Journal of Chemical Crystallography, VoL 26, No. 8, 1996 Note Molecular structure of 4-(3,5-dimethylpyrazol-l-yl)benzoic acid trifluoroacetate Foces-~oce~, Carlos Cativiela, (2)* Maria Mar Zurbano, (2) Concepci6n - - (1), Isabel Sobrados, (3) Nadine Jagerovic, (4) and Jos6 Elguero (4) Received December 5, 1995 The crystal and molecular structure of the title compound has been determined by X-ray analysis. 4-(3,5-Dimethylpyrazol-l-yl)benzoic acid trifluoroacetate crystallizes in the 12/a space groul~ with a = 20.6584(13), b = 9.9068(3), c = 14.9467(6) ,~,, 13 = 106.195(4), V = 2937.6(2) A 3, Dc = 1.494 glcm 3 and Z = 8. The ions pack in chains parallel to the a axis through O-H 9 9 9 O and N-H 9 9 9 O hydrogen bond interactions. Solid-state t3C CPMAS- NMR spectroscopy has been used to compare the structure of the trifluoracetate with that of the neutral molecule [4-(3,5-dimethylpyrazol-l-yl)benzoic acid]. KEY WORDS: Hydrogen bonds; t3C CPMAS NMR; benzoic acid; pyrazoles. Introduction Benzoic acids 11-3 and NH-pyrazoles 24 are two kinds of molecules which crystallize in dimers showing proton transfer in the solid state. R N--N 2 1" H 1 2 R 5 CO2H H3C~ CH3 N--N 2 1" H 3 ~U~Departamento de Cristalografia, Instituto de Qufmica F/sica 'Rocasolano', C.S.I.C., Serrano, 119, E-28006 Madrid, Spain. t2) Departamentode Quimica Org~inica,Instituto de Ciencia de Mat- eriales de Arag6n, C.S.I.C., Universidad de Zaragoza, E-50009 Zaragoza, Spain. (3)Instituto de Ciencia de Matefiales, C.S.I.C., Cantoblanco, E- 28048 Madrid, Spain. c4~ Instituto de Quimica M6dica, C.S.I.C., Juan de la Cierva 3, E- 28006 Madrid, Spain. *To whom correspondence should be addressed. 579 Benzoic acids and pyrazoles have in common a hydrogen-bond (HB) donor and a HB acceptor center in the same molecule: the OH and the C-O in the case of benzoic acids and the N(1)H and the N(2) in the case of pyrazoles. Due to these characteristics, they are able to self-replicate forming HB networks of a great diversity. We decided to explore the molecular structure and the HBs of one compound possessing both charac- teristics. For this purpose, compound 3 was synthesized and crystallized in trifluoroacetic acid. Experimental Synthesis Compound 3 was prepared from 4-iodoben- zoylchloride 4 using the sequence of reactions depicted in Scheme l (all compounds give correct microanalysis results at _+ 0.3 %). Solution NMR results (~H and L3C) were recorded with standard procedures using 200 and 300 MHz instruments. Solid-state t3C CPMAS NMR spectra were obtained with a Bruker MSL 400 spectrometer using the experimental conditions pre- viously described. 5 1074-1542/96/0800-0579509.50/0 C) 1996 Plenum Publishing Corporation