Kinetics of the base-catalyzed bromination of s -dichloroacetone

1960 ◽  
Vol 255 (1281) ◽  
pp. 214-217 ◽  
Keyword(s):  
Aqueous Solution ◽  
Carbonyl Group ◽  
Zero Order ◽  
Degree Of Hydration ◽  
Aqueous Buffer ◽  
Buffer Solutions ◽  
Polar Groups ◽  
Carboxylate Anions ◽  
Kinetics Of ◽  
Catalytic Effects

The kinetics of the bromination of s -dichloroacetone have been studied in aqueous buffer solutions. The reaction is of zero order with respect to bromine and exhibits general catalysis by bases, so that the observed rate is that of the ionization of the ketone. The catalytic effects of four carboxylate anions and of water are closely related to the basic strengths of the catalysts. In relating rates of ionization to the structures of substituted ketones it is neces­sary to correct the observed rates for the degree of hydration of the carbonyl group in aqueous solution. The corrected rates for acetone and its chloro-derivates are discussed in terms of the polar groups which they contain.

Kinetics of the base-catalyzed bromination of nitroacetone

1962 ◽  
Vol 270 (1342) ◽  
pp. 411-416 ◽  
Keyword(s):  
Zero Order ◽  
Aqueous Buffer ◽  
Buffer Solutions ◽  
Carboxylate Anions ◽  
Kinetics Of ◽  
Catalytic Effects

The kinetics of the bromination of nitroacetone at 0 °C have been studied in aqueous buffer solutions, the disappearance of bromine being followed by measuring the redoxpotential. The reaction is of zero order with respect to bromine and exhibits general catalysis by bases, so that the observed rate is that of the ionization of the ketone. The catalytic effects of five carboxylate anions are closely related to the basic strengths of the catalysts. The results are discussed in relation to the behaviour of analogous substances.

Kinetics of the base-catalyzed bromination of ethyl nitroacetate

1959 ◽  
Vol 251 (1264) ◽  
pp. 41-45 ◽  
Keyword(s):  
Zero Order ◽  
Aqueous Buffer ◽  
First Order ◽  
Keto Esters ◽  
Buffer Solutions ◽  
Pyridine Bases ◽  
Carboxylate Anions ◽  
Ethyl Nitroacetate ◽  
Kinetics Of ◽  
Catalytic Effects

The kinetics of the bromination of ethyl nitroacetate have been studied in aqueous buffer solutions. The reaction is of the first order with respect to the ester, and of zero order with respect to bromine; it exhibits general catalysis by bases. The catalytic effects of six carboxylate anions and two pyridine bases are closely related to their basic strengths, but in other respects the reaction does not conform to the regularities previously found for the rates of ionization of ketones and keto-esters.

Kinetics of the base-catalyzed halogenation of 2-carbetboxycyclobexanone

1952 ◽  
Vol 210 (1102) ◽  
pp. 322-326 ◽  
Keyword(s):  
Carboxylic Acids ◽  
Opposite Direction ◽  
Zero Order ◽  
Water Molecules ◽  
Ring Strain ◽  
Aqueous Buffer ◽  
First Order ◽  
Buffer Solutions ◽  
Carboxylate Anions ◽  
Kinetics Of

The kinetics of iodination of 2-carbethoxycyclohexanone have been studied colorimetrically in aqueous buffer solutions. The reaction is of the first order with respect to the ester, of zero order with respect to iodine, and is catalyzed by water molecules and by the anions of carboxylic acids. The catalytic constants of four carboxylate anions obey a relation of the Bronsted type, the exponent of which conforms to regularities previously established for a series of ketones and esters. Under comparable conditions 2-carbethoxycyclohexanone is halogenated 100 to 400 times more slowly than is 2-carbethoxycyclopentanone. This difference is in the opposite direction to that anticipated on the basis of ring strain, though it is paralleled by some other observations on 5- and 6-membered rings.

scholarly journals Kinetics of the base-catalyzed bromination of ethyl cyclopentanone 2 -carboxylate

1948 ◽  
Vol 192 (1031) ◽  
pp. 479-489 ◽  
Keyword(s):  
Aqueous Solution ◽  
Acid Catalysis ◽  
Bromine Atom ◽  
Acid Solutions ◽  
Buffer Solutions ◽  
Hydrochloric Acid Solutions ◽  
Carboxylate Anions ◽  
Basic Catalysts ◽  
Bromine Concentration ◽  
Kinetics Of

The kinetics of the bromination of ethyl cyclopentanone 2-carboxylate in the presence o f a number of basic catalysts have been investigated in aqueous solution at 25° C. Under the conditions chosen the bromination proceeds to completion and its rate is independent o f the bromine concentration, being determined by the rate of transfer of a proton to the catalyzing species. Since only one bromine atom is introduced, the kinetics are free from com plications due to successive stages. N o detectable acid catalysis occurs. Values o f the catalytic constants o f seven basic species have been determined from measurements in buffer solutions and in hydrochloric acid solutions. The relation between the catalytic constants o f the four carboxylate anions studied is accurately expressed by an equation of the form due to Bronsted. The ion H 2 P0 4 does not obey this equation. In its general kinetic behaviour the bromination of ethylcyclopentanone 2-carboxylate is found to conform to the regularities previously shown in the ionization of related substrates.

Kinetics of the iodination of ethyl pyruvate

1967 ◽  
Vol 298 (1453) ◽  
pp. 178-183 ◽  
Keyword(s):  
Aqueous Solution ◽  
Complex Formation ◽  
Equilibrium Constant ◽  
Pyruvic Acid ◽  
Ethyl Pyruvate ◽  
Acid Strength ◽  
Zero Order ◽  
Carboxylate Anions ◽  
Iodination Reaction ◽  
Kinetics Of

The iodination of ethyl pyruvate in aqueous solution is kinetically of zero order with respect to iodine and is catalysed by bases: the observed rate is therefore the rate of ionization of the ester. The rate of ionization in the absence of catalysts other than water is approxi­mately the same as that found previously for pyruvic acid, which weakens the evidence for intramolecular catalysis in the ionization of the latter substance. Basic catalysis by carboxylate anions in the iodination of ethyl pyruvate obeys the Brönsted relation, but the value of the exponent β does not fall into line with values previously found for monoketones or β -diketones. No complex formation is detectable between iodine and ethyl pyruvate. The iodination reaction does not go to completion, and its equilibrium constant was measured. Values for the acid strength of ethyl pyruvate estimated from this equilibrium constant and from the rate of ionization are p K = 16.6 and p K = 15.4 respectively.

scholarly journals Kinetics of the base-catalysed bromination of diethyl malonate

1946 ◽  
Vol 186 (1007) ◽  
pp. 443-453 ◽  
Keyword(s):  
Aqueous Solution ◽  
Dissociation Constants ◽  
Diethyl Malonate ◽  
Ester Group ◽  
Acid Solutions ◽  
Kinetic Behaviour ◽  
Buffer Solutions ◽  
Bromine Concentration ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of the bromination of diethyl malonate have been investigated in aqueous solution at 25°. Under suitable conditions the rate of bromination is independent of the bromine concentration, and is determined by the rate at which the ester loses a proton to basic ions or molecules in the solution. Measurements in buffer solutions were used to obtain values for the catalytic constants of ten basic species. There is no detectable catalysis by acids, a slight increase in velocity in strongly acid solutions being traceable to hydrolysis of the ester group. The catalytic constants of six basic anions are related to the dissociation constants of the corresponding acids by an expression of the type due to Bronsted. The ions OH - , H 2 BO - 2 and OBr - do not conform to this relation, and reasons for these discrepancies are discussed. In its general kinetic behaviour the bromination of diethyl malonate conforms to the regularities previously shewn to exist in the ionization of substituted ketones (Bell 1943).

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.

Rate of reaction of dithionite ion with oxygen in aqueous solution

1964 ◽  
Vol 19 (3) ◽  
pp. 522-525 ◽  
Author(s):  
J. A. Morello ◽  
Margot R. Craw ◽  
H. P. Constantine ◽  
R. E. Forster
Keyword(s):  
Aqueous Solution ◽  
Reaction Rate ◽  
Initial Rate ◽  
Sodium Dithionite ◽  
Zero Order ◽  
Flowing Liquid ◽  
First Order ◽  
Rate Of Reaction ◽  
Dithionite Ion ◽  
Kinetics Of

The rate of removal of oxygen from aqueous solution by sodium dithionite in 0.1 m sodium hydroxide was studied in a rapid-reaction apparatus using a membrane-covered polarographic cell to determine Po2 in the flowing liquid. The measurements were made at 37 C, so that the data would be applicable in studies of the kinetics of oxyhemoglobin in blood. The initial concentrations in the mixed reacting solution were between 8 x 10-5 m and 47.5 x 10-5 m for dithionite, and either 10 x 10-5 m or 47.8 x 10-5 m for O2. The reaction over the first 40 msec was found to be first order with respect to dithionite and zero order with respect to molecular oxygen. The initial rate constant was 42.5 ± sd 3.6 sec-1. oxygen reduction by dithionite; hemoglobin; deoxygenation rate; dithionite-oxygen reaction rate Submitted on June 17, 1963

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