEOS)) transesterification of ethyl hypophosphite with a cyclic alcohol to serve as a model for long chain ester synthesis. A one pot one-step synthesis of cyclohexanol, concentrated H3PO2 and TEOS all mixed at once in CH3CN and refluxed for 2 hours, generated 31P crude NMR yields from 41 to 64% depending on the number of equivalent of alcohol used. Similarly, 3-pentanol displayed crude yields ranging from 42 to 60%. The moderate yields can be linked to the alcohol replacement competition and steric hindrance of the secondary alcohols used. In an effort to optimize our percent yields, we varied the sequence of the esterification/transesterification synthesis to a one pot two-step synthesis, where the esterification was conducted first for 2 hours, and then the transesterification was initiated for 2 hours. The results show that four equivalence of alcohol in acetonitrile or toluene produced the cyclohexyl ester in 63 and 64% respectively. No significant yield increase was observed compared to the previous method but we are currently continuing our study with linear secondary alcohols such as 3-pentanol and 2-octanol to better understand the impact of the molecule’s geometry on the reaction’s efficiency. Future directions include yield optimization and hydrophosphinylation of the esters synthesized under Pd or Ni catalyzed conditions.

Transesterification of hypophosphorous esters: The tales of secondary alcohols

249th National Meeting (2015)

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