Here, both ν(C=O) modes are red-shifted, with the larger shift occurring for the ν(C2=O2) mode that participates in the stronger hydrogen bond. The ν(C=C) mode is also red-shifted, but not as strongly, resulting in partial overlap of the signals arising from these three modes. The Ofw-Hfw bending modes appear at 1237 and 1261 cm -1 , respectively, thus overlapping with the ν(C5-F) mode.