The kinetics and mechanisms of the acid-catalysed hydrolysis of t-butyl formate in aqueous solution.

1969 ◽  
Vol 22 (1) ◽  
pp. 19 ◽  
Author(s):  
RA Fredlein ◽  
I Lauder
Keyword(s):  
Aqueous Solution ◽  
Acid Solution ◽  
Rate Constants ◽  
Aqueous Acid ◽  
Hydronium Ion ◽  
Low Concentrations ◽  
Order Of Magnitude ◽  
Catalytic Rate ◽  
Hydrolysis Of ◽  
Tracer Experiments

The hydrolysis of t-butyl formate in aqueous acid solution has been studied over the range 35-83�. At low concentrations of catalysing acid, specific hydronium-ion catalysis is enhanced by the formic acid produced during the reaction. A series of oxygen-18 tracer experiments was performed, taking into account the formation of isobutylene, which is a by-product of hydrolysis by alkyl-oxygen fission. ��� The percentage alkyl-oxygen fission varies from 3 at 35� to 40 at 76�. Catalytic rate constants for reactions by the AAL1 and the AAC2 mechanisms are expressed respectively by the equations ���������������� k?1 = 1016.6exp(-28000/RT)�� 1. mole-1 sec-1���������������� k?2 = 107.8exp(-13600/RT)�� 1. mole-1 sec-1����������������� The rate constants found for the BAL1 mechanism are of order-of- magnitude significance only.

scholarly journals Aggregation of p-Nitrophenyl Alkanoates in Aqueous Solution. Limitations on Their Use as Substrates in Enzyme Model Studies

1973 ◽  
Vol 51 (21) ◽  
pp. 3494-3498 ◽  
Author(s):  
J. Peter Guthrie
Keyword(s):  
Aqueous Solution ◽  
Rate Constants ◽  
Critical Concentration ◽  
Solubility Limit ◽  
Modest Increase ◽  
Model Studies ◽  
Critical Concentrations ◽  
Low Concentrations ◽  
Enzyme Model ◽  
Hydrolysis Of

p-Nitrophenyl alkanoates are aggregated at extremely low concentrations in aqueous solution. Second-order rate constants for imidazole or hydroxide catalyzed hydrolysis are independent of ester concentration up to a critical concentration of ester, and then decrease with increasing ester concentration. The critical concentrations at 25 °C are: p-nitrophenyl hexanoate, 1 × 10−4 M; octanoate, 9.6 × 10−6 M; decanoate, 1.2 × 10−6 M. For the dodecanoate ester, the critical concentration was estimated as ca. 10−7 M. Addition of 10% methanol causes only a modest increase in the critical concentration. The critical concentration probably represents the solubility limit of the ester. The rate constants for the hydrolysis of the longer chain esters evaluated here are significantly larger than those in the literature, suggesting that the earlier work was done using conditions where the esters were aggregated.

THE CHEMISTRY OF ETHYLENE OXIDE: V. THE REACTION OF ETHYLENE OXIDE WITH HALIDE IONS IN NEUTRAL AND ACID SOLUTION

1952 ◽  
Vol 30 (3) ◽  
pp. 169-176 ◽  
Author(s):  
A. M. Eastham ◽  
G. A. Latremouille
Keyword(s):  
Aqueous Solution ◽  
Ethylene Oxide ◽  
Acid Solution ◽  
Activation Energies ◽  
Hydrogen Halide ◽  
Halide Ions ◽  
Neutral Aqueous Solution ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Hydrolysis Of

The rates of reaction of halide ions with ethylene oxide in neutral aqueous solution and the rate of hydrolysis of ethylene oxide in acid solution have been measured and the activation energies determined. From these data and from the ratio of glycol to chlorohydrin formed when ethylene oxide reacts with excess aqueous hydrogen halide, the rates of the acid-catalyzed addition of halide ions to ethylene oxide at 25 °C. have been estimated.

The acid-catalysed hydrolysis of α-methylallyl acetate in aqueous solution

1968 ◽  
Vol 21 (7) ◽  
pp. 1727
Author(s):  
RA Fredlein ◽  
I Lauder
Keyword(s):  
Aqueous Solution ◽  
Reaction Products ◽  
Arrhenius Parameters ◽  
Crotyl Alcohol ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Tracer Experiments

The kinetics of the acid-catalysed hydrolysis of a-methylallyl acetate in aqueous solution have been studied over the range 30-100�. Oxygen-18 tracer experiments reveal the mechanism to be solely Aac2 and the Arrhenius parameters are consistent with this conclusion. Crotyl alcohol is observed in the reaction products. The formation of rearranged alcohol is explained by allylic isomerization of the α-methylallyl alcohol produced by the hydrolysis.

Stability of the Nerve Gas Antidote BIS (4-Hydroxyiminomethyl-1-Pyridinomethyl) Ether Dichloride (Toxogonin®)

1968 ◽  
Vol 2 (9) ◽  
pp. 234-243 ◽  
Author(s):  
Inga Christenson
Keyword(s):  
Aqueous Solution ◽  
Hydrochloric Acid ◽  
Sodium Hydroxide ◽  
Rate Constants ◽  
Kinetics Of Hydrolysis ◽  
Dilute Aqueous Solution ◽  
Nerve Gas ◽  
Ph Range ◽  
Kinetics Of ◽  
Hydrolysis Of

The products and kinetics of hydrolysis of the nerve gas antidote bis(4-hydroxyiminomethyl - 1 - pyridinemethyl) ether dichloride (Toxogonin ®) have been investigated. A survey of these studies is given: The hydrolytic reactions were studied in the pH range 1 M hydrochloric acid to 1 M sodium hydroxide at 25, 45, 75 and 85° C. Rate constants were determined in dilute aqueous solution, generally with an initial Toxogonin concentration of 0.01 mg per ml. In addition, a report is given concerning two-year storage of 25 percent (w/v) Toxogonin solutions at pH 2.5, 3.0 and 3.5. The solutions were stored in glass or polypropylene ampuls at 5, 15, 25 and 45°C. At 5 and 15C° decomposition was negligible, at 25 and 45 °C average decomposition was 1.5 percent and 3.3 percent, respectively.

Acid-catalyzed hydrolysis of 2-methylene-1,3-dithiolane. 2. Remarkable effects of β substitution on reversibility of the carbon protonation

1986 ◽  
Vol 64 (6) ◽  
pp. 1116-1123 ◽  
Author(s):  
Tadashi Okuyama ◽  
Masayoshi Toyoda ◽  
Takayuki Fueno
Keyword(s):  
Aqueous Solution ◽  
Rate Constants ◽  
Isotope Exchange ◽  
Relative Stabilities ◽  
The Third ◽  
Initial Carbon ◽  
Acid Catalyzed ◽  
The Individual ◽  
Individual Rate ◽  
Hydrolysis Of

Hydrolyses of 2-ethylidene-(1b), 2-isopropylidene-(1c), and 2-benzylidene-1,3-dithiolane (1d) were kinetically investigated in aqueous solution. All the individual rate constants involved in this three-step reaction were evaluated. Initial carbon protonation is only partially reversible (k2/k−1 = 1.33, 0.68, and 1.02 for 1b, 1c, and 1d, respectively) at higher pH, while the protonation becomes completely reversible below pH 2 where the third step is rate determining. Complete H–D isotope exchange at the β-carbon of 1b and 1d was observed in deuterium media before appreciable hydrolysis took place. It was demonstrated that reversion from the tetrahedral intermediate 3 to 1 occurs extensively during the reaction in the latter acidity range. Relative stabilities and reactivities of the olefinic substrates 1 are discussed.

Kinetics and mechanism of gold(III) incorporation into tetrakis(1-methylpyridium-4-yl)porphyrin in aqueous solution

2004 ◽  
Vol 08 (11) ◽  
pp. 1269-1275 ◽  
Author(s):  
Ahsan Habib ◽  
Masaaki Tabata ◽  
Ying Guang Wu
Keyword(s):  
Aqueous Solution ◽  
Rate Constants ◽  
Kinetic Data ◽  
Ph Dependence ◽  
Equilibrium Constants ◽  
Hydroxyl Group ◽  
Net Charge ◽  
First Order ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of the reaction of the tetrakis(1-methylpyridium-4-yl)porphyrin tetracation, [ H 2( TMPyP )]4+, with gold(III) ions were studied along with equilibria of gold(III) species in aqueous medium at 25°C, I = 0.10 M ( NaNO 3). The equilibrium constants for the formation of [ AuCl 4-n( OH ) n ]- ( n = 0,…,4), defined as β n = [ AuCl 4- n ( OH ) n ]- [ Cl -] n / [ AuCl 4-][ OH -] n were found to be that log β1 = 7.94 ± 0.03, log β2 = 15.14 ± 0.03, log β3 = 21.30 ± 0.05 and log β4 = 26.88 ± 0.05. The overall reaction was first order with respect to each of the total [ Au (III)] and [ H 2 TMPyP 4+]. On the basis of pH dependence on rate constants and the hydrolysis of gold(III), the rate expression can be written as d [ Au ( TMPyP )5+]/ dt = ( k 1[ AuCl 4-] + k2[ AuCl 3( OH )-] + k3[ AuCl 2( OH )2-] + k4[ AuCl ( OH )3-])[ H 2 TMPyP 4+], where k1, k2, k3 and k4 were found to be (2.16 ± 0.31) × 10-1, (6.56 ± 0.19) × 10-1, (1.07 ± 0.24) × 10-1, and (0.29 ± 0.21) × 10-1 M -1. s -1, respectively. The kinetic data revealed that the trichloromonohydroxogold(III) species, [ AuCl 3( OH )]-, is the most reactive. The higher reactivity of [ AuCl 3( OH )]- is explained by hydrogen bonding formation between the hydroxyl group of [ AuCl 3( OH )]- and the pyrrole hydrogen atom of [ H 2( TMPyP )]4+. Furthermore, applying the Fuoss equation to the observed rate constants at different ionic strengths, the apparent net charge of [ H 2( TMPyP )]4+ was calculated to be +3.5.

Polyfluoroorganoboron-Oxygen Compounds. 7. Studies of Conversion of [(C6HnF5-n)B(OMe)3]- Into [(C6HnF5-n)2B(OMe)2]- (n = 0, 1)

2008 ◽  
Vol 73 (12) ◽  
pp. 1681-1692 ◽  
Author(s):  
Nicolai Yu. Adonin ◽  
Vadim V. Bardin ◽  
Hermann-Josef Frohn
Keyword(s):  
Aqueous Solution ◽  
Rate Constants ◽  
High Yields ◽  
Hydrolysis Of ◽  
Conversion Of Salts

Conversion of salts Li[(C6HnF5-n)B(OMe)3] (n = 0, 1) into (Li·DME)[(C6HnF5-n)2B(OMe)2] was studied in dichloromethane-DME solution. The observed rate constants k decrease from (21.4 ± 0.9) × 10-3 l mol-1 s-1 (Li[C6F5B(OMe)3]) over (6.99 ± 0.11) × 10-3 l mol-1 s-1 (Li[(2,3,5,6-C6HF4)B(OMe)3]) to (2.94 ± 0.05) × 10-3 l mol-1 s-1 (Li[(2,3,4,6-C6HF4)B(OMe)3]), while Li[(2,3,4,5-C6HF4)B(OMe)3] does not undergo any transformation. Hydrolysis of (Li·DME)[(C6HnF5-n)2B(OMe)2] leads to corresponding borinic acids, whereas treatment of them with aqueous solution of M[HF2] (M = Bu4N, K) acidified with HF results in M[(C6HnF5-n)2BF2] in high yields.

Facile Enrichment and Photocatalytical Degradation of Low Concentration MB in Aqueous Solution

2011 ◽  
Vol 110-116 ◽  
pp. 2308-2315
Author(s):  
Liu Xue Zhang ◽  
Xiu Lian Wang
Keyword(s):  
Electron Microscopy ◽  
Aqueous Solution ◽  
Fine Particles ◽  
X Ray Diffraction ◽  
High Concentration ◽  
X Ray ◽  
Selected Area Electron Diffraction ◽  
Transmission Electron ◽  
Low Concentrations ◽  
Hydrolysis Of

Fine particles of photoactive anatase-type TiO2, prepared by hydrolysis of tetrabutyl orthotitanate and crystallized under microwave (MV) irradiation, were loaded on adsorbent support attapulgite (ATP). The prepared hybrids TiO2-ATP were characterized with transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and X-ray diffraction (XRD) and photoactivity properties were evaluated separately. The substrates of target were adsorbed on the adsorbent support, and then a high concentration environments of the substrate was formed around the loaded TiO2, resulting in an increase in the photodestruction rate. One of the most interesting features of the resulting catalysts with low titania contain (<30%) is their fast decantability in comparison with that of TiO2. This way one of the most important drawbacks of photocatalysis, the catalysts separation from the solution, was overcome by simple sedimentation and decantation. The low concentrations MB may be removed through enrichment and photodegradation using the prepared TiO2-ATP photocatalyst.

Kinetics of acid-catalyzed hydration in aqueous solution of 1-methoxy- and 1-methylthio-2-phenylethyne and some related acetylenes

1987 ◽  
Vol 65 (2) ◽  
pp. 441-444 ◽  
Author(s):  
N. Banait ◽  
M. Hojatti ◽  
P. Findlay ◽  
A. J. Kresge
Keyword(s):  
Aqueous Solution ◽  
Proton Transfer ◽  
Isotope Effect ◽  
Rate Constants ◽  
Acid Catalysis ◽  
The Other ◽  
Buffer Solutions ◽  
Hydronium Ion ◽  
Acid Catalyzed ◽  
Kinetics Of

The rates of conversion of C6H5C≡COCH3 to C6H5CH2CO2CH3 were measured in dilute HClO4/H2O, DCIO4/D2O, and H3PO4–H2PO2−/H2O buffer solutions, and the rates of conversion of C6H5C≡CSCH3 to C6H5CH2COSCH3, C6H5C≡CH to C6H5COCH3, 2,4,6-(CH3)3C6H2C≡CH to 2,4,6-(CH3)3C6H2COCH3, and p-CH3OC6H4C≡CCH3 to p-CH3OC6H4COCH2CH3 were measured in concentrated HClO4/H2O solutions, all at 25 °C. The reaction of C6H5C≡COCH3 showed general acid catalysis and gave the isotope effect [Formula: see text], which indicates that it proceeds through rate-determining proton transfer from catalyst to substrate. The hydronium ion catalytic coefficient for this reaction is [Formula: see text], and those for the other four, in the order given above, are [Formula: see text], and 8.5 × 10−6 M−1 s−1. Relative reactivities based on these rate constants are discussed.

STUDIES ON THE SOLUBLE INTERMEDIATES IN THE HYDROLYSIS OF DIMETHYLTIN DICHLORIDE: EQUILIBRIUM CONSTANT FITTING WITH A HIGH SPEED DIGITAL COMPUTER

1964 ◽  
Vol 42 (4) ◽  
pp. 781-791 ◽  
Author(s):  
R. Stuart Tobias ◽  
M. Yasuda
Keyword(s):  
Aqueous Solution ◽  
Digital Computer ◽  
High Speed ◽  
Chloride Ion ◽  
Formation Constants ◽  
Data Sets ◽  
Ionic Strength Effect ◽  
Low Concentrations ◽  
Hydrolysis Of ◽  
Titration Technique

The hydrolysis of (CH3)2SnCl2 has been studied in a medium 0.1 M in (Na+)Cl− by a potentiometric titration technique. The complexes formed by the hydrolysis reactions together with their formation constants have been determined by analysis of the 394 data sets using a high speed digital computer. The data can be fitted equally well over the range pH 1.5 to 9 by the four formation constants for (CH3)2SnOH+ (log *β11 = −3.245 ± 0.004), [(CH3)2SnOH]2+2 (log *β22 = −5.00 ± 0.02), (CH3)2Sn(OH)2 (log *β21 = −8.516 ± 0.004), and [(CH3)2Sn]4(OH)6+2 (log *β64 = −16.85 ± 0.02) or by the five constants for (CH3)2SnOH+ (log *β11 = −3.251 ± 0.004), [(CH3)2SnOH]2+2 (log *β22 = −5.05 ± 0.02), (CH3)2Sn(OH)2 (log *β21 = −8.535 ± 0.005), ((CH3)2Sn)2(OH)3+ (log *β32 = −9.81 ± 0.01), and ((CH3)2Sn)3(OH)4+2 (log *β43 = −11.52 ± 0.03). Thus there is little question about the existence in the solutions of the simple monohydroxo complex and its dimer or of the neutral dihydroxide. Only very low concentrations of species containing more than four tin atoms can exist in aqueous solution. In addition, the data determined previously for the hydrolysis of (CH3)2Sn(ClO4)2 in a medium 3.0 M in (Na+)ClO4− have been refined by the least squares procedure. These 762 data sets can also be fitted equally well by the set of constants log *β11 = −3.55 ± 0.01, log *β22 = −4.52 ± 0.01, log *β21 = −9.00 ± 0.01, and log *β64 = −16.14 ± 0.03 or log *β11 = −3.54 ± 0.01, log *β22 = −4.60 ± 0.02, log *β21 = −8.98 ± 0.01, log *β32 = −9.76 ± 0.06, and log *β43 = −10.40 ± 0.05. The tendency of dimethyltin dichloride to form polycondensed species in aqueous solution is slight, and there is no evidence for the formation of large rings or chains. The solid stannoxane which precipitates from chloride solution was studied by infrared and X-ray powder photography and is essentially the same as the compound obtained by reaction of (CH3)2SnO and (CH3)2SnCl2 in a 1:1 mole ratio in 95% ethanol. This corresponds to a slightly different product than that obtained by a 1:1 reaction of these compounds in benzene which gives ((CH3)2SnCl)2O. This is in accord with the observation that precipitation occurs only at a pH higher than that at which ((CH3)2SnOH)2+2 has attained the maximum concentration, and hence precipitation is occasioned by the formation of larger polycondensed species. A comparison of the perchlorate and chloride data also indicates that the tendency to form polycondensed species is reduced by the presence bf chloride ion. This is partially an ionic strength effect and partially a result of chloride complexing of the simple aquodimethyltin (IV) ion, and the first chloro-complexing constant was Estimated to be 28 1. mole−1.

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