Aminolysis Of P-nitrophenyl Acetate Research Articles

Role of bifunctional catalyst 2-pyridone in the aminolysis of p-nitrophenyl acetate with n-butylamine: A computational study

The possible catalytic effects of 2-pyridone and its tautomeric form 2-hydroxypyridine on the aminolysis reaction of p-nitrophenyl acetate with n-butylamine have been theoretically studied at the B3LYP/6-31+G(d,p) level of theory. Solvent effect of chloroform is assessed using the MP2/CPCM/6-31++G(d,p)//B3LYP/6-31+G(d,p) method. In our work, three possible mechanisms are considered for the title reaction. The first mechanism is concerted via a four-membered ring transition state assisted by supramolecular effect of the catalyst. The second mechanism undergoes two sequential steps, where the intermolecular proton transfer bridged by the catalyst is the rate-determining process. And the third mechanism, forming a zwitterionic intermediate, is also stepwise via three steps, nucleophilic addition, double-proton transfer, and elimination of leaving group. Our calculations give a detailed picture of the whole stepwise pathway through zwitterionic intermediates for the first time, and indicate that this mechanism is the most favored pathway both in the gas phase and in chloroform.

Aminolysis reactions by glycine in AOT-based water-in-oil microemulsions

A kinetic study was carried out on the aminolysis of p-nitrophenyl acetate (NPA) by glycine (GLY) in AOT/isooctane/water (w/o) microemulsions. The experimental results show that the reaction by GLY occurs mostly in the aqueous microdroplet. On the basis of the analysis of the kinetic data, we have calculated the rate constants in the aqueous microdroplet, k 2 w , and it can be observed that these increase as the water content of the system decreases. In the aqueous microdroplet, the predominant interaction Na +···OH 2 causes a decrease in the strength of the hydrogen bonds and therefore facilitates the desolvation of the reagents as W decreases. This desolvation of the reagents causes the increase of k 2 w as W decreases.

Microheterogeneous Solvation for Aminolysis Reactions in AOT‐Based Water‐in‐Oil Microemulsions

A kinetic study was carried out on the aminolysis of p-nitrophenyl acetate (NPA) by n-decylamine (DEC), piperazine (PIP) and sarcosine (SAR) in AOT/isooctane/water (w/o) microemulsions. By using the pseudophase model both the rate constants at the interface, k2i, and the water microdroplet, k2w, can be obtained. The obtained results show that k2i increases together with the water content of the microemulsion, whereas k2w increases as the water content of the system decreases. In the aqueous microdroplet the predominant interaction Na+...OH2 causes a decrease in the strength of the hydrogen bonds and therefore facilitates the desolvation of the reagents as W decreases. This desolvation of the reagents causes the increase of k2w as W decreases. In the interface of the microemulsion the predominant interaction SO3-...HOH causes an increase in the electronic density on the water molecules and the consequent decrease in their efficiency in the solvation of the partial negative charge, which develops on the carbonyl oxygen atom in the transition state of the reaction. This decrease in the solvation causes k2i to decrease together with the water content of the system.

Catalysis of the aminolysis of p-nitrophenyl acetate by inverse nonionogenic surfactant micelles

1. A study was carried out on the catalytic activity of polyethyleneglycol-600 monolaurate in the aminolysis of p-nitrophenyl acetate in toluene. 2. The catalytic effect of the surfactant is the result of the formation of inverse micelles and the absorption of the amine and the substrate by these micelles. The enhancement of the reaction rate in the presence of surfactant is by two orders of magnitude and is accompanied by a change in the mechanism. 3. The catalytic effect of the inverse micelles drops with an increase in the amine concentration.

Aminolysis of Carboxylic Esters by Cationic Surfactants in Apolar Solvents

Aminolysis of p-nitrophenyl acetate (PNPA), p-nitrophenyl laurate (PNPL), phenyl acetate (PA), methyl acetylsalicylate (AMS), and ethyl benzoate (EB) catalyzed by dodecylammonium propionate (DAP) and monoethanolammonium dodecanoate (EAD) was studied in various apolar solvents. The dependence of pseoud-first order rate constants (κobs) on the concentration of surfactants in the micellarsystems differed markedly by the combination of the kinds of esters and the surfactants, while all kobsincreased linearly up to the cmc of surfactants in particular slopes. The extent of rate-enhancement was order of PNPA>>PNPL>PA≈AMS>EB in DAP/cyclohexane systems and of heptane>cyclohexane>benzene in PNPA/DAP systems. Further, the thermodynamic quantities of activation in both the monomer and micellar systems were evaluated from the temperature dependence of the rate constants. Remarkable decrease in the entropy of activation was observed and the results were compared with that in the hydrolysis of PNPA by aqueous micellar catalyst or that in the deacetylation of acetyl-enzyme (α-chymotrypsine) by α-chymotrypsine.

The Effect of Polar Substances on Aminolysis of p-Nitrophenyl Acetate by Reversed Micelle of Dodecylammonium Propionate

The Effect of Polar Substances on Aminolysis of p-Nitrophenyl Acetate by Reversed Micelle of Dodecylammonium Propionate

The aminolysis of p-nitrophenyl acetate by aminopyridines. Mechanisms in aqueous and aprotic solvents

In dimethyl sulfoxide, the aminolysis of p-nitrophenyl acetate by aminopyridines results in amide formation, through nucleophilic catalysis by the ring nitrogen for 4-aminopyridine, but by direct amino nitrogen attack for 2-aminopyridine (as previously found for acetic anhydride). In water, the aminopyridines catalyse the hydrolysis of the ester (unlike aniline, which still gives acetanilide). In general, this occurs by nucleophilic catalysis by the ring nitrogen. Even 4-amino-2- methylpyridine reacts by this route (though 2-picoline does not) and, of the compounds studied, only for 2-amino- 6-methylpyridine does general base catalysis occur instead. Reasons for these mechanism changes are discussed.

Effect of ionic surfactants on aminolysis of p-Nitrophenyl acetate by imidazoles in carbon tetrachloride

The pseudo-first order rate constant for the decomposition of p-nitrophenyl acetate in carbon tetrachloride was measured as a function of the concentration of imidazole and 2-alkylimidazoles solubilized by didodecyldimethylammonium chloride (DDAC) or bromide (DDAB) and dio(2ethylhexyl) sodium sulfosuccinate (AOT). The rate constants in the pure solvent and in the presence of surfactants were obtained from the slopes of straight lines over the lower concentration range of imidazole and 2-alkylimidazoles. It was observed that the addition of the surfactants to the reaction system increases the rate constants by several times over those in the pure solvent. The magnitude of the rate enhancement was of the order: DDAC > DDAB > AOT for the imidazole in the surfactant systems and imidazole > 2-undecylimidazole > 2-isopropylimidazole in the DDAB systems. The surfactant effect could be elucidated in terms of strength of the interaction between the surfactants and imidazole or 2-alkylimidazoles obtained from NMR and vapor pressure osmometry.

Kinetics of the reaction of p-nitrophenyl acetate with amines in the presence of dodecylammonium propionate and aerosol-OT aggregates in benzene

Aminolysis of p-nitrophenyl acetate (NPA) by dodecylamine (DA) is 53 times faster in the presence of dodecyclammonium propionate (DAP) aggregates than in pure.benzene. Reaction with imidazole (Imz) and N-methylimidazole (Melmz) in the presence of DAP displays much more micellar catalysis. Thus addition of 0.2M-DAP to 0.08M-Imz in benzene reduced the reaction half-life from 25 h to 3 min. Addition of water decreases the reaction rates. This decrease is mainly due to DAP head-group hydration with subsequent loss of catalytic activity. Reaction between NPA and the amines, is faster in presence of DAP than Aerosol-OT(AOT). Addition of water to the amine–AOT system increases the rates. The results are discussed in terms of bifunctional catalysis by DAP and the effects of the surfactants on the reactivities of substrates solubilized in their micellar cores.

Effect of hydrophobic interaction on the rate of aminolysis of p-nitrophenyl acetate by decylamine

The self-catalysed reaction of decylamine with p-nitrophenyl acetate is at least 200 times faster than the corresponding reaction of ethylamine.

Acylation. Part XXIX. The mechanism of ester aminolysis in non-hydroxylic media and the effect of nitrogen-containing leaving groups

At 25° the aminolysis of p-nitrophenyl acetate and of various p,p′-disubstituted phenyl benzoates in diethyl ether solution obeys the rate equation –d[Ester]/dt=(k1[Ester][Amine]+k2[Ester][Amine]2). In acetonitrile solution this equation is simplified to –d[Ester]/dt=k1[Ester][Amine]. The aminolysis of esters of the form R1CO·O·NR22 obeys the rate equation –d[Ester]/dt=k1[Ester][Amine] in both ether and acetonitrile. The change of solvent has little effect on k1 for the latter esters, but k1 is notably increased in acetonitrile for the phenyl esters. The amines studied were n-butylamine, diethylamine, t-butylamine, and piperidine. The form of the rate equation is unchanged for the secondary amines, contrary to the findings of Shawali and Beichler for dioxan solutions. Steric effects affect both k1 and k2 and it is unlikely that the aminolysis of esters R1CO·O·NR22 are any more subject to these effects than are the phenyl esters. Under conditions of constant steric requirement the ratio k2 : k1 increases as electron withdrawing substituents are introduced into the acyl portion of phenyl benzoates. Substituent changes in the leaving group have a more complex effect on this ratio. In no case was there detectable catalysis of aminolysis by triethylamine. In ether all the esters were subject to catalysis by carboxylic acids, the N-containing compounds being particularly susceptible. In acetonitrile there is no detectable acid catalysis for the phenyl esters and that for the N-containing esters is greatly reduced.Rationalisation of the foregoing facts leads to aminolysis mechanisms resembling those we have previously established for acyl cyanides and ketens in non-hydroxylic solvents. The route employing two amine molecules involves a hydrogen-bonded, cyclic transition state. A cyclic, hydrogen-bonded transition state is also likely with the nitrogen-containing esters, as suggested by Young and co-workers. Shawali and Beichler's general conclusions about the mechanism of ester aminolysis cannot be sustained.