Norman Kulevsky

Infrared spectra of the iodine complexes of mono N-oxides of some heterocyclic diazines

Abstract The N-O stretching frequencies of the I 2 , complexes of the mono N-oxides of some heterocylic diazines have been observed. These data give some indication that in all the compounds investigated, it is the oxygen and not the ring nitrogen that acts as a donor site.

PHOTOCHEMICAL OXIDATIONS—IV. THE PHOTOOXIDATION OF CYCLOHEXANE WITH OXYGEN

Abstract— –For the photooxidation of cyclohexane, data on the rates of formation of cyclohexanol (I), cyclohexanone (II), and cyclohexylhydroperoxide (III) are presented. There are induction periods for the formation of I and II but not for III. The alcohol (I) is not the precursor of II in this reaction. The photooxidation does not occur when optical filters eliminate wavelengths of 260 nm or less from the incident light, and therefore the contact charge transfer absorption is responsible for the initiation of the reaction. Ozone is not involved to any significant extent in this reaction. The photodecomposition of III produces I and II, and this decomposition is first order during the initial stages. An overall 11 step mechanism is suggested for the photooxidation.

Molecular complexes of iodine with metal acetylacetonates

Abstract The ability of metal acetylacetonates to act as electron donors and form molecular complexes with I 2 was studied by examining the electronic, vibrational, and NMR spectra of the complexes. The specific compounds used in the study were Al(acac) 3 Sc(acac) 3 Zr(acac) 4 , and Th(acac) 4 . The electronic spectra of mixtures of the metal acetylacetonates with I 2 in CHCl 3 had, in addition to the absorption peaks characteristic of the free components, two peaks that were due to the charge transfer complexes. For each complex, the highest wavelength peak (near 360 nm) was assigned to the blue shifted I 2 band, while the lower peak (between 270 nm and 305 nm) was attributed to the intermolecular charge transfer. In the i.r. spectra of each complex, the major effect of complexation was to cause the I 2 stretching frequency to appear between 145 cm −1 and 160 cm −1 . The positions of the absorption peaks in both the electronic and vibrational spectra led to the conclusion that in these complexes, I 2 had received a large amount of charge from the donors. Complex formation had little effect on the NMR spectra of the donors. Association constants of 1:1 complexes were determined from the concentration dependence of the absorbance of the blue shifted I 2 bands. Values of Δ H dg and Δ S ° 298 for the complex formation were obtained from the temperature variation of the association constants. The data indicate that the complexes are extremely stable species. Both the stability of the complexes and the high degree of charge transfer were rationalized by considering a model for the intermolecular interactions that involved two M (acac) rings simultaneously transferring charge from one donor to an I 2 molecule.

PHOTOCHEMICAL OXIDATIONS — VI. THE NATURE OF THE DONOR SITE IN THE OXYGEN-HYDROCARBON CONTACT CHARGE-TRANSFER COMPLEX

Abstract— Two sets of experiments, designed to determine whether the C—C or C—H bonds of hydrocarbons act as the donor site in the contact charge‐transfer complex between oxygen and hydrocarbons, were performed. It was found that the rates of oxygen uptake during the photooxidation increase with decreasing ‘s character’ of the C—H bond. Also, the rates of product accumulation during the induction period were shown to increase with basicity of the C—H bond, i.e., tertiary C—H > secondary C—H > primary C—H. The conclusion from these data is that the C—H bond is the donor site.

The formation of bifurcated charge transfer complexes with molecular iodine

Abstract I 2 complexes with triptycene and several di- and triaryl derivatives of methane and ethane were studied. For these complexes the values of λ CT are virtually identical to those reported for the complexes with the analogous monoaryl donors, while the values of λ for their blue shifted I 2 peaks are significantly lower than those for the monoaryl complexes. Both the equilibrium constants and - ΔH 0 values for the formation of complexes from the components lead to the conclusion that the complexes with the di- and triaryl compounds are more stable than those with the monoaryl donors. For the diaryl donors, the Δ S 0 298 values for complex formation are less favorable than those of the monoaryl donors. The dipole moment for I 2 in diphenylmethane is larger than the moment of I 2 in toluene. All of these observations can be explained by taking into account the transannular effect of one aromatic ring on another and viewing the complexes as bifurcated ones in which the I atom at one end of an I 2 molecule simultaneously interacts with two rings in the donor molecules.