DOSY studies of hydrogen bond association: tetramethylsilane as a reference compound for diffusion studies

The use of tetramethylsilane (TMS) as an internal diffusion reference for DOSY measurements related to molecular association forced by H-bond in solution is proposed. By using such a reference, it is possible to determine the extent to which the diffusion of the solutes is affected by changes in viscosity or H-bonding, after modifications in the composition of the solution under study. Therefore, changes in hydrodynamic radii due to H-bonding can be calculated. Three examples of the use of this reference in diffusion studies related to H-bonding are presented: the addition of an H-bond acceptor to a mixture of two compounds with very similar hydrodynamic radii and molecular weights, but where only one can be involved in H-bonding, the addition of an H-bond acceptor to a mixture of alcohols with different H-bond acidities and the addition of an H-bond acceptor to a mixture of two isomeric alcohols with different steric hindrances.