{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,22]],"date-time":"2026-08-22T14:30:45Z","timestamp":1787409045853,"version":"build-2736575974"},"reference-count":0,"publisher":"National Academy of Sciences","issue":"3","content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[1971,3]]},"abstract":"<jats:p>\n                    Angular displacement from linear overlap of but a few degrees in the transition state of the enzyme-substrate complex has been postulated to be of great kinetic significance (\u201corbital steering\u201d). The concept of orbital steering is shown to have evolved from the orientation parameters of an equation previously proposed to evaluate the kinetic importance of propinquity. This equation is shown to be naive. Arguments provided against the concept of orbital steering include: (\n                    <jats:italic>a<\/jats:italic>\n                    ) force constants predicted from orbital steering are about 100 times those experimentally determined from displacement of nuclei in a direction normal to the axis of a covalent bond (for example, at room temperature vibrational bending amplitudes of +5\u00b0 or more are common); (\n                    <jats:italic>b<\/jats:italic>\n                    ) because of the lessened directionality of orbitals containing nonbonded electron pairs, the force constants in transition states should be even smaller than in the case of a covalent bond; and (\n                    <jats:italic>c<\/jats:italic>\n                    ) molecular orbital calculations predict shallow total energy minima for orbital alignment. The experimental rate data offered as a basis for the concept of orbital steering are shown to find rationalization in the previously observed dependence of \u0394S\u2021 on kinetic order and the energy requirements for the freezing-out of single bonds in the transition state leading to the formation of medium-size ring compounds from extended ground states. It is concluded that if orbital steering does exist, experimental and theoretical evidence to support this concept have yet to be presented.\n                  <\/jats:p>","DOI":"10.1073\/pnas.68.3.658","type":"journal-article","created":{"date-parts":[[2006,5,31]],"date-time":"2006-05-31T02:27:34Z","timestamp":1149042454000},"page":"658-661","update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":51,"title":["On the Concept of Orbital Steering in Catalytic Reactions"],"prefix":"10.1073","volume":"68","author":[{"given":"Thomas C.","family":"Bruice","sequence":"first","affiliation":[{"name":"Department of Chemistry, University of California, Santa Barbara, Calif. 93106"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Allister","family":"Brown","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of California, Santa Barbara, Calif. 93106"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David O.","family":"Harris","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of California, Santa Barbara, Calif. 93106"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"341","published-online":{"date-parts":[[1971,3]]},"container-title":["Proceedings of the National Academy of Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pnas.org\/doi\/pdf\/10.1073\/pnas.68.3.658","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2022,4,13]],"date-time":"2022-04-13T10:45:20Z","timestamp":1649846720000},"score":1,"resource":{"primary":{"URL":"https:\/\/pnas.org\/doi\/full\/10.1073\/pnas.68.3.658"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1971,3]]},"references-count":0,"journal-issue":{"issue":"3","published-print":{"date-parts":[[1971,3]]}},"alternative-id":["10.1073\/pnas.68.3.658"],"URL":"https:\/\/doi.org\/10.1073\/pnas.68.3.658","relation":{},"ISSN":["0027-8424","1091-6490"],"issn-type":[{"value":"0027-8424","type":"print"},{"value":"1091-6490","type":"electronic"}],"subject":[],"published":{"date-parts":[[1971,3]]},"assertion":[{"value":"1971-03-01","order":2,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}]}}