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Infrared spectroscopic studies of hydrogen bonding in substituted nitrophenols: substituent and solvent effects

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dc.contributor.authorCastilho, Paula C. M. F.
dc.contributor.authorCrampton, Michael R.
dc.contributor.authorYarwood, Jack
dc.date.accessioned2021-04-09T13:34:21Z
dc.date.available2021-04-09T13:34:21Z
dc.date.issued1992
dc.description.abstractA detailed infrared spectroscopic study of the substituted phenols 2-cyano-4,6-dinitrophenol and 4-cyano-2,6-dinitrophenol has been carried out (in several different solvents) in order to investigate the substituent and solvent effects on their intra- and inter-molecular hydrogen bonding properties. In benzene or dichloromethane it is found that both isomers form strong intramolecular hydrogen bonds with the 2-cyano (2CN) isomer having a stronger intramolecular interaction (in accordance with the higher pKa). The 4-cyano (4CN) isomer shows two distinct NO2 groups and exchange between the two possible hydrogen bonding sites is probably slow on the infrared time-scale. In protic solvents such as methanol the intramolecular hydrogen bonds are broken (more easily for the 4CN isomer) by intermolecular hydrogen bonding to the solvent. The differential “reactivity” towards methanol may be associated with steric congestion in the 4CN isomer leading to the forcing of at least one of the NO2 groups out of the aromatic plane. The use of mixed solvents (benzene-methanol) has established that the two hydrogen bonded species are observed together and that a high concentration of methanol is required to drive the equilibrium towards the intermolecular hydrogen bonded species. In dimethyl sulphoxide the behaviour of the two isomers is even more interesting. The 4CN isomer is ionised to produce the corresponding phenolate. However the 2CN isomer remains neutral (but highly solvated). We attribute this difference to the requirement for the 4CN isomer to allow the 2- and 6-NO2 groups to recover planarity with the aromatic ring. The energy compensation involved in this process is clearly sufficient to break a stronger intramolecular hydrogen bond.pt_PT
dc.description.versioninfo:eu-repo/semantics/publishedVersionpt_PT
dc.identifier.citationCastilho, P. C., Crampton, M. R., & Yarwood, J. (1992). Infrared spectroscopic studies of hydrogen bonding in substituted nitrophenols: substituent and solvent effects. Vibrational spectroscopy, 3(3), 167-180.pt_PT
dc.identifier.doi10.1016/0924-2031(92)87001-Vpt_PT
dc.identifier.urihttp://hdl.handle.net/10400.13/3272
dc.language.isoengpt_PT
dc.peerreviewedyespt_PT
dc.publisherElsevierpt_PT
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/pt_PT
dc.subjectInfrared spectrometrypt_PT
dc.subjectHydrogen bondingpt_PT
dc.subjectNitrophenolspt_PT
dc.subject.pt_PT
dc.subjectFaculdade de Ciências Exatas e da Engenhariapt_PT
dc.titleInfrared spectroscopic studies of hydrogen bonding in substituted nitrophenols: substituent and solvent effectspt_PT
dc.typejournal article
dspace.entity.typePublication
oaire.citation.endPage180pt_PT
oaire.citation.issue3pt_PT
oaire.citation.startPage167pt_PT
oaire.citation.titleVibrational Spectroscopypt_PT
oaire.citation.volume3pt_PT
person.familyNameCastilho
person.givenNamePaula C
person.identifierA-4412-2013
person.identifier.ciencia-id6D15-8C69-A2E0
person.identifier.orcid0000-0002-8303-4286
rcaap.rightsopenAccesspt_PT
rcaap.typearticlept_PT
relation.isAuthorOfPublicationd84fd917-438e-43bf-ac6f-256562481c05
relation.isAuthorOfPublication.latestForDiscoveryd84fd917-438e-43bf-ac6f-256562481c05

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