Micellar catalysis of organic reactions. XIV. Hydrolysis of some 1,4-Benzodiazepin-2-one drugs in acidic solution

1984 ◽  
Vol 37 (9) ◽  
pp. 1895 ◽  
Author(s):  
TJ Broxton ◽  
T Ryan ◽  
SR Morrison
Keyword(s):  
Acid Concentration ◽  
Acidic Solution ◽  
Sodium Dodecyl ◽  
Kinetic Studies ◽  
Micellar Catalysis ◽  
Amide Bond ◽  
First Order ◽  
Amide Hydrolysis ◽  
Hydrolysis Of ◽  
Azomethine Bond

Kinetic studies of the acidic hydrolysis of diazepam and nitrazepam were carried out in the presence of micelles of sodium dodecyl sulfate (sds). The hydrolysis of diazepam was shown to occur with biphasic kinetics. This is consistent with initial hydrolysis of the azomethine bond followed by very slow hydrolysis of the amide bond as found for hydrolysis in aqueous solution. Nitrazepam, however, was found to decompose with monophasic kinetics consistent with initial amide hydrolysis. Reactions involving the hydrolysis of the azomethine bond were shown to be independent of acid concentration and subject to inhibition by micelles of sds. Reactions involving amide hydrolysis were shown to be first order in acid concentration and subject to micellar catalysis. The mechanistic change for the hydrolysis of nitrazepam on transfer from water (initial azomethine cleavage) to micelles of sds (initial amide cleavage), was presumably the result of the inhibition of azomethine hydrolysis and the catalysis of amide hydrolysis by the micelles.

Micellar Catalysis of Organic Reactions. XXX. A Study of the Mechanism of Hydrolysis of Oxazepam and 2'-Methyldiazepam in the Presence of Micelles and in Water

1991 ◽  
Vol 44 (1) ◽  
pp. 103 ◽  
Author(s):  
TJ Broxton ◽  
S Wright
Keyword(s):  
Cetyltrimethylammonium Bromide ◽  
Sodium Dodecyl ◽  
Basic Solution ◽  
Acidic Hydrolysis ◽  
First Order ◽  
Amide Hydrolysis ◽  
Mechanism Of Hydrolysis ◽  
Basic Hydrolysis ◽  
High Base ◽  
Hydrolysis Of

Acidic hydrolysis of oxazepam in water involved initial azomethine cleavage at low acid concentrations (0.1-0.2 M) with initial amide hydrolysis occurring concurrently at higher acid concentrations (0.3-0.6 M). In the presence of micelles of sodium dodecyl sufate the percentage of initial amide cleavage increased. For the basic hydrolysis of oxazepam in water the rate was dependent on [ NaOH ] indicating at least some initial amide hydrolysis. At higher base concentrations the rate became independent of [ NaOH ], because of the ionization of the NH group of oxazepam, producing an unreactive nitranion. In the presence of cetyltrimethylammonium bromide, the rate of basic hydrolysis was slower than in water, due to the increased amount of ionization in the presence of micelles. Acidic hydrolysis of 2′-methyldiazepam in water was independent of [ HCl ] in the range 0.1-0.3 M, indicating initial azomethine hydrolysis. The rate was slower than for diazepam itself, indicating the existence of steric hindrance by the 2′-methyl group to water attack at C5. In basic solution, a biphasic reation was observed. The rate of the first phase was dependent on [ NaOH ], indicating the presence of initial amide hydrolysis for 2′-methyldiazepam, cf. initial azomethine hydrolysis for diazepam. At high base concentrations, a greater than first-order dependence on base concentration was observed. This was attributed to the formation of dianionic intermediates, as previously reported for the hydrolysis of similar anilides at high base concentrations.

KINETIC STUDIES ON THE HYDROLYSIS OF BENZOYLCHOLINE BY HUMAN SERUM CHOLINESTERASE

1956 ◽  
Vol 34 (1) ◽  
pp. 637-653 ◽  
Author(s):  
W. Kalow ◽  
K. Genest ◽  
N. Staron
Keyword(s):  
Kinetic Studies ◽  
Reaction Rates ◽  
Serum Cholinesterase ◽  
Initial Reaction ◽  
Ultraviolet Spectrophotometry ◽  
First Order ◽  
Low Concentrations ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Substrate Concentrations

Benzoylcholine stands out from other known substrates of serum cholinesterase because of its high apparent affinity for this enzyme combined with a rapid rate of destruction. The reaction kinetics of the hydrolysis of benzoylcholine can be studied by ultraviolet spectrophotometry, since the absorbance decreases in proportion to the concentration of substrate. Kinetic data obtained by measuring initial reaction rates, and by analyzing continuous hydrolysis curves, are the same within the range of experimental error. The enzymatic data are compatible with the assumption that in the presence of high substrate concentrations a complex consisting of esterase and two substrate molecules is formed. This complex is hydrolyzed more slowly than the complex containing one molecule of substrate which is formed at low concentrations of benzoylcholine. Alkaline hydrolysis of benzoylcholine follows the kinetics of a first order reaction.

Micellar catalysis of organic reactions. 22. A comparison of the basic hydrolysis of benzodiazepinones in the presence of reactive counterion micelles and vesicles

1988 ◽  
Vol 66 (7) ◽  
pp. 1566-1570 ◽  
Author(s):  
Trevor J. Broxton ◽  
Xenia Sango ◽  
Sallyanne Wright
Keyword(s):  
Surfactant Concentration ◽  
Biological Membranes ◽  
Micellar Catalysis ◽  
Organic Reactions ◽  
Conductivity Measurements ◽  
Amide Hydrolysis ◽  
Rate Of Hydrolysis ◽  
Basic Hydrolysis ◽  
Hydrolysis Of ◽  
Good Agreement

The basic hydrolysis of diazepam and several N-alkyl nitrazepam derivatives has been studied in the presence of reactive counterion micelles of cetyltrimethylammonium hydroxide (CTAOH) and vesicles of didodecyldimethylammonium hydroxide (DDAOH). In both surfactants, the rate of hydrolysis of all compounds was found to be dependent on the hydroxide concentration at constant surfactant concentration and this was interpreted as evidence for initial amide hydrolysis. The hydrolysis in CTAOH was inhibited by added salts in the order Br− < NO3− < SO42−. At concentrations above 3 mM surfactant, the rate of hydrolysis of each compound was similar in CTAOH and in DDAOH. At lower concentrations of CTAOH, however, the rate of hydrolysis was significantly lower than that in DDAOH. On the basis of this evidence, it was concluded that the cmc of CTAOH was between 2–3 mM, which is in good agreement with the value of 1.8 mM obtained by Zana from conductivity measurements. For diazepam, a mechanistic change is indicated on transfer from water to either micelles or vesicles and since vesicles are considered good models of biological membranes, this suggests that conclusions concerning the bioavailability of diazepam should not be based on studies in water but rather on studies in either micelles or vesicles.

Kinetic Studies of Gold Recovery from Diluted Chloride Aqueous Solutions Using Activated Carbon Organosorb 10 CO

2016 ◽  
Vol 69 (3) ◽  
pp. 254 ◽  
Author(s):  
Marek Wojnicki ◽  
Ewa Rudnik ◽  
Magdalena Luty-Błocho ◽  
Robert P. Socha ◽  
Zbigniew Pędzich ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Acidic Solution ◽  
Activation Parameters ◽  
Kinetic Studies ◽  
Reaction Model ◽  
Surface Functional Groups ◽  
Complex Ions ◽  
First Order ◽  
Material Theory

The kinetic studies of gold(iii) chloride complex ions recovery from acidic solution using activated carbon (AC) were carried out using spectrophotometry. AC samples were characterized in terms of surface area, porosity, and zeta potential. The surface functional groups were also identified. It was found that adsorption of AuCl4– onto AC was followed by reduction of the ions to the metallic form. The process obeyed the first order reaction model, but the reaction was controlled by diffusion. Arrhenius and Eyring–Polanyi equations were used for determination of the activation parameters. Distribution of gold across the AC pellets was also determined and discussed according to the porous material theory.

Hydrolysis of amides. I. The hydrolysis of acetamide and chloroacetamide in dilute acid

1965 ◽  
Vol 18 (6) ◽  
pp. 795
Author(s):  
PD Bolton ◽  
IR Wilson
Keyword(s):  
Recent Work ◽  
Acidic Solution ◽  
Kinetic Studies ◽  
Systematic Errors ◽  
Dilute Acid ◽  
Compound A ◽  
Satisfactory Correlation ◽  
Entropy Of Activation ◽  
Consistent Treatment ◽  
Hydrolysis Of

Kinetic studies of the hydrolysis of acetamide in dilute acidic solution are reported. These reveal the presence of systematic errors in some previous work on this compound. A consistent treatment is given, leading to values of the energy and entropy of activation (at 75�) of 19.8 kcal and -17.8 e.u. and satisfactory correlation of most previous results. Similar defects are present in recent work on chloroacetamide hydrolysis and the same approach is used in a reinterpretation.

KINETIC STUDIES ON THE HYDROLYSIS OF BENZOYLCHOLINE BY HUMAN SERUM CHOLINESTERASE

1956 ◽  
Vol 34 (3) ◽  
pp. 637-653 ◽  
Author(s):  
W. Kalow ◽  
K. Genest ◽  
N. Staron
Keyword(s):  
Kinetic Studies ◽  
Reaction Rates ◽  
Serum Cholinesterase ◽  
Initial Reaction ◽  
Ultraviolet Spectrophotometry ◽  
First Order ◽  
Low Concentrations ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Substrate Concentrations

Benzoylcholine stands out from other known substrates of serum cholinesterase because of its high apparent affinity for this enzyme combined with a rapid rate of destruction. The reaction kinetics of the hydrolysis of benzoylcholine can be studied by ultraviolet spectrophotometry, since the absorbance decreases in proportion to the concentration of substrate. Kinetic data obtained by measuring initial reaction rates, and by analyzing continuous hydrolysis curves, are the same within the range of experimental error. The enzymatic data are compatible with the assumption that in the presence of high substrate concentrations a complex consisting of esterase and two substrate molecules is formed. This complex is hydrolyzed more slowly than the complex containing one molecule of substrate which is formed at low concentrations of benzoylcholine. Alkaline hydrolysis of benzoylcholine follows the kinetics of a first order reaction.

Hydrolysis of 4-Nitro-2-(trifluoroacetylamino)benzoic acid: Buffer catalysis, micellar catalysis and intramolecular general acid catalysis

1984 ◽  
Vol 37 (5) ◽  
pp. 977
Author(s):  
TJ Broxton
Keyword(s):  
Benzoic Acid ◽  
Acid Catalysis ◽  
Acidic Solution ◽  
Micellar Catalysis ◽  
Bond Breaking ◽  
Solution Rate ◽  
Solution Ph ◽  
General Acid ◽  
Ph Range ◽  
Hydrolysis Of

The hydrolysis of 4-nitro-2-(trifluoroacetylamino)benzoic acid was studied over the pH range 0-13. In strongly acidic solution (pH 0-3), intramolecular general acid catalysis was observed. In alkaline solution, rate determining protonation of the nitrogen atom of the intermediate complex formed by attack of hydroxide ion on the substrate, was observed. The alkaline hydrolysis was subject to significant micellar catalysis and this was accompanied by a change of mechanism to solvent assisted C-N bond breaking. At intermediate pH (4-8), the reaction was subject to significant buffer catalysis, and deprotonation of the intermediate formed by the attack of water on the substrate was proposed.

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