ALBERT

Description: The effect of metal ions (M n+  = Na + , K + , Mg 2+ , Ca 2+ , Zn 2+ and hydrated Mg 2+ ions) and water molecules on the tautomerism of adenine induced by single intramolecular proton transfer (SPT) have been investigated theoretically. Calculated results show that the single proton transfer process in adenine base is favored and even becomes thermodynamically spontaneous because of the presence of M n+ interacting at the N 3 position of adenine. On the contrary, if M n+ coordinated to N 7 site, the single proton transfer process will become unfavorable than that in the neutral system. The effects of metal ions on the SPT of adenine base are more pronounced if Lewis acidity of metal ion is increased. Water plays a more important role than metal ions during the SPT process. It is found that water can act not only as a solvent but also as a mediator which gives and accepts protons to promote SPT, playing a bridge role. As a result, inclusion of a water molecule drastically reduces the energy barrier for the SPT. Moreover, two water molecules can yield larger assisting effect on the SPTs compared with one water molecule. We can conclude that the tautomerism of DNA adenine base can be modulated by the metal ions and water molecules. Copyright © 2015 John Wiley & Sons, Ltd. Single intramolecular proton transfer (SPT) is favored when M n+ interacting at the N 3 position of adenine. SPT becomes unfavorable if M n+ coordinated with N 7 atom of adenine. Water can act as a mediator to assist the SPT in adenine base.

Description: This study reports a facial regio-selective synthesis of 2-alkyl- N -ethanoyl indoles from substituted- N -ethanoyl anilines employing palladium (II) chloride, which acts as a cyclization catalyst. The mechanistic trait of palladium-based cyclization is also explored by employing density functional theory. In a two-step mechanism, the palladium, which attaches to the ethylene carbons, promotes the proton transfer and cyclization . The gas-phase barrier height of the first transition state is 37 kcal/mol, indicating the rate-determining step of this reaction. Incorporating acetonitrile through the solvation model on density solvation model reduces the barrier height to 31 kcal/mol. In the presence of solvent, the electron-releasing (–CH 3 ) group has a greater influence on the reduction of the barrier height compared with the electron-withdrawing group (–Cl). These results further confirm that solvent plays an important role on palladium-catalyzed proton transfer and cyclization . For unveiling structural, spectroscopic, and photophysical properties, experimental and computational studies are also performed. Thermodynamic analysis discloses that these reactions are exothermic. The highest occupied molecular orbital lowest unoccupied molecular orbital gap (4.9–5.0 eV) confirms that these compounds are more chemically reactive than indole. The calculated UV–Vis spectra by time-dependent density functional theory exhibit strong peaks at 290, 246, and 232 nm, in good agreement with the experimental results. Moreover, experimental and computed 1 H and 13 C NMR chemical shifts of the indole derivatives are well correlated. Copyright © 2015 John Wiley & Sons, Ltd. A facial route has been adopted to synthesize 2-alkyl- N -ethanoyl indoles, which are more chemically reactive than indole. Solvent and electron-releasing group play important roles on lowering the barrier height of the rate-determining step of the palladium-catalyzed cyclization reaction. Moreover, details structural, spectroscopic, and photophysical properties of these compounds are explored by density functional (DFT) and time-dependent density functional theories (TD-DFT).

Description: The kinetics of oxidation of methylxanthine drug, theophylline (TP), by diperiodatocuprate(III) (DPC) has been investigated in the absence and presence of ruthenium(III) (Ru(III)) as homogeneous catalyst in alkaline medium at a constant ionic strength of 0.21 mol dm −3 spectrophotometrically. The reaction exhibits 1:4 stoichiometry ([TP] : [DPC]) in both the cases. The order of the reaction with respect to [DPC] was unity, while the order with respect to [TP] was less than unity over the concentration range studied in both the cases. The rate was increased with an increase in [OH − ] and decreased with an increase in [IO 4 − ]. The order with respect to [Ru(III)] was unity. The ionic strength and dielectic constant of the medium did not affect the rate significantly. The main product 1-methyl-(3-N-formyl)-2,4-purinodione was identified by spot tests, Fourier transform infrared spectroscopy and liquid chromatography–mass spectrometry spectral studies. Based on the experimental results, the possible mechanisms were proposed. The reaction constants involved in the different steps of the mechanisms were evaluated. The catalytic constant (K c ) was also calculated for Ru(III) catalysis at different temperatures. The activation parameters with respect to the catalyst and slow step of the mechanisms were computed, and thermodynamic quantities were determined. Kinetic studies suggest that the active species of DPC and Ru(III) are found to be [Cu(H 2 IO 6 )(H 2 O) 2 ] and [Ru(H 2 O) 5 OH] 2+ , respectively. Copyright © 2015 John Wiley & Sons, Ltd. The title reaction exhibits 1:4 stoichiometry ([theophylline]:[diperiodatocuprate(III)]) in both the cases. Based on the experimental results, the plausible mechanisms were proposed, and rate laws were derived. The reaction constants involved in the different steps of the mechanisms were evaluated.

Description: The two conceptual systems of organic homologous compounds and homo-rank compounds give insight into the influence of structures on the properties of mono-substituted alkanes X i –(CH 2 ) j –H from the transverse (change of repeating unit number j of CH 2 ) and longitudinal (change of functional group X i ) perspectives, respectively. This paper aims to combine the organic homo-rank compounds approach together with the homologous compounds approach to explore the property change rules of mono-substituted alkanes involving various substituents. Firstly, based on the concept of organic homologous compounds, the properties of mono-substituted straight-chain alkane homologues were linearly correlated to the two-thirds power of the number of carbon atoms ( N 2/3 ) in alkyl, and regression equations such as Q  =  A  +  BN 2/3 were obtained. The regression coefficients A and B vary with different substituents X i , so coefficients A and B were employed to characterize the structural information of substituent X i . The structural features of alkyls (–(CH 2 ) j –H, that is, –C j H 2 j +1 ) were described by the polarizability effect index ( PEI (R) ) and vertex degree–distance index ( VDI ). Then based on four parameters A , B , PEI (R) , and VDI , quantitative structure–property relationship models were built for the boiling points ( Bp ) and refractive indexes ( n D ) of each mono-substituted alkane homo-rank series, where j  = 3–10 and the substituents X i involve F, Cl, Br, I, NO 2 , CN, NH 2 , COOH, CHO, OH, SH, and NC. Good results indicate that the combination of an organic homo-rank compounds method and a homologous compounds method has exhibited obvious advantages over traditional methods in the quantitative structure–property relationship study of mono-substituted alkanes concerning various substituents. Copyright © 2015 John Wiley & Sons, Ltd. This paper aims to combine the organic homo-rank compounds approach together with homologous compounds approach to explore the property change rules of organic compounds. Quantitative structure–property relationship models were built for the boiling points ( Bp ) and refractive indexes ( n D) of each mono-substituted alkane homo-rank series X i –(CH2) j –H. Good results indicate that the combination of organic homo-rank compounds method and homologous compounds method can contribute to further understand the properties change rules of organic compounds.

Description: The effect of the electron–acceptor substituent CF 3 SO 2 at the imine nitrogen atom on the basicity and the electron distribution in N,N -alkylformamidines ( ) was studied experimentally by the FTIR spectroscopy and theoretically at the DFT (B3LYP/6-311+G(d,p)) level of theory, including the natural bond orbital (NBO) analysis. The calculated proton affinities of the imine nitrogen atom and the sulfonyl oxygen (PA N′ and PA O ) depend on the atomic charges, the C N′ and N′―S bond polarity and on the energy of interaction of the amine nitrogen and the oxygen lone pairs with antibonding π* and σ*-orbitals. The basicity of the imine nitrogen atom is increased with the increase of the electron-donating power of the substituent at the amine nitrogen atom due to stronger interaction n N    π* C N′ , but is decreased for the electron-withdrawing groups MeSO 2 and CF 3 SO 2 at the imine nitrogen atom in spite of the increase of this conjugation. Protonation of ( ) in CH 2 Cl 2 solution in the presence of CF 3 SO 3 H occurs at the imine nitrogen atom, while the formation of hydrogen bonds with 4-fluorophenol takes place at the sulfonyl oxygen atom, whose basicity is lower than that of N,N′ -dimethylmethanesulfonamide but higher than of N,N′ -dimethyltrifluoromethanesulfonamide. Copyright © 2015 John Wiley & Sons, Ltd. The electron-donating substituents at the amine nitrogen in trifluoromethylsulfonylamidines expectedly increase the proton affinity of the imine nitrogen because of the enhanced orbital interaction n N π* C=N′ , whereas the electron-withdrawing groups MeSO 2 and CF 3 SO 2 at the imine nitrogen decrease these proton affinity values in spite of the increased conjugation, apparently, because of the strong inductive effect.

Description: Hypobromous acid and molecular bromine have been described as the active species involved in the oxidative bromination using perhydrolase, which catalyzes the reaction from acetic acid and hydrogen peroxide to peracetic acid (AcOOH). However, the brominating activity of them in a chemical model system was lower than that of the active species produced by the spontaneous reaction between AcOOH and Br − . Consequently, acetyl hypobromite (AcOBr) was suggested as new active species on the bromination by detection of the decarboxylation in the reaction between AcOOH and Br − and the strong brominating power with some tolerance against H 2 O 2 . Its production mechanism was explained as the ionic reaction involving the protonated intermediate of AcOOH by kinetic analysis. Copyright © 2015 John Wiley & Sons, Ltd. It was clarified that the oxidative bromination using perhydrolase, which catalyzes the reaction from acetic acid and hydrogen peroxide to peracetic acid (AcOOH) contains a new active species produced by the spontaneous reaction between AcOOH and Br − in non-enzymatic step under mild condition. Acetyl hypobromite (AcOBr) was suggested as the active species possessing strong brominating power. Kinetic analysis enabled to explain that its production mechanism in catalytic cycle is involved with the protonated intermediate of AcOOH (AcOOH 2 + ) in ionic reaction.

Description: Persistent carbocations generated by the protonation of hetero-polycyclic aromatic compounds with oxygen atom(s) were studied by experimental NMR and density function theory calculations. Benzo[ kl ]xanthene ( ), dibenzo[ d , d ′]benzo[1,2- b :4,3- b ′]difuran ( ), and dibenzo[ d , d ′]benzo[1,2- b :4,5- b ′]difuran ( ) were synthesized by the annulation of arenediazonium salts. Compound in FSO 3 H-SbF 5 (4:1)/SO 2 ClF and in FSO 3 H-SbF 5 (1:1)/SO 2 ClF ionized to with protonation at C(4) and to with protonation at C(6), and these cations were successfully observed by NMR at low temperatures. The density function theory calculations indicated that and were the most stable protonated carbocations and that should ionize to with protonation at C(6). According to the changes in 13 C chemical shifts (Δδ 13 C), the positive charge was delocalized into the naphthalene unit for , into one benzo[ b , d ]furan unit for , and into one benzo[ b , d ]furan unit for . Copyright © 2015 John Wiley & Sons, Ltd. The most stable persistent cations derived from the title compounds, 1–3 , were found to be 1aH+ with protonation at C(4), 2aH + with protonation at C(6), and 3aH + with protonation at C(6) by experimental and theoretical methods.