13C n.m.r. studies of some phenanthrene and fluorene derivatives

✍ Scribed by J. B. Stothers; C. T. Tan; Nancy K. Wilson

• Publisher: John Wiley and Sons
• Year: 1977
• Tongue: English
• Weight: 603 KB
• Volume: 9
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270090708

✦ Synopsis

Abstract

The ^1^H and ^13^C spectra of fluorene, fluorenone, phenanthrene and their 4‐methyl and 4,5‐dimethyl derivatives have been examined. To complete the analyses for fluorenone and 4‐methylfluorenone, ^1^H spectra were recorded at 270 MHz. The results from the ^1^H spectra permitted unequivocal assignments for the protonated aryl carbons by selective proton decoupling. A consistent set of assignments for the quaternary carbons was obtained through consideration of the dominant relaxation processes operative at these centres. This series of compounds was examined to investigate the shielding effects produced by the close approach of methyl groups separated by five bonds for comparison with the contrasting trends found for methyl carbons separated by three and four bonds. The results indicate that the relative orientation of the methyl groups is an extremely critical factor governing their shieldings and those of neighboring centres.