Methoxymethane C-O Bond Strengths: Do Their Changes Result from Hyperconjugation or Polar Effects?

Area of Science:

• Computational Chemistry
• Quantum Chemistry

Background:

• Methoxymethanes and fluoromethanes are important chemical compounds.
• Understanding their bonding properties is crucial for predicting reactivity.

Purpose of the Study:

• To computationally investigate and compare the chemical properties of methoxymethanes and fluoromethanes.
• To elucidate the factors influencing bond dissociation enthalpies (BDE) and conformational energies.

Main Methods:

• High-level computational methods including MP2/aug-cc-pVTZ for energies and atomic charges.
• Configuration Interaction (CBS-QB3) calculations for group separation energies and BDEs.
• Analysis of electronic spatial extent and its correlation with conformational energies.

Main Results:

• Group separation energies for methoxymethanes are endothermic.
• Bond dissociation enthalpies increase with additional substitution due to increased central carbon charge.
• A linear correlation was observed between BDE and atomic charge at carbon in methoxymethanes.
• Conformational energies generally increase with electronic spatial extent, supporting Gillespie's proposal.

Conclusions:

• The charge on the central carbon atom significantly influences bond strength in methoxymethanes.
• Computational methods provide valuable insights into the electronic structure and bonding of these compounds.
• The role of hyperconjugation in these systems requires further investigation.