Conformational analysis and crystal structure of {[1-(3-chloro-4-fluorobenzoyl)-4-fluoropiperidin-4yl]methyl}[(5-methylpyridin-2-yl)methyl]amine, fumaric acid salt

{[1-(3-Chloro-4-fluorobenzoyl)-4-fluoropiperidin-4yl]methyl}[(5-methylpyridin-2-yl)methyl]amine, fumaric acid salt (C(20)H(22)ClF(2)N(3)O, C(4)H(4)O(4)) (1) was synthesized and characterized by the complete (1)H, (13)C and (19)F NMR analyses. The conformation of the piperidin ring, in the solution state, was particularly studied from the coupling constants determined by recording a double-quantum filtered COSY experiment in phase-sensitive mode. (1)H NMR line-shape analysis was used, at temperatures varying between -5 and +60 degrees C, to determine the enthalpy of activation of the rotational barrier around the CN bond. Compound 1 crystallizes in the triclinic space group P1 with a=8.517(3) Angstrom, b=12.384(2) Angstrom, c=12.472(3) Angstrom, alpha=70.88(2) degrees, beta=82.04(2) degrees, gamma=83.58(2) degrees. The results strongly indicate that the solid and solution conformations are similar. Thermal stability and phases transitions were investigated by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). Furthermore polymorphism screening was studied from recrystallization of 1 performed in seven solvents and by slurry conversion in water. The X-ray powder diffraction (XRPD) and differential scanning calorimetry results suggested that 1 crystallizes into one crystalline form which melts at 157 degrees C (DeltaH=132 J g(-1)).     

马尿酸及乙酰苯胺燃烧能的测定

设计并建立一台精密转动弹热量计,能在恒温和绝热两种模式下操作.测量数据的采集由在线微机自动完成,测量结果通过适当的程序计算.用量热标准物质NBS39i苯甲酸标定其能当量,偏差约为±0.006%.马尿酸及乙酰苯胺的燃烧能测定值分别为-(23542.7±0.9)J/g和-(31245.8±2.4)J/g(平均值和标准偏差).不确定度为总标准偏差的2倍,分别为±4.5J/g和±7.5J/g.结果与推荐值一致.还讨论了这两个化合物作为低含氮量量热参考物质的性质.     

Automatic twin vessel recrystallizer. Effective purification of acetaminophen by successive automatic recrystallization and absolute determination of purity by DSC

I describe an interchangeable twin vessel (J, N) automatic glass recrystallizer that eliminates the time-consuming recovery and recycling of crystals for repeated recrystallization. The sample goes in the dissolution vessel J containing a magnetic stir-bar K; J is clamped to the upper joint H of recrystallizer body D. Empty crystallization vessel N is clamped to the lower joint M. Pure solvent is delivered to the dissolution vessel and the crystallization vessel via the head of the condenser A. Crystallization vessel is heated (P). The dissolution reservoir is stirred and heated by the solvent vapor (F). Continuous outflow of filtrate E out of J keeps N at a stable boiling temperature. This results in efficient dissolution, evaporation and separation of pure crystals Q. Pure solvent in the dissolution reservoir is recovered by suction. Empty dissolution and crystallization vessels are detached. Stirrer magnet is transferred to the crystallization vessel and the role of the vessels are then reversed. Evacuating mother liquor out of the upper twin vessel, the apparatus unit is ready for the next automatic recrystallization by refilling twin vessels with pure solvent. We show successive automatic recrystallization of acetaminophen from diethyl ether obtaining acetaminophen of higher melting temperatures than USP and JP reference standards by 8× automatic recrystallization, 96% yield at each stage. Also, I demonstrate a novel approach to the determination of absolute purity by combining the successive automatic recrystallization with differential scanning calorimetry (DSC) measurement requiring no reference standards. This involves the measurement of the criterial melting temperature T₀ corresponding to the 100% pure material and quantitative ΔT in DSC based on the van’t Hoff law of melting point depression. The purity of six commercial acetaminophen samples and reference standards and an eight times recrystallized product evaluated were 98.8 mol%, 97.9 mol%, 99.1 mol%, 98.3 mol%, 98.4 mol%, 98.5 mol% and 99.3 mol% respectively.     

Thermal transformations and stability of organometallic materials with electrical and optical properties: the case of polycrystalline cis-[Ir(CO)2Cl(C5H5N)

In this paper the solid-state transformations under heating of cis-[Ir(CO)2Cl(C5H5N)] are discussed. The complexity of the transformations was revealed by integrating infrared spectroscopy, conventional and bidimensional X-ray diffraction, thermal analysis, and hot stage optical microscopy. During heating anisotropic expansion of the lattice along the Ir-Ir stacking takes place. Then cis-[Ir(CO)2Cl(C5H5N)] undergoes an irreversible solid-solid phase transition to a lattice of higher symmetry followed by a reversible transition into the amorphous phase. Under proper cooling a partial recrystallization takes place. Experiments in the presence of oxygen must be carried out in short time periods to avoid oxidation from Ir(I) to Ir(III).     

Reactions of the ionized enol tautomer of acetanilide: elimination of HNCO via a novel rearrangement

The reactions of ionised acetanilide, C(6)H(5)NH(=O)CH(3)(.+), and its enol, C(6)H(5)NH(OH)=CH(2)(.+), have been studied by a combination of tandem mass spectrometric and computational methods. These two isomeric radical cations have distinct chemistries at low internal energies. The keto tautomer eliminates exclusively CH(2)=C=O to give ionised aniline. In contrast, the enol tautomer loses H-N=C=O, via an unusual skeletal rearrangement, to form predominantly ionised methylene cyclohexadiene. Hydrogen atom loss also occurs from the enol tautomer, with the formation of protonated oxindole. The mechanisms for H-N=C=O and hydrogen atom loss both involve cyclisation; the former proceeds via a spiro transition state formed by attachment of the methylene group to the ipso position, whereas the latter entails the formation of a five-membered ring by attachment to the ortho position. The behaviour of labelled analogues reveals that these two processes have different site selectivities. Hydrogen atom loss involves a reverse critical energy and is subject to an isotope effect. Surprisingly, attempts to promote the enolisation of ionised acetanilide by proton-transport catalysis were unsuccessful. In a reversal of the usual situation for ionised carbonyl compounds, ionised acetanilide is actually more stable than its enol tautomer. The enol tautomer was resistant to proton-transport catalysed ketonisation to ionised acetanilide, possibly because the favoured geometry of the encounter complex with the base molecule is inappropriate for facilitating tautomerisation.     

Synthesis, spectroscopic characterization and X-ray structure of [1,2a]benzimidazol-2-yl amidine

[1,2a]Benzimidazol-2-yl amidine was synthesized by adding cyclopentanamine to iminoester in ethanol. The structure of amidine 1 was characterized by IR, 1H NMR, 1H-1H NOESY, 13C NMR, DEPT, XHCOR spectra, thermogravimetric analysis (TGA), differential thermal analysis (DTA), differential scanning calorimetry thermograms (DSC), elementary analysis as well as by X-ray diffraction. The single crystals suitable for X-ray measurement were obtained by recrystallization at room temperature. The amidine group of a model was found to have Z configuration in the crystal. This compound crystallizes in a P2(1)/n monoclinic unit cell with parameters a=12.679(2) ?, b=8.468(3) ?, c=13.108(2) ?, β=96.538(2)°, V=1398.2 ?3 and Z=4.     

Unexpected Spiroproducts from the Reaction of N‐Benzoylglycine with Ortho‐Formylbenzoic Acids −3,5′‐Dioxo‐2′‐Phenyl‐1,3‐Dihydrospiro[Indene‐2,4′‐[1,3]Oxazol]‐1‐yl Acetates: Establishments of Their Structure

This paper describes a method of preparation of new 3,5′‐dioxo‐2′‐phenyl‐1,3‐dihydrospiro[indene‐2,4′‐[1,3]oxazol]‐1‐yl acetate and its 5‐chloro‐ and bromoderivatives as products of interaction of N‐benzoylglycine (hippuric acid) with corresponding ortho‐formylbenzoic acids. The reaction carried out in acetic anhydride media in the presence of piperidine as catalyst. The novel spirocompounds were purified by column chromatography from multicomponent reaction mixtures. The composition of the spiro‐products was confirmed by C, H, N element analysis. The structure was established by IR, MS, ¹H‐ and ¹³C‐NMR analysis including COSY ¹H‐¹³C experiments.     

Thermodynamic analysis of precipitation processes in Nb–Ti-microalloyed Si–Al TRIP steel

The work deals with the thermodynamic calculations of precipitation processes in austenite of the Nb–Ti-microalloyed steel with increased Si and Al content dedicated for the automotive industry. The analysis is based on the equilibrium precipitation of individual MX-type interstitial phases, as well as the effect of various Mn and Si additions is included. The solubility products and corresponding limits of the mutual solubility of microalloy and metalloid additions in austenite were calculated. The temperature sequence of the precipitation under equilibrium conditions was determined. The Dutta–Sellars model has been applied for determination of recrystallization stop temperature of austenite and time needed for Nb(C,N) precipitation. The calculations were verified by microstructure investigations including revealing prior austenite grain size as a function of austenitizing temperature and the identification of complex carbonitrides using transmission electron microscopy. The model calculations are in good agreement with experimental results.     

微量注射进样法测定汽油窄馏分的氢/碳原子比

根据不称重法测定化合物碳、氢、氮原子比的理论,建立了微量注射法测定强挥发性液体样品的氢／碳原子比的方法。考察了方法的准确度和精密度,并成功测定了一组汽油窄馏分（初馏点－200℃）的氢／碳原子比（2.368-1.941)。微量注乘风破浪地可用于测定强挥发性液体样品。