The Elusive Nature of Aromatic Carbocation Intermediates in Confined Catalytic Environments

The Elusive Nature of Aromatic Carbocation Intermediates in Confined Catalytic Environments | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article The Elusive Nature of Aromatic Carbocation Intermediates in Confined Catalytic Environments GiovanniMaria Piccini, Chintu Das, Princy Jarngal, Fabian Berger, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9418332/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted You are reading this latest preprint version Abstract Wheland intermediates play a pivotal role in the mechanistic understanding of electrophilic aromatic substitution, yet their existence under realistic conditions remains debated. Here, we address this question for aromatic alkylation in acidic zeolites, where charged intermediates are strongly influenced by confinement, electrostatics, hydrogen bonding, and finite-temperature dynamics. By combining enhanced free-energy sampling based on machine-learning interatomic potentials with free energy perturbation and embedded-cluster CCSD(T) calculations, we construct chemically accurate free-energy surfaces for the alkylation of benzene and phenol by cyclohexene in H-BEA. We find that the classical stepwise picture breaks down when the free-energy surface is described at gold-standard coupled-cluster accuracy. For benzene alkylation, both the carbenium ion and the Wheland intermediate are transient configurations rather than genuine intermediates. For phenol alkylation, the OH substituent provides additional stabilization, yielding metastable cationic species that nevertheless remain short-lived. These results show that the existence and lifetime of reactive intermediates are not inherent to the reaction class but emerge from the interplay of substituent effects, confinement, and finite-temperature dynamics. More broadly, we demonstrate that free-energy surfaces beyond DFT quality are required to obtain chemically accurate insights necessary for truly predictive materials design. Physical sciences/Chemistry/Theoretical chemistry/Computational chemistry Physical sciences/Chemistry/Catalysis/Heterogeneous catalysis Physical sciences/Chemistry/Theoretical chemistry/Molecular dynamics Physical sciences/Chemistry/Theoretical chemistry/Reaction mechanisms Physical sciences/Chemistry/Catalysis/Catalytic mechanisms Full Text Additional Declarations There is NO Competing Interest. Supplementary Files files.zip Input files for reproducing the simulazions SIFriedelCraftSEAr.pdf Supplementray Information to The Elusive Nature of Aromatic Carbocation Intermediates in Confined Catalytic Environments Cite Share Download PDF Status: Under Review Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9418332","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":624763861,"identity":"d1bc9a62-aab5-41be-9a79-ada6cadd6dd2","order_by":0,"name":"GiovanniMaria 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