The title compound, C(19)H(20)O(6), crystallizes in the centrosymmetric space group P2(1)/c with one molecule in the asymmetric unit. The molecule is approximately planar and the dihedral angle between the phenyl rings is 11.0 (1) degrees. The H atoms of the central propenone group are trans. There is an intramolecular O-H.O hydrogen bond and the molecules are crosslinked by four intermolecular C-H.O hydrogen bonds, producing a three-dimensional network.

N-(2-Chlorobenzyl)-1,2,3,4-tetrahydroisoquinoline-1,3-dione, C(16)H(12)ClNO(2), crystallizes in P2(1)/n with three crystallographically independent molecules in the asymmetric unit, which differ slightly in conformation, N-(2-bromo-4-methylphenyl)-1,2,3,4-tetrahydroisoquinoline-1,3-dione, C(16)H(12)BrNO(2), crystallizes in P2(1)/n with one molecule in the asymmetric unit and N-(2,3-dichlorophenyl)-1,2,3,4-tetrahydroisoquinoline-1,3-dione, C(15)H(9)Cl(2)NO(2), crystallizes in P2(1)/c with one molecule in the asymmetric unit. In all three structures, the heterocyclic rings adopt approximately planar conformations. The pyridine rings are orthogonal to the substituted phenyl rings. In all three structures, the crystal packing is stabilized by intermolecular C-H...O hydrogen bonds.

10-(4-fluorophenyl)-3,3,6,6,9-pentamethyl-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-dione, C24H28FNO2, (I), crystallizes with two crystallographically independent molecules (which differ slightly in conformation), while 10-(4-fluorophenyl)-9-propyl-3,3,6,6-tetramethyl-3,4,6,7,9,10-hexahydroacridine-1,8(2H,5H)-dione, C26H32FNO2, (II), crystallizes with one molecule per asymmetric unit. In both structures, the central ring in the acridine moiety is in a sofa conformation, while the outer rings adopt intermediate half-chair/sofa conformations. The central pyridine ring is orthogonal to the substituted phenyl ring. In both structures, the packing of the crystal is stabilized by C--H...O intermolecular hydrogen bonds.

The title compound, CH7N4 +·C4H3O4 −, is a molecular salt in which the amino­guanidinium cations and fumarate monoanions are close to planar, with maximum deviations of 0.011 (1) and 0.177 (1) Å, respectively. The crystal packing is stabilized by inter­molecular N—H⋯O and O—H⋯O hydrogen bonds.

The crystal structures of two biphenyl compounds 3‐amino ‐2,4 dicyano ‐ 3',4',5' trimethoxy ‐ 1,3 terphenyl (I) and 3‐amino ‐2,4,dicyano ‐5‐ methyl ‐ 4'‐N,N diethyl amino biphenyl (II) are described here (CCDC NO. : 134369 & 134370). The title compounds C23H15N3O3 (I) and C19 H19N4 (II) crystallized in the centrosymmetric triclinic space group P‐1 and non‐centrosymmetric orthorhombic space group Fdd2 respectively. The unit cell parameters are : (I) a = 10.3555(2), b = 10.7103(2), c = 11.0096(0)Å, α = 64.1(0), β = 65.9(0), γ = 89.6(0)° ; Z=2 and (II) a = 23.0364(1), b = 37.2165(1), c = 7.7491(0)Å, α = β = γ = 90.0(0)°; Z=16. The R factors for compound (I) and (II) are 0.053 and 0.064 respectively.