Abstract
The crystal structures of eight new co-crystals of quinol with pyrazine, piperazine, morpholine, pyridine, piperidine, 4,4'-bipyridine, N-methylmorpholine and N,N'-dimethylpiperazine are reported. Quinol forms 1:1 co-crystals with pyrazine, piperazine and N,N'-dimethylpiperazine, but 1:2 co-crystals with morpholine, 4,4'-bipyridine, N-methylmorpholine, pyridine and piperidine. This difference can be rationalized in most cases by the presence of, respectively, two or one strong hydrogen-bond acceptor(s) in the guest molecule. The exception to this generalization is 4,4'-bipyridine, which forms a 1:2 co-crystal, possibly to optimize crystal packing. All structures are dominated by hydrogen bonding between quinol and the guest molecules. A doubly bridging motif, which connects pairs of quinol and guest molecules via NH...O or CH...O interactions, is present in all but the sterically hindered N,N'-dimethylpiperazine and N-methylmorpholine co-crystals.
Highlights
Quinol, or hydroquinone, is widely used to stabilize compounds that are susceptible to polymerization
Previous paper by our group (Oswald et al, 2002) described how molecules analogous to dioxane yielded a series of crystal structures with closely related packing motifs, and in this paper we report the crystal structures of co-crystals of quinol with pyrazine, piperazine, morpholine, pyridine, piperidine and 4,4H-bipyridine
The quinol molecule resides on a crystallographic inversion centre. The stoichiometry of this co-crystal is 1:2, we have recently shown that quinol forms a 1:1 co-crystal with pyridine (Oswald, Motherwell & Parsons, 2004)
Summary
Hydroquinone, is widely used to stabilize compounds that are susceptible to polymerization. A previous paper by our group (Oswald et al, 2002) described how molecules analogous to dioxane yielded a series of crystal structures with closely related packing motifs, and in this paper we report the crystal structures of co-crystals of quinol with pyrazine, piperazine, morpholine, pyridine, piperidine and 4,4H-bipyridine (hereafter referred to as guest molecules). The solution was allowed to cool to room temperature to produce crystals in the form of colourless blocks. The solution was allowed to cool to room temperature to produce crystals as colourless blocks. Quinol (0.65 g, 5.90 mmol) was reuxed with dimethylpiperazine (3 cm3, 20.10 mmol) in a little ethanol until the solid dissolved. The solution was held at 277 K to produce colourless crystalline blocks
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