Hydrogen exchange extraction

The purpose of this experiment was to investigate the extent and the structural specificity of hydrogen exchange during the extraction of bituminous coal with naphthalene. Table I includes the data of an extraction experiment (E20) conducted with naphtha-lene-d8 using nitrogen as the cover gas. In the experiment, the reactants were heated at 380°C for 1 hour at 2200 psi the same apparatus was applied as in E19. After the run, the spent solvent was separated from the coal by distillation, and the coal and solvent were examined for deuterium and protium incorporation. 

If reactions of the above type occur during extraction, one would expect that gradually less hydrogen exchange takes place as the extraction proceeds because the number of reactive groups decreases. This assumption was tested in the last experiment shown in Table V. The coal was heated for 6 hours at 340°C. with nontritiated phenanthrene prior to extraction with tritiated phenanthrene. When this pretreated coal was extracted, the tritium content of the product was only 15.6% as compared with 21.4%, in the nonpretreated product. This decreased tritium content supports the above assumption and agrees with the proposed reaction mechanism. 

Extracting Information from Hydrogen Exchange Mass Spectrometry Data... 

Hydrogen Exchange Mass Spectrometry of Proteins 7.3.5 Extracting Protection Factors by HX Modeling... 

Abzalimov, R.R., Kaltashov, I.A. (2006) Extraction of local hydrogen exchange data from HDX CAD MS measurements by deconvolution of isotopic distributions of fragment ions. J Am Soc Mass Spectrom, 17(11), 1543-1451. 

Chang et al. [109] discussed the stabilizing effects of extractives in A. confuse wood during weathering and proposed the possible mechanisms, as shown in Fig. 20. These extractives, such as melanoxetin, transiUtin, and okanin, could quench the new-formed radicals by hydrogen exchange. Ultimately, these extractives transfer into orf/io-quinone, para-quinoid, dimer or other derivatives. 

A number of researchers have used specially chosen reactions isodesmic, hydrogenation, exchange, etc.) in high-level correlation calculations to obtain accurate thermochemical data for selected species. In this approach an appropriate reaction is chosen for which all species have accurate experimental thermochemical data available except the species of interest. A high level of theory is used to calculate the reaction energy and the enthalpy of formation of the unknown species is then extracted. Often more than one reaction is used to assess the reliability of the calculation. Use of specially chosen reactions can give quite accurate enthalpies of formation because of cancellation of correlation effects and also because they make use of accurate experimental data. However, suitable reference molecules are often not available, making this method inapplicable in many cases. 

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