The RRKM calculation and bonding evolution theory analysis coupled with quantum theory of atoms in molecules have been used to investigate kinetics and molecular mechanism of gas phase thermal decomposition of methyl benzoylformate. The pressure-dependent rate coefficients, by applying different collisional efficiency values, indicated that the atmospheric pressure is in high-pressure limit of fall-off curve and low-pressure limit rate coefficients are in the range of 10-13-10-12 cm3 molec-1 s-1. Temperature dependence of high-pressure limiting of rate coefficient over the temperature range 733 ± 20% K was estimated to be k∞RRKM(CBS-QB3)=2.92×1013s-1exp(227.4kJmol-1/RT) and k∞RRKM(PBE1PBE)=2.67×1013s-1exp(232.8kJmol-1/RT). Topological analysis of electron localization function and electron density at the B3LYP/6-311G(d,p) level reveal that the reaction can be occurred as going through seven turning points defined as methyl benzoylformate 8-CF†FF†TSFC†[CF†]-0: methyl benzoate + carbon monoxide. The molecular mechanism can be categorized in three fundamental sections A) heterolytic rupture of O3C8 bond and detachment of methoxy part; B) formation of O3C7 bond via donation bond formation mechanism; and C) heterolytic rupture of C7C8 bond and detachment of carbon monoxide. The electron density ρ(3,-1)(r) in the region of bond forming and breaking increases and decreases along the reaction course to reflect bond strengthening and weakening, respectively. AIM parameters revealed that so long as chemical bonds are unformed/ruptured, interactions at related BCPs are covalence in nature, otherwise the nature of chemical bonds are strong shared covalence.

Reaction of 2-mercaptopropargylquinazoline-4-one with various aryliodides catalyzed by Pd-Cu leads to the regioselective formation of 1-arylsubstituted-5H-[1,3] thiazolo[ 3,2-a] quinazoline-5-ones.

Ab initio density functional theory (DFT) calculations have been performed on the 3,3-sigmatropic rearrangements of 3-(vinyloxy)prop-1-ene (Claisen) and allyl vinyl sulfide (thio-Claisen) in the gas phase. The barrier height of the Claisen rearrangement calculated at the B3LYP/6-311G** level of theory was in good agreement with the corresponding experimental value. Optimized transition states at the B3LYP/6-311G** level were used for calculating of nucleus independent chemical shift (NICS) and also natural bond orbital (NBO) analysis at the same level. Our results indicate that aromaticities of the transition states are controlled by the out-of-plane component and that the strongest aromatic character is for the chair-like transition state of the thio-Claisen rearrangement. Analysis of donor-acceptor (bonding and antibonding) interactions suggests that the aromatic character of TS structure in the allyl vinyl sulfide reaction (the thio-Claisen rearrangement) is more than the 3-(vinyloxy)prop-1-ene reaction (the Claisen rearrangement). The NBO results show that in these rearrangements, activation energies are controlled by resonance energies. GRAPHICAL ABSTRACT[image omitted].

AbstractIn this work, ab initio density functional theory (DFT) calculations have been performed on the 3,3-sigmatropic rearrangements of hexa-1,5-diene (Cope) and N-vinylprop-2-en-1-amine (3-aza-Cope) in the gas phase. The barrier heights and heats of reactions calculated at the B3LYP/6-311G** level of theory were in good agreement with experimental data. Transition states optimized with B3LYP/6-311G** theory were used for calculating the nucleus independent chemical shift (NICS) and, a natural bond orbital (NBO) analysis was also performed at the same level of theory. Our results indicate that the aromaticities of the transition states are controlled by the out-of-plane component and that the chair-like transition state of the Cope rearrangement exhibits the strongest aromatic character. Analysis of donor-acceptor (bonding and anti-bonding) interactions of σ3–4 → π*1–2 suggests that the TS structure in the hexa-1,5-diene reaction (the Cope rearrangement) has more aromatic character than the N-vinylprop-2-en-1-amine reaction (the 3-aza-Cope rearrangement). The NBO results show that in the hexa-1,5-diene and N-vinylprop-2-en-1-amine rearrangements, activation energies are controlled by σ3–4 → π*1–2 and σ3–4 → π*1–2 resonance energies.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Synthesis of the novel compounds 3-substituted-6-arylimidazo[3,2-d][1,2,4]triazolo[3,4-b][1,3,4]thiadiazines was achieved by the reaction of 6-amino-3-substituted-7H-[1,2,4]triazolo[3,4-jb][1,3,4]thiadiazines with 4-substituted-phenacyl bromides in refluxing ethanol.

A new, simple and inexpensive kinetic catalytic spectrophotometric method for the determination of oxalate is described. The method is based on an activation effect of oxalate on a catalytic effect of iron(II) on the oxidation of iodide by bromate. The reaction is monitored by measuring the absorbance of triiodide ion at Amax = 352 nm. A calibration graph was obtained from 0.10 - 7.0 μg cm-3 of oxalate with a detection limit of 0.080μg cm-3. The standard deviations for ten replicate determinations of 0.50, 1.0 and 5.0 μg cm-3 of oxalate were 4.0, 2.6 and 1.8%, respectively. The applicability of the method was demonstrated by the determination of oxalate ion in real samples.