In the previous post, I discussed the structure of the free base form of tetrodotoxin, often represented as originally suggested by Woodward[cite]10.1351/pac196409010049[/cite] below in an ionic form: Quantum calculations suggested that this form was higher in energy than neutral forms devoid of the zwitterionic charge separation in a relatively non polar solvent such as chloroform. For this, a so-called continuum solvation model was used.