NMR Studies on Solution Structures of Methanol and Ethanol Saturated with CO sub(2)

2H and 17O NMR relaxation times, T 1(2H) and T 1(17O), and 2H NMR chemical shifts, delta (2H), in CO2-saturated CD3OD and C2D5OD solutions were measured at 313.2 K over the pressure range up to ~6 MPa. The rotational correlation times, [tau] r, of the CD and OD axes within CD3OD and C2D5OD molecules and the CO axis within the CO2 molecule were determined from T 1(2H) and T 1(17O), and the magnetic susceptibility-corrected chemical shifts, delta corr, were derived from delta (2H). The differences in [tau] r and delta corr observed between the two alcohol systems: [tau] r and delta corr of OD in C2D5OD, decreased rapidly with increasing CO2 concentration, while those of OD in CD3OD remained almost unchanged at mole fractions of CO2, x sub(CO2). lower than ~0.25 and then slightly decreased at higher x sub(CO2). The hydrogen bonding structure in C2D5OD was found to be gradually broken down by CO2 dissolution. On the other hand, in CD3OD, it has been revealed that the hydrogen bonding structure can persist at x sub(CO2) < ~0.25 but then collapses at higher x sub(CO2).