NMR detects p-anisonium ion in strong acid Phenonium-type ions formed by way of phenyl (aryl) participation exist at —70° C. in antimony(V) fluoride-sulfur dioxide solutions, according to Dr. George Olah of Case and Western Reserve University, Cleveland, Ohio. The existence of p-anisonium and 2,4,6-trimethylphenonium ions was indicated by nuclear magnetic resonance measurements [/. Am. Chem. Soc, 89, 711 (1967)]. Dr. Olah believes this is the first "ironclad" proof that these ions exist in acid systems. Dr. Olah and his coworkers, Dr. Eli Namanworth and Melvin B. Comisarow and Dr. Brian Ramsey of Akron University, Ohio, dissolved /?-p-anisylethyl chloride and /?-mesitylethyl chloride in solutions of antimony (V) fluoride-sulfur dioxide at - 7 0 ° C. The NMR spectra of the ion formed from /?-p-anisylethyl chloride show three types of protons. The cyclopropane protons appear at —3.47 p.p.m., the methoxy protons at —4.25 p.p.m., and the AB-type ring quartet at —8.12 and —7.47 p.p.m. The ion that evolves from /?-mesitylethyl chloride has an NMR spectrum with peaks for the 2- and 6-methyl protons at —2.38 p.p.m. and the 4-methyl protons at —2.60 p.p.m. The cyclopropyl protons show a sharp singlet at —3.77 p.p.m. and the 3- and 5-ring protons appear at —7.66 p.p.m. If the phenonium ions were quenched with methanol at —80° C , an 80% yield of the ^-methyl ethers CH 3 OC 6 H 4 CH 2 CH 2 OCH 3 and 2,4,6(CH 3 ) 3 C 6 H 2 CH 2 CH 2 OCH3 was obtained along with some a-methyl ethers, styrene, and polymers. When the Ohio chemists tried to generate the p-anisonium ion from /?-p-anisylethanol in fluorosulfonic acid-antimony(V) fluoride-sulfur dioxide, a stable diprotonated dication formed. If the temperature was higher than —70° C , /?-p-anisylethyl chloride in antimony(V) fluoride was partially converted to p-anisylmethylcarbonium ion. This carbonium ion is formed via a hydride shift from the openchain primary carbonium ion. The same ion appeared if a-p-anisylethanol was dissolved in fluorosulfonic acidantimony (V) fluoride-sulfur dioxide or if the chlorosulfite derivative was dissolved in thionyl chloride-antimony (V) fluoride-sulfur dioxide. Likewise, when the Ohio chemists tried to generate the phenonium ion from /?-2,4,6-trimethylphenylethyl alcohol in excess fluorosulfonic acidantimony (V) fluoride-sulfur dioxide, 56
C & E N FEB. 6, 1967
Aromatics form carbonium ions, dications, and phenonium ions at low temperatures 0CH3
SbF5Cf p-AMAA9Y*AL*4,
VOW
CM 3
SbF-
CHXCHZCI
2,4,6-l^xi^-
OCH3
HOcH3 FS0 3 H-SbF 5 -5o 2
(s^>
-6o°C. CHtCHjOH
CHXH,OK CH3
-,
o
FSo 3 H-SbF 5 -So,. c*SbF 5 -So 2
O
CH»
CH-CH* OH 2, A,
