Effect of solvent structure on electron reactivity: tert-butyl alcohol/water mixtures

PIUS K. KIPKEMBOI, and ALLAN J. EASTEAL. Can. J. Chem. 72, 1937Chem. 72, (1994. The density and shear viscosity of mixtures of tert-butyl alcohol (BuOH) and tert-butylamine (TBA) with water have been determined for various temperatures (288 to 318 K for H20 + BuOH and 288 to 308K for H20 + TBA) over the whole composition range. Excess molar volumes and apparent molar volumes of the components of each system were calculated from the density data. In both systems the apparent molar volume of the organic component passes through a minimum in the water-rich region. Both systems exhibit large negative excess molar volumes which are essentially independent of temperature at all compositions. The two systems show pronounced maxima in their shear viscosity isotherms. Chem. 72, 1937Chem. 72, (1994. On a determint les densites et les viscosites de cisaillement de melanges d'alcool tert-butylique (BuOH) et de tert-butylamine (TBA) avec de I'eau, sur l'ensemble des compositions possibles et B diverses temptratures (allant de 288 K B 318 Kj pour H20 + BuOH et de 288 K B 308 pour H20 + TBA). Utilisant les donnkes de densite, on a calculk les volumes molaires en excbs et les volumes molaires apparents des composants de chaque systkme. Dans les deux systkmes, le volume molaire apparent du composant organique passe par un minimum dans la region riche en eau. Les deux systbmes presentes des volumes molaires en excbs largement negatifs qui sont essentiellement independants de la temperature, B toutes les compositions. Les deux systbmes prtsents des maxima importants dans leurs isothermes de viscosite de cisaillement.[Traduit par la redaction]

Section: Resultssupporting

confidence: 91%

Section: Resultssupporting

confidence: 88%

Densities and viscosities of binary aqueous mixtures of nonelectrolytes: tert-Butyl alcohol and tert-butylamine

Kipkemboi¹,

Easteal²

1994

“…A plot of (E2-EA) against EA for the various solvent compositions breaks the data into alcohol-rich and water-rich regions, which have been demonstrated in greater detail for other alcohols by plots of k2 against rl at 298 K (21,22). The (E2 -EA) plot is therefore not shown.…”

Section: Activation Energies Ez and Eamentioning

confidence: 96%

Solvent effects on the reactivity of solvated electrons with ions in isobutanol/water mixed solvents

Chen¹,

Avotinsh²,

Freeman³

1994

RUZHONG CHEN, YURIS AVOTINSH, and GORDON R. FREEMAN. Can. J. Chem. 72, 1083 (1994.The effective reaction radii a,, where R, is the reactive encounter radius and K is the probability of reaction per encounter, for e; with H: , NH,',,, Ag:, Cu?, and NOT, are all 0.7 f 0.1 nm in isobutanol containing 1G20 mol% water. The value remains at 0.7 f 0.1 nm for H: , Ag:, and Cu? in pure isobutanol, and for the two transition metal ions in pure water solvent.The value for NO;, reduces to 0.35 nm in pure isobutanol and pure water solvents, whereas for H: and NH;, in pure water solvent it is only 0.14 nm and 2.6 x nm, respectively. The low reactivity of NH,',, with e; in water is attributed to the symmetry of the hydrogen-bonded solvation structure of NH; in water, and the higher reactivity of H: (OH;,,) is attributed to the lower symmetry of its hydrogen-bonded solvation structure. The NH,' and OH; ions have no low-lying orbital for an electron to occupy, so either reaction occurs by proton transfer to the electron site or the neutral species must decompose. We suggest that the proton transfer or the decomposition of the neutral species is facilitated by an unsymmetrical solvation structure.Reaction of e; in A1(C104)3 solutions in water is due mainly to H: from hydrolysis of Alp, and partly to partially hydroxylated aluminum(II1) species. Reaction of e; with A12 itself appears to be negligible in water. The reactivity of the solutions of Al(C104)3 in isobutanol-rich solvents is 3-5 times greater than that in water.In pure CI to C4 1-alcanol solvents the value of k2(e; +NO,,) increases linearly with the dielectric relaxation time z, of the solvent. In these solvents the probability of permanent capture per encounter increases approximately as the square of the encounter duration. On attribue la faible rCactivitC du NH,',, avec les e; dans l'eau i la symCtrie de la structure de solvatation comportant des liaisons hydrogknes du NH,',, dans l'eau et on attribue la rCactivitC plus ClevCe des H: (OH;,) B la symCtrie plus faible de sa structure de solvatation comportant une liaison hydrogkne. Les ions NH; et OH; n'ont aucune orbitale de bas niveau pour accommoder un Clectron; la rkaction se produit donc par un transfert de proton vers un site dlClectron ou les espkces neutres doivent se dicomposer. On suggkre que le transfert de proton ou la dCcomposition d'espkces neutres est rendu plus facile par une structure de solvatation qui n'est pas symttrique.La rCaction des e; dans des solutions de A1(C104)3 dans l'eau est principalement due aux H: provenant de l'hydrolyse

“…The reactivities of solvated electrons with neutral solutes in primary (1, 2) and tertiary (3) alcohol/water mixed solvents are strongly dependent on solvent composition. Aqueous mixtures of the secondary alcohol 2-butanol have also been studied (4), but the alcohol is not completely miscible with water.…”

Section: Introductionmentioning

confidence: 99%

Effect of solvent structure on electron reactivity: 2-propanol/water mixtures

Maham¹,

Freeman²

1988

YAWLLAH MAHAM and GORDON R. FREEMAN. Can. J. Chem. 66, 1706(1988. The reactivity of solvated electrons (e;) with efficient (nitrobenzene, acetone) and inefficient (phenol, toluene) scavengers is affected greatly by the solvent composition in 2-propanol/water mixed solvents. 2-Propanol is the only secondary alcohol that is completely miscible with water. The variation of the nitrobenzene rate constant k2 with solvent composition displays four viscosity zones, as in primary and tertiary alcohol/water mixtures. In zone (c), where the Stokes-Smoluchowski equation applies, the nitrobenzene k2 values in the secondary alcohol/water mixtures are situated between those in the primary and tertiary alcohols, due to the relative values of the dielectric permittivity E. The charge-dipole attraction energy varies as E-' .The two water-rich zones (c) and (6) are characterized by a large change of viscosity q and a small change in e;solvation energy (trap depth) E,; here k2 for all the scavengers correlates with the inverse of the viscosity. In the two alcohol-rich zones ( a ) and (b) the change of q is small but that of E, is large; here k2 of inefficient scavengers correlates with the inverse of E,, due to the difficulty of electron transfer out of deeper traps. Activation energies E2 and entropies AS^ also show composition zone behaviour. The value of AS^ is more negative for less efficient scavengers; E2 varies less and does not correlate with reactivity or E,. Electron transfer from solvent to inefficient scavenger is driven by solvent rearrangement around the reaction center, reflected in ASf . Chem. 66, 1706Chem. 66, (1988 La rtactivitt des electrons solvatCs (e;) avec des pieges efficaces (nitrobenzene ou acttone) ou inefficaces (phenol ou tolukne) est fortement affectte par lacomposition des solvants mixtes propanol-2/eau. Le propanol-2 est le seul alcool secondaire qui soit completement miscible avec l'eau. La variation de la constante de vitesse, k-, , du nitrobenzene en fonction de la composition du solvant prisente quatre zones de viscositi, comme dans le cas des mtlanges eau/alcools primaire ou tertiaire. Dans la zone (c), ou I'tquation de Stokes-Smoluchowski s'applique, les valeurs k2 du nitrobenzkne dans les mtlanges alcool secondaireleau se situent entre celles des alcools primaire et tertiaire; cette situation resulte des valeurs relatives des permitivitts diilectriques E. L'tnergie d'attraction charge-dipble varie en fonction de E -' .Les zones (c) et (4, qui sont riches en eau, sont caracttristes par un changement important de la viscositt q et de faibles changements dans I'tnergie de solvatation des e; (profondeur de la trappe) E,; dans ce cas, il existe une corrtlation entre la valeur de k2 pour tous les pikges et I'inverse de la viscositt. Dans les zones (a) et (b) riches en alcools, le changement dans la valeur de q est faible alors que celui de E, est grand; dans ce cas, il existe une corrtlation entre la valeur de k2 pour les pikges inefficaces et IntroductionThe reactivities of solvated electrons...