The adsorption isotherm of 2-pyrrolidinone on gamma-alumina shows an initial rapid uptake of solute followed by a plateau. In contrast, N-ethylacetamide gives a gradual increase in adsorption. For both solutes, DRIFTS data indicate that the carbonyl and N-hydrogen functionalities are involved in bonding, and the most probable conformation of N-ethylacetamide on the surface is as the trans isomer. Theoretical calculations show that in the linear molecule the C-N linkage has a marked double bond character, which results in the molecule remaining in the trans form. The energies of interaction of the linear and cyclic molecules with one and two aluminium "sites" are calculated. The cyclic molecule can adsorb on a single surface "site" through both functionalities. Adsorption of the trans linear molecule on two "sites" gives a comparable interaction energy. Though both molecules adsorb sufficiently strongly from single solute solutions to survive washing, only 2-pyrrolidinone is adsorbed from a solution of the two amides, The differences in behavior are attributed to the steric restraints for adsorption on a real surface.