Abstract
The low-temperature and high-pressure crystal structures of cyclobutanol (C4H7OH) have been determined using single-crystal X-ray diffraction techniques. At temperatures below 220 K, cyclobutanol crystallizes in the Aba2 space group (Z' = 2) and its crystal structure is composed of pseudo-threefold hydrogen-bonded molecular catemers [assigned as C_2;2(4) in graph-set notation], which lie parallel to the crystallographic a axis. At a pressure of 1.3 GPa, the crystal symmetry changes to Pna2(1) (Z' = 1) and the molecular catemers [expressed as C2 in graph-set notation] adopt a pseudo-twofold arrangement. This structural behaviour is in agreement with our previous observations for phenol and its halogenated derivatives 2-chlorophenol and 4-fluorophenol, where pressure was found to favour a molecular packing more closely associated with small alkyl groups rather than that of relatively bulky alkyl groups. In addition, an examination of the molecular coordination environment in the low-temperature and high-pressure structures of cyclobutanol reveals that the change in structure on application of pressure appears to be driven by the molecules assuming a packing arrangement which more closely resembles that adopted in hard-sphere structures.
Highlights
In the mono-alcohols (ROH) there is competition between the packing requirements of the relatively bulky R group and the demand for the small hydroxyl groups to be sufficiently close for hydrogen bonding to occur
All three systems form crystal structures at ambient pressure, characterized by the formation of hydrogen-bonding schemes associated with bulky R groups
The crystal structure of phase I of cyclobutanol has two molecules in the asymmetric unit and it is characterized by the presence of binary hydrogen-bonded chains of cyclobutanol molecules aligned parallel to the crystallographic a axis
Summary
In the mono-alcohols (ROH) there is competition between the packing requirements of the relatively bulky R group and the demand for the small hydroxyl groups to be sufficiently close for hydrogen bonding to occur. Brock & Duncan (1994) have described the general features of the packing motifs adopted by mono-alcohols. Brock & Duncan (1994) have described the general features of the packing motifs adopted by mono-alcohols They found that if the molecules containing the hydroxyl groups are relatively ‘thin’ (by Brock and Duncan’s terminology) they can form catemers where the molecules are symmetry-related by either a glide plane or a 21screw axis so that the molecules form an approximately coplanar alternating sequence about the central chain of hydrogen bonds. All three systems form crystal structures at ambient pressure, characterized by the formation of hydrogen-bonding schemes associated with bulky R groups Both phenol and 2-chlorophenol form crystal structures where the molecules are hydrogen bonded into pseudo-threefold chains. At high-pressure, the crystal symmetry changes to Pna (Z0 = 1) and the molecular catemers, which are generated by the aglide symmetry, adopt a pseudo-twofold arrangement This structural behaviour parallels what we have observed previously for phenol and 2-chlorophenol and is in agreement with the favouring of a small-group packing behaviour under pressure
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
