The role of ion-molecule pair intermediates in acid-catalyzed solvolysis. General base-catalyzed formation of 4-methylbenzyl carbocation and its trapping by nucleophiles

1993 ◽  
Vol 58 (26) ◽  
pp. 7427-7433 ◽  
Author(s):  
Alf Thibblin
Keyword(s):  
General Base ◽  
Acid Catalyzed

Kinetics of cyclization of S-ethoxycarbonylmethylisothiouronium chloride to 2-imino-4-thiazolidone

1979 ◽  
Vol 44 (3) ◽  
pp. 912-917 ◽  
Author(s):  
Vladimír Macháček ◽  
Said A. El-bahai ◽  
Vojeslav Štěrba
Keyword(s):  
Hydrochloric Acid ◽  
Dilute Hydrochloric Acid ◽  
Base Catalysis ◽  
General Base ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Rate Limiting ◽  
Kinetics Of

Kinetics of formation of 2-imino-4-thiazolidone from S-ethoxycarbonylmethylisothiouronium chloride has been studied in aqueous buffers and dilute hydrochloric acid. The reaction is subject to general base catalysis, the β value being 0.65. Its rate limiting step consists in acid-catalyzed splitting off of ethoxide ion from dipolar tetrahedral intermediate. At pH < 2 formation of this intermediate becomes rate-limiting; rate constant of its formation is 2 . 104 s-1.

Role of polycation promoters in the cobalt(II) phthalocyaninetetracarboxylic and -octacarboxylic acid-catalyzed autoxidation of mercaptoethanol

1995 ◽  
Vol 33 (11) ◽  
pp. 1841-1848 ◽  
Author(s):  
Eugène T. W. M. Schipper ◽  
Johan P. A. Heuts ◽  
Ralph P. M. Pinckaers ◽  
Pieter Piet ◽  
Anton L. German
Keyword(s):  
Acid Catalyzed

Critical role of Bronsted acid in Lewis-acid-catalyzed synthesis of Amadori and Heyns compounds of β-amino acids

2021 ◽  
pp. 1-11
Author(s):  
Debasree Chanda ◽  
Gangothri M. Venkataswamy ◽  
Lagamawwa V. Hipparagi ◽  
Nanishankar V. Harohally
Keyword(s):  
Amino Acids ◽  
Lewis Acid ◽  
Critical Role ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Brönsted Acid ◽  
Acid Catalyzed

DNA and RNA enzymes with peroxidase activity — An investigation into the mechanism of action

2006 ◽  
Vol 84 (4) ◽  
pp. 613-619 ◽  
Author(s):  
Paola Travascio ◽  
Dipankar Sen ◽  
Andrew J Bennet
Keyword(s):  
Nucleic Acid ◽  
Hydrophobic Interactions ◽  
Basic Component ◽  
Axial Position ◽  
General Base ◽  
Dna And Rna ◽  
Polar Environment ◽  
Guanine Quadruplex ◽  
Acid Catalyzed ◽  
Catalyzed Reactions

A DNA–hemin complex (PS2.M–hemin), and its RNA counterpart (rPS2.M–hemin), have previously been reported, in the presence of nitrogenous buffers such as HEPES, to show enhanced peroxidative activity relative to both uncomplexed hemin and a control DNA–hemin complex (Chem. Biol. 5, 505, 1998). A kinetic analysis of these two hemin-utilizing nucleic acid enzymes provides key insights into the mechanisms for their catalyzed peroxidation reactions. First, control experiments indicate that charge on the added detergent, required for solubility reasons, has little effect on the efficiency of the nucleic-acid-catalyzed reactions. Second, the key functional impact of the two nucleic acid frameworks, either DNA or RNA, appears to be a reduction in the acidity of a water molecule coordinated to the iron atom of the hemin that is bound to the ribozyme and DNAzyme scaffolds. This effect could result from a polar environment and possibly hydrogen bond(s) at the axial position of the hemin, along with favourable hydrophobic interactions for the periphery of the porphyrin ring. Third, the basic component of the buffer enhances the activities; this likely results from a general-base-catalyzed process. Cumulatively, these data supply important clues as to how biopolymers other than a protein can complex with hemin to form productive peroxidase enzymes.Key words: ribozyme, DNAzyme, hemin, peroxidase, mechanism, guanine quadruplex.

Elucidating the role of solvents in acid catalyzed dehydration of biorenewable hydroxy-lactones

2020 ◽  
Vol 5 (4) ◽  
pp. 651-662 ◽  
Author(s):  
Gourav Shrivastav ◽  
Tuhin S. Khan ◽  
Manish Agarwal ◽  
M. Ali Haider
Keyword(s):  
Free Energy ◽  
Transition State ◽  
Energy Barrier ◽  
Free Energy Barrier ◽  
Activation Free Energy ◽  
Acid Catalyzed

Utilizing the differential stabilization of reactant and transition state in the polar and apolar solvents to lower the activation free energy barrier for acid-catalyzed dehydration of hydroxy lactones.

Deuterium exchange of C-methyl protons in lumazine derivatives

1970 ◽  
Vol 48 (2) ◽  
pp. 263-270 ◽  
Author(s):  
J. M. McAndless ◽  
Ross Stewart
Keyword(s):  
Proton Magnetic Resonance ◽  
Proton Magnetic Resonance Spectroscopy ◽  
Acid Catalysis ◽  
Deuterium Exchange ◽  
Base Catalysis ◽  
Resonance Spectroscopy ◽  
Methyl Group ◽  
General Base ◽  
General Acid ◽  
Acid Catalyzed

Proton magnetic resonance spectroscopy has been used to examine the deuterium exchange of the methyl protons in two lumazine derivatives. The exchange occurs at the C-7 methyl group in 6,7,8-trimethyllumazine (2) and at the C-6 methyl group in 1,7-dihydro-6,7,8-trimethyllumazine (3). The former reaction is subject to both general acid- and general base-catalysis but the latter only to general acid-catalysis. Plausible mechanisms for the reactions of both compounds are advanced, involving in the case of 3, acid-catalyzed addition of water across the C6—N5 double bond.

Acid-catalyzed production of biodiesel over arenesulfonic SBA-15: Insights into the role of water in the reaction network

2015 ◽  
Vol 75 ◽  
pp. 425-432 ◽  
Author(s):  
Juan A. Melero ◽  
L. Fernando Bautista ◽  
Gabriel Morales ◽  
Jose Iglesias ◽  
Rebeca Sánchez-Vázquez
Keyword(s):  
Reaction Network ◽  
Acid Catalyzed

Role of keto–enol tautomerization in a chiral phosphoric acid catalyzed asymmetric thiocarboxylysis of meso-epoxide: a DFT study

2015 ◽  
Vol 13 (45) ◽  
pp. 10981-10985 ◽  
Author(s):  
Manjaly J. Ajitha ◽  
Kuo-Wei Huang
Keyword(s):  
Density Functional Theory ◽  
Phosphoric Acid ◽  
Dft Calculations ◽  
Density Functional ◽  
Dft Study ◽  
Functional Theory ◽  
Chiral Phosphoric Acid ◽  
Acid Catalyzed

The mechanism of a chiral phosphoric acid catalyzed thiocarboxylysis of meso-epoxide was investigated by density functional theory (DFT) calculations (M06-2X).

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