Conformational Equilibria in Adducts of Alcohols with Ethers: The Rotational Spectrum of Ethylalcohol-Dimethylether

The rotational spectra of two conformers of the molecular complex ethylalcohol-dimethylether were measured with pulsed-jet Fourier transform microwave spectroscopy. Both trans and gauche conformations of ethylalcohol are preserved in the complex, originating two conformations with dimethylether as the proton accepting unit. A switch of the conformational stability of ethyl alcohol is observed upon complexation with dimethyl ether, with the gauche form becoming the global minimum. The investigation of the OD deuterated species allowed observing quantitatively the Ubbelohde effect, which is the shrinkage of the O···O distance of about 6 m upon H!D isotopic substitution of the hydroxylic hydrogen participating in the OH···O hydrogen bond.