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Rates and pH‐dependent product distributions of the CuCl 2 ‐catalyzed dediazoniation of p ‐nitrobenzenediazonium tetrafluoroborate in aqueous acid
Author(s) -
BravoDíaz Carlos,
Romsted Laurence S.,
Harbowy Mathew,
RomeroNieto Ma. Emma,
GonzalezRomero Elisa
Publication year - 1999
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/(sici)1099-1395(199902)12:2<130::aid-poc107>3.0.co;2-9
Subject(s) - chemistry , nitrobenzene , yield (engineering) , aqueous solution , heterolysis , tetrafluoroborate , kinetics , catalysis , resorcinol , medicinal chemistry , inorganic chemistry , photochemistry , organic chemistry , thermodynamics , physics , ionic liquid , quantum mechanics
The rates of formation and yields of products from the dediazoniation of p ‐nitrobenzenediazonium tetrafluoroborate (PNBD) in aqueous solutions over a range of HCl, NaCl and CuCl 2 concentrations at 60 °C were examined. Two main products were observed: p ‐nitrophenol (ArOH) and p ‐nitrochlorobenzene (ArCl). Trace amounts of nitrobenzene (ArH) and p ‐nitrofluorobenzene (ArF) were detected. Added CuCl 2 speeds the reaction and both the rate of dediazoniation and ArOH yield (unlike ArCl) are very sensitive to pH. The results are completely consistent with the heterolytic dediazoniation mechanism, i.e. rate‐determining formation of a highly reactive aryl cation followed by competitive formation of dediazoniation products. PNBD kinetics are first order (with respect to PNBD) in the absence of and presence of CuCl 2 , except at low acidity and in the presence of low to moderate CuCl 2 concentrations. The non‐first‐order kinetics are attributed to a competing reaction between PNBD and the ArOH product. The results suggest a simple method for preparing halobenzenes in high yield. Copyright © 1999 John Wiley & Sons, Ltd.