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Different acid–base behaviour of a pyrazole and an isoxazole with organic acids: crystal and molecular structures of the salt 3‐(4‐fluorophenyl)‐1 H ‐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)
Author(s) -
Girisha Marisiddaiah,
Yathirajan Hemmige S.,
Jasinski Jerry P.,
Glidewell Christopher
Publication year - 2016
Publication title -
acta crystallographica section c
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.304
H-Index - 17
ISSN - 2053-2296
DOI - 10.1107/s2053229616010494
Subject(s) - isoxazole , chemistry , pyrazole , hydrogen bond , cocrystal , protonation , ring (chemistry) , crystallography , delocalized electron , medicinal chemistry , crystal structure , stereochemistry , molecule , ion , organic chemistry
Pyrazole and isoxazole rings differ only in the notional replacement of a potential hydrogen‐bond‐donor NH unit in pyrazole by a potential hydrogen‐bond‐acceptor O atom in isoxazole. It is thus of interest to compare the hydrogen‐bonding characteristics of these rings. (4‐Fluorophenyl)pyrazole undergoes protonation in the presence of 2,4,6‐trinitrophenol to yield the salt 3‐(4‐fluorophenyl)‐1 H ‐pyrazolium 2,4,6‐trinitrophenolate, C 9 H 8 FN 2 + ·C 6 H 2 N 3 O 7 − , (I), whereas there is no proton transfer between 4‐amino‐ N ‐(3,4‐dimethyl‐1,2‐oxazol‐5‐yl)benzenesulfonamide and 3,5‐dinitrobenzoic acid, whose reaction gives the 1:1 cocrystal, C 11 H 13 N 3 O 3 S·C 7 H 4 N 2 O 6 , (II). The bond lengths in salt (I) provide evidence for aromatic‐type delocalization in the pyrazolium ring and for extensive delocalization of the negative charge into the ring of the trinitrophenolate anion. The O atoms of one of the nitro groups in the trinitrophenolate anion are disordered over two sets of atomic sites having occupancies of 0.571 (6) and 0.429 (6), but all of the other substituents on the carbocyclic rings are fully ordered. The ions in salt (I) are linked by an extensive series of N—H…O hydrogen bonds to form a three‐dimensional framework structure, and in cocrystal (II), the molecular components are linked by a combination of O—H…N and N—H…O hydrogen bonds to form complex bilayers. Comparisons are made with some related compounds.