Steric effects in hydrogen bonded columns of salts of benzoic acid and 1-adamantanecarboxylic acid with the cyclic amines CnH2n+1NH2, n = 5, 6, 7, 8 and 12

Abstract

The hydrogen bonded columns of salts of benzoic acid or adamantanecarboxylic acid and five cyclic amines are reported. During solution crystallization, the H from the carboxylic acid transfers to the amine to form ammonium carboxylate salts which feature three charge-separated N⁺–H⋯O⁻hydrogen bonds to form two types of 1-D hydrogen bonded columns. Of the ten structures, viz. (cyclopentylammonium·benzoate) (1), (cyclohexylammonium·benzoate) (2), (cyclododecylammonium·benzoate) (5), (cyclopentylammonium·adamantanecarboxylate) (6), (cyclohexylammonium·adamantanecarboxylate) (7) and (cyclododecylammonium·adamantanecarboxylate) (10) form a type IIhydrogen bonded column which consists of repeating R³₄(10) hydrogen bonded rings whereas (cycloheptylammonium·benzoate) (3), (cyclooctylammonium·benzoate) (4), (cycloheptylammonium·adamantanecarboxylate) (8), and (cyclooctylammonium·adamantanecarboxylate) (9) form a type IIIhydrogen bonded column, which consists of alternating R²₄(8)/R⁴₄(12) hydrogen bonded rings. Even with two sterically different anions, the type of hydrogen bonded column formed is the same for each counter cation and hence it is the size of the cyclic ammonium rings that influences the type of hydrogen bonded column. From this we can gather clues about the effect of the steric size of the cation and anion and its effect on the overall packing.