The potential energy surface for rotation about C-C and CN bonds with two dihedral angles (theta, phi) fixed at 15(degrees) intervals in the title compound was generated by full geometry optimization using the HF/6-31G* level of theory. The global minimum on the potential energy surface (the s-cis conformer of C-1 symmetry with a pyramidal amino group) and those for the protonated species were optimized at the MP2(FC)/6-31G* level of theory. Protonation at the four most probable sites, namely, 0, N, Ci, and C-2 Of acrylamide, yields six protonated species which are characterized to be at local minima. The computed proton affinities at MP2(FC)/6-31G*//MP2(FC)/6-31G* are 206.8, 202.4, 198.9, 198.0, 184.5, and 162.0 kcal/mol for the O-protonated species, 2-aminooxetanyl cation (derived from the protonation at C-2), propiolactone (derived from the protonation also at C-2), and the N-protonated, C-1-protonated, and C-2-protonated species, respectively. The energy profile of the interconversion of the protonated acrylamide at the HF/6-31G*//HF/6-31G* level was computed in order to discuss the proton transfer among the protonated species. Vibrational frequencies of acrylamide and the O-protonated species were calculated at the MP2(Full)/6-31G* level of theory and compared with experimental data, when available.