| Autor: |
Kita, Ewa, Pietkiewicz, Aleksandra |
| Zdroj: |
Transition Metal Chemistry; Apr2000, Vol. 25 Issue 2, p126-132, 7p |
| Abstrakt: |
Oxidation of 2-(2-hydroxyethyl)pyridine (pyeol) to 2-pyridylacetaldehyde (pyeal) by CrVI has been studied in the 0.5–2.0 M HClO4 range at I = 2.2 M and in super acidic media within the 3–7 M HClO4 range. In all cases the reaction has been examined under pseudo-first order conditions keeping the alcohol and H+ aq in excess. CrIII-complexes formed during reduction of CrVI by pyeol at different molar ratios of the reactants, were isolated chromatographically and identified as [Cr(H2O)6]3+ and [Cr(pyeac)(H2O)4]2+ ions (pyeac = 2-pyridylacetic acid). Free 2-pyridylacetaldehyde (pyeal) was separated and determined as its 2,4-dinitro-phenylhydrazone derivative. A dependence of the rate constants on [pyeol] and [H+] has been established at I = 1.2 M and I = 2.2 M. The apparent activation parameters at [H+] = 1 and 2 M have been determined. A rate law of the form d[CrVI]/d t= ( k1[ H+]+ k2[ H+]2)[pyeol][CrVI] is proposed. A linear dependence of log kobs on H0 in the super acidic media is obeyed. A rate decrease is observed if oxygen instead of argon is in the reaction cell. The reaction mechanism has been discussed. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
|
Full text from SpringerLink