Theoretical determination of the H-1 NMR spectrum of ethanol

GIAO calculations of the H-1 NMR chemical shifts for ethanol at the SCF and DFT levels of theory are presented. The importance of molecular geometry a nd basis set is discussed. Vibrational correction to the hydroxyl proton ch emical shift is also considered in calculations for the monomer of ethanol. The final theoretical results for the monomer obtained at the optimized DF T/B3LYP/6-311G(d,p) geometry with the 6-311G++ (d, p) basis set for NMR are in very good agreement with gas phase experimental data. For the liquid ph ase ethanol the hydrogen bonding effects are taken into account by performi ng calculations on various clusters of ethanol. It is shown that inaccuracy due to molecular geometry and basis set in the monomer of ethanol is magni fied significantly in calculations for its clusters. In this context the st ructure of liquid ethanol as predicted recently by quantum cluster equilibr ium (QCE) theory is discussed.