Acid-induced 13C nuclear magnetic resonance chemical shift changes of ether and ester carbon atoms

Abstract

¹³ C N.m.r. chemical shifts of ethers dissolved in tetrachloromethane are displaced on addition of trifluoroacetic acid. The displacements result from independent interactions of the acid with the substrate oxygen atoms and alkyl residues. The structure-dependent and stereoselective shift changes are useful for signal assignments, structure determination, conformational analysis, assessment of the distribution of rapidly interconverting conformers of esters, and estimation of the relative basicity of ethers.