When an element has a range of oxidation states, there exist a number of reduction potentials for conversions between the various oxidation states. So, many redox couples may exist for a given element, and their identities may also depend on the pH of the solution, as different species exist in acidic and basic solutions. We need a systematic way to show … Read more
The use of reduction potentials to predict the course of reactions is limited to thermodynamic considerations only: if the overall reduction potential for the reaction, which is the difference of the reduction potentials of the individual couples, is positive, then there is a negative Gibbs free reaction energy and the reaction is thermodynamically spontaneous. Whether the reaction occurs, however, and the … Read more
The use of standard reduction potentials to predict the course of a reaction is somewhat limited, in that they are only valid under standard conditions. However, they can be used to predict the course of redox reactions under nonstandard conditions. This process of extrapolation of the properties of a reaction under one set of conditions to those under … Read more
Having defined the half-reaction and a potential associated with the reduction depicted by the half-reaction, we need to determine what the potential is. There need to be two half-cells to make up the whole cell, just as there are two half reactions which make up the full redox reaction. In defining potentials, they are made relative to the H+/H2 redox … Read more
When a redox operation proceeds, one species is oxidised and the other is reduced. It is useful to think of these two processes separately. For example, in the dissolution of zinc metal in acid: Oxidation: Reduction: The zinc metal is oxidized, and the protons are reduced to hydrogen gas. The splitting up of the overall … Read more
In a redox process, the oxidizing and reducing centers can react with or without a change in their coordination spheres. In some reactions, the electron transfer can only be accomplished by the transfer of a ligand from reducing agent to the oxidizing agent. There are two stoichiometric mechanisms: the inner sphere mechanism involves a ligand transfer, and a transient shared ligand, while … Read more
Base Catalyzed Hydrolysis: The CB Mechanism The rates of substitution of octahedral complexes are not sensitive to the nature of the entering group, with on exception. In basic media, CoIII complexes having ligands of the type NH3, RNH2, and R2NH are sensitive to the nature of the entering group. The base catalyzed reactions are generally much more rapid than hydrolyses in acid … Read more
The reactions of complexes are governed by the same kinetics as ordinary reactions. Transition State Theory says that the rate of a reaction is proportional to the equilibrium constant for formation of the activated complex, and leads to the result that fast reactions are favoured by positive activation entropies and small activation enthalpies (ΔG* = Eact). Reaction pathway for the complex reaction … Read more
Types of Mechanism for Substitution Reactions The mechanism of a reaction can be discussed in different ways. The sequence of elementary steps by which the reaction takes place is known as the stoichiometric mechanism, and the details of the activation process and formation of the activated complex in the rate determining step are known as the intimate mechanism. The Stoichiometric Mechanism Investigation of the dependence … Read more
There are various types of reactions of metals coordination complexes. These can be described as association and dissociation, substitution, oxidation and reduction, insertion and elimination, and oxidative addition and reductive elimination. This page aims to categorise each of the above reaction types, and list how the total number of electrons in the complex, the oxidation state of the metal and its d-electron count … Read more