Phenols are hygroscopic and form a red liquid, upon contact with air. Yet, Phenol’s solubility in water is said to be moderate. ( Tilted to the low solubility side) This is explained with the benzene ring being non polar. Then how can it be hygroscopic? Are solubility and hygroscopicity even related at all, then?

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    $\begingroup$ Phenol's solubility in water is not all that low, and grows with temperature until at some point phenol becomes infinitely soluble. Then again, there certainly are some compounds which are hygroscopic and insoluble. How can that be? Well, just like that. $\endgroup$ – Ivan Neretin Nov 30 '17 at 18:03
  • $\begingroup$ related chemistry.stackexchange.com/questions/34636/… $\endgroup$ – Mithoron Nov 30 '17 at 18:30

Hygroscopicity is measure of how much the molecule likes to bond molecules of water, by hydrating/covering charged part of the molecule with molecule/s of water, which relates to it having some polar or charged functional groups, like hydroxyl group for phenols.

Solubility is about how molecule likes to be surrounded by water, so in this case the structure of whole molecule makes a difference. Since water is a polar solvent it likes polar solutes. If a molecule despite having one or more polar groups has, for example, a huge part which is not polar, like a carbon chain, then it will not be soluble even though it may be hygroscopic.


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