Efeito de detergentes na velocidade de: transferência intramolecular de acila-tiolise de acetato de p-nitrofenila / Effect of detergents on the rate of: Intramolecular acyl-transfer. Thiolysis of p-noitrophenylacetate

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

15/07/1977

RESUMO

Two systems were used in order to investigate some of the factors that modify the reaction rate in micelles. The rate of S to N acyl transfer of S-octanoyl-β- mercaptoethylamine (OMA) is enhanced by hexadecyl trimethylammonium bromide (CTAB) micelles by 4.6 fold and slightly inhibited by the non ionic detergent Brij-35. The rate of S to N transfer of S-acetyl-β-mercaptoethylamine (AMA) is unaffected by CTAB or Brij-35. Micelles of a negative detergent, sodium dodecyl sulfate inhibit the rate of S to N transfer of AMA by 100 fold, the inhibition in the case of OMA is 1.7 x 103 fold. An increase in the apparent pK of the ammonium ion and a decrease in the conformational mobility of OMA is proposed to account for the observed results. CTAB increases the rate of thiolysis of p-nitrophenyl acetate by substituted thiophenols by approximately 50 fold. The calculated rate constant in the micellar phase (k2m) is identical to that in the aqueous phase (k2w) for thiophenol, p-methoxithiophenol and p-metilthiophenol. k2m is 40% less than k2w in the case of p-clorothiophenol. The observed rate acceleration can be attributed, exclusively, to substrate concentration in the micellar phase.

ASSUNTO(S)

biochemistry química de superfície surface chemistry thiolysis tiólise transferência intramolecular de acila acetato de p-nitrofenila bioquímica detergentes detergents intramolecular acyl-transfer p-nitrophenylacetate

ACESSO AO ARTIGO

Documentos Relacionados