Different acid-base behaviour of a pyrazole and an isoxazole with organic acids: crystal and molecular structures of the salt 3-(4-fluorophenyl)-1H-pyrazolium 2,4,6-trinitrophenolate and of the cocrystal 4-amino-N-(3,4-dimethyl-1,2-oxazol-5-yl)benzenesulfonamide-3,5-dinitrobenzoic acid (1/1).

摘要: Pyrazole and isoxazole rings differ only in the notional replacement of a potential hydrogen-bond-donor NH unit pyrazole by hydrogen-bond-acceptor O atom isoxazole. It is thus inter­est to compare hydro­gen-bonding characteristics these rings. (4-Fluoro­phen­yl)pyrazole undergoes protonation presence 2,4,6-tri­nitro­phenol yield salt 3-(4-fluoro­phen­yl)-1H-pyrazolium 2,4,6-tri­nitro­phenolate, C9H8FN2+·C6H2N3O7−, (I), whereas there no proton transfer between 4-amino-N-(3,4-dimethyl-1,2-oxazol-5-yl)benzene­sulfonamide 3,5-di­nitro­benzoic acid, whose reaction gives 1:1 cocrystal, C11H13N3O3S·C7H4N2O6, (II). The bond lengths (I) provide evidence for aromatic-type delocalization pyrazolium ring extensive negative charge into tri­nitro­phenolate anion. atoms one nitro groups anion are disordered over two sets atomic sites having occupancies 0.571 (6) 0.429 (6), but all other substituents on carbocyclic fully ordered. ions linked an series N—H⋯O hydrogen bonds form three-dimensional framework structure, cocrystal (II), mol­ecular components combination O—H⋯N complex bilayers. Comparisons made with some related compounds.