Prediction of olefin IR spectra reasoning from their mass spectra

Possible appliance of low resolution mass spectra in QSPR studies to predict IR spectra of olefins in gas phase is considered. The prediction quality is characterized by values of correlation coefficients from 0.961 to 1.00 between computed and experimental vector representations of IR spectra.     

QSPR-modeling of oligophenylene melting points

QSPR-modeling of melting temperatures has been performed for oligophenylenes of diverse structures and different molecular weights. It has been shown that optimization of correlation weights of graph local invariants can be used for prediction of melting points of oligomers. The best statistical quality of the model is observed for correlation weights calculated using third-order Morgan degrees.     

An artificial intelligence system for computer-aided mass spectra interpretation of saturated aliphatic monohydric alcohols

The mass spectra of saturated monohydric alcohols are used in structure elucidation by means of computer programs of the artificial intelligence type. The structure generator is constrained by a structure predictor to show the sub-group structure in a fairly definite area, and spectral characteristics are also predicted. According to the commands of the structure predictor, sub-groups conforming to the mass spectra studied are then combined into molecular structures which are ranked for output. The system was tested for 218 mass spectra of 115 alcohols from different laboratories: all the correct answers were included in the 6 highest scores, with 78% for the highest score and 91% for the highest 2 scores.     

脂肪醇的味阈值与分子结构之间的定量关系

通过拓扑方法探讨了脂肪醇的味阈值与分子结构之间的关系,发现脂肪醇的味阈值主要取决于分子的大小和羟基在分子中的位置(且羟基的位置对味阈值的影响十分显著),提出一个既能表征脂肪醇结构与味阈值之间关系、又能预测味阈值的定量关系式,发展了一种设计具有特定味阈值的脂肪醇分子结构的方法。对99种脂肪醇的计算结果表明,味阈值预测值与计算值与实验值的一致性令人满意。     

An infrared spectroscopic study on the influence of water on alcohols

Summary The influence of the water content on absorption bands in FTIR spectra of monohydric alcohols was studied and the effects were compared to changes in spectra of absolute solvents at various temperatures. The FTIR spectra were recorded by the ATR technique in order to distinguish the weak bands of the solvents from the intensive water bands more easily. By addition of water to anhydrous alcohols both OH stretching and bending bands increased in intensity and width. Similar changes in spectra of anhydrous alcohols can be obtained by decreasing the temperature. Addition of water to monohydric alcohols causes the lengthening of the intramolecular OH bonds to a smaller extent than the shortening of the intermolecular OH bonds. This contraction of the liquid structure is also reflected in other physical and chemical properties.

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Eine infrarotspektroskopische Untersuchung über den Einfluß von Wasser auf Alkohole

Zusammenfassung Der Einfluß des Wassergehalts auf die Absorptionsbanden in den FTIR-Spektren einwertiger Alkohole wurde untersucht und die Effekte mit den Veränderungen der Spektren der absoluten Lösungsmittel bei Temperaturvariationen verglichen. Die FTIR-Spektren wurden mit Hilfe der ATR-Technik aufgenommen, um die meist nur schwachen Banden der Lösungsmittel neben den intensiven Wasserbanden besser erkennen zu können. Es zeigte sich, daß durch Zugabe von Wasser zu absoluten Alkoholen sowohl die OH-Streckschwingungs- als auch die Deformationsschwingungsbande an Intensität und Breite zunehmen. Ähnliche Veränderungen der Banden lassen sich auch in den Spektren von absoluten Alkoholen bei Temperaturerniedrigung feststellen. Diese spektroskopischen Veränderungen werden in folgender Weise interpretiert. Die Zugabe von Wasser zu einwertigen Alkoholen bewirkt die Verlängerung der intramolekularen O-H-Bindungen in schwächerem Ausmaß als die Verkürzung der Intermolekularen O...H-Bindungen, d.h. sie bewirkt eine Erhöhung der Symmetrie der H-Brückenbindungen und eine Verstärkung der O...O-Wechselwirkungen. Diese Verdichtung der Flüssigkeitsstruktur spiegelt sich auch in anderen physikalischen und chemischen Eigenschaften wider.

     

Vapor pressure of selected aliphatic alcohols by ebulliometry. Part 2

Vapor pressures of six pentanols, 2-methyl-1-butanol (CAS Registry Number 137-32-6), 2-methyl-2-butanol (CAS Registry Number 75-85-4), 3-methyl-1-butanol (CAS Registry Number 123-51-3), 3-methyl-2-butanol (CAS Registry Number 598-75-4), 2-pentanol (CAS Registry Number 6032-29-7) and 3-pentanol (CAS Registry Number 584-02-1), were measured by the precision ebulliometry over an approximate pressure range from 9 to 99 kPa. The absolute uncertainties in pressure and temperature are estimated to be less than or equal to 7 Pa and 0.02 K, respectively. The results are represented by the Antoine equation and compared with available literature data.     

Vapor pressure of selected aliphatic alcohols by ebulliometry. Part 1

Vapor pressures for liquid 2,2-dimethyl-1-propanol (CAS Registry Number 75-84-3), 1-hexanol (CAS Registry Number 111-27-3), 1-heptanol (CAS Registry Number 111-70-6), 1-octanol (CAS Registry Number 111-87-5) and 1-tetradecanol (CAS Registry Number 112-72-1) were measured by the precision comparative ebulliometry over an approximate pressure range from 8 to 100 kPa. The relative uncertainty in pressure is estimated to be less than or equal to 0.05% of the measured value and the absolute uncertainty in temperature is estimated at less than or equal to 0.01 K on ITS-90. The results are represented by the Antoine equation and compared with available literature data. A new transformation of vapor pressure data, which facilitates the detection of systematic errors, is presented.     

Kinetics and mechanism of oxidation of aliphatic alcohols by tetrabutylammonium tribromide

Oxidation of nine primary aliphatic alcohols by tetrabutylammonium tribromide (TBATB) in aqueous acetic acid leads to the formation of the corresponding aldehydes. The reaction is first order with respect to TBATB. Michaelis-Menten type kinetics is observed with respect to alcohols. The reaction failed to induce the polymerization of acrylonitrile. Tetrabutylammonium chloride has no effect on the reaction rate. The proposed reactive oxidizing species is the tribromide ion. The oxidation of [1,1-²H₂]ethanol exhibits a substantial kinetic isotope effect. The effect of solvent composition indicates that the rate increases with increase in the polarity of the solvent. The reaction is susceptible to both polar and steric effects of substituents. A mechanism involving transfer of a hydride ion in the rate-determining step has been proposed.     

Sorption of aliphatic alcohols from aqueous solutions by starch cryotextures

Capillary GLC was applied to study the sorption ofn-butanol,n-hexanol,n-octanol, and linalood from aqueous solutions by com starch cryotextures. The concentrations of alcohols in aqueous solutions were varied from 0.5 to 15 mmol L⁻¹. The sorption of alcohols by crytotextures formed of sols containing these alcohols and the coefficients of their. distribution depend on the initial concentration and structure of the alcohols.n-Butanol is not sorbed by the corn starch cryotextures over the range of 0.5–80 mmol L⁻¹. The sorption of other alcohols increases with increasing length of the alkyl substituent and the concentration of the alcohol. The highest sorption capacity of the cryotexture (88%) was observed forn-octanol. The sorption of linalool decreases due to the double bonds and branching in its molecules. Translated fromIzestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 734–737, April, 1999.     

Pd-catalyzed nucleophilic allylic alkylation of aliphatic aldehydes by the use of allyl alcohols

Under catalysis of Pd(OAc)₂-(P-n-Bu)₃, Et₂Zn promotes a variety of allyl alcohols to undergo nucleophilic allylation of aliphatic aldehydes and ketones at room temperature and provides homoallyl alcohols in 60-90 and ca. 60% isolated yield, respectively. The reaction is irreversible and kinetically controlled, and unique regio- and stereoselectivities observed for the allylation with unsymmetrically substituted allyl alcohols are discussed.     

Properties of carbon-silica adsorbents prepared by pyrolysis of aliphatic and aromatic alcohols

Summary A comparison of surface properties of complex carbonsilica adsorbents, obtained by pyrolysis of aliphatic and aromatic alcohols on silica gel is presented. The pyrolysis reactions of alcohols were carried out at mild conditions, above 300°C. The surface properties of these adsorbents depend upon the chemical character of the alcohol used in the pyrolysis reaction. Dedicated to Professor A. V. Kiselev on the occasion of his 70th birthday.     

量化参数对脂肪醇的Tb,-1gSW,1gKOW的QSPR研究

利用C-O键上C原子电荷Qc和分子所含C原子个数Ⅳ作为醇分子结构描述符对其沸点巩、在水中的溶解度Sw及辛醇／水分配系数（k）进行了QSPR研究．Qc的计算采用Chemoffice 8．0中的MOPAC-AM1量子化学法,容易获取,它表征了醇分子同分异构体之间的结构差异．多元回归分析结果表明醇分子的Tb,-lg Sw,lgKow都随分子所含C原子数Ⅳ的增加而增加,随着C-O键上C原子电荷Qc的增大而减小,复相关系数均在0．99以上．MOPAC-AM1方法计算的量化参数Qc用于与脂肪醇的水溶解性关联优于分子连接性指数．     

Effect of molecular and crystal structure ofN-naphthylurethanes (carbamates) on their IR spectra

A comparative analysis of the IR spectra in the region of 3000–400 cm⁻¹ of four urethanes (methyl-(N-(1-naphthyl) carbamate, ethyl-N-(1-naphthyl) carbamate, dimethyl-N,N′-(1,5-naphthylene) dicarbamate, and diethyl-N,N′-(1,5-naphthylene) dicarbamate) with known molecular and crystal structures was carried out. The assignment of the bands related to the vibrations of the urethane and naphthyl fragments was refined on the basis of the study of the crystalline samples, melts, solutions, and deuterated analogs. The effect of the degree of conjugation of the urethane group with the naphthalene ring on the Amide II vibration frequency in the crystals was shown. It was suggested that the stretching vibrations of the C(Ar)−N bond in naphthylurethanes (unlike aliphatic derivatives) make a considerable contribution to the Amide II vibration, while the planar deformation vibration of the N−H bond was proved to be more significant for Amide III than for Amide II. In addition, strong nonspecific intermolecular interactions in the crystal can weaken valent bonds. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 300–303, February, 1998.     

Solvates with anomalous low melting points

Single crystals of the N,N-dimethylformamide (DMF) solvate (1:1) of flurbiprofen (FBP) were grown for the first time and characterised by X-ray diffraction, IR spectrophotometry, DSC and solution calorimetric methods. The structure may be characterised as a layer-structure, where DMF double-sheets are arranged between FBP double-sheets. The FBP and DMF molecules are linked to each other by a hydrogen bond, which is formed between the hydroxyl group of FBP and the carbonyl group of DMF. The conformation of FBP molecules in the DMF solvate differs from analogous enantiomers in the unsolvated form. The differences are discussed from the point of view of the influence of the nature of the solvent on selective crystallisation of the enantiomers. A peculiarity of the solvate is its low melting point, 37.3±0.2°C, with respect to the unsolvated phase, 113.5±0.2°C. Based on solution enthalpies of the solvated and unsolvated phases dissolved in DMF, the difference in crystal lattice energies, 9.8 kJ mol^-1, was calculated and the difference in entropies, 33 J mol^-1 K^-1 estimated. A possible mechanism explaining the low melting point of the solvate is discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis of alkyl (3-pyridyl)hydroxymethylphosphonates and their IR spectra

The reaction of dialkyl H-phosphonates with pyridine-3-carbaldehyde gives alkyl (3-pyridyl)hydroxymethylphosphonates. In liquid systems, the hydrogen atom is localized at the oxygen atom of the hydroxyl group; in crystals, the existence of a zwitter-ionic form could not be excluded. In CHCl₃ solutions, isolated molecules and cyclic dimeric H-complexes exist in an equilibrium.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1674–1676, September, 1994.     

The structure of liquid alcohols and the temperature dependence of vibrational bandwidth

To obtain the information about the structure peculiarities of liquid alcohols the temperature dependence of Raman profiles widths for these objects was studied. The results of these investigations have shown that in the region 150–340 K the widths of Raman bands in liquid methanol and ethanol are constant. From the data on the constancy of the number of hydrogen bonds per one molecule (in the same temperature range) the conclusion on the dynamic stability of the cluster structure of alcohols was made. The broadening of vibrational bands is determined by inhomogeneous broadening and by the dephasing of intramolecular vibrations due to the hydrogen bond dissociation.     

基于DFT和分子连接性指数方法研究醇类化合物的水溶解度和分配系数

将DFT方法计算得到的量化参数和分子连接性指数联合应用到60个醇类化合物的溶解度和辛醇/水分配系数的QSPR研究中,分别通过逐步回归得到具有显著统计意义的4个参数和5个参数的QSPR方程.以此4个参数和5个参数分别作为输入参数,采用BPNN,RBFNN方法建立了QSPR预测模型,使用Latin-partition交叉验证方法评价模型的预测能力.BPNN,RBFNN模型对溶解度预测的相关系数分别为0.993和0.994,而对辛醇/水分配系数预测的相关系数分别0.990和0.997,结果令人满意.     

The equilibrium melting points of random ethylene‐octene copolymers: A test of the Flory and Sanchez–Eby theories

Ethylene/l‐octene copolymers produced with metallocene catalysts are believed to have a homogeneous comonomer content with respect to molecular weight. Two series of copolymers of different molecular weights with a 1‐octene content ranging from 0 to 39 branches per 1000 carbon atoms were studied. The influence of branch content on structure and melting behavior as well as on isothermal and nonisothermal bulk crystallization was studied. In this article, the equilibrium melting temperatures of ethylene/l‐octene random copolymers is the focus. The principal techniques used were thermal analysis and small‐angle X‐ray scattering. The use of Hoffman–Weeks plots to obtain the equilibrium melting temperatures of ethylene/l‐octene random copolymers resulted in nonsensical high values of the equilibrium melting point or showed behavior parallel to the T_m = T_c line, resulting in no intercept and, hence, an infinite equilibrium melting point. The equilibrium melting temperatures of linear polyethylenes and homogeneous ethylene/l‐octene random copolymers were determined as a function of molecular weight and branch content via Thompson–Gibbs plots involving lamellar thickness data obtained from small‐angle X‐ray scattering. This systematic study made possible the evaluation of two equilibrium melting temperature depression equations for olefin‐type random copolymers, the Flory equation and the Sanchez–Eby equation, as a function of defect content and molecular weight. The range over which the two equations could be applied depended on the defect content after correction for the effect of molecular weight on the equilibrium melting temperature. The equilibrium melting temperature, T(n, p_B), of the ethylene/l‐octene random copolymers was a function of the molecular weight and defect content for low defect contents (p_B ≤ 1.0%). T(n, p_B) was a weak function of molecular weight and a strong function of the defect content at a high defect content (p_B ≥ 1.0%). The Flory copolymer equation could predict T(n, p_B) at p_B ≤ 1.0% when corrections for the effect of molecular weight were made. The Sanchez–Eby uniform inclusion model could predict T(n, p_B) at a high defect content (1.6% ≤ p_B ≤ 2.0%). We conclude that some defects were included in the crystalline phase and that the excess free energies (18–37 kJ/mol) estimated in this study were within the theoretical range. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 154–170, 2000     

Kinetics and mechanism of Ru(III)-catalyzed oxidation of aliphatic alcohols by trichloroisocyanuric acid in HClO4 medium

The kinetics and mechanism of Ru(III)-catalyzed oxidation of some aliphatic alcohols by trichloroisocyanuric acid (TCICA) has been studied in aqueous HOAc-HClO₄ medium. The reaction is zero order in [TCICA], fractional order in [alcohol] and first order in [Ru(III)]. The reaction is insensitive towards changes in acid concentration. The rate is not affected by an increase in [Cl⁻]. The polar reaction constant (ρ*) was found to be −1.27 at 308 K. A mechanism involving complex formation between the substrate and catalyst in the fast equilibrium step followed by its decomposition in a slow step is proposed.