Organic Synthesis in Water/Carbon Dioxide Microemulsions

Abstract

Nucleophilic substitution reactions were performed in H2O/CO2 (w/c) microemulsions formed with an anionic perfluoropolyether ammonium carboxylate (PFPE COO-NH4 +) surfactant. These reactions between hydrophilic nucleophiles and hydrophobic substrates were accomplished in an environmentally benign microemulsion without requiring toxic organic solvents or phase transfer catalysts. For the synthesis of benzyl bromide from benzyl chloride and KBr, the yield was an order of magnitude higher in w/c microemulsions versus conventional water-in-oil (w/o) microemulsions. Benzoyl chloride and p-nitrophenyl chloroformate were hydrolyzed in w/c microemulsions with rate constants an order of magnitude faster than those in w/o microemulsions.

Hydrocarboxylation of Terminal Alkenes in Supercritical Carbon Dioxide

“…[5c,11] These dispersions have been used to solubilize hydrophilic substances into CO 2 , applied to organic reactions [11] and used to perform aqueous/scCO 2 biphasic metal-catalyzed reactions with water-soluble catalysts. [12] In a preliminary communication, we have recently reported that the use of a perfluoro-polyether surfactant enhances the activity and the regioselectivity to the linear acid although the selectivity decreases.…”

Hydroformylation of 1‐Octene in Supercritical Carbon Dioxide with Alkyl P‐Donor Ligands on Rhodium Using a Peracetylated β‐Cyclodextrin as a Solubiliser

“…[4] To overcome this limitation, ligands modified by the incorporation of perfluorinated chains, [5] polysilanes [6] and carbonyl groups [7] have been employed. Other possibilities include the use of soluble surfactants or mass transfer agents, which induce the formation of micelles with a high-density fluid phase [8,9] and thus increase the solubility of the catalyst in the scCO 2 .…”

Selective Oxidations on Recoverable Catalysts Assembled in Emulsions

“…One of the most general and efficient methods that can overcome this disadvantage is to use surfactants, which solubilize the reactants or form colloidal dispersion in reaction systems. The biphase systems thus obtained include phase-transfer catalysis [4][5][6][7][8], micellar catalysis [9][10], and microemulsion [11][12][13] or emulsion [14][15][16][17][18] according to the different reaction circumstances.…”

“…With the exception of the emulsion polymerization in chemical manufacturing [19], however, only a limited number of practical examples have been reported for catalytic reactions to date [11][12][13][14][15][16]. For the reactions in the emulsions, colloidal particles are formed with surfactant molecules that provide a high interfacial surface area and intensify the reaction.…”

“…However, one major shortcoming is that the emulsion droplet is usually difficult to demulsify after the reaction. Thus it is uneasy to separate the catalyst, surfactant and products from the reaction system [2,[13][14][15][16].…”