4-{[4-(Hy-droxy-meth-yl)piperidin-1-yl]meth-yl}phenol.

In the title compound, C(13)H(19)NO(2), the piperidine ring has a chair conformation with the exocyclic N-C bond in an equatorial position. In the crystal, mol-ecules are linked head-to-tail by phenol O-H⋯O hydrogen bonds to hy-droxy-methyl-ene O-atom acceptors, forming chains which extend along [100]. These chains form two-dimensional networks lying parallel to (101) through cyclic hydrogen-bonding associations [graph set R(4) (4)(30)], involving hy-droxy O-H donors and piperidine N-atom acceptors.

Pseudopolymorphism in hydroxybenzophenones: the dihydrate of 2,2',4,4'-tetrahydroxybenzophenone.

A dihydrate pseudopolymorph of bis(2,4-dihydroxyphenyl)methanone, C(13)H(10)O(5)·2H(2)O, (I), was obtained during polymorphism screening of hydroxybenzophenone derivatives. This structure, in which the molecule sits on a twofold axis, was compared with the known anhydrous form of (I) [Schlemper (1982). Acta Cryst. B38, 554-559]. The role of water in the crystal assembly was established on the basis of the known monohydrate pseudopolymorph of 3,4-dihydroxybenzophenone [Landre, Souza, Corrêa, Martins & Doriguetto (2010). Acta Cryst. C66, o463-o465].

A monohydrate pseudopolymorph of 3,4-dihydroxybenzophenone and the role of water in the crystal assembly of benzophenones.

During a polymorphism screening of hydroxybenzophenone derivatives, a monohydrate pseudopolymorph of (3,4-dihydroxyphenyl)(phenyl)methanone, C(13)H(10)O(3).H(2)O, (I), was obtained. Structural relationships and the role of water in crystal assembly were established on the basis of the known anhydrous form [Cox, Kechagias & Kelly (2008). Acta Cryst. B64, 206-216]. The crystal packing of (I) is stabilized by classical intermolecular O-H...O hydrogen bonds, generating a three-dimensional network.

Methyl 4-(piperidin-1-ylcarbon-yl)benzoate.

In the title compound, C(14)H(17)NO(3), the piperidine ring has a chair conformation and an intra-molecular C-H⋯O inter-action stabilizes the mol-ecular conformation. In the crystal, weak inter-molecular C-H⋯O inter-actions occur.