Broensted superacidity of HCl in a liquid chloroaluminate. AlCl sub 3 -1-ethyl-3-methyl-1H-imidazolium chloride

Journal Article · Wed Jan 18 00:00:00 EST 1989 · Journal of the American Chemical Society; (USA)

DOI:https://doi.org/10.1021/ja00184a020· OSTI ID:5093894

Smith, G P; Dworkin, A S; Zingg, S P ^[1]; Pagni, R M ^[2]

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1. Oak Ridge National Lab., TN (USA)
2. Univ. of Tennessee, Knoxville (USA)

The system HCl (0.1-1 atm)/AlCl{sub 3}-EMIC (55.0 mol % AlCl{sub 3}) (EMIC = 1-ethyl-3-methyl-1H-imidazolium chloride) at 23{degree}C is a Broensted superacid capable of protonating arenes to a degree similar to that of liquid HF at 0{degree}C (H{sub 0} = {minus}15.1). Arenes used in this investigation were biphenyl (I), naphthalene (II), 9H-fluorene (III), chrysene (IV), 2-methylnaphthalene (V), mesitylene (VI), pentamethylbenzene (VII), hexamethylbenzene (VIII), anthracene (IX), and 9,10-dimethylanthracene (X). In both the chloroaluminate melt and HF I is a weak base while VIII-X are strong bases. In between these extremes the order of basicities in both media is II < III and IV < V < VI < VII < VIII. A study of the effect of HCl partial pressure showed, for example that V is 50% protonated at 0.3 atm HCl. The overall reaction is arene + HCl + Al{sub 2}Cl{sub 7}{sup {minus}} {r reversible} arene {times} H{sup +} + 2AlCl{sub 4}{sup {minus}} and is reversible. The degree of protonation was measured by optical absorption spectrophotometry. The arenes are stable in the liquid chloroaluminate for many hours, and their protonated forms (arenium ions) are stable for 1 h or more. A new procedure for the preparation of EMIC was developed that yields exceptionally clean AlCl{sub 3}-EMIC melts with very low concentrations of protic and oxidizing impurities. 17 refs., 6 figs., 2 tabs.

• DOE Contract Number: AC05-84OR21400
• OSTI ID: 5093894
• Journal Information: Journal of the American Chemical Society; (USA), Vol. 111:2; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
HYDROCHLORIC ACID
PH VALUE
ALUMINIUM CHLORIDES
EXPERIMENTAL DATA
IMIDAZOLES
ORGANIC CHLORINE COMPOUNDS
ALUMINIUM COMPOUNDS
AZOLES
CHLORIDES
CHLORINE COMPOUNDS
DATA
HALIDES
HALOGEN COMPOUNDS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
INFORMATION
INORGANIC ACIDS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
400201* - Chemical &amp; Physicochemical Properties