Novel Photochemical Hydrolysis of o-Acetylphenylacetonitriles to Amides

Irradiation of o-acetylphenylacetonitriles 1a,b in methanol (lambda >280 nm) leads to essentially quantitative photohydrolysis with formation of the corresponding ketal amides 3a,b. The mechanism proposed for this novel reaction is supported by the qualitatively different photochemical behavior of 1c and by a labeling experiment with 1a-L that confirms transfer of the carbonyl oxygen atom of 1a to the amide oxygen atom of 3a.     

Effect of Pr-Ca substitution on the transport and magnetic behavior of LaMnO3 perovskite

The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO₃ perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good example of these properties is (La_1−2x Pr _x Ca _x )MnO₃ (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T _c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for understanding the structural, transport and magnetic properties are discussed in detail.     

Light-induced reactions of 1,1,1-trifluoro-3-decyn-2-one with olefins

Irradiation ( λ = 300 nm) of 1,1,1-trifluoro-3-decyn-2-one in the presence of olefins affords RH-reduction products (tertiary alcohols) in addition to [2+2] -(oxetans) and [3+2] -(dihydrofurans) cycloadducts.     

Origin of the Hydrophobic Behaviour of Hydrophilic CeO2

The nature of the hydrophobicity found in rare-earth oxides is intriguing. The CeO₂ (100) surface, despite its strongly hydrophilic nature, exhibits hydrophobic behaviour when immersed in water. In order to understand this puzzling and counter-intuitive effect we performed a detailed analysis of the confined water structure and dynamics. We report here an ab-initio molecular dynamics simulation (AIMD) study which demonstrates that the first adsorbed water layer, in immediate contact with the hydroxylated CeO₂ surface, generates a hydrophobic interface with respect to the rest of the liquid water. The hydrophobicity is manifested in several ways: a considerable diffusion enhancement of the confined liquid water as compared with bulk water at the same thermodynamic condition, a weak adhesion energy and few H-bonds above the hydrophobic water layer, which may also sustain a water droplet. These findings introduce a new concept in water/rare-earth oxide interfaces: hydrophobicity mediated by specific water patterns on a hydrophilic surface.     

Photochemical [3 + 2] cycloaddition of α,β-acetylenic ketones with simple olefins

Irradiation of 3-pentyn-2-one (1) in the presence of tetramethylethylene, isobutylene, and cis- and trans -2-butene leads to vinyldihydrofurans 3,5,6, 8 and 9 (Table 1) in a novel [3 + 2] photochemical cycloaddition reaction. A related adduct 13 is formed between tetramethylethylene and 5,5-dimethyl-3-hexyn-2-one (2). A mechanism incorporating an initial biradical that closes to a carbene (eqn 3) is proposed to account for these reactions.     

Time-dependent Rayleigh-Bénard convection and instrumental attenuation

We present new thermal data on time-dependent convection in a cylindrically confined layer of helium with aspect ratio Γ=7.87 (Γ≡layer radius/layer height). Experimental data and an analysis of attenuation effects indicate broadband spectral features obtained by a global probe tend to be independent of Γ for Γ?5.     

Photochemical fragmentation of 4-alkylpyrimidines and 2-alkylquinolines

Hydrogen abstraction and fragmentation occur on acetone-sensitized photolysis of 4-alkylpyrimidines 1a-c with formation of 4-methylpyrimidine (2); the selectivity for primary, secondary, and tertiary hydrogen transfer is considerably greater in 1a-c than in 2-alkylquinolines 7a-c.