The energetics of naphthalene derivatives, III: Phenylacetic acid and the isomeric 1- And 2-naphthylacetic acids

Phenylacetic acid and the isomeric 1- and 2-naphthylacetic acids are at the confluence of diverse concepts, techniques and classes of organic compounds. Summing the results of our new enthalpy of formation of the gaseous phenylacetic acid reported herein, and of literature enthalpy of formation of the isomeric solid naphthylacetic acids and of our new sublimation enthalpies reported herein, we derive gas phase enthalpies of formation of −314.7±3.1, −246.9±2.0 and −247.4±2.1kJmol−1 respectively. This corresponds to 1- and 2-naphthylacetic acid having indistinguishable enthalpies of formation. We also performed MP2(full)/6-31G(d) calculations on these species, resulting in enthalpies of formation of −307.3±0.8, −247.4±3.4 and −247.5±3.4kJmol−1 for phenylacetic acid and 1- and 2-naphthylacetic acid in satisfactory agreement with the above experimental results.We acknowledge the Spanish MCyT/DGI under Projects BQU2003-05827 (MVR) and BQU2000-1499 (RN). MT thanks MECD/SEEU, AP2002-0603, Spain for financial support. RN thanks CESGA for computing facilities. VE acknowledges gratefully a research scholarship from the DAAD (Deutscher Akademischer Austauschdienst)