unstable

https://doi.org/10.1351/goldbook.U06569
The opposite of @[email protected], i.e. the @[email protected] concerned has a higher molar Gibbs energy than some assumed standard. The term should not be used in place of @[email protected] or @[email protected], although more reactive or transient species are frequently also more unstable. (Very unstable chemical species tend to undergo exothermic @[email protected] decompositions. Variations in the structure of the related chemical species of this kind generally affect the energy of the @[email protected] for these decompositions less than they affect the stability of the decomposing chemical species. Low stability may therefore parallel a relatively high rate of @[email protected] @[email protected])
Source:
PAC, 1994, 66, 1077. (Glossary of terms used in physical organic chemistry (IUPAC Recommendations 1994)) on page 1175 [Terms] [Paper]