NUCLEAR MAGNETIC RESONANCE STUDIES OF THE PROTONATION OF WEAK BASES IN FLUOROSULPHURIC ACID: III. METHYLBENZENES AND ANISOLE

1964 ◽  
Vol 42 (3) ◽  
pp. 502-513 ◽  
Author(s):  
T. Birchall ◽  
R. J. Gillespie
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Carbon Atom ◽  
Proton Magnetic Resonance ◽  
Exchange Process ◽  
Proton Exchange ◽  
Magnetic Resonance Studies ◽  
Ring Carbon ◽  
Weak Bases ◽  
Ring Carbon Atom

The proton magnetic resonance spectra of solutions of mesitylene, durene, pentamethylbenzene, hexamethylbenzene, m- and p-xylenes, and anisole have been studied in fluorosulphuric acid and protonation on the ring carbon atom established. Rates of proton exchange have been measured and activation energies calculated for the proton exchange process. Intermolecular exchange with the solvent is suggested as the most probable exchange process in all cases.

NUCLEAR MAGNETIC RESONANCE STUDIES OF THE PROTONATION OF WEAK BASES IN FLUOROSULPHURIC ACID: II. AMIDES, THIOAMIDES, AND SULPHONAMIDES

1963 ◽  
Vol 41 (10) ◽  
pp. 2642-2650 ◽  
Author(s):  
T. Birchall ◽  
R. J. Gillespie
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Proton Magnetic Resonance ◽  
Carbonyl Oxygen ◽  
Conclusive Evidence ◽  
Sulphur Atom ◽  
Magnetic Resonance Studies ◽  
Weak Bases ◽  
Strong Acids ◽  
Magnetic Resonance Spectra

The proton magnetic resonance spectra of solutions of amides in fluorosulphuric acid confirm previous results which indicated that protonation of amides occurs on the carbonyl oxygen. A similar study of solutions of thioacetamide, thioacetanilide, thiourea, and N-methylthiourea provides conclusive evidence that the sulphur atom is protonated in these bases. In the case of N-methyl- and N,N′-dimethyl-p-toluenesulphonamide and sulphamide protonation occurs on nitrogen rather than on oxygen. It was not possible to obtain any conclusive evidence on the site of protonation of urea and N,N′-dimethylurea. Evidence is presented which indicates that thiourea and N-methylthiourea are diprotonated in solution in strong acids such as fluorosulphuric acid, and diprotonation of urea and N,N′-dimethylurea under the same conditions also seems very likely.

NUCLEAR MAGNETIC RESONANCE STUDIES OF THE PROTONATION OF WEAK BASES IN FLUOROSULPHURIC ACID: IV. PHENOLS AND AROMATIC ETHERS

1964 ◽  
Vol 42 (6) ◽  
pp. 1433-1439 ◽  
Author(s):  
T. Birchall ◽  
A. N. Bourns ◽  
R. J. Gillespie ◽  
P. J. Smith
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Perchloric Acid ◽  
Ultraviolet Spectroscopy ◽  
Aromatic Carbon ◽  
Magnetic Resonance Studies ◽  
Weak Bases ◽  
Nuclear Magnetic

The n.m.r. spectra of phenol, anisole, and other phenols and aromatic ethers in solution in fluorosulphuric acid and in 70% perchloric acid show that in every case they protonate on an aromatic carbon. Earlier evidence from ultraviolet spectroscopy that phenol and anisole protonate on oxygen is reinterpreted.

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