IUPAC definition : As applied to chemical species, the term expresses a thermodynamic property, which
is quantitatively measured by relative molar standard Gibbs energies. A chemical species
A is more stable than its isomer B if Δ r G 0 for the (real or hypothetical) reaction
\[{A}\quad \rightarrow \quad {B}\] under standard conditions. If for the two reactions:
\[{P}\rightarrow {X} {Y}\qquad (Δ _{{r}}G_{1} {{o}})\] \[{Q}\rightarrow {X} {Z}\qquad
(Δ _{{r}}G_{2} {{o}})\] Δ r G 1 o Δ r G 2 o, P is more stable relative to the product
Y than is Q relative to Z. Both in qualitative and quantitative usage the term stable
is therefore always used in reference to some explicitly stated or implicitly assumed
standard. The term should not be used as a synonym for unreactive or 'less reactive'
since this confuses thermodynamics and kinetics. A relatively more stable chemical
species may be more reactive than some reference species towards a given reaction
partner.;
As applied to chemical species, the term expresses a thermodynamic property, which
is quantitatively measured by relative molar standard Gibbs energies. A chemical species
A is more stable than its isomer B if Δ r G 0 for the (real or hypothetical) reaction
\[{A}\quad \rightarrow \quad {B}\] under standard conditions. If for the two reactions:
\[{P}\rightarrow {X} {Y}\qquad (Δ _{{r}}G_{1} {{o}})\] \[{Q}\rightarrow {X} {Z}\qquad
(Δ _{{r}}G_{2} {{o}})\] Δ r G 1 o Δ r G 2 o, P is more stable relative to the product
Y than is Q relative to Z. Both in qualitative and quantitative usage the term stable
is therefore always used in reference to some explicitly stated or implicitly assumed
standard. The term should not be used as a synonym for unreactive or 'less reactive'
since this confuses thermodynamics and kinetics. A relatively more stable chemical
species may be more reactive than some reference species towards a given reaction
partner.