{"doi":"10.1021/acs.joc.3c01748","title":"Polar Effects in Hydrogen Atom Transfer Reactions from a Proton-Coupled Electron Transfer (PCET) Perspective: Abstractions from Toluenes","abstract":"Rate constants for hydrogen atom transfer (HAT) reactions of substituted toluenes with tert -butyl, tert -butoxy, and tert -butylperoxyl radicals are reanalyzed here using the free energies of related proton transfer (PT) and electron transfer (ET) reactions, calculated from an extensive set of compiled or estimated p K a and E ° values. The Eyring activation energies Δ G HAT ‡ do not correlate with the relatively constant Δ G° HAT, but do correlate close-to-linearly with Δ G° PT and Δ G° ET . The slopes of correlations are similar for the three radicals except that the t Bu • barriers shift in the opposite direction from the oxyl radical barriers─a clear example of the qualitative “polar effect” in HAT reactions. When cast quantitatively in free energy terms (Δ G HAT ‡ vs Δ G ° PT/ET ), this effect is very small, only 5–10% of the typical Bell–Evans–Polanyi (BEP) effect of changing Δ G° HAT . This analysis also highlights connections between polar effects and the concepts of “asynchronous” or “imbalanced” HAT reactions in which the PT and ET components of Δ G° HAT contribute differently to the barrier. Finally, these observations are discussed in light of the traditional explanations of polar effects and the potential for a rubric that could predict the extent to which contra-thermodynamic selectivity may be achieved in HAT reactions.","journal":"The Journal of Organic Chemistry","year":2023,"id":327832,"datarank":0.7581888491010718,"base_score":3.4011973816621555,"endowment":3.4011973816621555,"self_citation_contribution":0.5101796072493234,"citation_network_contribution":0.24800924185174839,"self_endowment_contribution":0.5101796072493234,"citer_contribution":0.24800924185174839,"corpus_percentile":null,"corpus_rank":null,"citation_count":29,"citer_count":25,"citers_with_citation_signal":14,"citers_with_endowment":14,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9467,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2023-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":758923,"name":"Brian Koronkiewicz","orcid":"0000-0002-9892-7837","position":1,"is_corresponding":false},{"id":513494,"name":"James M. Mayer","orcid":"0000-0002-3943-5250","position":2,"is_corresponding":false},{"id":823572,"name":"Benjamin D. Groff","orcid":"0000-0001-9779-2697","position":0,"is_corresponding":true}],"reference_count":88,"raw_metadata":{"citation_network_status":"fetched"},"created_at":"2026-07-19T01:08:47.581262Z","pmid":"37978890","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}