Calculated CNO2 bond dissociation energies

✍ Scribed by Michael L. McKee

• Publisher: Elsevier Science
• Year: 1989
• Tongue: English
• Weight: 524 KB
• Volume: 164
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(89)85250-9

✦ Synopsis

The effect of substituents on C-NO, bond energies was explored with high level calculations. Geometries for the compounds NO,-CXH,; X=H, F, OH, NH,, CH, and NO,-CH=Y, Y=O, CH, were optimized with the 3-21G basis set. Bond energies, calculated with full MP4/6-31G* energies, were corrected to 298 K by including scaled zero-point corrections and heat capacity corrections. In the series where X was varied, the bond dissociation energy (BDE) remained nearly constant (59.0-62.3 kcal/ mol). In contrast, the NO*-CH=O bond is much weaker (52.0 kcal/mol) and the NOI-CH=CH, bond is much stronger (7 1.0 kcal/mol) compared to the C-NO* bond in the NO*-CXH2 series. Bond strengths were compared when H replaces NO*. It was found that the constant C-NO2 bond energy in the N02-CXHZ series is due to two offsetting effects. Namely, substituents which increase the intrinsic bond energy (IBE) also increase the stability of the radical.