13C N.M.R. study of site effect in van der waals interactions

✍ Scribed by Denis Cans; Bernard Tiffon; Jacques-Emile Dubois

• Book ID: 104226109
• Publisher: Elsevier Science
• Year: 1976
• Tongue: French
• Weight: 214 KB
• Volume: 17
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)93822-x

✦ Synopsis

In a recent 13 C N.M.R. study on a linear alkane (n-pentane), Tiffon and Doucet (1)

showed that the screening constant u

resulting from the Van der Waals solute-solvant interactions, varies markedly with the position of the carbon in the chain.

We now report much greater variations in sensitivity for sequences of sp2 and sp3 carbons substituted in various ways. These results shows the increased importance of the site effect in the sensitivity of the carbon atoms to Van der Waals interactions.

The study is carried out in non anisotropic solvents on various solutes (ramified alkenes and alkanes). For each carbon of each solute, the chemical shifts ( ) obtained ( ) are correlated with the function proposed by Rummens (3-5) : g2 = , where n is the refractive index of the solvent.