Electrofugalities of 1,3-diarylallyl cations

Area of Science:

• Organic Chemistry
• Reaction Kinetics
• Physical Organic Chemistry

Background:

• Understanding the heterolysis of organic compounds is crucial for predicting reaction pathways.
• 1,3-Diarylallyl systems offer a unique structural motif for studying carbocation intermediates.
• Previous work has established correlations for related systems, but specific deviations require further investigation.

Purpose of the Study:

• To determine heterolysis rate constants (k1) for various 1,3-diarylallyl halides and carboxylates.
• To develop and validate a linear free energy relationship (LFER) for predicting these rates.
• To investigate systematic deviations from the LFER and elucidate their mechanistic origins.

Main Methods:

• Kinetic studies in diverse solvent systems.
• Determination of heterolysis rate constants (k1).
• Application and analysis of a linear free energy relationship (log k1 = s(f)(N(f) + E(f))).

Main Results:

• A predictive LFER was established with a standard deviation of 0.26 (factor of 1.82).
• Systematic deviations were observed: carboxylates reacted faster, and chlorides reacted slower than predicted.
• 1,3-Diarylallyl cations exhibit lower intrinsic barriers compared to benzhydrylium ions.

Conclusions:

• The developed LFER provides a valuable tool for predicting heterolysis rates of 1,3-diarylallyl derivatives.
• Leaving group effects significantly influence the reactivity and mechanistic pathways.
• The study advances the understanding of carbocation reactivity and reaction mechanisms in solvolysis reactions.