ABSTRACT
The switchable polarity solvent (SPS) of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and an alcohol (e.g. 1-propanol) reversibly switches to a higher polarity ionic liquid, [DBUH(+)][RCO3(-)], when treated with CO2. A long-lived species with unique properties was detected in an investigation into the use of SPS to control the lifetime of the merocyanine (MC) form in a spiropyran (SP)-MC molecular photoswitch. Irradiation of SP in 1-propanol (PrOH) in the presence of DBU generates a new species (λmax = 420 nm). This species converts to MC upon bubbling with CO2, which produces [DBUH(+)][PrOCOO(-)]. It is proposed that a mixture of 1,2 and 1,4 alkoxide addition products form as a result of nucleophilic attack on the conjugated diene system of MC, where alkoxide formation arises from equilibration of highly basic DBU and the alcohol. These adducts revert to MC upon application of CO2 or addition of acid. Determination of the overall equilibrium constant for alkoxide adduct formation involving DBU was afforded through Benesi-Hildebrand analysis.
Subject(s)
1-Propanol/chemistry , Benzopyrans/chemistry , Bridged Bicyclo Compounds, Heterocyclic/chemistry , Indoles/chemistry , Nitro Compounds/chemistry , Molecular Structure , Photochemical Processes , Solvents/chemistryABSTRACT
A switchable hydrophilicity solvent (SHS) was studied for its effectiveness at extracting lipids from freeze-dried samples of Botryococcus braunii microalgae. The SHS N,N-dimethylcyclohexylamine extracted up to 22 wt.% crude lipid relative to the freeze-dried cell weight. The solvent was removed from the extract with water saturated with carbon dioxide at atmospheric pressure and recovered from the water upon de-carbonation of the mixture. Liquid chromatography-mass spectrometry (LC-MS) showed that the extracted lipids contained high concentrations of long chain tri-, di- and mono-acylglycerols, no phospholipids, and only 4-8% of residual solvent. Unlike extractions with conventional organic solvents, this new method requires neither distillation nor the use of volatile, flammable or chlorinated organic solvents.
