Calorimetric and computational study of 3-buten-1-ol and 3-butyn-1-ol. Estimation of the enthalpies of formation of 1-alkenols and 1-alkynols

The enthalpies of combustion and vaporization of 3-buten-1-ol and 3-butyn-1-ol have been measured by static bomb combustion calorimetry and correlation gas chromatography techniques, respectively, and the gas-phase enthalpies of formation, Delta(f)H degrees (m)(g), have been determined, the values being -147.3 +/- 1.8 and 16.7 +/- 1.6 kJ mol(-1), for 3-buten-1-ol and 3-butyn-1-ol, respectively. High level calculations at the G2 and G3 levels have also been carried out. Relationships between the enthalpies of formation of 1-alkanols, 1-alkenols and 1-alkynols and with the corresponding hydrocarbons have been discussed. From the calculated contributions to Delta(f)H degrees (m)(g) for the substitutions of CH(3) by CH(2)OH, CH(3)CH(2) by CH(2)=CH and CH(3)CH(2) by CH triple bond C, we have estimated the Delta(f)H degrees (m)(g) values for 3-buten-1-ol and 3-butyn-1-ol, in excellent agreement with the experimental ones. Delta(f)H degrees (m)(g) values for 1-alkenols and 1-alkynols up to 10 carbon atoms have also been estimated.     

Persistence of layer motifs in the crystal structures of [1,4-bis-(2-methoxy-2-carbonylethyl)piperazinium (2’)] chloride and [1,4-bis-(2-amidoethyl)piperazinium (2’)] perchlorate

Two structures of the closely related piperazinium salts, [1,4-bis-(2-methoxy-2-carbonylethyl)piperazinium (2+)] chloride (1) and [1,4-bis-(2-amidoethyl)piperazinium (2+)] perchlorate (2) reveal the persistence of a layer structure, interspersed with anions, held in place by N–H···Cl, C–H···O and C–H···Cl interactions in the case of 1, and N–H···O and C–H···O interactions in the case of 2. Compound 1 crystallizes in the triclinic space group P-1 with a=6.7667(6) ?, b = 6.9467(6) ?, c=9.3880(18) ?, α=105.845(9)°, β=99.896(16)°, γ=103.600(9)°, and Z=1. Compound 2 crystallizes in the monoclinic space group P2₁/c with a = 9.0930(8) ?, b=10.0525(11) ? c=10.2104(13) ?, β=114.279(9)°, and Z=2.     

HRGC/FID and HRGC/MSD Analysis of the Secondary Metabolites Obtained by Different Extraction Methods from Lepechinia schiedeana,and in Vitro Evaluation of Its Antioxidant Activity

Steam distillation (SD), simultaneous distillation-solvent extraction (SDE), microwave-assisted solvent extraction (MWE), and supercritical (CO₂) extraction (SFE) were used to isolate secondary metabolites from Lepechinia schiedeana. The various extracts were analyzed by capillary gas-chromatography, on poly (dimethylsiloxane) (DB-1) and poly(ethyleneglycol) (INNOWAX), 60 m columns, using FID or MSD (EI, 70 eV). Kováts indexes, mass spectra, or standard compounds were employed for compound identification. 43, 61, 67, and 79 compounds at concentrations above 0.01% were detected in the SD, SDE, MWE, and SFE extracts, respectively. Ledol, C₁₅H₂₆O, was the major constituent (20.04–36.87%) in all extracts. Oxygenated sesquiterpenes (24.36–43.14%), C₁₀H₁₆, monoterpenes (27.70–39.87%), and C₁₅H₂₄, sesquiterpenes (10.04–22.22%) were the main groups of compounds present in SD, SDE, MWE, and SFE extracts. Heavy hydrocarbons (C_n > 15), diterpenoids, and phytosterols were found only in MWE and SFE extracts. The antioxidant activity of Lepechinia schiedeana was measured by the HRGC quantification of the volatile carbonyl compounds, final products of lipoxidation, released in a model lipid system (sunflower oil) by the effect of the Fenton reagent. The concentration of volatile carbonyl compounds decreased by 65% when lipid oxidation was induced in the presence of macerated Lepechinia plant. The protection of polyunsaturated acids in sunflower oil was also studied by measuring their concentrations after heating of the oil (180°C, 2 h) with and without macerated Lepechinia plant.     

4-(4-Chlorophenyl)-3,7,7-trimethyl-1-[2-(4-nitrobenzoyl)ethyl]-4,7,8,9-tetrahydro-1H-pyrazolo[3,4-b]quinolin-5(6H)-one–ethanol (1/1)

Molecules of the title compound, C₂₈H₂₇ClN₄O₄·C₂H₆O, form a C(6) chain via an N—H⋯O hydrogen bond along the c axis by the operation of a c-glide plane, with N⋯O = 2.761 (3) Å and N—H⋯O = 165°. The mol­ecules are further linked by a weak C—H⋯O interaction, with C⋯O = 3.344 (4) Å and C—H⋯O = 150°. Pendant hydrogen-bonded ethanol solvent mol­ecules are attached to the chains by O—H⋯N hydrogen bonds, with O⋯N = 2.904 (3) Å and O—H⋯N = 175°.     

Reaction of 4,5-diamino-3-methyl-1-phenylpyrazole with 3-dimethylaminopropiophenones. Synthesis of new 4-aryl-6-methyl-8-phenyl-2,3-dihydropyrazolo[3,4-b]diazepines and 4-aryl-8-methyl-6-phenyl-2,3-dihydropyrazolo[4,3-b]diazepines

New 4-Aryl-6-methyl-8-phenyl-2,3-dihydropyrazolo[3,4-b]diazepines and 4-aryl-8-methyl-6-phenyl-2,3-dihydropyrazolo[4,3-b]diazepines were obtained from the reaction of 4,5-diamino-3-methyl-1-phenylpyrazole 1 with one equivalent of the 3-dimethylaminopropiophenones 2 in absolute ethanol. The structures of 4-aryl-6-methyl-8-phenyl-2,3-dihydropyrazolo[3,4-b]diazepines 3 and 4-aryl-8-methyl-6-phenyl-2,3-dihydropyrazolo[4,3-b]diazepines 4 were determined by detailed nmr measurements.     

Reaction of 4,5-diamino-1,6-dihydropyrimidin-6-ones with two equivalents of chalcones

The reaction of 4,5-diamino-1,6-dihydropyrimidin-6-ones 1 with two equivalents of the chalcones 2 leads in an acidic medium to the formation of the 2,3,6,7-tetrahydro-1H-pyrimido[4,5-b][1,4]diazepin-6-one derivatives 3a-d . The structure elucidation of the products is based on nmr measurements and an X-ray diffraction.     

8‐tert‐Butyl‐7‐(4‐chlorophenyl)‐10‐phenyl‐5,6‐dihydro‐10H‐benzo[h]pyrazolo[3,4‐b]quinoline

The title compound, C₃₀H₂₆ClN₃, crystallizes with Z′ = 3 in the P space group. The three independent molecules have very similar, although not identical, conformations, with almost perfect screw‐boat forms adopted by the non‐aromatic carbocyclic rings. Four independent C—H...π(arene) hydrogen bonds link the molecules into centrosymmetric six‐component aggregates.     

Synthesis and structural analysis of 5‐cyanodihydropyrazolo[3,4‐b]pyridines

Several new 3‐aryl‐5‐cyanopyrazolo[3,4‐b]pyridines were easily prepared from 3‐amino‐5‐arylpyrazoles and α‐cyanochalcones. Structural analysis using NMR solution studies revealed the 2H‐tautomers as the preferred tautomer in solution (DMSO‐d₆). X‐ray diffraction confirmed the 2H‐tautomers as the unique tau‐tomer species in the crystalline state as well. Geometry optimization of 1H and 2H‐tautomers at semi‐empirical levels (AM1, MINDO/3) were performed, indicating that in all cases the 2H‐tautomers are more stable than the corresponding 1H‐tautomers.     

Effect of thermal annealing on r.f. sputtering-deposited nanocrystalline GaN<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>As<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript> thin films

GaNAs thin films were deposited on Corning glass substrates by radio frequency (r.f.) sputtering in molecular nitrogen ambient. The stoichiometry in the GaNAs alloy was controlled by changing the nitrogen incorporation in the film during the growth process, through the variation of the r.f. power in the range 30–80 watts which produced films with N concentrations in the range: x = 0.85–0.90. The structural and optical properties of the GaNAs thin films were studied by X-ray diffraction (XRD), photoacoustic (PA) and photoluminescence (PL) spectroscopies. XRD measurements show a broad diffraction band with a peak close to the (002) diffraction line of the GaN hexagonal phase, and a slight shoulder at the position corresponding to the (111) GaAs cubic phase. The PA absorption spectra showed a remarkable shift to higher energies of the absorption edge as the r.f. power decreases corresponding to the films with higher N concentrations. Thermal annealing of the GaNAs films at temperatures of 450 °C produced a GaAs nanocrystalline phase with grain sizes in the range 10–13 nm, as confirmed by the XRD measurements that showed a well-defined peak in the (111) GaAs direction, and also by the PA spectra which showed an absorption band at energies around 1.45 eV due to the quantum confinement effects. PL spectra of thermal-annealed GaNAs films showed a very intense emission at 1.5 eV which we have associated to transitions between the first electron excited level and acceptor states in the GaAs nanocrystallites.