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Investigations on Croconic Acid in Superacidic Media
Author(s) -
Schickinger Manuel,
Jessen Christoph,
Morgenstern Yvonne,
Muggli Katharina,
Zischka Florian,
Kornath Andreas
Publication year - 2018
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201801035
Subject(s) - chemistry , triclinic crystal system , monoclinic crystal system , protonation , crystal structure , crystallography , stoichiometry , infrared spectroscopy , lewis acids and bases , x ray crystallography , stereochemistry , ion , organic chemistry , physics , diffraction , optics , catalysis
Croconic acid reacts in superacidic solutions HF/ M F 5 ( M = As, Sb) to yield its corresponding salts [H 3 O 5 C 5 ][ M F 6 ] and [(H 3 O 5 C 5 )H(H 3 O 5 C 5 )][ M F 6 ] 3 · 2HF ( M = As, Sb). The degree of protonation is strongly dependent on the stoichiometric ratio of the Lewis acid regarding croconic acid. Monoprotonated salts were characterized by vibrational spectroscopy and in the case of [H 3 O 5 C 5 ][AsF 6 ] ( 1 ) by a single‐crystal X‐ray structure analysis. [H 3 O 5 C 5 ][AsF 6 ] crystallizes in the monoclinic space group P 2 1 / c with four formula units per unit cell. The sesquiprotonated species of croconic acid [(H 3 O 5 C 5 )H(H 3 O 5 C 5 )][SbF 6 ] 3 · 2HF ( 4 ) was also characterized by single‐crystal X‐ray structure analysis. It crystallizes in the triclinic space group P 1 with one formula unit per unit cell. The vibrational spectra of the monoprotonated salts were compared to quantum chemical calculations of the [H 3 O 5 C 5 ] + · 3HF cation and experimental data reported for croconic acid.