Density, ρ, and speed of sound, u, were measured for two binary mixtures, 1-ethyl-3-methylimidazolium tetrafluoroborate (1) + N,N-dimethylformamide (2) and 1-ethyl-3-methylimidazolium tetrafluoroborate (1) + N,N-dimethylacetamide (2), over the entire range of compositions at T = 293.15–343.15 K in 5 K intervals using an Anton Paar density and sound velocity analyzer (DSA 5000). Also excess molar volume, V m E, isentropic compressibility, k s, and isentropic compressibility deviation, Δk s, were calculated. For these two binary mixtures, the V m E values were negative in x 1 = 0.1–0.8, they were positive in x 1 ≥ 0.8, and they became more negative with increase in the temperature from 293.15 to 343.15 K. For both systems, the most negative V m E values were observed in the region of x 1 = 0.5. The V m E values were fitted to the Redlich–Kister polynomial equation. The perturbed chain statistical associating fluid theory (PC-SAFT) was also employed in order to correlate the densities of the binary mixtures at the temperature range of 293.15–343.15 K. The results obtained were in good agreement with the experimental data.

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In 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.

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 λmax = 352 nm. A calibration graph was obtained from 0.10 -7.0 µg cm -3 of oxalate with a detection limit of 0.080 µg 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.

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.