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Alkali metal salts of 4-hy­droxy­benzoic acid: a structural and educational study

As part of an educational exercise designed to introduce school students to the technique of single-crystal X-ray diffraction and enhance their understanding of primary and secondary bonding, a group of nine secondary school students was given the opportunity to prepare new com­pounds and to solve a...

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Detalles Bibliográficos
Autores principales: Abrahams, Brendan F., Commons, Christopher J., Hudson, Timothy A., Sanchez Arlt, Robin, White, Keith F., Chang, Michael, Jackowski, John J., Lee, Matthew, Lee, Shang X., Liu, Harrison D., Mei, Bill M., Meng, Joshua E., Poon, Lincoln, Xu, Xiaolin, Yu, Zekai
Formato: Online Artículo Texto
Lenguaje:English
Publicado: International Union of Crystallography 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8254528/
https://www.ncbi.nlm.nih.gov/pubmed/34216439
http://dx.doi.org/10.1107/S2053229621005465
Descripción
Sumario:As part of an educational exercise designed to introduce school students to the technique of single-crystal X-ray diffraction and enhance their understanding of primary and secondary bonding, a group of nine secondary school students was given the opportunity to prepare new com­pounds and to solve and refine data collected on the crystalline materials they had prepared. Their investigation of the alkali metal salts of 4-hy­droxy­benzoic acid (H(2)hba) yielded nine new com­pounds and their structures are described in this article. Whilst the salts might be expected to have similar atomic arrangements, there are significant differences in their structures. Although H(2)hba is a relatively simple organic mol­ecule, it displays remarkable coordinative flexibility, forming ionic solids containing the uncharged mol­ecule, the monoanion Hhba(−) or the dianion hba(2−). A common feature of the structures is their layered arrangement: alternating hydro­philic layers made up of closely packed metal–oxygen polyhedra separated by the hydro­phobic com­ponent of the hy­droxy­benzoate linking units. Close packing of these units seems to be a dominant influence in determining the overall structure. The hy­droxy­benzoate units are usually both parallel and anti­parallel with their immediate neighbours, with packing that can be edge-to-face, face-to-face or a mixture of the two. Hydrogen bonding plays a key role in the structure of most com­pounds and a short strong hydrogen bond (SSHB) is observed in two of the networks. The com­pounds of 4-hy­droxy­benzoic acid, C(7)H(6)O(3), described here are: poly[di-μ-aqua-μ-4-oxidobenzoato-dilithium], [Li(2)(C(7)H(4)O(3))(H(2)O)(2)]( n ), 1, poly[tri­aqua-μ-4-oxidobenzoato-dilithium], [Li(2)(C(7)H(4)O(3))(H(2)O)(3)]( n ), 2, poly[μ-4-hy­droxy­benzoato-lithium], [Li(C(7)H(5)O(3))]( n ), 3, catena-poly[4-hy­droxy­benzoate [[di­aqua­sodium]-di-μ-aqua]], {[Na(H(2)O)(4)](C(7)H(5)O(3))}( n ), 4, poly[di-μ-aqua-aqua-μ-4-hy­droxy­benzoato-potassium], [K(C(7)H(5)O(3))(H(2)O)(3)]( n ), 5, poly[μ-aqua-μ-4-hy­droxy­benzoato-potassium], [K(C(7)H(5)O(3))(H(2)O)]( n ), 6, poly[aqua-μ-4-hy­droxy­benzoato-rubidium], [Rb(C(7)H(5)O(3))(H(2)O)]( n ), 7, poly[aqua-μ-4-hy­droxy­benzoato-caesium], [Cs(C(7)H(5)O(3))(H(2)O)]( n ), 8, poly[[μ-aqua-aqua­(μ-4-hy­droxy­benzoato)(4-hy­droxy­benzoic acid)sodium] monohydrate], {[Na(C(7)H(5)O(3))(C(7)H(6)O(3))(H(2)O)(2)]·H(2)O}( n ), 9, poly[[(μ-4-hy­droxy­benzoato)(μ-4-hy­droxy­benzoic acid)rubidium] monohydrate], {[K(C(7)H(5)O(3))(C(7)H(6)O(3))]·H(2)O}( n ), 10, and poly[[(μ-4-hy­droxy­benzoato)(μ-4-hy­droxy­benzoic acid)rubidium] monohydrate], {[Rb(C(7)H(5)O(3))(C(7)H(6)O(3))]·H(2)O}( n ), 11.