Vacuum Structure Group Analysis

Table 4-164 Structure Group Analysis of Vacuum Distillates. ...

High-resolution fluorine 19 NMR was used to investigate the structural changes resulting from PTFE electron irradiation under vacuum. A quantitative analysis of the data was used to establish the density of side groups and branches. 20 refs. 

The surface analysis of solids has benefited greatly from the introduction of various high vacuum techniques, from electron microscopy through LEED, AES, ESCA, ISS, SIMS, etc. These techniques have given detailed information on atomic composition and structure, but rather limited information on the capability for chemical reactivity of surface groups. This latter type of information has much practical value, and is often more easily obtained by wet chemical techniques than high vacuum techniques. 

The bis(pyrrolidinyl)silanes, IVa-IVh, which are colorless liquids and highly moisture sensitive, were purified by vacuum distillation. Compounds IVa-IVh were characterized by elemental analysis (Table I) and and NMR spectroscopy (Table IV). The NMR spectra confirmed the structure shown in the equation. Table IV lists the chemical shifts for the R and R groups in these compounds. The pyrrolidinyl group showed two resonances at about 1.7 and 2.9 ppm in the NMR spectra and at about 26 and 46 ppm in the NMR spectra for the two methylene groups, which, for simplicity, are not shown in Table IV. 

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