
TY  - JOUR
A1  - Brasch, NE 
A1  - Buckingham, DA 
A1  - Clark, CR 
T1  - Nucleophilic Catalysis by HPO<sub>4</sub><sup>2-</sup> in the Hydrolysis of Cr<sub>2</sub>O<sub>7</sub><sup>2-</sup>. Formation and Decay of HO<sub>3</sub>POCrO<sub>3</sub><sup>2-</sup>
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1994
VL  - 47
IS  - 12
SP  - 2283
EP  - 2289
KW  - 
UR  - https://doi.org/10.1071/CH9942283 
N2  - The initial reaction of Cr2O72- in phosphate buffer (pH 6.03-8.54, 25.0&#176;C, I = 1.0 M NaClO4) follows the rate law kobs = kK [HPO42]/(1+K[HPO42-]). This is interpreted as arising from the reversible and rapid formation of a chromium(VI)- phosphato intermediate of increased coordination number (K = 5.5±1.3M-1), and rate-determining loss of CrO42- from this species (k = 4.4±0.5 s-1) to give HO3POCrO32- ( pKc a= 6.96). This appears to be the first clear demonstration of an addition-elimination (stepwise) mechanism for substitution at chromium (VI). Subsequent equilibration of HO3POCrO32- to give HCrO4- and H2PO4- (K = 5.95±1.90 M-1) is seen as a separate process which is subject to specific H+ and OH-, and general base (HPO42-) catalysis, in addition to a spontaneous reaction. 
ER  -

