2,6,6-Trimethylcyclohex-2-enecarboxylic acid

In the title crystal structure, C10H16O2, inversion-related molecules are linked by pairs of O—H⋯O hydrogen bonds involving carboxyl groups to form R 2 2(8) dimers. The cyclohexene ring displays a half-chair conformation.

In the title crystal structure, C 10 H 16 O 2 , inversion-related molecules are linked by pairs of O-HÁ Á ÁO hydrogen bonds involving carboxyl groups to form R 2 2 (8) dimers. The cyclohexene ring displays a half-chair conformation.
PTM and SJJ thank the DST India (FIST programme) for the use of the diffractometer at the School of Chemistry, Bharathidasan University, Tiruchirappalli, Tamil Nadu, India.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: LH5406).

O-H···O hydrogen bonds is frequently observed in carboxylic acids
Experimental A solution of 8 g (0.07 mol) of 80% sodium chlorite in 70 ml H 2 O was added drop wise for 2 h at room temperature to a stirred mixture of 6.6 g (0.05 mol) of cyclo citral in 50 ml Me 2 SO and of 1.6 g NaH 2 PO 4 in 20 ml of water. The mixture was left overnight at room temperature, then 100 ml of water was added to the reaction mixture. The solid geranic acid was collected and crystallized from hexane.

Refinement
The H atom attached to O2 was located in a difference Fourier map and refined freely. The remaining H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms, with C-H distances in the range 0.93-0.97 Å, and with U iso (H) set at 1.2U eq (C), except for the methyl hydrogen atoms which were refined with U iso (H) set at 1.5U eq (C). Fig. 1. The molecular structure of the title compound, with anisotropic displacement ellipsoids drawn at 50% probability level.