## Z-value

https://doi.org/10.1351/goldbook.Z06737
An index of the @[email protected] of a solvent based on the frequency of the longest @[email protected] electronic absorption maximum of 1-ethyl-4-methoxycarbonylpyridinium iodide in the solvent. The Z-value is defined by: $Z = \frac{2.859\,\times\,10^{4}}{\lambda}$ where $$Z$$ is in $$\text{kcal mol}^{-1}$$ and $$\lambda$$ is in $$\text{nm}$$.