The rate constant, k1, for the following addition reaction between 4-isopropyltropolonate (ipt-) and meta-nitrophenylboronic acid (m-NO2PhB(OH)2) in acetonitrile was measured at various temperatures by using a low-temperature stopped-flow spectrophotometer:m-NO2PhB(OH)2+ipt -⇌k-1k1m-NO2PhB(OH) 2(ipt)-;k1 = 7.9 × 104M -1 s-1 at 25°C, ΔH1*=34. 7±1.0kJmol-1,ΔS1*=-34.8±3. 8Jmol-1K-1, which indicates that the interconversion between the trigonal boronic acid and the tetrahedral boronate ion is much faster than the chelate formations for the complexation of boronic acid with bidentate ligands, but much slower than the diffusion-controlled reactions.
- m-Nitrophenylboronic acid
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry