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SIZING THE UBBELHODE EFFECT: THE ROTATIONAL SPECTRUM OF TERT -BUTYLALCOHOL DIMER.

SHOUYUAN TANG, College of Bioengineering, ChongQing University, ChongQing, 400044, P. R. China; IRENA MAJERZ, Faculty of Chemistry, University of Wroclaw, Joliot-Curie 14, 50-383 Wroclaw, Poland; WALTHER CAMINATI, Dipartimento di Chimica "G. Ciamician" dell'Università, Via Selmi 2, I-40126 Bologna, Italy.

We measured the molecular beam Fourier transform microwave spectra of four isotopic species of of the dimer of tert -butanol, that is C₄H₉-OH cdots O(H)-C₄H₉, C₄H₉-OH cdots O(D)-C₄H₉, C₄H₉-OD cdots O(H)-C₄H₉, and C₄H₉-OD cdots O(D)-C₄H₉. We observed that the H -- D isotopic substitution of the hydroxylic hydrogen participating in the O-H cdots O Hydrogen bond in the tert -butanol dimer produces an increase of the B and C rotational constants, according to the shrinkage of the O cdots O distance, underlying and sizing the associated Ubbelhode effect. The conformation and structure of the complex, and an estimation of the Ubbelhode effect have been obtained by combining the experimental data with the results of MP2/6-311++G** ab initio calculations.