The low temperature crystalline and glassy states of methyl -hydroxy-isobutyrate
Autor(a) principal: | |
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Data de Publicação: | 2001 |
Outros Autores: | , , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
Texto Completo: | http://hdl.handle.net/10316/10718 https://doi.org/10.1039/b007722o |
Resumo: | The low temperature crystalline and glassy phases of methyl -hydroxy-isobutyrate (MHib) were identified and characterized structurally by differential scanning calorimetry, IR and Raman spectroscopy and molecular modeling. Within the temperature range 13–171 K, MHib exists as a glassy state, where individual molecules may assume the two conformational states previously observed for this compound isolated in an argon matrix and in the liquid phase [S. Jarmelo and R. Fausto, J. Mol. Struct., 1999, 509, 193]. At ca. 171 K, devitrification occurs and a crystalline phase may then be formed [T(onset)213 K], the enthalpy of crystallization being ca. 5 kJ mol–1. The crystalline phase was found to exhibit conformational selectivity—in this phase all individual molecules assume a conformation analogous to the most stable conformer found for the isolated molecule and in the liquid (the Syn-syn s-cis conformer, where the H–O–C–C, O–C–CO and OC–O–C dihedrals are ca. 0°). Molecular modeling and Raman data are consistent with a structural unit within the crystal where two MHib molecules form a centrosymmetrical hydrogen bonded dimer. The observed temperature of fusion [Tf(peak)] for the crystal is 240 K. |
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The low temperature crystalline and glassy states of methyl -hydroxy-isobutyrateThe low temperature crystalline and glassy phases of methyl -hydroxy-isobutyrate (MHib) were identified and characterized structurally by differential scanning calorimetry, IR and Raman spectroscopy and molecular modeling. Within the temperature range 13–171 K, MHib exists as a glassy state, where individual molecules may assume the two conformational states previously observed for this compound isolated in an argon matrix and in the liquid phase [S. Jarmelo and R. Fausto, J. Mol. Struct., 1999, 509, 193]. At ca. 171 K, devitrification occurs and a crystalline phase may then be formed [T(onset)213 K], the enthalpy of crystallization being ca. 5 kJ mol–1. The crystalline phase was found to exhibit conformational selectivity—in this phase all individual molecules assume a conformation analogous to the most stable conformer found for the isolated molecule and in the liquid (the Syn-syn s-cis conformer, where the H–O–C–C, O–C–CO and OC–O–C dihedrals are ca. 0°). Molecular modeling and Raman data are consistent with a structural unit within the crystal where two MHib molecules form a centrosymmetrical hydrogen bonded dimer. The observed temperature of fusion [Tf(peak)] for the crystal is 240 K.Fundação para a Ciência e Tecnologia, programas PRAXIS QUI/10137/98 e SFRH/157/2000.Royal Society of Chemistry2001-01-15info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articlehttp://hdl.handle.net/10316/10718http://hdl.handle.net/10316/10718https://doi.org/10.1039/b007722oengPhysical Chemistry Chemical Physics. 3 (2001) 387-3921463-9076Jarmelo, SusanaMaria, Teresa M. R.Leitão, Maria Luísa P.Fausto, Ruiinfo:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2021-09-17T08:31:40Zoai:estudogeral.uc.pt:10316/10718Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-19T21:01:37.286068Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse |
dc.title.none.fl_str_mv |
The low temperature crystalline and glassy states of methyl -hydroxy-isobutyrate |
title |
The low temperature crystalline and glassy states of methyl -hydroxy-isobutyrate |
spellingShingle |
The low temperature crystalline and glassy states of methyl -hydroxy-isobutyrate Jarmelo, Susana |
title_short |
The low temperature crystalline and glassy states of methyl -hydroxy-isobutyrate |
title_full |
The low temperature crystalline and glassy states of methyl -hydroxy-isobutyrate |
title_fullStr |
The low temperature crystalline and glassy states of methyl -hydroxy-isobutyrate |
title_full_unstemmed |
The low temperature crystalline and glassy states of methyl -hydroxy-isobutyrate |
title_sort |
The low temperature crystalline and glassy states of methyl -hydroxy-isobutyrate |
author |
Jarmelo, Susana |
author_facet |
Jarmelo, Susana Maria, Teresa M. R. Leitão, Maria Luísa P. Fausto, Rui |
author_role |
author |
author2 |
Maria, Teresa M. R. Leitão, Maria Luísa P. Fausto, Rui |
author2_role |
author author author |
dc.contributor.author.fl_str_mv |
Jarmelo, Susana Maria, Teresa M. R. Leitão, Maria Luísa P. Fausto, Rui |
description |
The low temperature crystalline and glassy phases of methyl -hydroxy-isobutyrate (MHib) were identified and characterized structurally by differential scanning calorimetry, IR and Raman spectroscopy and molecular modeling. Within the temperature range 13–171 K, MHib exists as a glassy state, where individual molecules may assume the two conformational states previously observed for this compound isolated in an argon matrix and in the liquid phase [S. Jarmelo and R. Fausto, J. Mol. Struct., 1999, 509, 193]. At ca. 171 K, devitrification occurs and a crystalline phase may then be formed [T(onset)213 K], the enthalpy of crystallization being ca. 5 kJ mol–1. The crystalline phase was found to exhibit conformational selectivity—in this phase all individual molecules assume a conformation analogous to the most stable conformer found for the isolated molecule and in the liquid (the Syn-syn s-cis conformer, where the H–O–C–C, O–C–CO and OC–O–C dihedrals are ca. 0°). Molecular modeling and Raman data are consistent with a structural unit within the crystal where two MHib molecules form a centrosymmetrical hydrogen bonded dimer. The observed temperature of fusion [Tf(peak)] for the crystal is 240 K. |
publishDate |
2001 |
dc.date.none.fl_str_mv |
2001-01-15 |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/10316/10718 http://hdl.handle.net/10316/10718 https://doi.org/10.1039/b007722o |
url |
http://hdl.handle.net/10316/10718 https://doi.org/10.1039/b007722o |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
Physical Chemistry Chemical Physics. 3 (2001) 387-392 1463-9076 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.publisher.none.fl_str_mv |
Royal Society of Chemistry |
publisher.none.fl_str_mv |
Royal Society of Chemistry |
dc.source.none.fl_str_mv |
reponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação instacron:RCAAP |
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Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
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RCAAP |
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RCAAP |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
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Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
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