The diagram shows an electrochemical process to form a useful dibenzocycloheptenone product. Several quaternary ammonium perchlorates were cited as electrolytes for this reaction. Tetraethyl ammonium perchlorate was used in several examples.
Sodium benzenesulfinate (PhSO2-Na+, not PhSO3- Na+ sulfonate) oxidizes at the anode to the benzensulfonate radical which in turn adds to the triple bond carbon alpha to the carbonyl to form an alkenyl radical that ring closes to form the seven membered ring in the product shown (dibenzocycloheptenone) after additional movement of electrons and loss of a proton.
It is interesting to note that the molar amount of the tetraethylammonium perchlorate is enough to oxidize the sulfinate to the sulfonate radical without the electrolytic cell, It makes one wonder if it would be worthwhile to try the oxidation with the quat perchlorate and see if the electrolytic setup is even necessary. For now, we assume that the quat ion pair is acting as an electrolyte in this system and not as an oxidizing reagent.
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!).
