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Description of key information

In contact with water the substance will not hydrolyse at pH=4 and will hydrolyze rapidly at pH=7 and 9.

Key value for chemical safety assessment

Additional information

In water Basazol Yellow 8511-MS dissociates into i) two molecules methane sulfonate (CAS 75-75-2) and ii) one molecule 2,4-bis[2,2'-[2-(N,N-dimethylamino)ethyloxycarbonyl]phenylazo]-1,3-dihydroxybenzene.

Methane sulfonate is an NLFG (no labile functional group) compound and hence not susceptible to hydrolysis (Kollig et al., 1993).

The two key studies were conducted with the structurally related substance Basazol Yellow 8511 (CAS 118208-02-9) which is the the analogue chloride salt.

At pH=4 and 50 °C less than 10 % hydrolysis occurred which means: t0.5 > 1y at 25 °C. Therefore no further hydrolysis tests at pH=4 were necessary according to OECD111.

At pH=7 and 25 °C t0.5 was already clearly below 24 h. Therefore a precise determination of t0.5 was not necessary according to directive 67/548/EWG.

The hydrolysis rates of aromatic esters generally increase with increasing pH (Mabey & Mill, 1978). At pH=9 and 25 °C t0.5 has to be even lower than at pH=7. Therefore a precise determination of t0.5 was not necessary.

Apart from the two esterbonds which are susceptible to hydrolysis at pH 7 and 9 (see above) the molecule does not contain hydrolysable functional groups. Hence the two hydrolysis products which were formed are: i) the aromatic diazo core with two carboxylic groups, ii) 2-dimethylaminoethanol (CAS 108-01-0).

The aromatic diazo core is not susceptible to further hydrolysis. 2-dimethylaminoethanol (CAS 108-01-0) is stable against hydrolysis (Harris, 1990; Kollig et al., 1993; Wolfe & Jeffers, 2000).