The negative of the Gibbs energy (\(\Delta G_{\text{r}}^{\,\unicode{x26ac}}\)) change for the reaction:
G02587.png
in the gas phase.
Source: PAC, 1994,
66, 1077. (
Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1116 [
Terms] [
Paper]