Hydroquinone solid-state forms

Desiraju distinguishes two types of inclusion complexes in the solid state. In the first type (Fig. 6.1) the guest molecule is embedded inside the host cavity. In the second two or more different molecules form the cavity to include another one. It should be stressed that the decision about which is the host and which is the guest is not always obvious. For instance, the complex of three hydroquinone molecules 142 with C60 [20] reflects this ambiguity since the molecular mass of... 

Fullerenes C60 and C70 form supramolecular adducts with a variety of molecules, such as crown ethers, ferrocene, calixarene, and hydroquinone. In the solid state, the intermolecular interactions may involve ionic interaction, hydrogen bonding, and van der Waals forces. Figure 14.2.9 shows a part of the structure of [K(18C6)]3-C6o-(C6H5CH3)3, in which Cgg is surrounded by a pair of [K+(18C6)] complexed cations. 

Hydroquinone and A-methyl-p-aminophenol (Metol) form superadditive mixtures and a complex, Metoquinone , consisting of one hydroquinone and two Metol molecules, was proposed by Lumiere, Lumiere and Seyewtz [44] to be the species with higher activity than the separate agents. A similar complex between hydroquinone and l-phenyl-3-pyrazolidinone (Phenidone) consisting of one molecule of hydroquinone and one molecule of Phenidone has been observed in the solid state by Kurosaki [45] and Mutter and Schneider [46]. Although these complexes can be crystallized from concentrated solutions of hydroquinone and Metol, and hydroquinone and Phenidone, there is no evidence of their existence in solution. 

Hydroquinone (4,2) exists in multiple forms in the solid state (a, (3 and y) but only p-hydroquinone is observed to form clathrates. The general formula for... 

Nematic polyurethanes derived from 4,4 -dihydroxybiphenyl and 4,4 -bipiperidine, ethylene-4,4 -bipiperidine, or trimethylene-4,4 -bipiperidine have been reported [254]. 4,4 -Bipiperidine, l,2-bis(4-piperidinyl)ethane, and l,3-bis(4-piperidinyl)pro-pane were condensed with the dichloroformates of p-phenylene, 2-methyl-l,4-phenylene, or 2,5-biphenylylene. Furthermore, two copolyurethanes were prepared either by mixing 4,4 -bipiperidine and l,2-bis(4-piperidinyl)ethane or by mixing the dichloroformates of p-phenylene and 2,5-biphenylene. The polyurethanes derived from hydroquinone or methylhydroquinone were semicrystalline polymers with a short-term thermostability up to 310 °C. The polyurethanes derived from phenyl-hydroquinone were amorphous with a thermostability up to 360 °C. The homo-and co-polyurethanes containing 4,4 -biphenylylene units formed a smectic layer structure in the solid state and a nematic melt above the melting point [254]. 

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