Molecular mechanism of the transformation of oxidized lignin to -substituted aromatics.

The cleavage of C-C bonds in oxidized lignin model compounds is a highly effective methodology for achieving lignin depolymerization, as well the generation of -substituted aromatics. Here, density functional theory calculations were performed to understand the mechanism of the transformation of an oxidized lignin model compound (ligninox) and hydroxylamine hydrochloride to -substituted aromatics. The reaction was proposed to proceed an energetically viable mechanism featuring the initial production of HOAc acting as proton bridge.

Evolution of time-delay signature of polarized chaos in a unidirectional-coupling VCSEL system with variable-polarization optical injection.

The evolution characteristics of the time-delay signature (TDS) of polarized chaos is systematically investigated in a unidirectional-coupling vertical-cavity surface-emitting (VCSEL) scheme with variable-polarization optical injection (VPOI), by means of the time series, optical spectra, power spectra, and autocorrelation function. In this scheme, the polarized chaos with TDS from a master VCSEL (M-VCSEL) with the external cavity is unidirectionally injected into another solitary slave VCSEL (S-VCSEL) through VPOI. The numerical results show that the VPOI can exert significant influence on the TDS characteristics of polarized chaos in the S-VCSEL.

Time-delay signature suppression of polarization-resolved wideband chaos in VCSELs with dual-path chaotic optical injections.

The combining investigation on the time-delay signature (TDS) and chaos bandwidth have been theoretically investigated in a vertical-cavity surface-emitting laser (VCSEL) system with dual-path chaotic optical injections. In this scheme, the polarized chaos with the TDS from an external-cavity master VCSEL is routed into two different paths and then unidirectionally injected into another solitary slave VCSEL. With the aid of the autocorrelation function and the effective bandwidth calculation, the TDS and bandwidth of polarized chaos from the chaotic system are quantitatively evaluated.

How and Why a Protic Ionic Liquid Efficiently Catalyzes Chemical Fixation of CO to Quinazoline-2,4-(1,3)-diones: Electrostatically Controlled Reactivity.

A density functional theory study has been conducted to gain insight into the intriguing experimental observations on the synthesis of quinazoline-2,4-(1,3)-diones from 2-aminobenzonitriles reacting with CO catalyzed by protic ionic liquids (ILs). We explored the molecular mechanism of the titled reaction, as well as the origin and catalytic nature of different ILs toward the reaction in detail. The calculated energetically viable mechanism involves CO attack, intramolecular rearrangement, and intramolecular cyclization stages.

Reaction mechanism of organoselenium-catalyzed syn-dichlorination of alkenes: a DFT study.

A new method for the syn-dichlorination of alkenes at room temperature has been proposed by Denmark et al. The method uses diselenide (PhSeSePh) as the precatalyst, benzyltriethylammonium chloride (BnEtNCl) as the source of chlorine, and an N-fluoropyridinium salt as the oxidant to recover the catalyst. This approach has achieved exquisite diastereocontrol on a number of alkene substrates.

New Insight into the Formation Mechanism of Imidazolium-Based Ionic Liquids from N-Alkyl Imidazoles and Halogenated Hydrocarbons: A Polar Microenvironment Induced and Autopromoted Process.

To illustrate the formation mechanism of imidazolium-based ionic liquids (ILs) from N-alkyl imidazoles and halogenated hydrocarbons, density functional theory calculations have been carried out on a representative system, the reaction of N-methyl imidazole with chloroethane to form 1-ethyl-3-methyl imidazolium chloride ([Emim]Cl) IL. The reaction is shown to proceed via an S2 transition state with a free energy barrier of 34.4 kcal/mol in the gas phase and 27.

Theoretical study of the reaction of chitosan monomer with 2,3-epoxypropyl-trimethyl quaternary ammonium chloride catalyzed by an imidazolium-based ionic liquid.

The molecular mechanism of the graft reaction of 2,3-epoxypropyl-trimethyl quaternary ammonium chloride with chitosan monomer was investigated by performing density functional theory (DFT) calculations. The calculated results show that the -NH2 group of chitosan monomer is more reactive than its -OH and -CH2OH groups, and the graft reaction on the -NH2 group is calculated to be exothermic by 20.5kcal/mol with a free energy barrier of 42.

A simple and convenient method to synthesize N-[(2-hydroxyl)-propyl-3-trimethylammonium] chitosan chloride in an ionic liquid.

N-[(2-Hydroxyl)-propyl-3-trimethyl ammonium] chitosan chloride (HTCC) was synthesized through nucleophilic substitution of 2,3-epoxypropyltrimethyl ammonium chloride (EPTAC) onto chitosan using ionic liquid of 1-allyl-3-methylimidazole chloride (AmimCl) as a homogeneous and green reaction media. The chemical structure of HTCC was confirmed by FTIR, (1)H NMR and (13)C NMR. The FTIR peak intensity of amino group at 1595 cm(-1) decreased and that of [Formula: see text] at 1475 cm(-1) increased with the increase of reaction time, confirming the substitution of EPTAC on CS.