Carbon-13 nuclear magnetic resonance model compounds

In an attempt to relate calculated results to experimental findings for monomeric, lignin model compounds, preliminary work has compared theoretically determined electron densities and chemical shifts reported from carbon-13 nuclear magnetic resonance spectroscopy (62). Although chemical shifts are a function of numerous factors, of which electron density is only one, both theoretical and empirical relationships of this nature have been explored for a variety of compound classes, and are reviewed by Ebra-heem and Webb (63), Martin et al. (64), Nelson and Williams (65), and Farnum (66). 

Abstract—The nature of the product of the reaction between an aminated silane and carbon dioxide was re-examined with the aid of simple model compounds, several amines, and several aminosilanes. Since the reaction products previously proposed include the amine bicarbonate and a carbamate derived from the amine, ammonium bicarbonate and ammonium carbamate were studied as models for the anions. Carbon dioxide adducts of neat model amines were prepared and studied. Results from a variety of techniques are summarized. Among the most useful was Fourier transform infrared (FTIR) spectroscopy of fluorolube mulls. FTIR spectra were distinctive and assignments characteristic of the two species were extracted from the spectral data. Comparisons of these assignments with the products of the reaction between carbon dioxide and various amines were made. The results indicate that alkylammonium carbamates are the principal product. Nuclear magnetic resonance (NMR) spectra in D20 indicated much dissociation and were not helpful in defining the products. 

The carbon-13 nuclear magnetic resonance spectrum of lovastatin shown In Figure 3 was obtained using a Bruker instruments Model AM-300 NMR spectrometer and an approximately 4% w/v solution of the compound In deuterochloroform. Signal assignments are tabulated below and refer to the numbered structure shown in Section 4.2... 

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