Sometimes, we don’t choose a phase-transfer catalyst based on how much reactivity it will induce, but rather based on how efficiently we can recycle the catalyst and at minimal cost.
In a PTC dehydrofluorination patent that issued this month, Aliquat 336 was chosen to selectively produce 1-chloro-2,3,3-trifluoropropene from 3-chloro-1,1,2,2-tetrafluoropropane with only 5% byproducts. The base was aqueous KOH.
We speculate, but do not know, that the reason for choosing Aliquat 336 instead of TBAB for example, was that Aliquat 336 is so hydrophobic that it will not distribute significantly into the aqueous phase, even during workup which usually involves dilute aqueous solutions. TBAB distributes into dilute aqueous solution and would likely be lost to the aqueous waste stream during workup. The losses of Aliquat 336 into the aqueous waste stream in such systems are often negligible.
If you want to learn how to choose PTC conditions like an expert, including how to simultaneously optimize reactivity and catalyst separation from product, bring the course “Industrial Phase-Transfer Catalysis” to your department in-house or register for a public PTC course. The next public PTC course will be conducted in Philadelphia in October 2018.
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!).
