Alkylating potential of potassium sorbate.
A kinetic study of the alkylating potential of potassium sorbate (S)-a food preservative used worldwide-in 7:3 water/dioxane medium was performed. The following conclusions were drawn: (i) Potassium sorbate shows alkylating activity on the nucleophile 4-(p-nitrobenzyl)pyridine (NBP), a trap for alkylating agents with nucleophilic characteristics similar to those of DNA bases, (ii) The NBP alkylation reaction complies with the rate equation r = k(alk)[H+][S][NBP]/(K(a) + [H+]), K(a) being the sorbic acid dissociation constant and k(alk) the rate constant of NBP alkylation by the undissociated acid. In the range of pH 5-6, the alkylation time ranges between 18 days (pH 5.2) and >1 month (pH > or = 6). (iii) NBP alkylation occurs through a reaction with deltaH# = 78 kJ mol(-1), which is much higher than those of NBP alkylation by stronger alkylating agents. (iv) The absorption coefficient of the sorbate-NBP adduct was determined to be epsilon = 204 M(-1) cm(-1) (lambda = 580 nm), this value being rationalized in terms of the adduct structure. (v) The results can help to establish suitable expiration times for products preserved with potassium sorbate.
Pérez-Prior
M Teresa
MT
Departamento de Química física, Universidad de Salamanca, E-37008 Salamanca, Spain.
Manso
José A
JA
García-Santos
M Del Pilar
Mdel P
Calle
Emilio
E
Casado
Julio
J
D000477:Alkylating Agents; D000478:Alkylation; D005520:Food Preservatives / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D013011:Sorbic Acid / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
D000477:Alkylating Agents; D005520:Food Preservatives; D013011:Sorbic Acid