Structure of 2-methoxy-6-nonyl-1,4-benzoquinone, C16H24O3, a synthetic contact allergen related to the naturally occurring primin.

C16H24O3, Mr = 264.36, triclinic, P1, alpha = 4.167 (1), b = 9.658 (1), c = 19.093 (1) A, alpha = 89.66 (1), beta = 87.27 (1), gamma = 79.07 (1) degrees, V = 753.65 (1) A3, Z = 2, D chi = 1.165 Mg m-3, lambda(Cu K alpha) = 1.5418 A, mu = 0.595 mm-1, F(000) = 288, T = 295 K, R is 0.047 for 1682 observed unique reflections. The angle between the quinone ring plane and the mean plane defined by the aliphatic nonyl chain atoms is 17.4 (3) degrees. The average Csp3--Csp3 bond distance and corresponding angle of the side chain are 1.522 (3) A and 113.2 (2) degrees. The average dimensions of the quinone ring are C--C 1.485 (3), C = C 1.337 (3), C = O 1.209 (3) A, C--C--C 118.4 (2), C = C--C 120.8 (2), O = C--C 120.8 (2) degrees. Neighboring molecules form dimers across centres of symmetry which are linked by C--H...O hydrogen bonds, with H(3)...O(4i) 2.42 (4), C(3)...O(4i) 3.29 (2) A, and angle C(3)--H(3)...O(4i) 164 (3) degrees. The dimers are held together by van der Waals forces between the nonyl side chains, and by C(16)--H...O(2ii) hydrogen bonds, with H(163)...O(2ii) 2.56 (4), C(16)...O(2ii) 3.357 (3) A, and angle C(16)--H(163)...O(2ii) 140 (3) degrees [(i) -x, 1 -y, -z; (ii) -1 -x, 1-y, -z].