Another reminder was reported this month that described how easy it is to form quat salts with organic anions.
In this case, an organic N-sulfate salt dissolved in water was first produced by reacting the hydroxyl amine shown in the diagram with a pyridine-sulfur trioxide complex in methylene chloride, then was treated with aqueous sodium bicarbonate.
The aqueous solution of the salt was contacted with an organic solution of tetrabutylammonium hydrogen sulfate in chloroform (not our first choice for an industrial process) and was stirred for 10 minutes. Finally, “the resulting organic layer was dried over anhydrous sodium sulfate, filtered, and then concentrated under reduced pressure to afford the product (yield 91%).”
As we teach in the 2-day course “Industrial Phase-Transfer Catalysis,” tetrabutylammonium hydrogen sulfate is often used to exchange anions since sulfate, formed from the hydrogen sulfate under basic conditions, is a dianion that is disfavored for pairing with the tetrabutylammonium cation. In this case, the anion to be paired with the quat, has 13 carbon atoms and therefore has a much higher affinity to the quat than the inorganic sulfate dianion.
In any case, liquid-liquid ion exchange of the anion paired with the quat cation is very often a simple procedure to execute and yield are high…when the anion desired to be paired with the quat at the end is more organophilic than the anion that is being replaced.
About Marc Halpern
Dr. Halpern is founder and president of PTC Organics, Inc., the only company dedicated exclusively to developing low-cost high-performance green chemistry processes for the manufacture of organic chemicals using Phase Transfer Catalysis. Dr. Halpern has innovated PTC breakthroughs for pharmaceuticals, agrochemicals, petrochemicals, monomers, polymers, flavors & fragrances, dyes & pigments and solvents. Dr. Halpern has provided PTC services on-site at more than 260 industrial process R&D departments in 37 countries and has helped chemical companies save > $200 million. Dr. Halpern co-authored five books including the best-selling “Phase-Transfer Catalysis: Fundamentals, Applications and Industrial Perspectives” and has presented the 2-day course “Practical Phase-Transfer Catalysis” at 50 locations in the US, Europe and Asia.
Dr. Halpern founded the journal “Industrial Phase-Transfer Catalysis” and “The PTC Tip of the Month” enjoyed by 2,100 qualified subscribers, now beyond 130 issues. In 2014, Dr. Halpern is celebrating his 30th year in the chemical industry, including serving as a process chemist at Dow Chemical, a supervisor of process chemistry at ICI, Director of R&D at Sybron Chemicals and founder and president of PTC Organics Inc. (15 years) and PTC Communications Inc. (20 years). Dr. Halpern also co-founded PTC Interface Inc. in 1989 and PTC Value Recovery Inc. in 1999. His academic breakthroughs include the PTC pKa Guidelines, the q-value for quat accessibility and he has achieved industrial PTC breakthroughs for a dozen strong base reactions as well as esterifications, transesterifications, epoxidations and chloromethylations plus contributed to more than 100 other industrial PTC process development projects.
Dr. Halpern has dedicated his adult life to his family and to phase-transfer catalysis (in that order!).
