Spectral data

Usually no single spectral technique is sufficient to answer complex questions such as a chemical structure determination. Jurs et. al. C1303 combined mass spectra, infrared spectra, melting point, and boiling point to pattern vectors. Combined patterns have been formed for 291 compounds with chemical formulas -24 0-4 0-3 pattern contained 

132 components from mass positions and 130 components from absorption wavelengths. The relative contributions of the two types of data grossly affected the classification behaviour. Therefore, the data were normalized so that each data source contributed equally to the total amplitude of the pattern set. 

The Learning machine was used to train classifiers for the recognition of ethyl groups, vinyl groups and C=C double bonds. A significant improvement of the classifier performance with combined spectral data was only found for the determination of double bonds. The number of features could be reduced to 20 without a decrease of the predictive ability. 

A combination of the infrared spectrum and the Raman spectrum to a single pattern vector has been successfully applied by Comerford et. al. 1533 (Chapter 13.3). 

The comparison of frequencies shown in Table V.2. indicates that the highest Ln-H frequency is observed in the ytterbium and lutetium hydrides, but the lowest one is 

Zavadovskaya E.N., Scharaev O.K., Borisov G.K., Yampolsky Yu.B., Tinyakova E.L, Dolgoplosk B.M., Dokl. Acad. Nauk SSSR. (Russ.), 284 (1985) 143. 

Pauling L., The nature of the chemical bonds. 3rd ed. N.Y. Cornell Univ. press, (1960) 460. 

Almost all REM amides of the (R2N) Ln (x 2,3) type appear to be trimethylsilylamide complexes. Besides these compounds only (Et2N)2Yb(TllF)o5 [1] and isopropilamides of yttrium, neodymium and ytterbium are known, which are shortly mentioned in review [2] without a description of their synthesis and properties (Table VI. 1). 

Divalent metal silylamide complexes are easily obtained from the interaction of the corresponding REM with mercury amide in DME medium at room temperature [15]  

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Pretsch E, Clerc T, SeibI J and Simon W 1983 Tables of Spectral Data for Structural Determination of Organic Compounds Engl. edn. (Berlin Springer)... 

Figrue BE 16.20 shows spectra of DQ m a solution of TXlOO, a neutral surfactant, as a function of delay time. The spectra are qualitatively similar to those obtained in ethanol solution. At early delay times, the polarization is largely TM while RPM increases at later delay times. The early TM indicates that the reaction involves ZnTPPS triplets while the A/E RPM at later delay times is produced by triplet excited-state electron transfer. Calculation of relaxation times from spectral data indicates that in this case the ZnTPPS porphyrin molecules are in the micelle, although some may also be in the hydrophobic mantle of the micelle. Furtlier,... 

Multichannel time-resolved spectral data are best analysed in a global fashion using nonlinear least squares algoritlims, e.g., a simplex search, to fit multiple first order processes to all wavelengtli data simultaneously. The goal in tliis case is to find tire time-dependent spectral contributions of all reactant, intennediate and final product species present. In matrix fonn tliis is A(X, t) = BC, where A is tire data matrix, rows indexed by wavelengtli and columns by time, B contains spectra as columns and C contains time-dependent concentrations of all species arranged in rows. 

Decades of work have led to a profusion of LEERs for a variety of reactions, for both equilibrium constants and reaction rates. LEERs were also established for other observations such as spectral data. Furthermore, various different scales of substituent constants have been proposed to model these different chemical systems. Attempts were then made to come up with a few fundamental substituent constants, such as those for the inductive, resonance, steric, or field effects. These fundamental constants have then to be combined linearly to different extents to model the various real-world systems. However, for each chemical system investigated, it had to be established which effects are operative and with which weighting factors the frmdamental constants would have to be combined. Much of this work has been summarized in two books and has also been outlined in a more recent review [9-11]. 

A.J. Davies, Spectral Data Standard Exchange Formats. CSA23. 

Speclnfo Chemical Concepts GmbH, Germany spectral data nu- meric, struc- ture 150000 subst., 80000 C-NMR, 850 N-NMR, 670 O-NMR, 1750 F-NMR, 2000 P-NMR, 17000IR, 65 000 MS Chemical Concepts GmbH online periodi- cally www.chemicaJ- conctpts.com/ products.htm... 

To identify the main methods and tools available for the computer prediction of spectra from the molecular structure, and for automatic structure elucidation from spectral data... 

In contrast to IR and NMR spectroscopy, the principle of mass spectrometry (MS) is based on decomposition and reactions of organic molecules on theii way from the ion source to the detector. Consequently, structure-MS correlation is basically a matter of relating reactions to the signals in a mass spectrum. The chemical structure information contained in mass spectra is difficult to extract because of the complicated relationships between MS data and chemical structures. The aim of spectra evaluation can be either the identification of a compound or the interpretation of spectral data in order to elucidate the chemical structure [78-80],... 

Other methods consist of algorithms based on multivariate classification techniques or neural networks they are constructed for automatic recognition of structural properties from spectral data, or for simulation of spectra from structural properties [83]. Multivariate data analysis for spectrum interpretation is based on the characterization of spectra by a set of spectral features. A spectrum can be considered as a point in a multidimensional space with the coordinates defined by spectral features. Exploratory data analysis and cluster analysis are used to investigate the multidimensional space and to evaluate rules to distinguish structure classes. 

D. Dolphin, A. Wick, Thbulation of Infrared Spectral Data, Wley, New York, 1977. 

E. Pretsch, T. Cletc, J. Seibl, W. Simon, Tables of Spectral Data for Structure Determination of Organic Compounds, Springer-Verlag, Berlin, 1989. 

This does not have to be so Why not build an uninterrupted stream of information from the producer (the bench chemist) to the consumer (the reader of a journal or book, or the scientist that puts a query into a database) It is quite clear that the producers of information knows best what experiments were done, what observations were made, what results have been obtained. They should put this information into electronic laboratory books, augmented with spectral data (that they can obtain directly from the analytical laboratory). From this electronic repository aU other information sources -manuscripts, journals, books, databases - could be filled, clearly sometimes by manual selection, but not by changing data ... 

Several excellent print collections of spectra are available but are beyond the budgets of most col lege libraries Fortunately vast numbers of NMR IR and mass spectra are freely accessible via the Spectral Data Base System (SDBS) maintained by the Japanese National Institute of Advanced Industrial Science and Technology at... 

Mass spectra are reproduced with permis Sion from EPA/NIH Mass Spectral Data Base Supplement I S R Heller and G W A l lne National Bureau of Stan dards 1980... 

A very good general survey for interpreting mass spectral data is given by R. M. Silverstein, G. C. Bassler, and T. C. Morrill, Spectrometric Identification of Organic Compounds, 4th ed., Wiley, New York, 1981. 

Table 7.76 is condensed, with permission, from the Catalog of Mass Spectral Data of the American Petroleum Institute Research Project 44. These, and other tables, should be consulted for further and more detailed information. 

Apart from the actual acquisition of the mass spectrum and its subsequent display or printout, the raw mass spectral data can be processed in other ways, many of which have been touched on in other chapters in thi.s book. Some of the more important aspects of this sort of data manipulation are explained in greater detail below. 

Stauffer, D.B. and McLafferty, F.W., The Wiley/NBS Registry of Mass Spectral Data, Wiley Interscience, New York, 1989. 

EPA.INIH Mass Spectral Data Base, Vol. 1, U.S. National Bureau of Standards, Wasliiagton, D.C., 1978, p. 5. 

Bromine Trifluoride. Bromine trifluoride is a colorless Hquid. The commercial grade is usually amber to red because of slight bromine contamination. The molecule has a distorted T stmeture (26). Infrared spectral data (26—30), the uv-absorption spectmm (31), and vapor pressure data (32) may be found in the Hterature. 

The stmcture of O2F2 is that of a nonlinear FOOF chain, having the foUowiag molecular constants (56,57) O—O distance, 0.122 nm OOF angle, 109°30 dihedral angle, 87°30 dipole moment, 4.8 x 10 ° C-m (1.44 D). Additional physical and spectral data are summarized ia References 4 and 58. 

Selected physical properties are given ia Table 4. The nmr data (97) and ir and Raman spectra (98) have also been determined. Thermodynamic functions have been calculated from spectral data (99). 

Gestodene Gestodene (54), along with norgestimate and desogestrel, are the progestin components of the third-generation oral contraceptives (see Contraceptives). It may be crystallised from hexane/acetone (81) or ethyl acetate (82), and its crystal stmcture (83) and other spectral data have been reported (84). 

Norethindrone may be recrystakhed from ethyl acetate (111). It is soluble in acetone, chloroform, dioxane, ethanol, and pyridine slightly soluble in ether, and insoluble in water (112,113). Its crystal stmcture has been reported (114), and extensive analytical and spectral data have been compiled (115). Norethindrone acetate can be recrystakhed from methylene chloride/hexane (111). It is soluble in acetone, chloroform, dioxane, ethanol, and ether, and insoluble in water (112). Data for identification have been reported (113). The preparation of norethindrone (28) has been described (see Fig. 5). Norethindrone acetate (80) is prepared by the acylation of norethindrone. Norethindrone esters have been described ie, norethindrone, an appropriate acid, and trifiuoroacetic anhydride have been shown to provide a wide variety of norethindrone esters including the acetate (80) and enanthate (81) (116). 

Physical constants for saUcylaldehyde and -hydroxybenzaldehyde are Hsted in Table 2. Spectral data have been pubHshed (Table 2). 

SPECINEO Chemical Concepts GmbH spectral data for a representative section of organic chemistry... 

Spectra. The abiHty to consult collections of standard spectra is cmcial in the analysis of unknown compounds. A long history of data collection efforts has been aimed at these appHcations. Among the best known of the pubHshed handbooks are the Sadtkr Spectral Data Sheets which include ir,... 

Miscellaneous. NIST has a reference database of criticaUy evaluated x-ray photoelectron and Auger spectral data, which is designed to mn on PCs. It is searchable by spectral lines as weU as by element, line energy, and chemical data (82). The Nuclear Quadrapole Resonance Spectra Database at Osaka University of over 10,000 records is avaUable in an MS-DOS version (83). The NCLl system, SDBS, has esr and Raman spectra, along with nmr, ir, and ms data, as described. 

The in, uv, mass, nmr, and C-nmr spectral data for naphthalene and other related hydrocarbons have been reported (7—11). Additional information regarding the properties of naphthalene has been pubUshed (3,6,12,13). 

B. J. Zwolinski and co-workers. Selected Eltraviolet Spectral Data, American Petroleum Institute Research Project 44, Thermodynamics Research Center, Texas A M University, College Station, Tex., 1961. 

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