Ozone oxidation of surface-adsorbed polycyclic aromatic hydrocarbons: role of PAH-surface interaction

The heterogeneous chemistry of surface-adsorbed polycyclic aromatic hydrocarbons (PAHs) plays key roles in nanoscience, environmental science, and public health. Experimental evidence shows that the substrate can influence the heterogeneous oxidation of surface-bound PAHs, however, a mechanistic understanding of the role of the surface is still lacking. We examine the effects of the PAH-substrate interaction on the oxidation of surface-adsorbed anthracene, pyrene, and benzo[a]pyrene by ozone (O(3)) using density functional theory. We find that some O(3) oxidation mechanisms for these planar PAH molecules lead to nonplanar intermediates or products, the formation of which may necessitate partial desorption or "lift-off" from a solid substrate. The energy penalty for partial desorption of each PAH from the surface is estimated for four different substrate types on the basis of literature data and accounted for in the thermodynamic analysis of the reaction pathways. We find that the attractive PAH-substrate interaction may render oxidation pathways involving nonplanar intermediates or products thermodynamically unfavorable. The influence of the PAH-substrate interaction could contribute in part to the variations in PAH oxidation kinetics and product distributions that have been observed experimentally. Our choice of test molecules enabled us to identify trends in reactivity and product formation for four types of potentially reactive site (zigzag, armchair, bridge, and internal), allowing us to infer products and mechanisms of O(3) oxidation for PAHs of larger sizes. Implications for atmospheric chemistry and the stability of graphene in the presence of O(3) are discussed.     

Viscosimetric evaluation of solvent effects

The intrinsic viscosities of methylene blue, glucose and dextran were determined in various solvents. They are linear againstY Winstein-Grunwald solvent parameters. The relation observed offers an alternative route of the evaluation of the solvent effects by means of viscosimetric measurements.

---

Viskosimetrische Auswertung von Lösungsmittel-Effekten

Zusammenfassung Die Grenzviskositäten von Methylenblau, Glukose und Dextran wurden in verschiedenen Lösungsmitteln bestimmt. Sie sind gegen denWinstein-Grunwald-LösungsmittelparameterY linear. Die festgestellte Beziehung bietet einen alternativen Weg zur Bestimmung von Lösungsmitteleffekten mittels viskosimetrischer Messungen.

     

Re-examination of Nucleophilic Substitutionin Chlorokojic Acid

 Chlorokojic acid was reacted with S₂O₃ ²⁻, NO₃ ⁻, N₃ ⁻, I⁻, and SCN⁻. Only the three latter nucleophiles substituted the chlorine atom in the 2-CH₂Cl group of kojic acid. In none of the products nucleophilic substitution at position 6 of the 4-pyrone could be found. Regular substituion of chlorokojic acid with I⁻ (iodokojic acid), N₃ ⁻ (azidokojic acid), and SCN⁻ (thiocyanato and isothiocyanato kojic acids) was accompanied by formation of allomaltol. Reaction pathways for the formation of allomaltol and 6-substituted allomaltol derivatives are proposed. The latter has been formerly discovered in the reaction of chlorokojic acid with secondary amines.     

Illumination of Cellulose with Linearly Polarized Visible Light

Summary: Aqueous suspensions of cellulose of long polysaccharide chains, were illuminated with visible polarized light (VPL) for 20 and 50 hrs. Crystal structure, thermal properties with Differential Scanning Calorimetry (DSC) and degree of polymerization (DP) of the samples were determined. Additionally, kinetic of enzymatic as well as acid-catalyzed hydrolysis of cellulose was estimated. Illumination of cellulose with VPL for 50 hrs increased its DP by 15%. X-ray diffraction patterns revealed that the illumination resulted in an increase in the amount of cellulose crystalline phase. The DSC measurements indicated differences in the water molecules distribution depending on the sample treatment confirming an increase in the crystallinity of the illuminated cellulose. After prolonged illumination, cellulose was resistant to oxidation and had lower susceptibility to enzymatic and acid-catalyzed hydrolysis.     

Reduced products which are not saturated

Summary IfT is a complete theory of Boolean algebra, then we writeA ⊲_T B to denote that for every cardinal κ and every κ-regular filter over a setI such that the Boolean algebra 2 _F ^I of all subsets ofI reduced byF is a model ofT, the reduced powerA _F ^I isK ⁺-saturated wheneverB _F ^I isK ⁺-saturated. The relation ⊲_T generalizes the relation ◃ introduced by Keisler. As in the case of Keisler's ◃ it happens that ⊲_T’s are relations between complete theories, i.e. ifA≡B thenA ⊲_T B andB ⊲_T A. In this paper some examples of theories which are maximal (minimal) with respect to ⊲_T’s are provided and the relations ⊲_T are compared with each other. Presented by J. Mycielski     

Friedländer condensation of 1H-pyrazolin-5-ones with O-aminobenzaldehydes. Synthesis of 1H-pyrazolo[3,4-B]quinolines

All the possible 1- and 3-monomethyl, monophenyl, dimethyl, diphenyl, and methylphenyl-1H-pyrazolin-5-ones have been condensed with o-aminobenzaldehyde. In some cases (but not all) 1-H-pyrazolo[3,4-b]quinolines (10) are formed together with a variety of other products. The balance between formation of hydrazone 11 and the ring-closed 10 is discussed, as is the formation of other products obtained in these condensations.