Monalazone disodium

Hydrolysis

Link to relevant study record(s)

Reference

Endpoint:

hydrolysis

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because the substance is readily biodegradable

Justification for type of information:

Halogen in N-halamines is formally positive, ie, the oxidation state is + 1. N-Halamines hydrolyze yielding hypohalous acid, which ionizes to hypohalite ion depending on pH.

RR'NX + H20 :;:=: RR'NH + HOX :;:=: RR'NH + H+ + xo- (1)

The extent of hydrolysis is a function of the polarity of the N-X bond, which is determined by the electronegativity of X and the nature of the other substituents; the lower the polarity the lower the extent of hydrolysis. In general, electrondonating groups retard hydrolysis whereas electron-withdrawing groups enhance it. Presence of charges and steric and resonance effects also influence the extent of hydrolysis. Bromo compounds hydrolyze to a greater extent than chloro compounds.
The equilibrium expressions for the hydrolysis reactions (eq. 1) follow; Ka and Kw are the ionization constants of HOX and water, respectively.

Khox = [RR'NH][HOX]/[RR'NX] (2)

Kox=[RR´NH] [OX] / [RR´NX] [HO-] = K hox Ka/k (3)

Equation 2 rearranged for the concentration of HOX, shows that the percent hydrolysis increases with decreasing concentration of N-halamine.

[HOX] = KHox[RR'NX]/[RR'NH]

However, as HOX is consumed, hydrolysis is retarded because of build-up offree amine. Consumption of hypohalous acid through reaction with HX can result in formation of elemental halogen: HOX + H+ + x- ~ ~ + H20 (1-3). The tendency for halogen formation is much greater for HO Br and becomes significant
at moderately acidic pH.
In the case of multiple halogen atoms, the hydrolysis constant Kh decreases significantly for successive halogens. For example, in the case of trichloroisocyanuric acid, Kh ranges from 1.6 X 10-2 to 8.5 X 10-4 for the first to the third chlorines (4). The presence of negative charge also reduces Kh significantly, eg, 1.2 x 10-3 and 3.2 x 10-4 for dichloroisocyanuric acid and ion, respectively.

Level III Fugacity Environmental Partitioning

EPI Level III Fugacity Model	Air	Water	Soil	Sediment
Mass Amount (%)	0.00024	29.9	70	0.0689
Half-Life (hr)	315	360	720	3240
Emissions (kg/hr)	1000	1000	1000	0

 

Persistence time (hr): 645

Persistence time (days): 26.875

 

Conclusions:

The following parameters has been taken into account for CSA:
-Half life in water (hr): 360 (EPI Level III Fugacity model)
-Half life in soil (hr): 720 (EPILevel III Fugacity Model)
-Half life in sediment (hr): 3240 (EPI Level III Fugacity Model)

Description of key information

Hydrolysis as a function of pH testing according to method 111 of the OECD Guidelines for Testing of Chemicals, 13 April 2004 was not feseable.

The following parameters has been taken into account for CSA:

-Half life in water (hr): 360 (EPI Level III Fugacity model)

-Half life in soil (hr): 720 (EPILevel III Fugacity Model)

-Half life in sediment (hr): 3240 (EPI Level III Fugacity Model)

Key value for chemical safety assessment

Half-life for hydrolysis:

360 h

at the temperature of:

20 °C