A patent just issued last week to Sachem, one of the most veteran manufacturers of high purity quaternary ammonium phase-transfer catalysts, that describes how to inhibit color formation of quat hydroxides in non-aqueous solvents (glycols). Sachem has been a leader in the commercial supply of quat hydroxides, especially those used in the manufacture of semiconductors.
Quat hydroxides that contain at least one ethyl or higher alkyl group, can undergo Hofmann Elimination. Quat hydroxides are relatively stable to this decomposition at room temperature, though decomposition is possible with extended shelf life if not stored in a cool environment. It is speculated that the amine liberated by this quat decomposition mechanism can oxidize when exposed to air over time and create color compounds.
Sachem inventors found that the addition of small amount of hydantoin (10-5000 ppm) to non-aqueous solutions of quat hydroxide (20 wt%-50 wt%) containing less than 0.5 wt% water, can effectively inhibit color formation. Engel, T.; Van Lier, A.; (Sachem) US Patent 9,944,853, 17-Apr-2018
It is important to note that hydantoin (imidazolidine-2,4-dione) has two active N-H bonds, so if the quat hydroxide is being used to perform base-promoted alkylations or other reactions that may be affected by active N-H groups, small amounts of impurities may be formed by the reaction of hydantoin with reaction components unless the hydantoin is removed prior to the reaction.
Now contact Marc Halpern of PTC Organics if your company needs expert input for choosing the optimal phase-transfer catalyst for your commercial PTC application.
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!).
