Daniel Bruck

Protonation of acenaphthoquinone. A novel peripheral 10 π-electron aromatic system

Acenaphthoquinone (1) undergoes ppotonation to afford the respective double protonation product 2. The proton and carbon NMR parameters of 2 are discussed.

Observation of stable arylalkoxycarbenium ions: a nuclear magnetic resonance study

Stable carbenium ions are formed by treatment of acetals of aromatic aldehydes with BF3 or fluorosulphonic acid. The structure of these ions has been elucidated from their 1H chemical shifts. Additional evidence is the presence of a common counter ion in the series. Very good correlations were observed between the 1H chemical shifts and the respective Brown σ+ substituent constants emphasizing the dependence of these quantities on the charge density of the ions. The value of σ+ for the H–C+–OCH3 group is + 1.074 in the para-position and +0.916 in the meta-position, reflecting the strong electron-withdrawing properties of this group.