Vibrational spectra, assignments and normal coordinate calculation of acrylamide

The infrared spectra, low temperature infrared spectra, polarized infrared spectra and Raman spectra of acrylamide have been recorded and observed frequencies were assigned to various modes of vibrations on the basis of normal coordinate analysis, assuming C(s) point group symmetry. The potential energy distribution associated with normal modes is also reported. The assignment of fundamental vibrations agrees well with the calculated frequencies.     

Infrared and polarized Raman spectra of a noncentrosymmetric compound "sodium samarium fluorosilicate" NaSmSiO4.0.25NaF

Chemical preparation, infrared and Raman spectra of sodium samarium fluorosilicate, NaSmSiO(4).0.25NaF are presented. The spectra are analyzed with regard to the symmetry, and the numbers of the SiO(4)(4-) internal vibrational modes observed in the Raman and infrared spectra are consistent with the predictions.     

Infrared spectra of phthalic acid, the hydrogen phthalate ion, and the phthalate ion in aqueous solution

The infrared spectra of a series of aqueous solutions containing phthalic acid (1,2-benzenedicarboxylic acid) and varying pH were examined using attenuated total reflection Fourier transform infrared spectroscopy and potentiometry. The basis spectra of phthalic acid, the hydrogen phthalate ion, and the phthalate ion were isolated using a factor analysis in which the absorbance of these species varies with pH and total phthalate concentration according to equilibrium and mass balance relations. Assignments of these basis spectra were made by comparison with spectra calculated ab initio. The conditional formation constants of phthalic acid and the hydrogen phthalate ion were determined at 25.0+/-0.1 degrees C in 0.6 M NaCl ionic media using infrared spectroscopy and in 1.5 M NaCl ionic media using both infrared spectroscopy and potentiometry.     

顺1,4-聚丁二烯在不同溶剂中的环化反应及其机理的研究

以烯丙基氯 一氯二乙基铝 (CH2 CHCH2 Cl AlEt2 Cl)催化体系研究了顺 1 ,4 聚丁二烯在不同溶剂(三甲苯、二甲苯、甲苯、苯和环己烷 )中的环化反应 .结合环化产物红外光谱的测定 ,提出芳烃溶剂分子经受阳碳离子亲电取代作用而参与环化的机理 ,以此解释了若干实验事实 ,并对已有文献报道进行了讨论 .     

镁离子作用下乙醇溶液的红外光谱研究

采用红外光谱法对MgCl2乙醇溶液进行了研究.乙醇分子的谱带变化表明,Mg<'2+>与乙醇分子中C-O发生强烈作用,同时,随着MgCl2的加入,原有氢键结构遭到破坏,形成新的结构,计算得到其溶剂化数为3.87～1.83.针对溶液中各聚体氢键峰面积的变化进行了定量分析,确定了在0.3406～1.6083mol/kg浓度范围内二聚体含量与MgCl2浓度呈线性关系,其线性方程为△A=0.24202+16.65859 C;,相关系数R=0.9922,二聚体和多聚体呈可逆平衡关系,进一步揭示了溶液溶剂化的微观过程.     

Infrared studies on Co and Cd complexes of sulfamethoxazole

In this study, the new Co and Cd complexes of sulfamethoxazole (SMX) (drug substance) [4-amino-N-(5-methyl-3-isoxazolyl) benzenesulfonamide] have been prepared for the first time and their infrared spectra have been investigated. The infrared spectra of the samples were recorded in the range 4000-400 cm(-1) and their fundamental vibrational wave numbers were obtained. The vibrational assignments were determined by using the group frequency tables and compared with the wave numbers of SMX found in the literature. The SMX wave numbers observed in the infrared spectra of the metal complexes were compared with those of free SMX. Investigations of the infrared spectra of the metal complexes indicated the vibrations due to the amino and sulfonamido groups are shifted with respect to the free molecule in line with their coordination to the metal. In the cadmium complex, the active binding sites of SMX are the sulfonamide nitrogen and sulfonic oxygen; in cobalt compound, the metal atom coordinates through the sulfonamide and amino nitrogens. The low energy calculations were also carried out by using geometry optimization. It is shown that the proposed structure for the metal complexes of SMX derived from the infrared spectra are consistent with the theoretical results.     

A new approach to the spectral study of unstable radicals and ions in solution by the use of an inert gas glovebox system: observation and analysis of the infrared spectra of the radical anion and dianion of p-terphenyl

By using a Fourier-transform infrared spectrometer contained in an inert gas glovebox system (oxygen and water concentrations: <0.1 ppm), high-quality infrared absorption spectra have been observed for the radical anion and dianion of p-terphenyl in tetrahydrofuran solutions. Density functional theory with the B3LYP nonlocal exchange-correlation functional and the 6-311+G** basis set has been used for the calculations of the structures and infrared spectra of the neutral species, radical anion, and dianion of p-terphenyl. The observed infrared spectra of the radical anion and dianion are in good agreement with those calculated by density functional theory. The origin of the strong infrared absorption intensities characteristic of the radical anion and dianion are discussed in terms of changes in electronic structures induced by specific normal vibrations (electron-molecular vibration interaction).     

Infrared spectra of homogeneous and heterogeneous proton-bound dimers in the gas phase

Infrared multiphoton dissociation spectra of three homogeneous and two heterogeneous proton-bound dimers were recorded in the gas phase. Comparison of the experimental infrared spectra recorded in the fingerprint region of the proton-bound dimers with spectra predicted by electronic structure calculations shows that all modes which are observed contain motion of the proton oscillating between the two monomers. The O-H-O asymmetric stretch for the homogeneous dimers is shown to occur at around 800 cm-1. As expected, the O-H-O asymmetric stretching modes for the heterogeneous proton-bound dimers are observed to shift to significantly higher energy with respect to those for the homogeneous proton-bound dimers due to the asymmetry of the O-H-O moeity. This shift is shown to be predictable from the difference in proton affinities between the two monomers. Density functional predictions of the infrared spectra based on the harmonic oscillator model are demonstrated to predict the observed spectra of the homogeneous proton-bound dimers with reasonable accuracy. Calculations of the structure and infrared spectrum of protonated diglyme at the B3LYP/6-31+G** level and basis also agree well with an infrared spectrum recorded previously. For both heterogeneous proton-bound dimers, however, the predicted spectra are blue-shifted with respect to experiment.     

Infrared and Raman spectra of cytosine and cytidinium salts

Studies of the infrared and Raman spectra of cytidinium salts are presented. They are supplemented by the measurements of the infrared spectra of the c     

酰胺型双冠醚的振动光谱分析

对邻苯-二(氧乙酰胺-4'-本并-15-冠-5)、间苯-二(氧乙酰胺-4'-苯并-15-冠-5)、对苯-二(氧乙酰胶-4'-苯并-15-冠-5)三种酰胺型双冠醚和苯并15-冠-5的喇曼光谱及红外光谱进行了测定和归属分析,并与15-冠-5的喇曼及红外光谱进行了比较研究.     

Rapid quality control of solid materials by diffuse reflectance FTIR spectrometry

This paper describes an approach to quantitative analysis using diffuse reflectance spectra of solid materials in conjunction with the infrared data processing technique CIRCOM, to calculate equations correlating the FTIR spectra with the constituents or properties for a calibration set of well-characterised samples. Unknown samples, similar to those in the calibration set, can then be analysed from their infrared spectra. An example from the minerals industry will be given.     

Theoretical modeling of infrared spectra of hydrogen-bonded crystals of salicylic acid

A theoretical model for the infrared spectra in the O-H stretching region of hydrogen-bonded salicylic acid is presented. Based on the model, infrared spectrum in the O-H stretching region is calculated for salicylic acid and compared with the experimental one. The experimental and theoretical spectra are in good agreement.     

A quantitative measure of the reliability of searches of spectral libraries

A quantitative measure of library search reliability has been developed. Applications of the quantitative reliability metric (QRM) for evaluating the reliability of library searches for unknown target spectra and the use of this measure to detect the failure of a library search caused by noise, contaminant peaks and missing library spectra are discussed. The effects of noise and composite infrared spectra of mixtures on the QRM are examined for test sets of 561 infrared spectra. The QRM is also used to evaluate the performance of a search of an infrared library compressed by eigenvector projection.     

Infrared intensity of 1-monolaurin-water systems in the gel phase

The infrared spectra of 1-monolaurin-water systems, where KSCN is added as the intensity standard, were observed and the infrared intensity of the bands due to acyl groups measured relatively to that of the CN stretching. The infrared intensities of the bands parallel and perpendicular to the paraffin chains decrease and increase, respectively, on going from the crystalline 1 phase to the gel phase, confirming that these intensity changes result from the long-range interaction among oscillating dipoles. The infrared spectra with no CH2 rocking and the splitting of the CH2 rocking are also discussed with the same interaction model.     

Vapor Phase Vibrational Spectra for Re(2)O(7) and the Infrared Spectrum of Gaseous HReO(4). Molecular Shapes of Mn(2)O(7), Tc(2)O(7), and Re(2)O(7)

The Raman and infrared spectra of gas phase Re(2)O(7) are reported. The experimental vibrational spectra of molecular Tc(2)O(7) and Re(2)O(7) are compared with calculated spectra. The results of these studies agree with a nonlinear M-O-M bridge for Tc(2)O(7) and Re(2)O(7). For infrared intensity calculations, the point charge approximation is used, while for the Raman calculations a combination of bond and atom polarizabilities is adopted. Pure Re(2)O(7) was prepared from rhenium wire, but attempts to prepare it from rhenium powder and oxygen always led to infrared spectra showing serious contamination from a species containing an -OH linkage. Detailed experiments identified this molecule as HReO(4), a unique transition metal analogue of the perhalic acids, and a partial infrared spectrum of this molecule is reported.     

傅里叶变换红外光谱体表无创探测乳腺肿瘤

利用傅里叶变换红外(FTIR)光谱仪联合衰减全反射(ATR)探头的中红外光导纤维对46名健康志愿者及113名乳腺肿物患者的体表皮肤进行无创红外光谱测定, 并从分子水平比较、分析了正常乳腺和有肿物乳腺体表皮肤的红外光谱特征. 结果表明, 健康志愿者乳房皮肤8个FTIR光谱测定部位的图谱趋于一致; 正常乳腺体表与有肿瘤乳腺体表的吸收峰差异明显, 而1080 cm^-1处核酸相关吸收峰的变化对鉴别肿瘤的良、 恶性有重要意义.     

Hierarchical clustering of infrared spectra

The generation of a hierarchical tree of 500 infrared spectra, using the recently proposed fractal or 3-distances-clustering method is described and discussed. The objects of clustering are infrared spectra of polymer compounds which are represented as sets of 80 complex Fourier coefficients, obtained by fast Fourier transformation of digitized absorbance spectra. The generated hierarchical tree, with a maximum height of 20 and an average height of 12 levels, yields a very satisfactory clustering scheme with respect to the structure of the compounds involved. In addition to very good clustering, a 100% retrieval (prediction) ability was obtained. This was achieved by the use of an iterative procedure after the initial tree had been generated. Additionally, the tree was tested with 240 infrared spectra of different compounds which were taken into account during the generation of the tree. The retrieval success of these test runs is discussed with respect to the structural similarity of the compounds to which the “unknown” spectra were linked.     

FT-Raman and FT-IR spectra, vibrational assignments and density functional studies of 5-bromo-2-nitropyridine

The Fourier transform Raman and Fourier transform infrared spectra of 5-bromo-2-nitropyridine were recorded in the solid phase. The equilibrium geometry, natural atomic charges, harmonic vibrational frequencies, infrared intensities and Raman scattering activities were calculated by density functional B3LYP method with the 6-311++G(d,p) basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental values. A detailed interpretations of the infrared and Raman spectra of 5-bromo-2-nitropyridine is reported on the basis of the calculated potential energy distribution (PED). The theoretical spectrograms for the Raman and IR spectra of the title molecule have been constructed.     

Infrared and Raman spectra of alkali metal salts of TCNQ

The infrared and Raman spectra of the series of alkali metal salts of the monoanion radical of tetracyanoquinodimethane MTCNQ (M = Li, Na and K) are observed and analysed both in the low-frequency lattice vibration region and in the intramolecular vibration region. The vibrational assignments are made, by comparing the spectra of MTCNQ with one another and investigating the difference between the powder and solution spectra and the temperature dependence of the spectra. The monomer—dimer phase transition in NaTCNQ and KTCNQ of the columnar stacking of TCNQ⁻ does not cause a marked change in the low-frequency spectra due to the lattice vibrations. The vibronically activated bands of the totally symmetric modes of the TCNQ⁻ anion are observed in the infrared spectra, which are associated with the charge-transfer intermolecular interaction. A lattice dynamical analysis for the optically active crystal vibrations of NaTCNQ and KTCNQ is performed, and the result of this calculation also verifies the vibrational assignments of the low-frequency infrared and Raman bands attributed experimentally to the translational and rotational lattice modes.     

近红外特征谱段相关系数法测定中药胶囊中添加枸橼酸西地那非

利用近红外特征谱段相关系数法对中药胶囊中是否添加枸橼酸西地那非进行快速定性分析.分别使用近红外光谱仪的积分球和光纤附件测定光谱,以枸橼酸西地那非化学对照品的近红外光谱为参照光谱,选择特定谱段,根据枸橼酸西地那非被掺入胶囊中的最小起效浓度建立待测样品光谱与参照光谱在该谱段的相似系数阈值,定性判断待测样品是否含有枸橼酸西地那非.积分球方法:选择6070～5800 cm~(-1)和4170～4070 cm~(-1)谱段,阈值为70%,用79个含枸橼酸西地那非的市售样品验证该方法,相关系数大于70%的有72个,占样品总量的91.14%;光纤方法:选定6070～5800 cm~(-1)谱段为特征谱段,设定阈值为65%,用247个含枸橼酸西地那非的市售样品进行验证,相关系数大于65%的有216个,占样品总量的87.45%.实验证明此方法具有较好的预测能力,可作为市场上该种非法添加药物的快速有效检查手段.