No abstract

No abstract

Hepta-lf6-dienes disubstituted at C -4 with certain carbonyl-containing groups cyclise, in good yield, to the corresponding 4,4-disubstituted 1,2-dirnethylcyclopent-2-enes when treated with a catalytic amount of palladium acetate in chloroform containing hydrogen chloride. Changing the catalyst precursor to chlorotris(triphenylphosphine)rhodium( I ) led to the formation of the corresponding 1 -methyl-2-methylenecyclopentanes which, in turn, isomerised to 1,2-dimethylcyclopent-I -enes in ethanolic hydrogen chloride containing the rhodium complex. The effect of terminal substitution of the dienes with methyl groups was examined. 1,7-and 1,8-Dienes give rise to mixtures of five-membered ring products. Possible mechanisms for the catalytic processes are discussed. The X-ray crystal structure ana I ysis of d ic h loro (4,4d iacetyl hepta -1 6d iene) platinum ( I I ) is reported.

No abstract

Optical absorption and fluorescence emission spectroscopic techniques were employed to investigate the solvent effects on 2-methyl-1,4-naphthoquinone (2-mNQ) and the molecular recognition of 2-mNQ in calix(8)arene. The orientation of 2-mNQ on a silver surface was analysed by SERS. The optical absorption and fluorescence emission spectra of 2-mNQ in different solvents reveal the n → p * transition and the observed features show that the singlet excited state is more stabilized in polar protic solvents by intermolecular hydrogen bonding and in polar aprotic solvents by dipole-dipole interaction. The evidence for the formation of inclusion complexes of calix(8)arene with 2-mNQ in dichloromethane was obtained by optical absorption and fluorescence emission studies. From the observations, the existence of association of molecules is proposed and the association constant is evaluated. The orientation of 2-mNQ on a silver surface was studied by SERS measurements, and was found to be 'flat-on.'