Tetracyclosqualene and its bearing on the structure of cyclized rubber

✍ Scribed by Morton A. Golub; Jorge Heller

• Book ID: 104242177
• Publisher: Elsevier Science
• Year: 1963
• Tongue: French
• Weight: 283 KB
• Volume: 4
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(01)90985-2

✦ Synopsis

Recently we reported that cyclized rubber consists of six-membered rings fused into predominantly bicyclic structures which are connected by methylene groups and/or uncyclized isoprene units (1). Each Of the fused ring structures is presumed to contain a single tetra-, tri-or disubstituted double bond, the relative amounts of which are in the order, tetra-> tri-> di-substituted. The predominantly bicyclic structure was not rigorously established, but it wes considered reasonable on the basis of a comparison of the n.m.r. spectra of cyclized cis polyisoprene and cyclized cis poly(2-methyl-$-1,3-butadiene-1,1-2). However, although a predominantly monocyclic structure was clearly excluded, it was not possible to rule out a structure in which the average number of rings per fused segment ("cyclicity") exceeds two and may even be es high as three. In an effort to determine this cyclicity more accurately, we now compare the n.m.r. and i-r. spectra of cyclized cis and trans polyisoprenes with the -corresponding spectra of tetracyclosqualene (TCS). The latter is known to