Reaction mechanism

The conjectured mechanism is chosen because it is thermodynamically feasible and has experimental support in isolated intermediates (see next section) or other quantitative and qualitative characteristics of the reaction.

A often quoted mechanistic experiment involved the reaction of the labile hexaaquo chromous reductant with the exchange inert pentammine cobalt(III) chloride.

The transition states are, in contrast, fleeting, high-energy species that cannot be isolated.

[2] Illustrative is the oxidation of carbon monoxide by nitrogen dioxide: The rate law for this reaction is:

A chain reaction is an example of a complex mechanism, in which the propagation steps form a closed cycle.

An example of a simple chain reaction is the thermal decomposition of acetaldehyde (CH3CHO) to methane (CH4) and carbon monoxide (CO).

The exact rate law may be even more complicated, there are also minor products such as acetone (CH3COCH3) and propanal (CH3CH2CHO).

For many combustion and plasma systems, detailed mechanisms are not available or require development.

Even when information is available, identifying and assembling the relevant data from a variety of sources, reconciling discrepant values and extrapolating to different conditions can be a difficult process without expert help.

Rate constants or thermochemical data are often not available in the literature, so computational chemistry techniques or group additivity methods must be used to obtain the required parameters.

Computational chemistry methods can also be used to calculate potential energy surfaces for reactions and determine probable mechanisms.

In general, reaction steps involving more than three molecular entities do not occur, because is statistically improbable in terms of Maxwell distribution to find such a transition state.

S N 2 reaction mechanism. Note the negatively charged transition state in brackets in which the central carbon atom in question shows five bonds, an unstable condition .
A reaction mechanism shows how acetone reacts with methanol in acidic environment using curved arrow (electron or arrow pushing method)
Henry Taube 's experiment establishing the role of a bridging ligand in inner sphere electron transfer .
Benzoin condensation reaction mechanism . Cyanide ion (CN − ) acts as a catalyst here, entering at the first step and leaving in the last step. Proton (H + ) transfers occur at (i) and (ii). The arrow pushing method is used in some of the steps to show where electron pairs go.