Reaction rates of electrons in liquid methanol and ethanol: Effect of temperature: Kinetics of electron reactions prior to solvation

. Can. J. Chem. 55, 3058 (1977). The solvated electron, e,-, decays with first-order kinetics in pulse-irradiated aliphatic alcohols, attributed to reaction 1 : e,-+ ROH + products. It is suggested that a recent report of curved Arrhenius plots for the temperature dependence of the rate constants for reaction 1 can be ascribed to reaction of e,-with impurities.J. H. BAXENDALE et PETER WARDMAN. Can. J. Chem. 55, 3058 (1977). Dans des alcools aliphatiques irradies par pulsation, l'electron solvate e,-se decroit avec une cinetique du premier ordre par une reaction attribute 9: e,-+ ROH + des produits [I].On attribue a la reaction de e,-avec des impuretes la nature recourbee des traces d'Arrhtnius, decrivant la relation entre les constantes de vitesse et la temperature, pour la reaction 1 qui ont ete rapportees dans un travail recent.[ duced by pulse radiolysis of liquid alcohols, and 1 0~~

Section: Ethanol (Lower Abscissa) a Methanol (Upper Ab-mentioning

confidence: 59%

Lifetimes of the solvated electron in liquid alcohols

Baxendale¹,

Wardman²

1977

“…8, 24, and Table 3). By contrast, the values of E l in the monohydric alcohols methanol and ethanol (25) were larger than E, by about 1.5-fold, and were similar to E, for dielectric relaxation (refs. 26-28 and Table 3).…”

Section: Decay Of E- Free Ions In Purijied Solventsmentioning

confidence: 82%

Temperature and molecular structure dependences of optical spectra of electrons in liquid diols

Okazaki¹,

Idriss-Ali²,

Freeman³

1984

Self Cite

at 215 K the optical spectrum of e-, shifted unsymmetrically towards higher energy the first 500 ns. Approximating the decay of the low energy side and the growth of the high energy side of the band as first order, the mean decay time at 0.5EA,,. (e-,) was T, = 160 ns and the mean growth time at E > E A ,~~ (e-5) was T, = 40 ns. The behavior in 1,3-butanediol (13BD) at 225 K was similar, with T~ = 170 ns at 0.5EAm,, and T , = 40 ns at E > EAmax. The solvation time constant T, is only slightly greater than 7,. The larger value of T~ is caused by replenishment of the state at 0.5EA,,, by relaxation from lower energy states. In all diols at T 2 240 K (2298 K for 14BD) the spectra reached their equilibrium shape within 150 ns after the start of the 100 ns radiation pulse. The value of EAm, , of e-, in the 1 ,2-diols is -0.1 eV greater than those in the other diols and 0.2-0.3 eV greater than that in a primary alcohol at the same temperature. In the secondary-secondary diol 23BD at 296 K, EAmnx is 0.6 eV greater than that in 2-propanol. The vicinal diol part of the molecule dominates the intermolecular solvation site of the electron. The temperature coefficient (-dE~,,,ldT) increases from 2.6 meV/K in 12 ED to 3.6 meV/K in 23BD. The asymmetry factors Wb/Wr of the e-, bands in the diols are 1.6-2.1, somewhat lower than those in the analogous alcohols, 1.9-2.4. The values of W, are similar, 0.54 k 0.04 eV, in all the diols, independent of T, with Wr/EA,,, = 0.24 + 0.02; dWb/dT < 1.0 meV/K. The value of (GE),,, has an upper limit of -2.5 X lo4 e-,/lo0 eV M cm in the low temperature liquid diols. The value of go^,,, is 1.2 X lo4 in all diols except 23BD, in which it is 1.3 x lo4, independent of T. Dans le propanediol-1,2 (PD12), a 215 K, le spectre optique des e-, glisse d'une faqon non symCtrique vers les hautes Cnergies pendant les 500 premikres nanosecondes. En faisant I'hypothkse que la dCcroissement du c8tC de faible Cnergie et que la croissance du cBtC de haute Cnergie de la bande sont d'ordre un, le temps moyen de dCcroissement a 0,5EA,,, (e-,) est T, = 160 ns et le temps moyen de croissance a E > E, , . , (e-,) est de T , = 40 ns. A 225 K, le butanediol-1,3 (BD13) se comporte de la m&me faqon et T, = 170 ns a 0,5EA,,, et T , = 40 ns a E > EAmax La constante de temps de solvatation T, n'est que 1Cgkrement sup6rieure a 7 , . La valeur plus ClevCe de T , est due au remplissage de 1'Ctat a 0,5EA,,, par une relaxation des Ctats de plus faible Cnergie. Dans tous les diols, a des T 2 240 K (2298 K pour le BD14), les spectres atteignent leur forme d1Cquilibre en moins de 150 ns aprks le dCbut de la radiation pulsCe de 100 ns. A des tempCratures constantes, la valeur de EAmax des e-,, dans les diols-1,2, est sup6rieure d'environ 0,l eV a celles observCes avec d'autres diols et de 0,2 0,3 eV sup6rieure a celle observke dans un alcool primaire. Dans le diol secondaire-secondaire (BD23), a 296 K, la valeur de E,,,, est de 0,6 eV sup6rieure a celle observke dans le propanol-2. La portion viccinale de la molCcule de diol domin...

“…The form [4] is conienient in the discussion of Gaussian-Losentzian bdnd shapes because the sum of g and I equals the band uidth a t lialf height. More frequently used forms in otiier areas are (17,18):…”

Section: Specfr~c~lz Shift T'itlz Tiruementioning

confidence: 99%

Optical spectra of electrons solvated in liquid ethers: temperature effects

Jou¹,

Freeman²

1976

Self Cite

FANG-YUAN JOG and GORDON R. FREEMAN. Can. J. Chem. 54, 3693 (1976). The optical absorption band of electron> solvated in ethers has an approximately Gaussian shape on the low energ) side of the absorption maximum. The high e n e r g side is ivider and has an approximately Lorentzian shape down to A A,,,, = 0.3. then extends into a long tail to high energies. The energy at the absorption maximum E,,,, and the Gau5bian and Lorentzian dispersion parameters g and I are reported as functions of temperature for electrons in dieihql ether (DFF), di-,I-propyl ether (DPE), di-11-butyl ether (DBE), and tetrahydrofuran ( I et g sont respectivement de --2 X 10-3 eV/K, -(1 5 1) X eV/K et +4 X lo4 eV/K. La bande devient moins asymetrique a mesure que la temperature augmente. Afin de faire des progrks dans le traiternent theorique des spectres d'electron solvate, on doit porter une attention particulikre aux valeurs respectives de g e t 1 ainsi qu'a leurs relations avec la temperature: la largeur a denii hauteur, W1/2, perd alors de son importance theorique. L'absorbance molaire decadique, em,, (IM-1 cni-1) est de 2.9 X 104 dans EDE et EDP, 2.6 X 104 dans EDB et de 2.1 X lo4 dans le THF. Les forces de l'oscillateur,f sont de 0.7 dans les Cthers lineaires et de 0.6 dans le THF. La valeur de E,,,,, dans le p-dioxane est de 0.1 eV plus grande que celle dans le T H F et environ 0.2 eV plus grande que celles des ethers lineaires. L,es resultats sont en accord avec la prediction qui peut &tre faite en se basant sur les mobititis relatives des Clectrons dans les ethers.[Traduit par le journal]