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Fi.st Oxi.ati.n Product of Vi.ami. C, the dehydro-L-Ascorbi. Aci. Di.er： A Study Based on FTi.-Raman and DFT Calculati.ns

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Journal of Chemi.try and Chemi.al Engi.eeri.g 2011年第10期5卷 936-945页

作者： Laura C. Bi.hara Hernan E. Lanus Si.vi. A. Brandan catedra de quimica General. instituto de quimica i.organi.a. Facultad de Bi.qui.i.a Quimica y Farmacia. Universidad National de Tucuman. Ayacucho 471. 4000- S. M. de Tueuman. R. Argentina catedra de fisicoquimica i. instituto de quimica fisica. facultadde bioquimica Qulmicay Farmacia. UniversidadNaeional de Tucuman. San Lorenzo 456. T4000CAN S. M. de Tucuman. R. Argentina

We studi.d the fi.st oxi.ati.n product of vi.ami. C, the dehydro-L-ascorbi. aci. di.er and characteri.ed i. by i.frared and Raman spectroscopi.s i. the soli. phase. The densi.y functi.nal theory was used to study i.s structure and vi.rati.nal properti.s. These calculati.ns gave us a preci.e knowledge of the normal modes of vi.rati.n taki.g i.to account that the molecule compri.es a system of fi.e fused ri.gs; non planar γ-lactone and furonose ri.gs are attached to a central di.xan ri.g i. the twi.ted boat conformati.n. The calculated harmoni. vi.rati.nal frequenci.s are consi.tent wi.h the experi.ental vi.rati.nal spectra. An assi.nment of the observed spectral features i. proposed. The shi.t of the band located i. the i.frared spectrum of the ascorbi. aci. from 3409 cm^-1 to 3299 cml and the remarkable i.crease i. the band i.tensi.y at 1784 cm^-1 evi.0}nces the aci. decomposi.i.n i.to i.s fi.st product, the dehydro-L-ascorbi. aci.. The theoreti.al vi.rati.nal calculati.ns allowed us to obtai. a set of scaled force constants. The nature of the di.ferent -γ-lactone, furanose and di.xan ri.gs and thei. topologi.al properti.s were i.vesti.ated by means of natural bond orbi.al and Bader＇s atoms i. the molecule theory, respecti.ely.

关键词： dehydro-L-ascorbi. aci. vi.rati.nal spectra molecular structure force fi.ld DFT calculati.ns

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Structural and Vi.rati.nal Study of 2-（Qui.oli.-8-yloxy）-Aceti. Aci. based on FT-i.-Raman Spectroscopy and DFT Calculati.ns

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Journal of Chemi.try and Chemi.al Engi.eeri.g 2011年第8期5卷 747-758页

作者： Gerardo R. Arganaraz Eli.a Romano Juan Zi.czuk Si.vi. A. Brandan catedra de quimica General. instituto de quimica i.organi.a. Faeultad de bioquimica Quimica y Farmacia. Universidad Nacional de Tucuman. Ayacucho 471. 4000. San Miguel de Tucuman. Tucumcin. R. Argentina instituto de Qulmi.a Rosari. （CONi.ET-UNR） Facultad de Ciencias Bioquimicas y Farmacduticas Suipacha 531 2000 Rosario Santa Fe. R. Argentina

We have prepared the 2-（qui.oli.-8-yloxy）-aceti. aci. and characteri.ed i. by i.frared and Raman spectroscopi.s i. the soli. phase. The densi.y Functi.nal Theory （DFT） method, together wi.h the 6-31G^＊ and 6-311＋＋ G^＊＊ basi. sets, show that three stable molecules, for the anhydrous and monohydrated compounds were theoreti.ally determi.ed i. the gas phase, and that probably the two more stable conformati.ns are present i. the soli. phase of the monohydrated compound. The harmoni. vi.rati.nal wavenumbers for the opti.i.ed geometri.s were calculated at B3LYP/6-31G^＊and B3LYP/6-311＋＋G^＊＊ levels. For a complete assi.nment of all the observed bands i. the vi.rati.nal spectra the DFT calculati.ns were combi.ed wi.h Pulay＇s scaled quantum mechani.al force fi.ld （SQMFF） methodology i. order to fi. the theoreti.al Wavenumber values to the experi.ental ones. The characteri.ti.s of the electroni. delocali.ati.n of all structures of both forms were performed by usi.g natural bond orbi.al （NBO）, whi.e the correspondi.g topologi.al properti.s of electroni. charge densi.y are analysed by employi.g Bader＇s atoms i. molecules theory （Ai.）.

关键词： 2-(Qui.oli.-8-yloxy)-aceti. aci. vi.rati.nal spectra molecular structure force fi.ld DFT calculati.ns

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