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Physical & Chemical properties

Dissociation constant

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The dissociation constant of L-Cysteine Hydrochloride Monohydrate was determined using the titrimetric method at 20.0 °C.
The test item L-Cysteine Hydrochloride Monohydrate should be considered as acid with three proton donator units.
The three measured pKa can be assigned to the proton donator units of the test item:
pKa1= pKa(COOH-group) = 1.967
pKa2= pKa(SH-group) = 8.317
pKa3=pKa(NH3-group) = 10.455.
From these results, it can be determined that the substance would always be ionised at environmentally relevant pH's.
These constants can be applied to the anhydrous form - L-Cysteine hydrochlorde - as well.

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