Some 13C NMR Applications

Source O. Sperber, W. Kaminsky, and A. Geissler, Structure Analysis of Paraffin Waxes by 13C NMR Spectroscopy, Petroleum Science and Technology, vol. 23, pp. 47-54 (2005). With permission. 

A number of papers have looked at the development of relationships between base stock composition as measured by NMR and either physi-cal/chemical properties or their performance.22 27 Most of this work has been focused on group II and III base stocks, with less or little attention paid to solvent extracted ones. These have all relied on various techniques to simplify the spectra and the assignments of peaks and make peak integration more reliable. These have many acronyms,23 for example, GASPE (gates spin echo), PCSE (proton coupled spin echo), INEPT (insensitive nuclei enhancement by polarization transfer), DEPT (distortionless enhancement by polarization), QUAT (quaternary-only carbon spectra), 2D COSY (two-dimensional homo-nuclear spectroscopy), and HETCOR (heteronuclear shift correlated spectroscopy)]. Table 4.10 provides an example of some of the chemical shift data generated26 and employed in this type of work, and Adhvaryu et al.25 were able to develop the correlations between base stock properties and carbon types in Table 4.11, whose main features correspond to intuition (e.g., the values of API and aniline points are both decreased by aromatic carbon and increased by the 

10-15 ch3 Terminal methyl groups in aliphatic chain (except the case where two methyl groups are terminal) and methyl groups branched to an aliphatic chain (except where they are branched in an a or P position to an alkyl chain from a ring). 

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