Preferred Label : isokinetic relationship;
IUPAC definition : When a series of structurally related substrates undergo the same general reaction
or when the reaction conditions for a single substrate are changed in a systematic
way, the enthalpies and entropies of activation sometimes satisfy the relation: \[Δ
{\ddagger}H - \beta \ Δ {\ddagger }S {constant}\] where the parameter β is independent
of temperature. This equation (or some equivalent form) is said to represent an 'isokinetic
relationship'. The temperature T β (at which all members of a series obeying the
isokinetic relationship react at the same rate) is termed the 'isokinetic temperature'.
Supposed isokinetic relationships as established by direct correlation of Δ‡H with
Δ‡S are often spurious and the calculated value of β is meaningless, because errors
in Δ‡H lead to compensating errors in Δ‡S. Satisfactory methods of establishing such
relationships have been devised.;
Origin ID : I03285;
See also
When a series of structurally related substrates undergo the same general reaction
or when the reaction conditions for a single substrate are changed in a systematic
way, the enthalpies and entropies of activation sometimes satisfy the relation: \[Δ
{\ddagger}H - \beta \ Δ {\ddagger }S {constant}\] where the parameter β is independent
of temperature. This equation (or some equivalent form) is said to represent an 'isokinetic
relationship'. The temperature T β (at which all members of a series obeying the
isokinetic relationship react at the same rate) is termed the 'isokinetic temperature'.
Supposed isokinetic relationships as established by direct correlation of Δ‡H with
Δ‡S are often spurious and the calculated value of β is meaningless, because errors
in Δ‡H lead to compensating errors in Δ‡S. Satisfactory methods of establishing such
relationships have been devised.
