Water structure and its kinetic effects on the neutral hydrolysis of two acyl activated esters

1975 ◽  
Vol 97 (6) ◽  
pp. 1563-1568 ◽  
Author(s):  
Johan F. J. Engbersen ◽  
Jan B. F. N. Engberts
Keyword(s):  
Water Structure ◽  
Activated Esters ◽  
Kinetic Effects ◽  
Hydrolysis Of

Synthesis of conjugates of 1-(carboxymethyl)cytosine and 1-(5-O-carboxymethyl-β-D-arabinofuranosyl)cytosine with proteins

1979 ◽  
Vol 44 (10) ◽  
pp. 3023-3032 ◽  
Author(s):  
Helmut Pischel ◽  
Antonín Holý ◽  
Günther Wagner
Keyword(s):  
Human Serum Albumin ◽  
Acetic Anhydride ◽  
Serum Albumin ◽  
Human Serum ◽  
Activated Esters ◽  
Hydrolysis Of

1-(Carboxymethyl)cytosine (Ia), 1-(5-O-carboxymethyl-β-D-arabinofuranosyl)cytosine (IIa) and 5'-O-carboxylmethylcytidine (IIIa) were transformed by treatment with acetic anhydride and 4-dimethylaminopyridine to the peracetyl derivatives Ib-IIIb. These products reacted with p-nitrophenol in the presence of N, N'-dicyclohexylcarbodiimide to give the activated esters Ic-IIIc which on reaction with ammonia, dimethylamine or 2-aminoethanol afforded the corresponding carboxamides Id-IIId, IIe,f. Reactions of Ic and IIc with human serum albumin and bovine γ-globulin at pH 9.2, followed by hydrolysis of the N- or O-acetyl groups at pH 9.5, gave 50% up to 64% yields of the respective conjugates Ig, IIg and Ih, IIh.

Δ-Sym-cis and Δ-unsym-cis-carbonato-(2S,2'S)-2,2'-ethylene-bis(2-amino-3-methylbutanoato)cabaltate(III) isomers

1987 ◽  
Vol 52 (6) ◽  
pp. 1488-1493 ◽  
Author(s):  
František Jursík ◽  
Samir Abdel-Moez
Keyword(s):  
Acid Hydrolysis ◽  
Absolute Configuration ◽  
Nmr Spectra ◽  
Tetradentate Ligand ◽  
Steric Crowding ◽  
The Absolute ◽  
Kinetic Effects ◽  
Hydrolysis Of ◽  
C Nmr

The tetradentate ligand (2S,2'S)-2,2'-ethylene-bis(2-amino-3-methylbutanoato) (eddval) is coordinated in the [Co(eddval)CO3]- anion to give 88% of Δ-sym-cis and 12% of Δ-unsym-cis isomers. The stereospecific formation of the Δ-sym-cis isomer is explained by steric crowding in the Λ-sym-cis isomer. The predominance of the sym-cis isomer indicates that the synthesis is also influenced by kinetic effects. These are particularly pronounced in the case of the Δ-unsym-cis isomer which for steric reasons is thermodynamically less stable than the Λ-unsym-cis isomer. The secondary nitrogen atoms in the Δ-sym-cis isomer are of the R configuration whereas in the Δ-unsym-cis isomer they have configuration R and S. The absolute configuration of the isomers has been determined from their absorption, CD, 1H and 13C NMR spectra. Acid hydrolysis of Δ-sym-cis-[Co(eddval)CO3]- proceeds with retention of configuration to give the Δ-[Co(eddval)(H2O)2]+ isomer.

scholarly journals Study of Extraction Equilibria in the Reaction of Alkaline Hydrolysis of Activated Amino Acid Esters / Badanie Równowag Ekstrakcji W Reakcji Zasadowej Hydrolizy Aktywowanych Estrów Aminokwasów

2014 ◽  
Vol 19 (1-2) ◽  
pp. 69-77
Author(s):  
Victor S. Doroshkevich ◽  
Oksana V. Baranova ◽  
Aleksandr N. Shendrik ◽  
Aleksandr S. Doroshkevich ◽  
Olena S. Lygina ◽  
...  
Keyword(s):  
Alkaline Hydrolysis ◽  
Phase Transfer ◽  
Phase System ◽  
Phosphonium Salts ◽  
Two Phase ◽  
Extraction Mechanism ◽  
Catalytic Reactivity ◽  
Kinetic Effects ◽  
Hydrolysis Of ◽  
Acid Esters

Abstract Correlation between observed kinetic effects of phase-transfer catalytic reaction of the alkaline hydrolysis of 4-nitrophenyl ester of N-benzyloxycarbonylglycine-4 in the two-phase system chloroform-borate buffer pH = 10 and a content of ionic forms of catalyst was investigated. The phosphonium salts QX (X = Cl¯, Br¯, I¯) shows high catalytic reactivity. Dependence of the reaction kinetics discussed in the framework of the extraction mechanism with a competitive extraction of a nucleophile ОН¯, nucleofuge 4-NO2C6H4O¯ and anion X¯ of the phase-transfer catalyst.

Kinetic effects induced by cellulose on water-catalyzed reactions. Hydrolysis of 2,4-dinitrophenyl cellulose xanthate and some sugar xanthate ester analogues

1998 ◽  
Vol 76 (6) ◽  
pp. 960-965 ◽  
Author(s):  
Eduardo Humeres ◽  
Luiz Fernando Sequinel ◽  
Mauricéa Nunes ◽  
Célia MS Oliveira ◽  
Patrick J Barrie
Keyword(s):  
Cellulose Xanthate ◽  
First Order Kinetics ◽  
Acetone Water ◽  
Spontaneous Hydrolysis ◽  
Hydrolysis Of Cellulose ◽  
Entropy Of Activation ◽  
Kinetic Effects ◽  
Catalyzed Reactions ◽  
Parallel Reactions ◽  
Hydrolysis Of

The hydrolysis of 2,4-dinitrophenyl cellulose xanthate (CelXDNP) was studied in 10% v/v aqueous ethanol at 25°C and μ = 0.1 (KCl). The water-catalyzed hydrolysis showed that, as for p-nitrobenzyl cellulose xanthate, it occurs through two parallel reactions with rate constants k'H2O = 4.40 x 10-3 s-1 for the fast hydrolysis, and k''H2O = 6.90 x 10-5 s-1 for the slow hydrolysis. The entropy of activation of the fast hydrolysis was 0.7 ± 1.8 cal K-1 mol-1. External nucleophiles such as hydroxide and simple amines show simple first-order kinetics. The spontaneous hydrolysis of CelXDNP in acetone-water mixtures indicates that the fast reaction does not occur through water polymers and that for water molarity higher than 30 M there are no acetone molecules (or very few) in the highly ordered cybotactic region of cellulose. The spontaneous hydrolysis of methyl 4,6-O-benzylidene- α -D-glucopyranoside 3-(S-p-nitrobenzyl-xanthate) although is faster than the 6-isomer, it is slower than the fast hydrolysis of p-nitrobenzyl cellulose xanthate (CelXNB). Also Δ Sdouble dagger is highly negative (-41.0 cal K-1 mol-1), as it is for alkyl and sugar analogues. Only for the fast hydrolyses of CelXDNP and CelXNB is the entropy of activation almost zero. It is concluded that there is no neighbouring OH effect on the fast hydrolysis of cellulose xanthate esters. Key words: hydrolysis, water catalysis, cellulose xanthate esters, methyl glucose, xanthate esters, neighbouring OH effect.

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