Weak Acidity of Vinyl CH Bonds Enhanced by Halogen Substitution

Title:
Weak Acidity of Vinyl CH Bonds Enhanced by Halogen Substitution
Authors:
Craig, Norman C.; Matlin, Albert
Abstract:
As shown by the rates of proton–deuteron exchange in ethylenes with halogen substituents, the weak acidity of vinyl CH bonds is enhanced by halogen substitution. Relative rates of exchange in basic deuterium oxide reflect the relative acidities. Substitution in the α position has the strongest effect. Less electronegative halogens such as bromine increase the acidity more than does fluorine. The vinyl CH acid strengths correlate closely with the energies of deprotonation of isolated molecules into isolated anions, as computed with the MP2/cc-pVQZ model. The smaller deprotonation energies are associated with the stronger acids. Atomic charges from a natural bond order analysis done with the MP2/aug-cc-pVQZ model show that the negative charge becomes more dispersed in the anions of the stronger acids. Results are given for 13 haloethylenes and for 6 halogen-substituted butadienes, cyclopropenes, and a cyclobutene.
Citation:
Craig, N.C. and A.R.  Matlin. 2014. “Weak Acidity of Vinyl CH Bonds Enhanced by Halogen Substitution.” Journal of Organic Chemistry 79(4): 1729-1731.
Publisher:
American Chemical Society
DATE ISSUED:
2014
Department:
Chemistry and Biochemistry
Type:
Article
PUBLISHED VERSION:
10.1021/jo402703v
PERMANENT LINK:
http://hdl.handle.net/11282/566911

Full metadata record

DC FieldValue Language
dc.contributor.authorCraig, Norman C.en
dc.contributor.authorMatlin, Alberten
dc.date.accessioned2015-08-13T10:36:45Zen
dc.date.available2015-08-13T10:36:45Zen
dc.date.issued2014en
dc.identifier.citationCraig, N.C. and A.R.  Matlin. 2014. “Weak Acidity of Vinyl CH Bonds Enhanced by Halogen Substitution.” Journal of Organic Chemistry 79(4): 1729-1731.en
dc.identifier.issn0022-3263en
dc.identifier.urihttp://hdl.handle.net/11282/566911en
dc.description.abstractAs shown by the rates of proton–deuteron exchange in ethylenes with halogen substituents, the weak acidity of vinyl CH bonds is enhanced by halogen substitution. Relative rates of exchange in basic deuterium oxide reflect the relative acidities. Substitution in the α position has the strongest effect. Less electronegative halogens such as bromine increase the acidity more than does fluorine. The vinyl CH acid strengths correlate closely with the energies of deprotonation of isolated molecules into isolated anions, as computed with the MP2/cc-pVQZ model. The smaller deprotonation energies are associated with the stronger acids. Atomic charges from a natural bond order analysis done with the MP2/aug-cc-pVQZ model show that the negative charge becomes more dispersed in the anions of the stronger acids. Results are given for 13 haloethylenes and for 6 halogen-substituted butadienes, cyclopropenes, and a cyclobutene.en
dc.language.isoen_USen
dc.publisherAmerican Chemical Societyen
dc.identifier.doi10.1021/jo402703ven
dc.subject.departmentChemistry and Biochemistryen
dc.titleWeak Acidity of Vinyl CH Bonds Enhanced by Halogen Substitutionen
dc.typeArticleen
dc.identifier.journalJournal of Organic Chemistryen
dc.subject.keywordResolution infrared-spectraen_US
dc.subject.keywordVibrational assignmentsen_US
dc.subject.keywordDeuterated modificationsen_US
dc.subject.keywordMicrowave spectroscopyen_US
dc.subject.keywordPotential constantsen_US
dc.subject.keywordCIS-Transen_US
dc.identifier.volume79en
dc.identifier.issue4en
dc.identifier.startpage1729en
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