Internal reference compounds table

For trypanosomal TIM we experimented with three different cocktails of 32 compounds (Table 4). Molecules were chosen in such a way that they would be compatible, soluble, cheap, and as varied as possible. Each compound was present at a concentration of 1 m M The final cocktail solutions were clear and devoid of precipitate. Since this was a pilot experiment both subcocktails were checked at each stage of the dichotomic strategy. Only the soak with cocktail 1 revealed electron density that could not be accounted for by water molecules, hereafter called peak X. The soaks with cocktails 2 and 3 led to featureless difference Fourier maps. The quality of the data and refinement can be inspected from Table 5, while Figure 9 illustrates the dichotomic search to identify peak X. An oxidized molecule of DTT, identified in the high-resolution structure of the native TIM crystals [24], served as an internal reference to judge the quality of the data and the noise level in the final difference Fourier maps. 

A reference standard compound is traditionally used [tetramethylsilane (TMS) Si(CH3)4 for both H1 and C13, 85% H3PO4 for P31], and the chemical shift 8, relatable to cr, is usually a down-shift of the resonance from the reference compound, a small amount of which is added to each sample as an internal standard Table 11.11 lists some typical H1 NMR chemical shifts <5. Table 11.12 shows some C13 chemical shifts. Sometimes rare-earth salts are added to the solution, to deliberately shift resonances by a Coulomb interaction these are called lanthanide shift reagents. 

To quantitatively determine the absolute amounts of certain esters present in the oxidation products, the mass spectrometer responses to these compounds were compared with the response to the internal reference, octadecane. Using authentic samples of the esters of interest, relative mass spectrometric response factors were determined. From these response factors, listed in Table I, the amounts of esters present in the oxidative degradation products were calculated using an INCOS subroutine. 

The carbon-13 magnetic resonance spectrum of lisinopril shown in Figure 5 was obtained using a Varian Associates Model XL-100A spectrometer and a 10% (VJ/W) solution of lisinopril in IN deuterium chloride in deuterium oxide. The reference compound (internal) was p-dioxane. An expansion of the spectrum in the 12.5-75 ppm region is shown in Figure 6. Chemical shifts and assignments for the numbered structure shown below are tabulated in Table III. 

When preparing a sample it is common practice to add a suitable compound to act as an internal chemical shift reference in the spectrum, and the selection of this must be suitable for the analyte and the solvent. In proton and carbon NMR, the reference used in organic solvents is tetramethylsilane (TMS, 0.0 ppm), which has a number of favourable properties it has a sharp 12-proton singlet resonance that falls conveniently to one end of the spectrum, and it is volatile so can be readily removed and it is chemically inert. In a few cases, this material may be unsuitable, such as in the study of silanes or cyclopropanes. For routine work, it is often not necessary to add any internal reference as the residual lines of the solvent itself can serve this purpose (Table 3.2). For aqueous solutions, the water soluble equivalent of TMS is partially deuterated sodium 3-(trimethylsilyl)propionate-d4 (TSP-dt), which is also referenced to 0.0ppm. A volatile alternative is 1,4-dioxane ( H 3.75 ppm,... 

Using the flame ionization detector and temperature programming Veening et al obtained results quoted in Table 149 for a mixture of five areue tricarbonylehromiurn compounds. Except where indicated the mesitylene compound was used as reference compound for quantitative analysis. Calibration curves for all four constituents were linear between 1.0 x 10 and 1.0 x 10 g/ml. From the results in Table 149 it can be seen that the accuracy of the method is good to within i 3.2% relative error. Table 149 also tabulates results obtained for benzene and mesitylene tricarbonylchromium using an electron capture detector and 2-bromonapthalene as internal standard. 

Tables 22" 78 present chemical shifts cs of RNA sequences, cs are expressed in parts per million (ppm) downfield from a chosen reference signal of an added internal standard compound.

MgQg, shown in Table 2, has a lower symmetry in the solid state and its resonances are split into several lines, but it is the common reference compound used as an internal standard for solid state Si NMR. The second tactic is to use no standard compound in the sample at all. The referencing is done externally relative to a separate sample that contains TMS in the same solvent as is used in the analysis sample. 

The reference compounds recommended by the International Union of Pure and Applied Chemistry (Harris et al. 2001) are included in Table 6.1. Several of them are liquids thus, a spectrum of the reference sample is acquired and referenced prior to the study of the sample under investigation. In practise, solid compounds with well-defined structures are often used as secondary reference materials, since it may be more convenient to test the setup of the experiment on the solid sample. 

References D. D. Wagman, et ah, The NBS Tables of Chemical Thermodynamic Properties, in J. Phys. Chem. Ref. Data, 11 2,1982 M. W. Chase, et ah, JANAF Thermochemical Tables, 3rd ed., American Chemical Society and the American Institute of Physics, 1986 (supplements to JANAF appear in J. Phys. Chem. Ref. Data) Thermodynamic Research Center, TRC Thermodynamic Tables, Texas A M University, College Station, Texas I. Barin and O. Knacke, Thermochemical Properties of Inorganic Substances, Springer-Verlag, Berlin, 1973 J. B. Pedley, R. D. Naylor, and S. P. Kirby, Thermochemical Data of Organic Compounds, 2nd ed.. Chapman and Hall, London, 1986 V. Majer and V. Svoboda, Enthalpies of Vaporization of Organic Compounds, International Union of Pure and Applied Chemistry, Chemical Data Series No. 32, Blackwell, Oxford, 1985. 

This table of the physical properties includes the organic compounds of most general interest. For the properties of other organic compounds, reference must he made to larger tables in Langes Handbook of Chemistiy (Handbook Publishers), Handbook of Chemistiy and Physics (Chemical Rubber Publishing Co.), Van Nostrand s Chemical Annual, International Ciitical Tables (McGraw-Hill), and similar works. 

Table 2.4) or proprietary test methods. Forrest [38] has listed 94 international rubber analysis standards (ISO) and 20 ISO standards in preparation referring to latices, carbon-black-filled compositions, raw and compounded rubbers. 

Various compilations of densities for organic compounds have been published. The early Landolt-Bomstein compilation [23-ano] contained recommended values at specific temperatures. International Critical Tables [28-ano-l] provided recommended densities at 0 °C and values of constants for either a second or third order polynomial equation to represent densities as a function of temperature. This compilation also gave the range of validity of the equation and the limits of uncertainty, references used in the evaluation and those not considered. This compilation is one of the most comprehensive ever published. Timmermans [50-tim, 65-tim], Dreisbach [55-die, 59-die, 61-dre] and Landolt-Bomstein [71-ano] published additional compilations, primarily of experimental data. These compilations contained experimental data along with reference sources but no estimates of uncertainty for the data nor recommended values. 

References on Solubility Comev and Hahn, A Dictionary of Chemical Solubilities (Inorganic) Seidell, Solubilities of Inorganic and Organic Compounds Landolt-Bornstein, Physikalisch-Chemische Tabellen International Critical Tables. 

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