1H and 19F nuclear magnetic resonance spectra of the adduct BF3.H2O

1967 ◽  
Vol 45 (8) ◽  
pp. 859-863 ◽  
Author(s):  
R. J. Gillespie ◽  
J. S. Hartman
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Low Temperatures ◽  
Boron Trifluoride ◽  
Proton Exchange ◽  
Rapid Proton ◽  
Rapid Proton Exchange ◽  
Nuclear Magnetic Resonance Spectra ◽  
Donor Acceptor ◽  
Nuclear Magnetic

It is shown by low-temperature 1H and 19F nuclear magnetic resonance (n.m.r.) spectroscopy that boron trifluoride monohydrate is formed in dilute solutions in acetone containing both water and BF3. In solutions in which [H2O] < [BF3], proton–fluorine coupling is observed which definitely establishes that in acetone solution at low temperatures the monohydrate is the simple donor–acceptor complex H2O → BF3. In solutions in which [H2O] > [BF3], no proton–fluorine coupling was observed because of rapid proton exchange.

EXCHANGE BROADENING OF SPIN–SPIN TRIPLETS IN NUCLEAR MAGNETIC RESONANCE SPECTRA. APPLICATION TO THE SYSTEM ETHANOL–WATER

1963 ◽  
Vol 41 (3) ◽  
pp. 714-720 ◽  
Author(s):  
W. G. Paterson
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Proton Exchange ◽  
Average Lifetime ◽  
Hydroxyl Proton ◽  
A Value ◽  
Nuclear Magnetic Resonance Spectra ◽  
Spin Triplets ◽  
Exchange Broadening ◽  
Nuclear Magnetic

Using an extension of the method of McConnell (1), an expression is derived for the nuclear magnetic resonance spectrum of a hydroxyl proton in a —CH2OH group which is undergoing intermolecular exchange. A graphical method is presented which enables a rapid evaluation of τ, the average lifetime of a hydroxyl proton between exchange events. Measurements of line widths and multiplet spacings in the n.m.r. spectra of ethanol—water solutions are interpreted in terms of the proton exchange reaction[Formula: see text]for which a value of 2.7 1. mole−1 sec−1 at 42 ± 1 °C is suggested as an upper limit to the rate constant.

Selenium-77 nuclear magnetic resonance studies of selenols, diselenides, and selenenyl sulfides

1988 ◽  
Vol 66 (1) ◽  
pp. 54-60 ◽  
Author(s):  
Khoon-Sin Tan ◽  
Alan P. Arnold ◽  
Dallas L. Rabenstein
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Chemical Shifts ◽  
Proton Exchange ◽  
Exchange Reactions ◽  
Nuclear Magnetic Resonance Spectra ◽  
Ph Range ◽  
Magnetic Resonance Spectra ◽  
Nuclear Magnetic

77Se and 1H nuclear magnetic resonance spectra have been measured for selenols (RSeH), diselenides (RSeSeR), and selenenyl sulfides (RSeSR′), including selenenyl sulfides formed by reaction of glutathione and penicillamine with selenocystine and related diselenides. Exchange processes strongly affect the 77Se and 1H nuclear magnetic resonance spectra of all three classes of compounds. Sharp, exchange-averaged resonances are observed in the 1H nuclear magnetic resonance spectra of selenols; however, selenol proton exchange causes the 77Se resonances to be extremely broad over the pH range where the selenol group is titrated. Selenol/diselenide exchange [Formula: see text] also results in exchange-averaged 1H resonances for solutions containing RSeH and RSeSeR; however, the 77Se resonances were too broad to detect. Exchange reactions have similar effects on nuclear magnetic resonance spectra of solutions containing selenols and selenenyl sulfides. The results indicate selenol/diselenide exchange is much faster than thiol/disulfide exchange. The 77Se chemical shift depends on the chemical state of the selenium, e.g., titration of the selenol group of selenocysteamine causes the 77Se resonance to be shielded by 164 ppm, oxidation of the selenol to form the diselenide selenocystamine causes a deshielding of 333 ppm, and oxidation to form the selenenyl sulfide [Formula: see text] results in a deshielding of 404 ppm. 77Se chemical shifts were found to be in the range −240 to −270 ppm (relative to (CH3)2Se) for selenolates, approximately −80 ppm for selenols, 230–360 ppm for diselenides, and 250–340 ppm for selenenyl sulfides. The 77Se chemical shift is also affected by titration of neighboring carboxylic acid and ammonium groups, and their pkA values can be calculated from 77Se chemical shift data.

Nuclear magnetic resonance studies of ketone•BF3 complexes. II. The boron trifluoride catalyzed condensation of acetone

1968 ◽  
Vol 46 (24) ◽  
pp. 3799-3811 ◽  
Author(s):  
R. J. Gillespie ◽  
J. S. Hartman
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Boron Trifluoride ◽  
Methylene Chloride ◽  
Aldol Condensation ◽  
Condensation Reaction ◽  
Magnetic Resonance Studies ◽  
Exchange Processes ◽  
Donor Acceptor ◽  
Nuclear Magnetic

A detailed study of the reactions of the acetone•BF3 complex in excess acetone has been carried out by "F nuclear magnetic resonance (n.m.r.) spectroscopy. It is shown that rapid reversible fluorine exchange processes occur in solution, in addition to the slower aldol condensation–dehydration reaction. Two of the new 19F absorptions which appear during the reaction are shown to arise from BF3 complexes of donors which are formed by condensation and dehydration of acetone. The rate of the aldol condensation reaction is shown to fall off markedly as an increasing proportion of the BF3 becomes complexed with water; thus BF3 catalysis of the reaction appears to depend on the existence of a ketone–BF3 donor–acceptor bond. 1H and 19F n.m.r. studies of the acetone•BF3 complex in methylene chloride throw some light on the apparent greatly decreased reactivity of the complex in this solvent. Evidence is presented for the reversibility of the first step of the condensation reaction.

A 19F Nuclear Magnetic Resonance Study of Halogen Exchange between Antimony Pentafluoride and Inorganic Chlorides. Complexes of Antimony and Arsenic Pentafluorides with Carbonyl Fluoride

1971 ◽  
Vol 49 (8) ◽  
pp. 1276-1283 ◽  
Author(s):  
J. Bacon ◽  
P. A. W. Dean ◽  
R. J. Gillespie
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Low Temperatures ◽  
Nuclear Magnetic Resonance Study ◽  
Antimony Pentafluoride ◽  
Magnetic Resonance Study ◽  
Halogen Exchange ◽  
Donor Acceptor ◽  
Carbonyl Fluoride ◽  
Nuclear Magnetic

19F nuclear magnetic resonance (n.m.r.) has been used to study the reactions occurring in the systems SbCl5–SbF5–SO2ClF, SO2Cl2–SbF5–SO2ClF, COF2–SbF5–SO2ClF, COF2–AsF5–SO2ClF, and COClF–SbF5–SO2ClF. Ionization occurs in SbCl5–SbF5–SO2ClF, yielding antimony chloro- and chloro-fluorocations and antimony polyfluoroanions. Donor-acceptor complexes are formed between SbF5 and SO2Cl2, COF2 or COClF at low temperatures and also between AsF5 and COF2. In all the complexes the ligand is oxygen-bonded. At higher temperatures halogen exchange and ionization occurs in SO2Cl2–SbF5–SO2ClF and COClF–SbF5–SO2ClF giving SO2ClF and COF2 complexes, respectively, together with antimony cations and polyfluoroanions. The alkyl chloride –SbF5 reaction is also shown to give chlorine-containing cations of antimony.

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