No abstract

ABMX analysis of the N.M.R. spectra of six bridged biquaternary salts of 2,2?-bipyridyl is reported. The difference in chemical shift between H3(3?) and H5(5?) varies with the length of the bridging group, and the results are discussed in relation to the probable conformation of the salts. The several factors determining the difference in chemical shift are discussed, and it is concluded that the diamagnetic anisotropy of the neighbouring pyridinium ring is the major contributor, with further significant contributions from the asymmetric distribution of positive charge in the pyridinium ring. Interplanar angles are calculated and compared with values estimated for the singly bridged biphenyls; evidence for mobile and frozen conformations is presented.

The preparation of the dipyrido[l,2-c:2?,1?-e]imidazolium cation (I) and some substituted cations from 2,2'-bipyridyls and gem-dihalides is described. As expected, (I) exhibits reactions typical for both a-electron excessive and n-electron deficient aromatic ring systems. Thus, (I) may be brominated, methylated, benzoylated, and acetylated at the 6-position; the cation (I) also adds to methyl vinyl ketone. The action of hydroxyl ions in the presence of air produces the corresponding 2,2'-bipyridyls, as does the action of light and air. The rate of bromination of the 6-phenyl derivative (XII) to give the 2,10-dibromo cation (XVI) is comparable to that of naphthalene. The 6-acyl derivatives (XIX) are converted to the parent cation (I) by the action of either acid or base.

No abstract

N-Acetyl-2,3,5,6-tetrachloro-p-benzoquinone imine is best prepared by direct chlorination of N-(4-hydroxyphenyl)acetamide. The tetrachloro quinone imine is a stable compound with a high oxidation-reduction potential and may be a useful addition to the range of conventional high potential quinones. Some typical oxidation reactions are described as well as some reactions with nucleophilic reagents.