C15H17C1FN30, Mr= 309"8, orthorhombic, P212121, a = 19-813 (8), b = 13-699 (6), c = 5.777 (3)A, V= 1568.0A 3, Z=4, Din= 1.29 (2), Dx=1.31Mgm -3, MoKa, 2=0.71069A, g= 0.213 mm -~, F(000)=648, room temperature, final R =0.053 for 1003 reflections classed as observed. C atom 1 of the phenyl ring and C atoms 1 to 4 of the pentanone function adopt an extended 'W' con- formation with the atoms essentially coplanar. The triazolyl ring, which shows significant delocalization (N--N bond length 1.357 (9) /k; C--N 1.324- 1.337 ,/k), and the chlorofluorophenyl ring are twisted by 86 (1) and 58 (1) °, respectively, out of this plane. The exocyclic angles of the triazolyl ring are very asymmetric with C-N-C (130.6 (7) °) significantly larger than C-N-N (119.1 (6)°). The F atom is disordered being distributed (80,20% occupancy) be- tween positions 2 and 6 in the phenyl ring. The title compound was recrystallized from a racemic mixture but the absolute configuration ((2S)-enantiomer) of the molecules in the crystal under investigation was established by comparison of wR values for the determined and the inverted structure.