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PTC Tip of the Month - Catalyst Separation
Sometimes we choose a phase-transfer catalyst more for its ability to be separated easily from the product than for its reactivity (e.g., in pharmaceutical applications in which product purity is more important than the cost of using twice as much quaternary ammonium salt). For example, it is often 50 to 1000 times easier to wash methyl tributyl ammonium into water away from the product than it is for the commonly used tetrabutyl ammonium (TBAB). This results in lower aqueous waste as well as lower residual catalyst in the product. On the other hand, if the product is water soluble (e.g., many carboxylate salts), then we would want to choose a catalyst which distributes 99.9% or more into the organic phase in the presence of an aqueous phase with high ionic strength. Such a catalyst may be methyl tricaprylyl ammonium.
Want to learn more about effective catalyst separation in real world PTC systems? Contact Marc Halpern at PTC Organics at tel +1 856-222-1146 or by E-mail.
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PTC 2-Hour Seminar - October
2003 in New Jersey
PTC Organics will conduct a free 2-hour PTC technical seminar entitled "Reducing Cost of Manufacture of Organic Chemicals Using Phase-Transfer Catalysis" at its Mt. Laurel, New Jersey office in October 2003 (date to be announced). Click here for abstract (2 hours = seminar + Q&A). The meeting will include lunch and will be held from noon to 2:00 pm for easy same day fly-in/fly-out (30 min from Philadelphia airport, 60 min from Newark airport). If you are interested in attending, please contact Marc Halpern at tel 856-222-1146 (US) or by E-mail.
PTC Reaction of the Month - Dehydrofluorination
US patent 6,548,719 (Honeywell) was issued just 3 weeks ago for a process for producing fluoroolefins by PTC dehydrofluorination of HFC's. The inventors demonstrate the effectiveness of crown ether. No examples using quats are given in the patent, but the use of quats is discussed and reads: "Among them [referring to quats], benzyltriethylammonium chloride is preferred for use under strongly basic conditions." Tip - That might not be the "preferred" quat. Take the short quiz below.
Quiz (see answers at bottom):
Question 1: Why did the inventors use crown ether and no examples with quats?
Question 2: Do you agree with the statement that benzyl triethyl ammonium chloride (TEBA) is preferred as a quat under strongly basic conditions? Why do you think the inventors would say this?
Question 3: Based on the TEBA statement, do you think that the inventors took our 2-Day PTC course?
PTC Breakthrough Process Screening
PTC Organics offers PTC Breakthrough Process Screening for rapid and highly effective evaluation of breakthrough phase-transfer catalysis processes. As the world leader in industrial phase-transfer catalysis, PTC Organics develops breakthrough high-performance low-cost PTC processes. Contact Marc Halpern at PTC Organics by E-mail, website, telephone (+1 856-222-1146) or fax (+1 856-222-1124).
PTC Organics at Chemspec
Learn how PTC Organics can help you improve process performance and process R&D effectiveness using Phase-Transfer Catalysis by scheduling a meeting with Marc Halpern at Chemspec to be held in Manchester, UK on June 5, 2003. The meetings will be held in the SOCMA lounge area (PTC Organics is a SOCMA member). Contact Marc Halpern at PTC Organics by E-mail, website, telephone (+1 856-222-1146) or fax (+1 856-222-1124).
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Answers to Quiz
Answer 1. I don't have a clue. The very expensive crown ether wouldn't be my first choice (a quat would), especially at the low temperature, though to be fair, they did use only 0.2 mole%.
Answer 2. TEBA is almost never preferred for strongly basic PTC reactions (by PTC experts in the past 10 years) because it is just about the least stable quat under strong base conditions (3 ethyl groups are particularly susceptible to Hofmann elimination and the benzyl group is susceptible to nucleophilic attack). Moreover, TEBA generally provides lower reactivity than other quats in published comparative PTC dehydrohalogenations (because most PTC dehydrohalogenations are "I-reactions"). So why do people use TEBA so often for PTC/OH reactions? Because Makosza used it in hundreds of publications for strong base PTC reactions in the 1960's and 1970's and that's what you find when you do a literature search for PTC/OH. Want to learn more about choosing a catalyst for PTC dehydrohalogenation? Contact Marc Halpern at PTC Organics at tel +1 856-222-1146 or by E-mail.
Answer 3. No. As of the public course this week, > 500 chemists from >90 companies have participated in the 2-day course "Practical PTC" and they should all know the answer to Question #2 (we even do an exercise comparing TEBA to other quats for dehydrohalogenation). Has your company participated?
performing any PTC reactions read this important message
Organic chemical reactions are inherently dangerous. Moreover, phase-transfer catalysis may provide rate and other enhancements which can intensify associated hazards. Under no circumstances should anyone perform any procedure on any scale based in whole or in part on any of the contents of this E-mail before thoroughly establishing safe operating procedures and performing a full and competent hazardous operations analysis with the participation of qualified technical personal trained in chemical, engineering, safety, industrial hygiene and environmental disciplines and sciences.
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PTC Tip of the Month #8 - May 2003
Copyright 2003 PTC Communications, Inc.
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