Tunneling in hydrogen-transfer isomerization of n-alkyl radicals.
Identifieur interne : 000058 ( PubMed/Checkpoint ); précédent : 000057; suivant : 000059Tunneling in hydrogen-transfer isomerization of n-alkyl radicals.
Auteurs : Baptiste Sirjean [États-Unis] ; Enoch Dames ; Hai Wang ; Wing TsangSource :
- The journal of physical chemistry. A [ 1520-5215 ] ; 2012.
Abstract
The role of quantum tunneling in hydrogen shift in linear heptyl radicals is explored using multidimensional, small-curvature tunneling method for the transmission coefficients and a potential energy surface computed at the CBS-QB3 level of theory. Several one-dimensional approximations (Wigner, Skodje and Truhlar, and Eckart methods) were compared to the multidimensional results. The Eckart method was found to be sufficiently accurate in comparison to the small-curvature tunneling results for a wide range of temperature, but this agreement is in fact fortuitous and caused by error cancellations. High-pressure limit rate constants were calculated using the transition state theory with treatment of hindered rotations and Eckart transmission coefficients for all hydrogen-transfer isomerizations in n-pentyl to n-octyl radicals. Rate constants are found in good agreement with experimental kinetic data available for n-pentyl and n-hexyl radicals. In the case of n-heptyl and n-octyl, our calculated rates agree well with limited experimentally derived data. Several conclusions made in the experimental studies of Tsang et al. (Tsang, W.; McGivern, W. S.; Manion, J. A. Proc. Combust. Inst. 2009, 32, 131-138) are confirmed theoretically: older low-temperature experimental data, characterized by small pre-exponential factors and activation energies, can be reconciled with high-temperature data by taking into account tunneling; at low temperatures, transmission coefficients are substantially larger for H-atom transfers through a five-membered ring transition state than those with six-membered rings; channels with transition ring structures involving greater than 8 atoms can be neglected because of entropic effects that inhibit such transitions. The set of computational kinetic rates were used to derive a general rate rule that explicitly accounts for tunneling. The rate rule is shown to reproduce closely the theoretical rate constants.
DOI: 10.1021/jp209360u
PubMed: 22129143
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A</title><idno type="eISSN">1520-5215</idno><imprint><date when="2012" type="published">2012</date></imprint></series></biblStruct></sourceDesc></fileDesc><profileDesc><textClass></textClass></profileDesc></teiHeader><front><div type="abstract" xml:lang="en">The role of quantum tunneling in hydrogen shift in linear heptyl radicals is explored using multidimensional, small-curvature tunneling method for the transmission coefficients and a potential energy surface computed at the CBS-QB3 level of theory. Several one-dimensional approximations (Wigner, Skodje and Truhlar, and Eckart methods) were compared to the multidimensional results. The Eckart method was found to be sufficiently accurate in comparison to the small-curvature tunneling results for a wide range of temperature, but this agreement is in fact fortuitous and caused by error cancellations. High-pressure limit rate constants were calculated using the transition state theory with treatment of hindered rotations and Eckart transmission coefficients for all hydrogen-transfer isomerizations in n-pentyl to n-octyl radicals. Rate constants are found in good agreement with experimental kinetic data available for n-pentyl and n-hexyl radicals. In the case of n-heptyl and n-octyl, our calculated rates agree well with limited experimentally derived data. Several conclusions made in the experimental studies of Tsang et al. (Tsang, W.; McGivern, W. S.; Manion, J. A. Proc. Combust. Inst. 2009, 32, 131-138) are confirmed theoretically: older low-temperature experimental data, characterized by small pre-exponential factors and activation energies, can be reconciled with high-temperature data by taking into account tunneling; at low temperatures, transmission coefficients are substantially larger for H-atom transfers through a five-membered ring transition state than those with six-membered rings; channels with transition ring structures involving greater than 8 atoms can be neglected because of entropic effects that inhibit such transitions. The set of computational kinetic rates were used to derive a general rate rule that explicitly accounts for tunneling. The rate rule is shown to reproduce closely the theoretical rate constants.</div></front></TEI><pubmed><MedlineCitation Owner="NLM" Status="PubMed-not-MEDLINE"><PMID Version="1">22129143</PMID><DateCreated><Year>2012</Year><Month>01</Month><Day>12</Day></DateCreated><DateCompleted><Year>2012</Year><Month>05</Month><Day>25</Day></DateCompleted><Article PubModel="Print-Electronic"><Journal><ISSN IssnType="Electronic">1520-5215</ISSN><JournalIssue CitedMedium="Internet"><Volume>116</Volume><Issue>1</Issue><PubDate><Year>2012</Year><Month>Jan</Month><Day>12</Day></PubDate></JournalIssue><Title>The journal of physical chemistry. A</Title><ISOAbbreviation>J Phys Chem A</ISOAbbreviation></Journal><ArticleTitle>Tunneling in hydrogen-transfer isomerization of n-alkyl radicals.</ArticleTitle><Pagination><MedlinePgn>319-32</MedlinePgn></Pagination><ELocationID EIdType="doi" ValidYN="Y">10.1021/jp209360u</ELocationID><Abstract><AbstractText>The role of quantum tunneling in hydrogen shift in linear heptyl radicals is explored using multidimensional, small-curvature tunneling method for the transmission coefficients and a potential energy surface computed at the CBS-QB3 level of theory. Several one-dimensional approximations (Wigner, Skodje and Truhlar, and Eckart methods) were compared to the multidimensional results. The Eckart method was found to be sufficiently accurate in comparison to the small-curvature tunneling results for a wide range of temperature, but this agreement is in fact fortuitous and caused by error cancellations. High-pressure limit rate constants were calculated using the transition state theory with treatment of hindered rotations and Eckart transmission coefficients for all hydrogen-transfer isomerizations in n-pentyl to n-octyl radicals. Rate constants are found in good agreement with experimental kinetic data available for n-pentyl and n-hexyl radicals. In the case of n-heptyl and n-octyl, our calculated rates agree well with limited experimentally derived data. Several conclusions made in the experimental studies of Tsang et al. (Tsang, W.; McGivern, W. S.; Manion, J. A. Proc. Combust. Inst. 2009, 32, 131-138) are confirmed theoretically: older low-temperature experimental data, characterized by small pre-exponential factors and activation energies, can be reconciled with high-temperature data by taking into account tunneling; at low temperatures, transmission coefficients are substantially larger for H-atom transfers through a five-membered ring transition state than those with six-membered rings; channels with transition ring structures involving greater than 8 atoms can be neglected because of entropic effects that inhibit such transitions. The set of computational kinetic rates were used to derive a general rate rule that explicitly accounts for tunneling. The rate rule is shown to reproduce closely the theoretical rate constants.</AbstractText></Abstract><AuthorList CompleteYN="Y"><Author ValidYN="Y"><LastName>Sirjean</LastName><ForeName>Baptiste</ForeName><Initials>B</Initials><AffiliationInfo><Affiliation>Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, California 90089-1453, USA. baptiste.sirjean@ensic.inpl-nancy.fr</Affiliation></AffiliationInfo></Author><Author ValidYN="Y"><LastName>Dames</LastName><ForeName>Enoch</ForeName><Initials>E</Initials></Author><Author ValidYN="Y"><LastName>Wang</LastName><ForeName>Hai</ForeName><Initials>H</Initials></Author><Author ValidYN="Y"><LastName>Tsang</LastName><ForeName>Wing</ForeName><Initials>W</Initials></Author></AuthorList><Language>eng</Language><PublicationTypeList><PublicationType UI="D016428">Journal Article</PublicationType></PublicationTypeList><ArticleDate DateType="Electronic"><Year>2011</Year><Month>12</Month><Day>27</Day></ArticleDate></Article><MedlineJournalInfo><Country>United States</Country><MedlineTA>J Phys Chem A</MedlineTA><NlmUniqueID>9890903</NlmUniqueID><ISSNLinking>1089-5639</ISSNLinking></MedlineJournalInfo></MedlineCitation><PubmedData><History><PubMedPubDate PubStatus="aheadofprint"><Year>2011</Year><Month>12</Month><Day>27</Day></PubMedPubDate><PubMedPubDate PubStatus="entrez"><Year>2011</Year><Month>12</Month><Day>2</Day><Hour>6</Hour><Minute>0</Minute></PubMedPubDate><PubMedPubDate PubStatus="pubmed"><Year>2011</Year><Month>12</Month><Day>2</Day><Hour>6</Hour><Minute>0</Minute></PubMedPubDate><PubMedPubDate PubStatus="medline"><Year>2011</Year><Month>12</Month><Day>2</Day><Hour>6</Hour><Minute>1</Minute></PubMedPubDate></History><PublicationStatus>ppublish</PublicationStatus><ArticleIdList><ArticleId IdType="doi">10.1021/jp209360u</ArticleId><ArticleId IdType="pubmed">22129143</ArticleId></ArticleIdList></PubmedData></pubmed><affiliations><list><country><li>États-Unis</li></country><region><li>Californie</li></region><settlement><li>Los Angeles</li></settlement><orgName><li>Université de Californie du Sud</li></orgName></list><tree><noCountry><name sortKey="Dames, Enoch" sort="Dames, Enoch" uniqKey="Dames E" first="Enoch" last="Dames">Enoch Dames</name><name sortKey="Tsang, Wing" sort="Tsang, Wing" uniqKey="Tsang W" first="Wing" last="Tsang">Wing Tsang</name><name sortKey="Wang, Hai" sort="Wang, Hai" uniqKey="Wang H" first="Hai" last="Wang">Hai Wang</name></noCountry><country name="États-Unis"><region name="Californie"><name sortKey="Sirjean, Baptiste" sort="Sirjean, Baptiste" uniqKey="Sirjean B" first="Baptiste" last="Sirjean">Baptiste Sirjean</name></region></country></tree></affiliations></record>Pour manipuler ce document sous Unix (Dilib)
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