13065-86-6Relevant articles and documents
Photochemistry of p-benzoquinone diazide carboxylic acids: Formation of 2,4-didehydrophenols
Sander, Wolfram,Bucher, G?tz,Wandel, Holger,Kraka, Elfi,Cremer, Dieter,Sheldrick, William S.
, p. 10660 - 10672 (2007/10/03)
The photochemistry of p-benzoquinone diazide carboxylic acids (7) was studied using matrix isolation spectroscopy, product analysis, and high-level ab initio molecular orbital theory. The general photochemical pathway observed includes primary carbene formation, followed by secondary photodecarboxylation to yield derivatives of 2,4-didehydrophenol 9. CCSD(T) calculations on the parent 2,4-didehydrophenol (9a) lead to an infrared spectrum which is in excellent agreement with the experiment alone. Furthermore; calculations predict 9a to be characterized by a distorted benzene ring with the hydroxy group pointing toward the radical center in ortho position. The heat of formation of 9a is predicted to be 85 kcal/mol. Its formation from 1-oxo-2,5-cyclohexadien-4-ylidene-2-carboxylic acid (8a) by decarboxylation is exothermic by 30 kcal/mol where strong H-bonding in 8a can be considered to facilitate the formation of 9a.
