Zur Taktizität von Poly(α‐methylstyrol), 4. Das ¹H‐ und ¹³C‐NMR‐Spektrum des 1,3,3‐Trimethyl‐1‐phenylbutyllithium

Abstract

Abstract The structure of 1,3,3‐trimethyl‐1‐phenylbutyllithium ( 1b ), which is a model compound for the active chain end in the polymerisation of α‐methylstyrene with butyllithium, was investigated with 1 H and 13 C NMR spectroscopy. The carbon‐13 chemical shift of the αC‐atom in benzene and tetrahydrofuran as solvent suggests a substantial sp 2 hybridisation. The rotation of the aromatic ring around the bond (C 6 H 5 )αC is hindered at room temperature. In benzene as solvent the carbon‐13 resonances of the αC‐atom and the aromatic C‐atoms are strongly broadened. This broadening, caused by exchange reactions or 13 C‐ 7 Li‐coupling, can be interpreted by an interaction of the lithium atom with the aromatic ring. This interpretation of the 13 C NMR spectra leads to a structure, in which the lithium is not located at the αC‐atom but in the space over the bond (C 6 H 5 )αC.