Kinetics and mechanism of malonate replacement in bis(malonato)oxovanadate(IV) by oxalate |
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| Institution: | 1. School of Chemistry & Chemical Engineering, Anhui University, Anhui 230039, China;2. School of Resources and Environmental Engineering, Anhui University, Anhui 230039, China;3. College of Environment, Hohai University, Jiangsu 210098, China;1. Pontifical Catholic University of Rio de Janeiro, Rio de Janeiro 22451900, Brazil;2. National Institute for Space Research, São José dos Campos 12227010, Brazil;1. National and Local Joint Engineering Laboratory of Mountain Road Engineering and Disaster Prevention and Mitigation Technology, Chongqing 400067, PR China;2. China Merchants Chongqing Communications Technology Research and Design Institute Co., Ltd., Chongqing 400067, PR China;3. School of Civil Engineering, Chongqing University, Chongqing 400045, PR China;4. China Construction Fourth Engineering Division Co., Ltd., Guangzhou, Guangdong 510663, PR China |
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| Abstract: | The kinetics of malonate replacement in bis- (malonato)oxovanadate(IV), VO(mal)2H2O]2?(hereafter water molecule will be omitted), by oxalate has been studied by the stopped-flow method. The reaction was found to consist of two consecutive steps (k1 and k2: first-order rate constants) passing through a mixed ligand complex, VO(mal)(ox)]2?. The rates for each step depended linearly on the concentrations of free oxalate species, Hox? and ox2?. The second-order rate constants for the replacement by ox2? were much larger in the k1 step than in the k2 step and the activation parameters were determined as follows: ΔH≠= 43.5 ± 5.6 kJ mol?1, ΔS±-53 ± 19 J K?1 mol?1 and ΔH≠= 43.6 ± 0.5 kJ mol?1, δS≠ = -62 ± 2 J K?l mol?1 for the k1 and k2 steps, respectively. The volume of activation was determined to be -0.65 ± 0.75 cm3 mol?1 at 20.2 °C by the high-pressure stopped-flow method for the apparent rate constants. |
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