Phase-Transfer Catalyzed Two-Phase Reactions in Preparative Organic Chemistry

Interfacial Processes—The Key Steps of Phase Transfer Catalyzed Reactions

After short historical introduction, interfacial mechanism of phase transfer catalyzed (PTC) reactions of organic anions, induced by aqueous NaOH or KOH in two-phase systems is formulated. Subsequently experimental evidence that supports the interfacial deprotonation as the key initial step of these reactions is presented.

Scale-up of N-alkylation reaction using phase-transfer catalysis with integrated separation in flow

Scaling-up phase-transfer catalysis in flow.

Determination of urinary steroid sulfate metabolites using ion paired extraction

The need for laboratories accredited by the World Anti-Doping Agency (WADA) to develop methods of analysis for steroids excreted primarily as their sulfate conjugates has faced significant analytical challenges. One of the issues relates to the extraction of these metabolites from urine in a relatively pure state. The use of (-)-N,N-dimethylephedrinium bromide as an ion pairing reagent was optimised to produce a method that is selective for the extraction of steroid sulfates prior to GC-MS or LC-MS analysis, with minimal contributions from the urine matrix. The recovery of androsterone from its sulfate conjugate was determined to be 67% with a relative quantitative uncertainty of +/-14% (k = 2).

Surfactant-assisted organic reactions in water. Effect of ultrasound on condensation reactions between active methylene compounds and arylaldehydes

A series of quaternary ammonium salts has been tested as phase transfer agents to promote condensation reactions in an aqueous solution of sodium hydroxide in the absence of any organic solvent. Methyltrioctylammonium chloride (Aliquat 336) emerges as the most efficient catalyst. Sonication of the reaction media has a poor but positive kinetic effect.

Emulsions from Aerosol Sprays

An electrostatic emulsification apparatus has been designed for the purpose of studying diffusion from oil droplets which have a mean size in the range of approximately 1.5-3.5 &mgr;m, with standard deviations of 40-50%. The emulsification technique involves the collection of a spray of electrically charged oil droplets onto a rotating water film which is sustained from a reservoir. In this way, emulsions with volume fractions of approximately 10(-3) are produced within several minutes at oil flow rates of around 10(-2) ml min-1. Phase-Doppler anemometry (PDA) was used to assess droplet size distributions for the sprays and emulsions. Results show that the mean emulsion droplet size was smaller than the mean spray droplet size by several orders of magnitude. At flow rates around 10(-2) ml min-1, the spray droplet size distribution was little affected by the applied potential between about -4.20 and -4.65 kV (mean droplet size between approximately 7.6 and 7.8 &mgr;m, with standard deviations of approximately 20%), whereas the mean droplet size of the corresponding emulsion decreased more rapidly with applied potential. Above an applied potential of approximately -4.30 kV, which corresponded to an emulsion droplet size below approximately 2 &mgr;m, the measured volume fraction of the emulsion decreased with respect to the volume fraction as calculated on the basis of total amount of injected oil. Copyright 1997 Academic Press. Copyright 1997Academic Press