ERRATUM

Hirsch, Joseph A.: "Structure-activity relationship between guanidine alkyl derivatives and norepinephrine release: Site(s) and mechanism(s) of action," vol. 230, no. 3, September, 1984, pp. 710-717.

The publisher regrets that the diagrams on p. 716 contained errors. The corrected version with accompanying text is reprinted below:

Guanidine belongs to the family of compounds known as amidines. Amidines are highly basic compounds; guanidine, for example, has a pK_a of 13.6, which makes it almost as strong a base as sodium hydroxide (Fastier, 1962; Durant et al., 1970). Accordingly, the following scheme describing the binding of amidinium ions to negatively charged species, especially the carboxylate ion, may be represented (Walker, 1949; Kennard and Walker, 1963):

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(Note: in guanidine R = NH₂). The carboxylate ion is also a resonating system, and may be represented:

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Since the resonance of both the cation and the anion are complementary to each other, ionic bonds may be formed simultaneously between the two nitrogen atoms sharing the positive charge and the two oxygen atoms sharing the negative charge, with the hydrogen bonds being short and relatively strong. This new structure, in which all the atoms shown are coplanar, may be represented:

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