{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2023,10,26]],"date-time":"2023-10-26T05:03:47Z","timestamp":1698296627861},"reference-count":8,"publisher":"Wiley","issue":"7","license":[{"start":{"date-parts":[[2004,9,7]],"date-time":"2004-09-07T00:00:00Z","timestamp":1094515200000},"content-version":"vor","delay-in-days":3721,"URL":"http:\/\/onlinelibrary.wiley.com\/termsAndConditions#vor"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["J Comput Chem"],"published-print":{"date-parts":[[1994,7]]},"abstract":"<jats:title>Abstract<\/jats:title><jats:p>A molecular dynamics (MD) simulation of 35,000 picoseconds (ps) has been carried out to study the conformational interconversions of 1,1\u2010difluoro\u20104,4\u2010dimethylcycloheptane at room temperature using the MM3 force field. The exchange between axial and equatorial fluorine atoms was the only conformational interconversion that occurred, and it took place via the process of pseudorotation. Ring inversions (twist\u2013chair &lt; twist\u2013boat &lt; twist\u2013chair) were not observed. The axial\u2010equatorial exchange of the two fluorine atoms took place five times during the MD trajectory of 35,000 ps. The two CH<jats:sub>3<\/jats:sub> groups occupied symmetrical positions (exchangeable by a C<jats:sub>2<\/jats:sub>\u2010like rotations, where C<jats:sub>2<\/jats:sub>\u2010like means it would be C<jats:sub>2<\/jats:sub> if the fluorines were not present) in the MM3 structures, and during most of the time of the MD trajectory. The methyls occasionally moved off the C<jats:sub>2<\/jats:sub>\u2010like axis in the simulated process, mostly because the C<jats:sub>2<\/jats:sub>\u2010like axis was momentarily moved so that it did not pass through the ring atom to which the two CH<jats:sub>3<\/jats:sub> groups are bonded. A C<jats:sub>2<\/jats:sub>\u2010like symmetry of the twist\u2010chair conformation was maintained approximately during most of the MD simulation. The conformational geometry with the highest energy obtained during the axial\u2010equatorial exchange process was found and used to locate the transition state. The energy barrier for this axial\u2010equatorial exchange was calculated to be 4.7 kcal\/mol, and it compares with the value (5.0 kcal\/mol) determined by dynamic nuclear magnetic resonance (NMR). \u00a9 1994 by John Wiley &amp; Sons, Inc.<\/jats:p>","DOI":"10.1002\/jcc.540150709","type":"journal-article","created":{"date-parts":[[2005,1,2]],"date-time":"2005-01-02T01:05:38Z","timestamp":1104627938000},"page":"769-781","source":"Crossref","is-referenced-by-count":1,"title":["Expanding molecular dynamics simulations to the NMR time scale. I. Studies of conformational interconversions of 1, 1\u2010difluoro\u20104, 4\u2010dimethylcycloheptane using MM3\u2010MD"],"prefix":"10.1002","volume":"15","author":[{"given":"Fanbing","family":"Li","sequence":"first","affiliation":[]},{"given":"Weili","family":"Cui","sequence":"additional","affiliation":[]},{"given":"Norman L.","family":"Allinger","sequence":"additional","affiliation":[]}],"member":"311","published-online":{"date-parts":[[2004,9,7]]},"reference":[{"key":"e_1_2_1_2_2","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1002\/9780470147108.ch1","volume":"1","author":"Mislow K.","year":"1967","journal-title":"Top. Stereochem."},{"key":"e_1_2_1_3_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja00205a001"},{"key":"e_1_2_1_4_2","doi-asserted-by":"publisher","DOI":"10.1002\/jcc.540110708"},{"key":"e_1_2_1_5_2","unstructured":"MM3 User Manual University of Georgia 1994."},{"key":"e_1_2_1_6_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja00060a049"},{"key":"e_1_2_1_7_2","first-page":"529","volume":"2","author":"Roberts J. D.","year":"1966","journal-title":"Chem. in Britain"},{"key":"e_1_2_1_8_2","doi-asserted-by":"publisher","DOI":"10.1021\/ja00772a015"},{"key":"e_1_2_1_9_2","unstructured":"Note that the numbering system used in this work has the geminal methyl groups at C3and the fluorines at C6. The ring carbon atoms are numbered consecutively from 1\u20137."}],"container-title":["Journal of Computational Chemistry"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/api.wiley.com\/onlinelibrary\/tdm\/v1\/articles\/10.1002%2Fjcc.540150709","content-type":"unspecified","content-version":"vor","intended-application":"text-mining"},{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/pdf\/10.1002\/jcc.540150709","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,10,25]],"date-time":"2023-10-25T08:43:56Z","timestamp":1698223436000},"score":1,"resource":{"primary":{"URL":"https:\/\/onlinelibrary.wiley.com\/doi\/10.1002\/jcc.540150709"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1994,7]]},"references-count":8,"journal-issue":{"issue":"7","published-print":{"date-parts":[[1994,7]]}},"alternative-id":["10.1002\/jcc.540150709"],"URL":"https:\/\/doi.org\/10.1002\/jcc.540150709","archive":["Portico"],"relation":{},"ISSN":["0192-8651","1096-987X"],"issn-type":[{"value":"0192-8651","type":"print"},{"value":"1096-987X","type":"electronic"}],"subject":[],"published":{"date-parts":[[1994,7]]}}}