Methyl Radical Addition Reaction to Substituted C═C Double Bonds.

Area of Science:

• Organic Chemistry
• Computational Chemistry
• Reaction Mechanisms

Background:

• Radical addition reactions are vital for carbon-carbon bond formation.
• Understanding the rules governing these reactions is crucial for synthetic chemistry.

Purpose of the Study:

• Investigate the fundamental methyl radical addition reaction (MRAR) to monosubstituted ethylenes.
• Analyze factors influencing regioselectivity and substituent effects.
• Advance mechanistic understanding of radical addition reactions.

Main Methods:

• Density Functional Theory (DFT) calculations using ZORA-(U)OLYP/TZ2P.
• Activation Strain Model (ASM) and Energy Decomposition Analysis (EDA).

Main Results:

• Radical addition preferentially occurs at the β-carbon over the α-carbon.
• Reduced Pauli repulsion and maximized orbital interactions favor β-addition.
• Electron-donating (NMe2) and electron-withdrawing (CHO) groups lower activation barriers via improved orbital interactions.
• CHO shows a greater barrier reduction than NMe2 due to altered orbital interaction mechanisms.

Conclusions:

• Provides a mechanistic understanding of regioselectivity and substituent effects in MRAR.
• Links qualitative theories (e.g., Frontier Molecular Orbital Theory) with computational insights.
• Offers a physically sound basis for understanding radical addition transformations.