Structural studies of 1‐(2‐hydroxy‐4‐bromophenyl)‐4‐methyl‐4‐imidazolin‐2‐ones

The crystal structure of 1‐(2‐hydroxy‐4‐bromophenyl)‐3‐methyl‐4‐methyl‐4‐imidazolin‐2‐one was determined by x‐ray diffraction. The structure is stabilized by intermolecular hydrogen bonds formed between the 2‐hydroxy and central groups. Molecular modelling including ab initio calculations at the HF/6–31+G** level revealed that in the gas phase the molecule is stabilized by an intramolecular hydrogen bond. The derivatives with 3‐alkyl, benzyl and phenyl substituents were studied by 13 C NMR including solid‐state 13 C CP/MAS NMR [for 1‐(2‐hydroxy‐4‐bromophenyl)‐3‐methyl‐4‐methyl‐4‐imidazolin‐2‐one] and FT‐IR methods. The differences in chemical shifts Δ = δliquid − δsolid are significant for aromatic carbons C(3) (−2.9 ppm), C(4) (3.6 ppm) and C(5) (−3.9 ppm) and, on the other side of the imidazoline ring, of C(7) (−1.5 ppm). These carbons are adjacent to N(1)—C(4), and are subject to the largest changes of the environment during reorientation of the imidazolin‐2‐one moiety. Copyright © 2001 John Wiley & Sons, Ltd.