Gaseous infrared spectra of the simplest geminal diol CH2(OH)2 and the isotopic analogues in the hydration of formaldehyde

2021 ◽  
Author(s):  
Hung-Yang Jain ◽  
Chih-Tsun Yang ◽  
Li-Kang Chu
Keyword(s):  
Infrared Spectrum ◽  
Infrared Spectra ◽  
Absorption Bands ◽  
Geminal Diol

The infrared spectrum of the simplest geminal diol, methanediol or methylene glycol (CH2(OH)2), was successfully probed in the gaseous hydration of formaldehyde. The observed absorption bands coincided with the anharmonic...

Infrared Analysis of Isomerized, Vulcanized, and Oxidized Natural Rubber

1955 ◽  
Vol 28 (1) ◽  
pp. 213-223 ◽  
Author(s):  
G. Salomon ◽  
A. Chr van der Schee
Keyword(s):  
Double Bond ◽  
Infrared Spectrum ◽  
Natural Rubber ◽  
Infrared Spectra ◽  
Infrared Analysis ◽  
Side Group ◽  
Oxidation Reactions ◽  
Absorption Bands ◽  
Group Ii

Abstract This paper is a continuation of our study on the infrared spectra of natural rubber and its derivatives. It was found previously that, in certain reactions of rubber, the original double bond (I) is shifted to the side group (II) and that this leads to significant changes in the chemical and mechanical behavior of the polymer. Others have also reported the occurrence of groups (II) and (III) in rubber and certain rubber derivatives. Group (II) is also found in synthetic polyisoprenes as a result of 3,4-polymerization. We have now measured the intensities of the absorption bands of the rubber spectrum and changes produced by cyclization and isomerization. Certain statements on the formation of (II) and (III) during vulcanization were at variance with our experience, but a detailed investigation cleared up some misconceptions. Modifications brought about by oxidation are chemically related to those produced by sulfuration reactions. A classification of oxidation reactions, based on typical changes in the infrared spectrum, will be proposed in the discussion.

scholarly journals Exploration of Free Energy Surface and Thermal Effects on Relative Population and Infrared Spectrum of the Be6B11− Fluxional Cluster

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 112
Author(s):  
Carlos Emiliano Buelna-Garcia ◽  
José Luis Cabellos ◽  
Jesus Manuel Quiroz-Castillo ◽  
Gerardo Martinez-Guajardo ◽  
Cesar Castillo-Quevedo ◽  
...  
Keyword(s):  
Free Energy ◽  
Infrared Spectrum ◽  
Infrared Spectra ◽  
Thermal Effects ◽  
Global Minimum ◽  
Energy Surface ◽  
Weighted Sums ◽  
Free Energy Surface ◽  
Temperature Dependent ◽  
Relative Population

The starting point to understanding cluster properties is the putative global minimum and all the nearby local energy minima; however, locating them is computationally expensive and difficult. The relative populations and spectroscopic properties that are a function of temperature can be approximately computed by employing statistical thermodynamics. Here, we investigate entropy-driven isomers distribution on Be6B11− clusters and the effect of temperature on their infrared spectroscopy and relative populations. We identify the vibration modes possessed by the cluster that significantly contribute to the zero-point energy. A couple of steps are considered for computing the temperature-dependent relative population: First, using a genetic algorithm coupled to density functional theory, we performed an extensive and systematic exploration of the potential/free energy surface of Be6B11− clusters to locate the putative global minimum and elucidate the low-energy structures. Second, the relative populations’ temperature effects are determined by considering the thermodynamic properties and Boltzmann factors. The temperature-dependent relative populations show that the entropies and temperature are essential for determining the global minimum. We compute the temperature-dependent total infrared spectra employing the Boltzmann factor weighted sums of each isomer’s infrared spectrum and find that at finite temperature, the total infrared spectrum is composed of an admixture of infrared spectra that corresponds to the spectra of the lowest-energy structure and its isomers located at higher energies. The methodology and results describe the thermal effects in the relative population and the infrared spectra.

Pyrrole Studies. I. The Infrared Spectra of 2-Monosubstituted Pyrroles

1963 ◽  
Vol 16 (1) ◽  
pp. 93 ◽  
Author(s):  
RA Jones
Keyword(s):  
Infrared Spectra ◽  
Infrared Absorption ◽  
Absorption Bands ◽  
Infrared Absorption Bands

The positions and intensities of the characteristic infrared absorption bands of the nucleus are recorded and discussed for thirty-five 2-monosubstituted pyrroles.

scholarly journals THE USE OF INFRARED SPECTROPHOTOMETRY FOR THE ESTIMATION OF SMALL QUANTITIES OF SOME HALOGENATED HYDROCARBONS

1953 ◽  
Vol 31 (4) ◽  
pp. 328-337 ◽  
Author(s):  
L. Breitman ◽  
E. W. R. Steacie
Keyword(s):  
Quantitative Analysis ◽  
Carbon Tetrachloride ◽  
Gas Phase ◽  
Infrared Spectra ◽  
Methyl Chloride ◽  
Ternary Mixtures ◽  
Halogenated Hydrocarbons ◽  
Infrared Spectrophotometry ◽  
Absorption Bands ◽  
Binary And Ternary Mixtures

The infrared spectra of chloral, carbon tetrachloride, and chloroform have been determined between 1500 and 650 cm.−1 over a range of pressures in the gas phase. Absorption bands suitable for the quantitative analysis of binary and ternary mixtures of the components have been selected and their peak intensities shown to obey Beer's Law over the range of pressures studied. Ternary mixtures have been analyzed from the spectra with an accuracy of about 20%.The spectra of dichloromethane and methyl chloride have also been measured under comparable conditions.

The Far Infrared Spectra of Partially Orientationally Ordered Water Molecules: Hexamethylenetetramine Hexahydrate at 95 K

1975 ◽  
Vol 53 (17) ◽  
pp. 2642-2645 ◽  
Author(s):  
John E. Bertie ◽  
Marco Solinas
Keyword(s):  
Infrared Spectrum ◽  
Infrared Spectra ◽  
Far Infrared ◽  
Clathrate Hydrate ◽  
Factor Group ◽  
Water Molecules ◽  
Disordered Solids ◽  
Ordered Water ◽  
Far Infrared Spectra ◽  
Three Phases

The far infrared spectra of four isotopic modifications of the partially orientationally ordered clathrate hydrate hexamethylenetetramine hexahydrate at 95 K are reported. The spectra are assigned to absorption allowed under the diffraction factor group, and to disorder-allowed absorption, following the theory for absorption by translational vibrations in orientationally disordered solids. Three phases formed primarily by hydrogen-bonded water molecules are known to be significantly, but only partially, orientationally ordered, hexamethylenetetramine hexahydrate, ice V, and ice VI. Of these phases, only ice VI fails to show sharp absorption in its far infrared spectrum in addition to the broad, disorder-allowed absorption.

scholarly journals Analysis of functional groups in atmospheric aerosols by infrared spectroscopy: sparse methods for statistical selection of relevant absorption bands

2016 ◽  
Vol 9 (7) ◽  
pp. 3429-3454 ◽  
Author(s):  
Satoshi Takahama ◽  
Giulia Ruggeri ◽  
Ann M. Dillner
Keyword(s):  
Infrared Spectra ◽  
Atmospheric Aerosols ◽  
Quantitative Prediction ◽  
Calibration Model ◽  
Vibrational Modes ◽  
Aerosol Composition ◽  
Absorption Bands ◽  
Calibration Models ◽  
Ft Ir ◽  
Selection Of

Abstract. Various vibrational modes present in molecular mixtures of laboratory and atmospheric aerosols give rise to complex Fourier transform infrared (FT-IR) absorption spectra. Such spectra can be chemically informative, but they often require sophisticated algorithms for quantitative characterization of aerosol composition. Naïve statistical calibration models developed for quantification employ the full suite of wavenumbers available from a set of spectra, leading to loss of mechanistic interpretation between chemical composition and the resulting changes in absorption patterns that underpin their predictive capability. Using sparse representations of the same set of spectra, alternative calibration models can be built in which only a select group of absorption bands are used to make quantitative prediction of various aerosol properties. Such models are desirable as they allow us to relate predicted properties to their underlying molecular structure. In this work, we present an evaluation of four algorithms for achieving sparsity in FT-IR spectroscopy calibration models. Sparse calibration models exclude unnecessary wavenumbers from infrared spectra during the model building process, permitting identification and evaluation of the most relevant vibrational modes of molecules in complex aerosol mixtures required to make quantitative predictions of various measures of aerosol composition. We study two types of models: one which predicts alcohol COH, carboxylic COH, alkane CH, and carbonyl CO functional group (FG) abundances in ambient samples based on laboratory calibration standards and another which predicts thermal optical reflectance (TOR) organic carbon (OC) and elemental carbon (EC) mass in new ambient samples by direct calibration of infrared spectra to a set of ambient samples reserved for calibration. We describe the development and selection of each calibration model and evaluate the effect of sparsity on prediction performance. Finally, we ascribe interpretation to absorption bands used in quantitative prediction of FGs and TOR OC and EC concentrations.

Investigation of Spectral Sensitization III. A Study of the Visible and Infrared Spectra of Some Very Pure Bis-Thiazolinyl and Bis-Thiazolyl Cyanine Iodides

1966 ◽  
Vol 20 (3) ◽  
pp. 150-158 ◽  
Author(s):  
A. Leifer ◽  
M. Boedner ◽  
P. Dougherty ◽  
A. Fusco ◽  
M. Koral ◽  
...  
Keyword(s):  
Infrared Spectra ◽  
Low Frequency ◽  
Red Shift ◽  
Absorption Bands ◽  
Spin Resonance ◽  
Visible Spectra ◽  
Bond System ◽  
Phenyl Rings ◽  
In Series ◽  
Systematic Group

A detailed study of the visible spectra in solution and the infrared spectra of the dyes in the solid state have been made for the following vinylogous series of cyanine dyes: [2-bis(3-ethylthiazolinyl)] cyanine iodides, I; [2-bis(3-ethyl-4-methylthiazolyl)] cyanine iodides, II; and [2-bis(3-ethyl-4,5-diphenylthiozolyl] cyanine iodides, III. Each dye, to be acceptable for study, had to be chromatographically pure, give a correct microchemical elemental analysis, and be free of electron-spin resonance (free radical) signals. These vinylogous series of dyes form a systematic group. That is, in series I there is only a resonant conjugated chain of alternate single and double bonds present between the two nitrogen atoms; in series II there are additional olefinic unsaturated bonds which are in conjugation with the resonant conjugated chain; and in series III there are additional phenyl rings in conjugation with the entire pi bond system present in II. The characteristic red shift of the principal absorption maxima was observed for these dyes in the visible as the number of methine linkages increased. Furthermore, a small relative red shift of the absorption maxima has been observed for this group of dyes and has been interpreted on the basis of the type of unsaturation present in conjugation with the resonant conjugated chain. Assignments of vibrational modes to separate absorption regions have been made for these vinylogous series of dyes. A correlation of the dye structure with the absorption bands has been made. Each vinylog gave rise to a characteristic pattern of resonant conjugated stretching modes in the region 1600 to 1400 cm−1. These modes exhibited a low frequency shift as the resonant conjugated chain-length increased. For a constant number of polymethine linkages these modes are a function of the type of unsaturation present which is in conjugation with the resonant conjugated chain.

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