Synthèse du mèthyl-1 diformyl-2,3 pyrrole,de la méthyl-1 pyrrolo[2,3-d] pyridazine et de la méthyl-1 oxo-6 (6h)cycloheptatrieno[b] pyrrole

This communication describes the synthesis of l-methyl-2,3-diformylpyrrole. This new compound is used to prepare a new heterocycle, l-methylcyclohepta[b]pyrrol-6-one and thus allows a new synthesis of l-methylpyrrolo[2,3-d]pyridazine.     

Adsorption and dissociation of the methanethiol (CH3SH) molecule on the Fe(100) surface

These contributions explore interaction modes between the methanethoil (CH₃SH) molecule and the Fe(100) surface via implementing accurate density functional theory (DFT) calculations with the inclusion of van der Waals corrections. We consider three adsorption sites over the Fe(100) surface, namely, top(T), bridge (B), and hollow (H) sites as potential catalytic active sites for the molecular and dissociative adsorption of the CH₃SH molecule. The molecular adsorption structures are found to occupy either B or T sites with former sites holding higher stability by 0.17 eV. The inclusion of van der Waals corrections refound to slightly alter adsorption energies. For instance, adsorption energies increased by ~ 0.18 and ~ 0.21 eV for B and T structure, respectively, in reference to values obtained by the plain generalized gradient approximation (GGA) functional. A stability ordering of the dissociation products was found to follow the sequence (CH₄, S) > (CH₃, S, H) > (─SCH_3, H) > (─CH₃, SH). The differential charge density distributions were examined to underpin prominent electronic contributing factors. Direct fission of C─S bond in the CH₃SH molecule attains exothermic values in the range 2.0 to 2.1 eV. The most energetically favorable sites for the surface-mediated fission of the thiol's S─H bond correspond to the structure where the ─SCH₃ and H are both situated on hollow sites with an adsorption energy of −2.43 eV. Overall, we found that inclusion of van der Waals functional to change the binding energies more noticeably in case of dissociative adsorption structures. The results presented herein should be instrumental in efforts that aim to design stand-alone Fe desulfurization catalysts.     

Thermal decomposition of model compound of algal biomass

This contribution investigates thermal decomposition of leucine, as a representative model compound for amino acids in algal biomass. We map out potential energy surface for a wide array of unimolecular and self-condensation reactions operating in the decomposition of leucine. Decarboxylation and dehydration of leucine ensues by eliminating CO₂ and –OH, respectively, from the –COOH group attached to the α-carbon. The molecular channel for deamination involves cleavage of NH₂ from α-carbon of leucine. The activation energies for direct elimination of CO₂, NH₃, and H₂O from a leucine molecule lie within 20.7 kJ/mol of each other. Activation energies for these decomposition pathways reside below the bond dissociation enthalpy of H–C(α) of 323.1 kJ/mol. The decarboxylation, deamination, and dehydration pathways, via radical-prompted pathways, systematically require lower energy barriers, in reference to closed-shell reaction corridors. Detailed computations at the CBS-QB3 level provide the Arrhenius rate parameters for the unimolecular and bimolecular reactions, and standard enthalpies of formation, standard entropies, and heat capacities for all the products and intermediates. A kinetic analysis of gas-phase reactions, within the context of a plug-flow reactor model, accounts qualitatively for the formation of major products observed experimentally in the thermal degradation of the condensed-phase leucine. Among notable N-containing species, the model predicts the prevailing of NH₃ over HCN and HNCO, in addition to corresponding appreciable concentrations of amines, imines, and nitriles. Our detailed kinetic investigation illustrates a negligible contribution of the self-condensation reactions of leucine in the gas phase.     

Theoretical investigation into competing unimolecular reactions encountered in the pyrolysis of acetamide

Motivated by the necessity to understand the pyrolysis of alkylated amines, unimolecular decomposition of acetamide is investigated herein as a model compound. Standard heats of formation, entropies, and heat capacities, are calculated for all products and transition structures using several accurate theoretical levels. The potential energy surface is mapped out for all possible channels encountered in the pyrolysis of acetamide. The formation of acetamedic acid and 1-aminoethenol and their subsequent decomposition pathways are found to afford the two most energetically favored pathways. However, RRKM analysis shows that the fate of acetamedic acid and 1-aminoethenol at all temperatures and pressures is to reisomerize to the parent acetamide. 1-Aminoethenol, in particular, is predicted to be a long-lived species enabling its participation in bimolecular reactions that lead to the formation of the major experimental products. Results presented herein reflect the importance of bimolecular reactions involving acetamide and 1-aminoethenol in building a robust model for the pyrolysis of N-alkylated amides.     

Theoretical study on the reaction of hydrogen atoms with aniline

The reaction of aniline with hydrogen atom is investigated herein using the hybrid meta-DFT functional of BB1 K. Hydrogen atom is found to preferentially add at an ortho position. However, the fate of the o-(C₆H₅NH₂)H adduct is found to be solely the deactivation of the initial addition channel. The rate constant for the abstraction channel (C₆H₅NH₂ + H → C₆H₅NH + H₂) is fitted by the expression 1.10 × 10⁻¹¹ exp(−4,200/T) cm³ molecule⁻¹ s⁻¹. Our calculated rate constant for the abstraction channel agrees very well with the available experimental measurements. Satisfactory agreement is found between calculated and experimental measurements for the displacement channel (C₆H₅NH₂ + H → C₆H₆ + NH₂). Our detailed analysis for the corresponding displacements in toluene and phenol suggests that the three systems exhibit similar behavior with regard to the relative importance of abstraction and displacement channels.     

Synthèse dc la pyrido[2,3-f] phtalazine et des diformyl-6,7; -4,6; -4,7; -2,4 quinoleines

This article describes the synthesis of a new heterocycle, pyrido[2,3,f]phtalazine and three new diformylquinolincs.     

Synthèse des pyrido[2,3-d] el [3,2-d] -s-triazolo[3,4-f] pyrimidines el de (pyrazolyl-1')-4 pyrido[2,3-d] et [3,2-d] pyrimidines

The synthesis of two new heterocycles is described: pyrido-[2,3-d]-.s-triazolo[ 3,4-f] pyrimidine and pyrido[3,2-d]-.s-triayzolo-[3,4-f] pyrimidine. 4-[I'-Pyrazolyl]pyrido[2,3-d]pyrimidines and 4-[1′-pyrazoly1] pyrido[ 3,2-d] pyrimidine are obtained by the action of 4-hydrazinopyrido[2,3-d]pyrimidine and 4-hydrazinopyrido-[3,2-d]pyrimidine with several β-diketones.