Infrared spectroscopy spectra interpretation

The infrared (IR) spectra of 1,10-phenanthroline, its hydrate and perchlorate in the region 600-2000 cm-1 have been obtained, and the principal features of the spectra interpreted.66 Further studies on the IR spectra of 1,10-phenanthroline,67-69 substituted 1,10-phenanthrolines,70,71 and 1,7-phenanthroline67 have also been reported. The IR spectrum of 4,7-phenanthroline in the region 650-900 cm-1 has been analyzed, and the C—H out-of-plane deformation frequencies were compared with those of phenanthrene and benzo[/]quinoline.72 The IR spectra of salts of 1,10-phenanthroline have been taken, and the NH vibrations determined.28,73 Infrared spectroscopy has been used to detect water associated with 1,10-phenanthroline and some of its derivatives on extraction into nitromethane from aqueous solution.74 The Raman spectrum of 1,10-phenanthroline has been compared with its IR spectrum.75 Recently, the Raman and IR spectra of all ten isomeric phenanthrolines were measured in solution and solid states, and the spectra were fully discussed.76... 

The identification of species adsorbed on surfaces has preoccupied chemists and physicists for many years. Of all the techniques used to determine the structure of molecules, interpretation of the vibrational spectrum probably occupies first place. This is also true for adsorbed molecules, and identification of the vibrational modes of chemisorbed and physisorbed species has contributed greatly to our understanding of both the underlying surface and the adsorbed molecules. The most common method for determining the vibrational modes of a molecule is by direct observation of adsorptions in the infrared region of the spectrum. Surface spectroscopy is no exception and by far the largest number of publications in the literature refer to the infrared spectroscopy of adsorbed molecules. Up to this time, the main approach has been the use of conventional transmission IR and work in this area up to 1967 has been summarized in three books. The first chapter in this volume, by Hair, presents a necessarily brief overview of this work with emphasis upon some of the developments that have occurred since 1967. 

O-H bond. Among such properties a prominent one is the ultraviolet absorption spectrum and the theory may therefore be used for the examination of some of the spectroscopic shifts which accompany the lactam-lactim tautomerization. Much caution must, however, be exercised in this respect. Thus, in a recent paper Kwiatkowski135,137 performed Pariser-Parr-Pople-type calculations on the electronic structure of hydroxypurines, essentially to interpret their ultraviolet spectra. In these calculations he assumed that these compounds exist predominantly in their lactim form, and the results of his calculations, at least for 6- and 8-hydroxypurine, did not seem to contradict this assumption. It is only in the case of the 2-hydroxy isomer that a particularly striking disagreement between theory and experiment led him to admit that this last compound may exist in the lactam form. Calculations carried out for this form gave, in fact, a more satisfactory agreement with experiment.138 As we have seen, unambiguous infrared spectroscopy evidence clearly show s that all three isomers exist essentially in the lactam form. This shows that ultraviolet absorption may provide only very uncertain evidence about the lactam-lactim tautomerism in hydroxypurines and related compounds. 

The Infrared Region 515 12-4 Molecular Vibrations 516 12-5 IR-Active and IR-lnactive Vibrations 518 12-6 Measurement of the IR Spectrum 519 12-7 Infrared Spectroscopy of Hydrocarbons 522 12-8 Characteristic Absorptions of Alcohols and Amines 527 12-9 Characteristic Absorptions of Carbonyl Compounds 528 12-10 Characteristic Absorptions of C—N Bonds 533 12-11 Simplified Summary of IR Stretching Frequencies 535 12-12 Reading and Interpreting IR Spectra (Solved Problems) 537 12-13 Introduction to Mass Spectrometry 541 12-14 Determination of the Molecular Formula by Mass Spectrometry 545... 

Figure 1 gives a typical infrared spectrum of lake humic acid. The interpretation of infrared spectra of humic substances is discussed in depth by -MacCarthy and Rice in Chapter 21. The similarity of infrared spectra of humic acids from different lakes suggests a similarity of the aspects of chemical structure that are related to their infrared absorptions. However, infrared spectroscopy is not sensitive enough to uncover minor structural differences among humic acids. In fact, humic acids were separated by organic solvents (chloroform, methylethylketone, methanol, dimethylformamide) into various fractions (Ishiwatari, 1969b, 1973). Infrared spectra of two of these fractions, the chloroform-soluble fraction and the methylethylketone-... 

The applicability of spectroscopic methods (other than NMR) for determining functionality in humic substances is reviewed. Spectroscopic methods, like all other investigational techniques, are severely limited when applied to humic substances. This is because humic substances are comprised of complicated, ill-defined mixtures of polyelectrolytic molecules, and their spectra represent the summation of the responses of many different species. In some cases only a small fraction of the total number of molecules contributes to the measured spectrum, further complicating the interpretation of spectra. The applicability and limitations of infrared spectroscopy, Raman spectroscopy, UV-visible spectroscopy, spectrofiuorimetry, and electron spin resonance spectroscopy to the study of humic substances are considered in this chapter. Infrared spectroscopy, while still very limited when applied to humic substances, is by far the most useful of the methods listed above for determining functionality in these materials. Very little information on the functionality of humic substances has been obtained by any of the other spectroscopic methods. 

I suggest the use of infrared spectroscopy for the laboratory tests. Samples of the him can be mounted in the path of the infrared light beam in an infrared spectrometer and the resulting infrared transmission spectra recorded. If your staff is not familiar with infrared spectroscopy or the interpretation of infrared transmission spectra, you might allow them some time to read some basic reference material on this technique. I can provide that for you. The transmission spectrum recorded by the spectrometer is like a fingerprint of the material in the path of the light. It is a pattern that is observed each time that material is tested. 

The study of fine structure in cellulose by infrared spectroscopy rests largely on the ease with which this technique can characterize the hydrogenbonding system of the hydroxyl groups. There are other changes in the spectrum caused by fine-structure changes (see, for example, Section III.2), but some of these are more difficult to interpret and are used in an empirical manner only. 

Infrared spectroscopy is a technique based on the vibrations of the atoms of a molecule. An infrared spectrum is obtained by passing infrared radiation through a sample and determining what fraction of the incident radiation is absorbed at a particular energy. The energy at which any peak in an absorption spectrum appears correspond to the frequency of a vibration of a part of the sample molecul pn this introductory chapter we will discuss the basic ideas and de itions associated with infrared spectroscopy. We will look in some detail at the vibrations of molecules as these are crucial to the interpretation of infrared spectra. 

Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy have also been used for analyses of complexes. Upon complexation of the guest, shifts or changes in the spectrum occur. There are interferences in the spectra from the CD, and some of the changes are very subtle, requiring careful interpretation of... 

Infrared spectroscopy can be used in turbid suspensions, such as membranes or with big proteins, but the methods for studying the spectrum are impaired by the difficult interpretation of the composite bands obtained from proteins. Thus, more powerful methods of spectral analysis are needed... 

The nature of the interactions between water molecules and monolayers or multilayers of Chi a, obtained by the L-B technique, has been examined by infrared spectroscopy (IR) [40]. Following deposition of the monolayer of Chi a, repetitive scans showed some modifications in the IR spectra which are interpreted as a reorganization of the molecules as some water molecules leave the array. Drying the sample further modifies the IR spectra, which indicates the departure of more tenacious water molecules. However, putting the sample in a moist atmosphere does not restore the original spectrum. This is an indication of a nonreversible reorganization in the Chi a array. 

Although samples can be rapidly analyzed using infrared spectroscopy, the technique works best for relatively pure samples. If impurities are present in the sample and they also absorb infrared radiation, the resulting spectrum contains contributions from both the sample and the impurities. This can complicate interpretation of the spectrum and subsequent identification of the sample. 

Spectroscopy and the Electromagnetic Spectrum Infrared Spectroscopy Interpreting Infrared Spectra... 

The complexity of the spectrum interpretation is one the drawbacks of FIR spectroscopy, the other one was for a long time the absence of any appropriate experimental instruments. However, recoitly ra M prc ess in the FIR technique, viz. commercial FT-IR spwtrometes as well as tunable lasers for the far infrared region, have ensured a successhil scdutimi to this proUem. 

Algorithms Infrared Data Correlations with Chemical Structure Infrared Spectra Interpretation by the Characteristic Frequency Approach Machine Learning Techniques in Chemistry Molecular Models Visualization Neural Networks in Chemistry NMR Data Correlation with Chemical Structure Partial Least Squares Projections to Latent Structures (PLS) in Chemistry Shape Analysis Spectroscopic Databases Spectroscopy Computational Methods Structure Determination by Computer-based Spectrum Interpretation Zeolites Applications of Computational Methods. 

Analysis of infrared spectra can teU you what molecules are present in a sample and at what concentrations this is why infrared spectroscopy is useful. There are several types of infrared spectrometers in the world, but the most widely used ones are FTlRs, which is the focus here. This book will teach you how FTlRs work, how to use them to obtain the best spectra, how to use FTIR software to assist in data analysis, how to properly prepare samples for FTIR analysis, how to quantify concentrations in samples using FTIR spectra, and infrared microscopy. In essence, we will be studying everything involved in obtaining a good infrared spectrum. For information on how to interpret an infrared spectrum to determine the structures of molecules present in a sample please consult my book on infrared spectral interpretation [1]. 

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