Functional groups, determination hydrogenation methods

Infrared spectroscopy, NMR spectroscopy, X-ray methods such as X-ray absorption near-edge structure spectroscopy and ESR spectroscopy have been used primarily to probe the detailed chemistry of heteroatom speciation, polar functional group determination, and hydrogen and carbon types in asphaltenes. The consensus seems to indicate that most asphaltene molecules have one to three heteroatoms (S, N, and O) per molecule. Sulfur exists predominantly as thio-phenic heterocycles (typically 65—85%) with the remainder as sulfidic groups (46,47). Thiophenic moieties are not... 

Quantitative analysis of copolymers is relatively simple if one of the comonomers contains a readily determinable element or functional group. However, C,H elemental analyses are only of value when the difference between the carbon or hydrogen content of the two comonomers is sufficiently large. If the composition cannot be determined by elemental analysis or chemical means, the problem can be solved usually either by spectroscopic methods, for example, by UV measurements (e.g., styrene copolymers), by IR measurements (e.g., olefin copolymers), and by NMR measurements, or by gas chromatographic methods combined with mass spectroscopy after thermal or chemical decomposition of the samples. 

The hydrogen distribution computed using the determined values of a = 1/900 and b = 1/800 are shown in Table II. In the present in vestigation it was felt that the determination of peak areas rather than peak intensities would be the more accurate method for determining quantitative functional group concentration. For comparison to other infrared investigations, useful relations are... 

The molecular structures and intramolecular hydrogen bonding for salicylic (I), 2-hydroxythiobenzoic (II), 2-hydroxythionobenzoic (III) and 2-hydroxy-dithiobenzoic acids (IV) were studied precisely by ab initio method and density functional theory. The carbonyl electrical field-gradient (EFG) tensor and chemical shift (CS) tensor of a urea-type functional group, R NH-C(0)-NHR were determined. Quantum chemical calculations revealed very large... 

Development of selective analytical method for the determination of artemisinin poses challenging problems because it lacks ultraviolet (UV) absorption or fluorescent chromophores and does not possess functional groups with potential for derivatization. This study reports the determination of artemisinin by liquid chromatography with on-line post-column UV irradiation and peroxyoxalate chemiluminescence (PO-CL) detection. A similar method as previously reported by us for the determination of organic peroxide. In this method, after artemisinin is eluted from the HPLC column, it is UV irradiated to generate hydrogen peroxide, which is determined by PO-CL detection. 

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