Electronic absorption spectra of polarity-polarizability indicators in the gas phase

Essfar, Mohammed; Guiheneuf, Georges; Abboud, José‐Luis M.

doi:10.1021/ja00388a054

Cited by 38 publications

(29 citation statements)

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“…Also, the value of a:%t which the increment becomes zero is -1.50, whereas a mean value of -1.06 + 0.10 has been reported for the gaseous state (16).…”

Section: Resultsmentioning

confidence: 92%

Enthalpies of transfer of alkane solutes from the vapor state to organic solvents

Fuchs¹,

Stephenson²

1985

Can. J. Chem.

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. Heats of solution of 5-8 Cs-C,, alkane liquids have been determined in each of 19 organic solvents covering the Taft-Kamlert T* (dipolarity-polarizability) range -0.08 to 1.00. Enthalpies of alkane transfer from vapor to solvents have been calculated (AH(v + S) = AH, -AH,). The methylene increments in AH(v + S) in the 19 solvents and water (-1.18 to -0.67 kcal/mol) are not well correlated with the Hildebrand solubility parameter 6, but an empirical correlation exists with solvent T* and polarizability:( n = 20, r = 0.977, see = 0.032). By this criterion the small methylenc increment in water appears to be associated with the high dipolarity and low polarizability of water.RICHARD FUCHS et W. KIRK STEPHENSON. Can. J. Chem. 63, 349 (1985). On a determine les chaleurs de solution de 5-8 alcanes liquides en C5-Clb dans 19 solvants organiques couvrant des valeurs de polaritC/polarisabilite (T* de Taft-Kamlet) allant de -0,08 a 1,OO. On a calculC les enthalpies de transfert (AH(v + S) = AH, -AH,). I1 n'y a pas de bonne correlation entre, d'une part, les valeurs des increments par methylhe pour le AH(v + S) dans les 19 solvants et I'eau (-1,18 2 -0,67 kcal/mol) et, d'autre part, le paramktre de solubilitb, 6, de Hildebrand; toutefois, il existe une correlation empirique entre la valeur T* du solvant et la polarisabilitC:(ou n = 20, r = 0,977, erreur st. = 0,032). En se basant sur ce critere, il semble que le faible increment par methylhe dans I'eau soit associe a la polarit6 6levCe et la faible polarisabiliti de I'eau.[Traduit par le journal] IThe free energy of transfer (AG(v -+ S)) of nonpolar solutes from the gas to liquid water is highly unfavorable (endogenic), and this is particularly true of alkane solutes (1). However, for the rare gases, several inorganic gases (H?, N?, CO, 0 2 ) , and C,-C, alkanes, the enthalpy contribution (AH(v + S)) is actually more favorable for transfers to water than for transfers to organic solvents (1). Entropies of transfer (TAS(v + S)) of I these species to water are particularly unfavorable (negative), leading to the observed endogenic values of AG(v + S), and low solute solubility. Alkane AG(v + w) values reach a minimum at ethane, and become increasingly endogenic with alkane molecular weight (1) (C1-C7 methylene increment, 0.16 kcal/mol). The corresponding methylene increment in AH(v + w) is -0.67 kcal/mol, which Abraham ( I ) regarded as the net result of a "normal" solvent effect (-0.97 kcal/mol), and an unfavorable hydrophobic effect. He concluded that the hydrophobic contribution to the free energy, 0.54 kcal/mol, is more an enthalpic effect (0.30-0.44 kcal/mol) than an entropic effect (0.10-0.24 kcal/mol). The rare gases and inorganic gases were regarded as "normal" solutes in water, and this behavior was used (1, 2) to predict the "normal" solvent effect of alkanes in water. Differences between the "normal" and experimental values of AH(v + w) were attributed to a special (hydrophobic) effect. Calculations of solvent-solute interaction terms and scaled particle theory...

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“…Also, the value of a:%t which the increment becomes zero is -1.50, whereas a mean value of -1.06 + 0.10 has been reported for the gaseous state (16).…”

Section: Resultsmentioning

confidence: 92%

Enthalpies of transfer of alkane solutes from the vapor state to organic solvents

Fuchs¹,

Stephenson²

1985

Can. J. Chem.

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“…An excellent linear relationship between p* OMe and f(n) exists that applies to aliphatic and acyclic hydrocarbons, in addition to the gas phase. 13,31 This plot also shows that CCl 4 , and CS 2 and weakly, dipolar or apolar aromatics have substantially enhanced p* OMe values. This behavior is similar to that of ' max and reflects the importance of multipolar interactions and also (perhaps) more specific interactions (such as donor-acceptor effects).…”

mentioning

confidence: 72%

Empirical treatment of solvent-solute interactions: medium effects on the electronic absorption spectrum of ?-carotene

Abe

Abboud

Belio

et al. 1998

J. Phys. Org. Chem.

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Solvent effects on the wavenumber of the maximum of the longest wavelength electronic absorption band of all-trans-b-carotene were determined in 34 solvents. Together with results from previous studies, a data set for 51 solvents, mostly non-hydrogen bond donors, was constructed. This information was analyzed in terms of reaction field models and also showed its value for correlation purposes when used either alone or in combination with standard empirical solvent polarity-polarizability scales.

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“…However, the calculated AGO value in the gas phase is not the same; if we take 6 = 0, P I = 0 and, from Abboud et a l . (31), T : = -1.1, then on eq.…”

Section: Application Of Mlra To Equilibriamentioning

confidence: 95%

“…The keto form should be more basic than the en01 form, certainly, but the effect is quite small. Emsley and Freeman (35) also gave results for 3-ethylpentane-2,Cdione in 6 solvents and for 3-methylhe gas phase value of -1.1 has been obtained from gas phase spectrophotometric data (31) whereas that of -0.44 is an indirect value from the known gas phase AGO value for the 1,2-dibromo-4-tbutylcyclohexane conformational equilibrium (32). Suppan (34) has suggested that gas phase spectrophotometric shifts should not be compared with those in solution, and it is possible that for chemical processes the value of -0.44 is better.…”

Section: Application Of Mlra To Equilibriamentioning

confidence: 99%

Solvent effects in organic chemistry — recent developments

Abraham¹,

Grellier²,

Abboud³

et al. 1988

Can. J. Chem.

283

126

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Solvent effects on a number of different processes have been surveyed, and results of the application of multiple linear regression analysis are discussed. The processes examined include examples of solubility of gases or vapours, distribution coefficients of solutes between water and a series of solvents, and solvent effects on conformational equilibria, on keto-en01 tautornerism, and on reaction rates. It is shown that two particular equations, that due to Koppel and palm and extended by Makitra and Pirig, and that due to Abraham, Kamlet, and Taft, can cope quite satisfactorily with solvent effects on these various processes. It is pointed out that interpretation of parameters obtained from equations that involve macroscopic quantities such as AG* or AGO is not necessarily straightforward, and that some model is needed in order to interpret these macroscopic quantities in terms of qicroscopic quantities that can characterise, for example, solute-solvent interactions.

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Electronic absorption spectra of polarity-polarizability indicators in the gas phase

Cited by 38 publications

References 0 publications

Enthalpies of transfer of alkane solutes from the vapor state to organic solvents

Enthalpies of transfer of alkane solutes from the vapor state to organic solvents

Empirical treatment of solvent-solute interactions: medium effects on the electronic absorption spectrum of ?-carotene

Solvent effects in organic chemistry — recent developments

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