Energetic processes compounds

It is significant that the earliest records of life on Earth start shortly after the period of impact frustration. Apparently life formed as soon as the conditions permitted it. Life originated from compounds produced by prebiotic organic chemistry. The source of the molecules included those produced on Earth by energetic processes such as impacts and electrical discharges as well as those that fell in from space. Whatever processes occurred, they would have had to happen either in the deep ocean or in what might have been rare regions of land and shallow water. 

Carbon compounds in the solar system can be traced in planetary atmospheres, on planetary surfaces, comets, asteroids, meteorites and in the interplanetary medium. Gas and solid state chemistry within the solar nebula was responsible for new organic material (49,50). Many organic compounds have been identified on outer solar system bodies, some of them originating in the surface ices through energetic processing (4). 

APCI is a more energetic process than ESI because of both the chemical reactions involved and the requirement for desolvation temperatures to be in the 200-500°C range. These conditions limit APCI to small molecules (<1 kDa) with intermediate polarity, i.e., to compounds that can be protonated readily and do not disintegrate when exposed to the heat necessary to remove the solvent. The technique falls between El and ESI with respect to the classes of compounds to which it can be applied e.g., steroids are readily accessible to APCI but are often transparent in ESI because of their low polarity. Nonpolar compounds, e.g., alkanes and polynuclear aromatic hydrocarbons, can be analyzed by El (and Cl) but not APCI. 

Step 1 of the parametrization process is the selection of the appropriate model compounds. In the case of small molecules, such as compounds of pharmaceutical interest, the model compound may be the desired molecule itself. In other cases it is desirable to select several small model compounds that can then be connected to create the final, desired molecule. Model compounds should be selected for which adequate experimental data exist, as listed in Table 1. Since in almost all cases QM data can be substimted when experimental data are absent (see comments on the use of QM data, above), the model compounds should be of a size that is accessible to QM calculations using a level of theory no lower than HE/6-31G. This ensures that geometries, vibrational spectra, conformational energetics, and model compound-water interaction energies can all be performed at a level of theory such that the data obtained are of high enough quality to accurately replace and... 

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