Fluorides and fluoro acids.  Part 18.  The system pyridine-hydrogen fluoride at low temperatures.  Formation and crystal structures of solid complexes with very strong NHF and FHF hydrogen bonding

Boenigk, D.; Mootz, D.

doi:10.1021/ja00215a021

Cited by 139 publications

(77 citation statements)

References 2 publications

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“…15 The evaluation can be also carried out by spectroscopic analysis using techniques such as IR spectroscopy to observe O-H, N-H, and COOH signals 7a,14b,16 and …”

Section: Resultsmentioning

confidence: 99%

The Salt−Cocrystal Continuum: The Influence of Crystal Structure on Ionization State

2007

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Salts and cocrystals are multicomponent crystals that can be distinguished by the location of the proton between an acid and a base. At the salt end of the spectrum proton transfer is complete, and on the opposite end proton transfer is absent in cocrystals. However, for acid-base complexes with similar pK a values, the extent of proton transfer in the solid state is not predictable and a continuum exists between the two extremes. For these systems, both the ∆pK a value (pK a of base -pK a of acid) and the crystalline environment determine the extent of proton transfer. A total of 20 complexes containing theophylline and guest molecules with ∆pK a values less than 3 have been prepared, resulting in 13 cocrystals, five salts, and two complexes with mixed ionization states based on IR spectroscopy and single-crystal diffraction data. We propose modifications to the ∆pK a rule for selecting salt screen counterions that focus on the discovery of solid forms with useful physical properties rather than an arbitrary cutoff value for ∆pK a .

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“…15 The evaluation can be also carried out by spectroscopic analysis using techniques such as IR spectroscopy to observe O-H, N-H, and COOH signals 7a,14b,16 and …”

Section: Resultsmentioning

confidence: 99%

The Salt−Cocrystal Continuum: The Influence of Crystal Structure on Ionization State

2007

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“…Consequently, the basicity of the N 2 nitrogen atom decreases, which is in favor of the protonation of the N 1 nitrogen atom of the pyridinic ring. Moreover, the C-N-C angles of the pyridine are very sensitive to protonation [32] [33]. A pyridinium cation always possesses an expanded C-N-C angle in comparison with the parent pyridine.…”

Section: Crystal Structurementioning

confidence: 99%

Synthesis, Crystal Structure and Infrared Characterization of Bis(4-dimethylamino-pyridinium) Tetrachlorocuprate

Nasr¹,

Lefèbvre²,

Nasr³

2015

AJAC

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“…These reactions are similar to the use of (HF); pyridine or trialkylamine complexes in the ring opening of cyclopropane (26), hydrocarbon epoxides (27), aziridines (28-3 l), and azirines (28,29); X-ray structures of (HF);py have recently been determined (32). The fluorinated heterocycles in this work, however, should be much less basic than the above examples and it is unlikely that (HF);py would be sufficiently acidic to protonate them.…”

Section: Resultsmentioning

confidence: 67%

Superacid-induced ring-opening reactions of fluorinated heterocycles

Kotun¹,

DesMarteau²

1989

Can. J. Chem.

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This paper is dedicated to Professor Ronald J . Gillespie on the occasion of his 65th birthday STEFAN P. KOTUN and DARRYL D. DESMARTEAU. Can. J. Chem. 67, 1724Chem. 67, (1989. HF/AsFS and HF/SbFS superacid mixtures react with fluorinated small-ring heterocycles such as 1,2-oxazetidines and oxetanes with consequent addition of HF to give alcohol and amine ring-opened products in high yield. Excess HF serves as solvent and reactant. Ring compounds containing both nitrogen and oxygen as heteroatoms protonate predominantly on nitrogen; a case with competing 0-protonation arises in the case of a chloro-substituted oxazetidine. In general, rings containing two heteroatoms retain the heteroatom-heteroatom bond and it is a carbon-heteroatom bond that opens. The resulting OH and NH functional groups are not protonated and lost in the superacid medium due to the instability of the highly fluorinated cations that would be left behind. Most of the heterocycles react at or below room temperature, although the very weakly basic 2,2-bis(trifluoromethyl)-3,3,4,4-tetrafluorooxetane requires the stronger HF/SbFS superacid system and more severe conditions. Key words: superacids, hydrogen fluoride, ring opening, fluorinated oxazetidines, fluorinated oxetanes.

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Fluorides and fluoro acids. Part 18. The system pyridine-hydrogen fluoride at low temperatures. Formation and crystal structures of solid complexes with very strong NHF and FHF hydrogen bonding

Cited by 139 publications

References 2 publications

The Salt−Cocrystal Continuum: The Influence of Crystal Structure on Ionization State

The Salt−Cocrystal Continuum: The Influence of Crystal Structure on Ionization State

Synthesis, Crystal Structure and Infrared Characterization of Bis(4-dimethylamino-pyridinium) Tetrachlorocuprate

Superacid-induced ring-opening reactions of fluorinated heterocycles

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