pentafluorobenzaldehyde,
water,
hydroxylamine hydrochloride,
sodium carbonate,
ethanol

To hydroxylamine (15 g; 0.22 mol) in water (200 cm³) was added pentafluorobenzaldehyde (12 g; 0.061 mol) in ethanol (30 cm³). The mixture was stirred vigorously, and sodium carbonate (23 g) added portionwise. After stirring over night, the mixture was cooled to 0 ^oC and the solid filtered and recrystallised (DCM) to give product as white crystals (12.68 g; 98%)

Literature procedure doesn't involve recrystallisation, and product is obtained fairly pure without it. The crystals are slightly yellow without recrystallisation. The product is the syn isomer (see Pejkovic-Tadic et al. Helv. Chim. Acta, 1965, 48, 1157). Other oximes were prepared by slightly different methods, and are reported separately. The reaction was performed only once.

¹H nmr (CDCl₃) 8.24 (1H, s), 9.09 (1H, s) m.p. 131-133 ^oC (Lit 132-133 ^o C [Aroskar et al.])

A. J. McCarroll and J. C. Walton, J. Chem. Soc. Perkin Trans. 2, 2000, 1868.

E. V. Aroskar, P. J. N. Brown, R. G. Plevey and R. Stephens, J. Chem. Soc. (C), 1968, 1569.