Showing papers on "Fluorenone published in 1974"

Effects of polar substituents on photoreduction and quenching of aromatic ketones by amines. Fluorenone and substituted dimethylanilines

Abstract: Photoreduction of fluorenone by dimethylaniline in benzene leads to the 9-hydroxy-9-fluorenyl radical I and the N-methylanilinomethyl radical II, addition of II to the oxygen of ground state fluorenone forming radical III, and combination and cross combination of radicals I and III. Hydrolysis of these products leads to fluorenone pinacol, 97 percent yield, and to high yields of N-methylaniline and formaldehyde. Quantum yields for the photoreduction are at a maximum, approximately 0.8, with the unsubstituted dimethylaniline and with weak electron donating or withdrawing substituents. Quantum yields decrease with strong electron donating or withdrawing substituents. Very strong electron donation may lead to no photoreduction but to efficient quenching, presumably due to excessive stability of the initially formed charge-transfer complex. Values of k/sub ir/, rate constant for charge-transfer interaction of excited fluorenone triplet with the substituted dimethylanilines, have been measured in quenching studies. They vary from 3.2 x 10/sup 6/ M/sup -1/ sec/sup -1/ for the p-CN compound to approximately 10/sup 10/ M/sup -1/ sec/sup -1/ for the p-OEt and p-N(CH/sub 3/)/sub 2/ compounds and lead to a linear plot of log k/sub ir/ vs. sigma values, sigma/sup +/ for the strong electron donating substituents, sigma/sup -/ for p-CN, with rho = -1.96. more » Photoreductions of Methylene Blue by substituted phenylglycines, of benzophenone by substituted dimethylanilines and benzylamines, and of p-aminobenzophenone by dimethylanilines are discussed. « less

Alkali N.M.R. experiments on the radical ion pairs of biphenyl and fluorenone

Abstract: Line widths in the 6Li, 7Li, 23Na, 39K, 85Rb, 87Rb and 133Cs N.M.R. spectra of solutions of the alkali salts of biphenyl and fluorenone are reported as a function of solvent and temperature. From a numerical analysis of the room temperature data the contribution of the various relaxation mechanisms to the line widths are established. It is shown that the results are consistent with the observed solvent and temperature dependence of the line widths. Values of the electron spin correlation time are obtained and a value of 1·6 ± 0·4 A is found for the ‘Van der Waals radius’ of the biphenyl anion. Line width expressions for the static and the dynamic ion pair model are presented. It is demonstrated that the static ion pair model applies to solutions of caesium biphenylide. Semi-empirical rules are presented concerning the importance of various relaxation mechanisms for the different alkali nuclei in the type of solution studied here.

Preparation of fluorenone

Abstract: Fluorenone can be prepared from fluorene by contacting a solution of the latter in dimethyl sulfoxide with molecular oxygen in the presence of a small amount of an alkali-metal hydroxide.

The Reactions of Several Carbonyl Compounds with Hexamethylphosphoric Triamide

Abstract: Non-enolizable carbonyl compounds were found to undergo intriguing reaction upon heating with hexamethylphosphoric triamide; benzophenone gave 1,1,2,2-tetraphenylethane and benzophenone methylimine, while fluorenone afforded 9-methylfluorene, 9-dimethylaminofluorene, and fluorene. In contrast, anthrone, an enolizable compound, was completely recovered unchanged under the the same reaction conditions.

Dichlorocarbene addition to 1-methoxybiphenylene. Formation of a benzo[3,4]cyclobuta[1,2-c]tropone derivative

Abstract: 1-Methoxybiphenylene (1) reacts with dichlorocarbene to give 1-chlorobenzo[3,4]cyclobuta-[1,2-c]tropone (2) and two fluorenone derivatives (3) and (4).

Electronic structure calculations for large planar molecules by scf-scattered wave method

Abstract: Electronic structure calculations using the SCF‐scattered wave program of Johnson and Smith for the molecules carbazole, fluorenone, dinitrofluorenone, and trinitrofluorenone are reported. A qualitative description of the lowest excited states of these molecules is presented and a brief review of the theory underlying the calculations is given. Our calculations predict that the lowest excitation in carbazole should be polarized along the short molecular axis and in fluorenone along the long molecular axis. Polarized light absorption experiments should then provide an excellent check on the validity of these calculations. It is also shown that the lowest excitation in carbazole, fluorenone, and dinitrofluorenone should be a π→π* transition whereas in trinitrofluorenone it is suspected to be an n →π* transition. Comparison with minimal basis LCAO Hartree‐Fock calculations and experiments is made where possible.