Presentation Title

Hypophosphite Ester Synthesis: A Comparison between Direct Esterification and Transesterification

Start Date

November 2016

End Date

November 2016

Location

HUB 269

Type of Presentation

Oral Talk

Abstract

Large oil spills in the ocean are catastrophic events which pose a threat to the environment and marine life. This project was inspired by the Deepwater Horizon oil spill that occurred in April 2010, and is relevant to the recent Santa Barbara oil spill from May 2015. Currently, oil dispersants containing carbon-based surfactants are commonly used for clean-up. Surfactants help the oil disperse into droplets, encouraging more efficient bioremediation by microorganisms. Our objective is to synthesize novel phosphorus-based surfactants. Phosphorus is a vital element for life, so it is anticipated that phosphorus-based surfactants could increase the growth of bioremediating organisms and generate phosphates as bi-products as they decompose, thus providing a more environmentally friendly alternative. Our three-step synthetic route involves hypophosphite esters and a palladium-catalyzed hydrophosphinylation with bromoalkenes, followed by a reaction with a tertiary amine. We have established Step 1 of our process by synthesizing long-chain hypophosphite esters, utilizing two different methodologies: direct esterification and transesterification. Direct esterification, or Dean-Stark method, allows for the removal of water during esterification, but uses only toluene as a solvent. In comparison, the transesterification method utilizes a broad solvent scope (acetonitrile, hexane, toluene, or cyclohexane) along with a silicon derivative. The 31P crude NMR yields from both methodologies have been compared using different classes of alcohols. Results show that primary and tertiary alcohols do not have a methodology preference, but secondary alcohols such as 2-pentanol favor direct esterification (85-100% yields), possibly due to steric hindrance. As for the transesterification method, the one-pot-two-step method displayed higher yields (up to ~85%) compared to the one-pot-one-step method (up to ~70%) due to the complete formation of the ethyl ester intermediate. Overall, the Dean-Stark method has shown high yields of hypophosphite esters formation, allowing us to continue with Step 2, the Pd-catalyzed hydrophosphinylation with bromoalkenes.

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Nov 12th, 11:00 AM Nov 12th, 11:15 AM

Hypophosphite Ester Synthesis: A Comparison between Direct Esterification and Transesterification

HUB 269

Large oil spills in the ocean are catastrophic events which pose a threat to the environment and marine life. This project was inspired by the Deepwater Horizon oil spill that occurred in April 2010, and is relevant to the recent Santa Barbara oil spill from May 2015. Currently, oil dispersants containing carbon-based surfactants are commonly used for clean-up. Surfactants help the oil disperse into droplets, encouraging more efficient bioremediation by microorganisms. Our objective is to synthesize novel phosphorus-based surfactants. Phosphorus is a vital element for life, so it is anticipated that phosphorus-based surfactants could increase the growth of bioremediating organisms and generate phosphates as bi-products as they decompose, thus providing a more environmentally friendly alternative. Our three-step synthetic route involves hypophosphite esters and a palladium-catalyzed hydrophosphinylation with bromoalkenes, followed by a reaction with a tertiary amine. We have established Step 1 of our process by synthesizing long-chain hypophosphite esters, utilizing two different methodologies: direct esterification and transesterification. Direct esterification, or Dean-Stark method, allows for the removal of water during esterification, but uses only toluene as a solvent. In comparison, the transesterification method utilizes a broad solvent scope (acetonitrile, hexane, toluene, or cyclohexane) along with a silicon derivative. The 31P crude NMR yields from both methodologies have been compared using different classes of alcohols. Results show that primary and tertiary alcohols do not have a methodology preference, but secondary alcohols such as 2-pentanol favor direct esterification (85-100% yields), possibly due to steric hindrance. As for the transesterification method, the one-pot-two-step method displayed higher yields (up to ~85%) compared to the one-pot-one-step method (up to ~70%) due to the complete formation of the ethyl ester intermediate. Overall, the Dean-Stark method has shown high yields of hypophosphite esters formation, allowing us to continue with Step 2, the Pd-catalyzed hydrophosphinylation with bromoalkenes.