When hydroxy proton shows chemical shift delta value above 10 in Proton NMR spectrum?

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Mikhail Yur'evich Ievlev

Very de-shielded and acidic protons are able to appear at more that 10 ppm.

OH group of carboxylic acids, enols, phenols an so on.

It also depends on the solvent.

Ahmed Al-Amiery

Depend on the solvent,

In DMSO solution, even the exchange between carboxylic acid protons and other OH groups can be slowed enough to allow individual observation, as in 2-hydroxycinnamic acid

Panagiotis Zoumpoulakis

Also keep in mind the occasion of deshielding due to intramolecular H-bond formation

Martha Leyte

due to an intramolecular hydrogen bond