Effect of pressure on the solvolysis of benzyl chloride in glycerol–water mixtures

1970 ◽  
Vol 48 (13) ◽  
pp. 2021-2024 ◽  
Author(s):  
D. L. Gay ◽  
E. Whalley
Keyword(s):  
Benzyl Chloride ◽  
Constant Pressure ◽  
Solvent Composition ◽  
Constant Volume ◽  
Glycerol Water ◽  
Effect Of Pressure ◽  
Solvent Dependence ◽  
Partial Volumes ◽  
Volume Energy ◽  
Entropy Of Activation

The effect of pressure up to 1.6 kbar on the rate of solvolysis of benzyl chloride in 0 to 75% v/v glycerol–water has been measured at 50 °C. The volume of activation is −10.7 ± ~ 0.4 cm3 mole−1, essentially independent of solvent composition. Therefore, the partial volumes of both benzyl chloride and the transition state depend on solvent composition in the same way. The constant-volume energy and entropy of activation are simple functions of the solvent composition, and resemble the constant-volume parameters in ethanol–water mixtures. It is concluded that constant-volume conditions are probably more appropriate than constant-pressure conditions for discussing the solvent dependence of these solvolyses.

EFFECT OF PRESSURE ON THE ACID-CATALYZED ENOLIZATION OF ACETONE AND ACETOPHENONE IN VARIOUS ETHANOL–WATER SOLVENTS. ORIGIN OF THE ENTHALPY–ENTROPY COMPENSATION EFFECT

1964 ◽  
Vol 42 (8) ◽  
pp. 1835-1850 ◽  
Author(s):  
B. T. Baliga ◽  
E. Whalley
Keyword(s):  
Isotope Effect ◽  
Atmospheric Pressure ◽  
Compensation Effect ◽  
Constant Pressure ◽  
Constant Volume ◽  
Deuterium Isotope Effect ◽  
Effect Of Pressure ◽  
Effect Of Solvent ◽  
Acid Catalyzed ◽  
Ethanol In Water

The effect of pressure, temperature, and solvent composition on the rate of the acid-catalyzed enolization of acetone and acetophenone, and the solvent deuterium isotope effect for the enolization of acetophenone, have been measured by following the iodination. The solvent deuterium isotope effect [Formula: see text] for the enolization of acetophenone in 16.2% w/w ethanol–water is 2.50 ± ~0.05, which undoubtedly proves that there is a pre-equilibrium proton transfer. The effect of solvent in the range water to 33.4% w/w ethanol in water on the rate of enolization of both acetone and acetophenone is small at atmospheric pressure, but is about four times larger at 3 kbar. This cannot be explained on simple electrostatic grounds, and indicates that any simple electrostatic explanation of the solvent effect at atmospheric pressure is invalid. The volumes of activation for the enolizations are strongly dependent on the solvent, that for acetone varying from −2.l ± ~0.5 to −6.9 ± ~ 0.7 cm3 mole−1 between solvents water and 33.4% w/w ethanol in water.An examination has been made of the enthalpyentropy compensation effect. It is shown that in general if the rate or equilibrium constant of a reaction does not change with changing conditions (such as solvent, substituents, etc.) then either the quantities of activation at constant pressure, ΔHp≠ and ΔSp≠, or the corresponding quantities at constant volume, ΔUv≠ and ΔSv≠, must vary in a compensating manner, and the existence of an energy–entropy compensation effect is inevitable. For the enolization of acetone and acetophenone in ethanol–water mixtures, ΔUv≠ and ΔSv≠ vary only slightly with solvent, whereas ΔHp≠ and ΔSp≠ vary in a compensating manner. The main causes of the compensation effect in the constant-pressure parameters are, in a sense, the change with changing solvent of the thermal expansion of the solvent and of the volume of activation of the reaction. On the other hand, both the constant-pressure and the constant-volume parameters vary with substituent from acetone to acetophenone, and the constant-volume parameters vary the more.

Effect of Pressure on the Alkaline Hydrolysis of Ethyl Acetate in Acetone–Water Solutions. Parameters of Activation at Constant Volume

1975 ◽  
Vol 53 (22) ◽  
pp. 3414-3418 ◽  
Author(s):  
M. L. Tonnet ◽  
E. Whalley
Keyword(s):  
Ethyl Acetate ◽  
Solvent Effect ◽  
Internal Energy ◽  
Alkaline Hydrolysis ◽  
Constant Pressure ◽  
Constant Volume ◽  
Acetone Water ◽  
Entropy Of Activation ◽  
Enthalpy And Entropy ◽  
Hydrolysis Of

The effect of pressures up to 3 kbar on the rate of the base-catalyzed hydrolysis of ethyl acetate in acetone–water mixtures has been measured. From these measurements and the enthalpy and entropy of activation at constant pressure measured by others, the internal energy and entropy of activation at constant volume have been obtained as a function of solvent composition. The constant-volume parameters of activation vary with composition in a simpler way than the constant-pressure parameters. It seems likely that theoretical discussions of the solvent effect are easier if they are based on the constant-volume parameters. At low acetone concentrations, the addition of acetone reduces the rate constant at low pressure, but increases it at 3 kbar.

Enthalpy and entropy of activation for benzyl chloride solvolysis in various alcohol–water solvent mixtures

1968 ◽  
Vol 46 (2) ◽  
pp. 125-129 ◽  
Author(s):  
H. S. Golinkin ◽  
J. B. Hyne
Keyword(s):  
Rate Constants ◽  
Benzyl Chloride ◽  
Solvent Composition ◽  
Solvent Mixtures ◽  
Methyl Ethyl ◽  
First Order ◽  
Water Solvent ◽  
Alcohol Water ◽  
Entropy Of Activation ◽  
Enthalpy And Entropy

The first order rate constants for the solvolysis of benzyl chloride in a series of mixtures of methyl, ethyl, i-propyl, and t-butyl alcohols with water are reported at 40.05 and 60.50 °C. The ΔH* and ΔS* values are calculated using these rate constants and those previously reported at 50.25 °C (1, 2). The dependence of these parameters on solvent composition is discussed.

scholarly journals Comparative Fingerprint and Extraction Yield of Medicinal Herb Phenolics with Hepatoprotective Potential, as Determined by UV-Vis and FT-MIR Spectroscopy

2011 ◽  
Vol 39 (2) ◽  
pp. 82 ◽  
Author(s):  
Simona ZAVOI ◽  
Florinela FETEA ◽  
Floricuta RANGA ◽  
Raluca M. POP ◽  
Anca BACIU ◽  
...  
Keyword(s):  
Phenolic Acids ◽  
Extraction Yield ◽  
Bioactive Molecules ◽  
Chelidonium Majus ◽  
Glycerol Water ◽  
Lycopodium Clavatum ◽  
Mir Spectroscopy ◽  
Polyphenolic Composition ◽  
Solvent Dependence ◽  
Fingerprint Region

The present study was aimed to compare the polyphenolic composition of six medicinal herbs, from wild flora of Romania. The plants investigated, Cynara scolimus (artichoke), Taraxacum officinalis (dandelion), Chelidonium majus (celandine), Hypericum perforatum (St. John’s wort), Silybum marianum (Mary thistle) and Lycopodium clavatum (Wolf’s claw) are known, to have hepatoprotective action. Using in parallel glycerol-water, ethanol-water and methanol, the solvent-dependence of the extract fingerprint and composition in bioactive molecules was studied by UV-Vis and Infrared (FT-MIR) spectrometry. The extraction yields, calculated as an extraction factor (EF) were superior in acidic methanol comparative to glycerin and ethanol, favorising the increase in phenolic acids against flavonoid derivatives . Based on the differences of polarity between the three solvents used, higher EF values were obtained for dandelion, artichoke, celandine and St. John wort, more rich in phenolic acids than flavonoids. Mary thistle and Wolf’s claw had lower concentrations of phenolics, but higher content of lignans and terpenoids. Based on the FT-MIR peaks from 8 regions, for each plant extract, has been determined the fingerprint region between 900 and 1500 cm-1and identified the specific functional groups. A good, significant correlation was found between the concentration of total phenolics calculated by UV-Vis spectrometry and FTIR methods, after calibration with gallic acid. The value of the MIR signal at 1743 cm-1 may be considered a good indicator of phenolics concentration in such extracts. Combined UV-Vis and FTIR spectroscopy are recommended as rapid and reliable tools to investigate the fingerprint and to predict the composition of medicinal plants or to evaluate the quality and authenticity of different standardized formulas.

scholarly journals On the temperature variation of the specific heats of hydrogen and nitrogen

1930 ◽  
Vol 126 (801) ◽  
pp. 204-212 ◽  
Keyword(s):  
Kinetic Theory ◽  
Temperature Variation ◽  
Characteristic Equation ◽  
Constant Pressure ◽  
Ideal Gas ◽  
Constant Volume ◽  
Specific Heats

The energy of a gram molecule of an ideal gas can be calculated from the kinetic theory. From this, by the application of the Maxwell-Boltzmann hypothesis, the molecular specific heats at constant volume, S v , of ideal monatomic and diatomic gases are deduced to be 3R /2 and 5R/2 respectively at all temperatures. R is the gas constant per gram molecule = 1⋅985 gm. cal./° C. The corresponding molecular specific heats at constant pressure, S p , can be obtained by the addition of R. In the case of real gases, which obey some form of characteristic equation other than P. V = R. T, it can be shown from thermodynamical considera­tions that the value of S p depends upon the pressure, but as the term involving the pressure also includes the temperature, S p is not independent of the tempera­ture but it increases in value as the temperature is reduced. Assuming the characteristic equation proposed by Callendar, i. e. , v - b ­­= RT/ p - c (where b is the co-volume, c is the coaggregation volume which is a function of the temperature of the form c = c 0 (T 0 /T) n , n being dependent on the nature of the gas), it is easy to show from the relation (∂S p /∂ р ) T = -T(∂ 2 ν /∂Τ 2 ) р , hat S p = S p 0 + n (n + 1) cp /T; and, by combining this with S p – S v = T(∂ p /∂Τ) v (∂ v /∂Τ) p = R(1 + ncp /RT) 2 , the corresponding values of S v can be obtained.

scholarly journals Thermodynamics and dynamics of a monoatomic glass former. Constant pressure and constant volume behavior

2008 ◽  
Vol 128 (14) ◽  
pp. 144505 ◽  
Author(s):  
Vitaliy Kapko ◽  
Dmitry V. Matyushov ◽  
C. Austen Angell
Keyword(s):  
Constant Pressure ◽  
Constant Volume ◽  
Thermodynamics And Dynamics
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