Why can the activation volume of the cycloadduct decomposition in isopolar retro-Diels–Alder reactions be negative?

✍ Scribed by Vladimir D. Kiselev

• Publisher: John Wiley and Sons
• Year: 2010
• Tongue: English
• Weight: 254 KB
• Volume: 42
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.20462

✦ Synopsis

Abstract

Rate constants of the Diels–Alder cycloaddition reaction of anthracene with tetracyanoethylene, enthalpy of solution of reactants and adduct, enthalpy of the reaction in solution, enthalpy and entropy of activation of the forward and retro‐Diels–Alder reactions were determined in 14 solvents. Temperature and pressure effects on the rate of the decomposition of the adduct formed from 9‐chloroanthracene and tetracyanoethylene were studied. Since the electrostriction effect can be excluded from the consideration of the isopolar Diels–Alder reaction, negative values of the activation volume in the retro‐Diels–Alder reactions can be caused by the different possibilities of penetration of the solvent molecules to large steric branched structures of the transition states and adducts. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 117–125, 2010