Nuclear Magnetic Resonance Spectroscopy. Carbon-13 Chemical Shifts of Methycyclopentanes, Cyclopentanols, and Cyclopentyl Acetates

The ^(13)C chemical shifts of the title compounds have been determined by high-resolution nmr spectroscopy with the aid of proton decoupling. Substituent effects have been computed and compared to those obtained for some corresponding cyclohexane compounds, with the hope of providing information about steric interactions and conformations of cyclopentane derivatives. Rather large downfield ɑ (up to ~24 ppm) and β (up to ~7 ppm) shifts were observed on dissolution of up to 0.5 M europium tris(dipiva1omethane) in cyclopentanols. The cis- and trans-3-methyl- and 1,3-dimethylcyclopentanols showed somewhat different chelate shifts which could be used to help assign the stereochemical configuration of these substances. The ^(13)C chemical-shift changes produced by chain branching in some aliphatic acetates and ethers are compared and rationalized.