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Dissociation constant

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Description of key information

pKa2= 3.59 ± 0.10 (calculated for C12 and C14 homologue)
Supporting data:
N-Acetyl glycinate: pKa = 3.6-3.8 (potentiometric titration)
N-Propionyl glycinate: pKa = 3.72 (potentiometric titration)

Key value for chemical safety assessment

pKa at 20°C:
3.59

Additional information

Due to difficulties to measure dissociation constants for complex UVCB mixtures with different dissociating species the dissociation constant of sodium alkanoyl glycinate was determined from the molecular structure using the ACD software tool. The pka values were i.a. calculated for the main chain length constituent C12).

pKa2 refers to the acid-base equilibrium of the carboxylic acid group. The values of pKa1 and pKa3 lie outside the range relevant for environmental considerations and correspond to protonation/deprotonation of the NH function.

pKa1= 16.0±0.46 (for C12 homologue)

pKa2= 3.59±0.10 (for C12 homologue)

pKa3= -1.01±0.70 (for C12 homologue)

The result of the calculation is supported by measured values for the shorther chain length homologues N-Acetylglycin (pKa = 3.6 -3.8) and N-Propionlyglycin (pKa = 3.72) which were determined by potentiometric titration.

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