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Figure 4
(a) Primary and secondary hydrogen-bond interactions. Through-space interactions, the secondary electrostatic interactions (dashed line), make phenol a better hydrogen-bond donor than carb­oxy­lic acid, which has repulsive secondary electrostatic interactions (Hunter, 2004BB21). (b) MEP surface calculations showed that the OH group is the best donor (D1) and the COOH group is the second-best donor (D2) (Aakeröy et al., 2013aBB101).

IUCrJ
Volume 6| Part 4| July 2019| Pages 751-760
ISSN: 2052-2525
https://doi.org/10.1107/S2052252519005037