Premium
Role of 2‐carboxyl substituent in the tautomerization between two equivalent enol forms of 3‐hydroxyphenalenone
Author(s) -
Matsumiya Shigeki,
Izuoka Akira,
Sugawara Tadashi,
Nakamura Nobuo
Publication year - 1990
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610030712
Subject(s) - chemistry , tautomer , enol , substituent , keto–enol tautomerism , nuclear magnetic resonance spectroscopy , proton nmr , proton , spectroscopy , stereochemistry , activation energy , computational chemistry , photochemistry , organic chemistry , catalysis , physics , quantum mechanics
The interconversion between two equivalent enol forms of 3‐hydroxyphenalenone took place predominantly through a diketo form with a free energy of activation of ca 14 kcal mol −1 in DMSO solution determined by 125·8 MHz 13 C NMR measurement. On the other hand, the corresponding interconversion in 2‐carboxy‐3‐hydroxyphenalenone was not frozen on the time scale of 13 C NMR spectroscopy down to −60°C. This acceleration in the interconversion rate of the latter may be interpreted by a double proton switching between the hydrogen‐bonded 2‐carboxyl and 3‐hydroxyenone moieties.