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Flash point

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Description of key information

Flash point (HEBMP-H): not relevant to solid or aqueous solution

Key value for chemical safety assessment

Additional information

The requirement to test the substance for flash point is waived in accordance with Section 2 of REACH Annex XI, because it is not applicable for the solid forms or the aqueous solutions.

In solution, HEBMP-H (CAS 5995-42-6) undergoes a reversible internal condensation reaction to form a pH-dependent equilibrium mixture with the cyclised structure 4-(Phosphonomethyl)-2-hydroxy-2-oxo-1,4,2-oxaza-phosphorinane (CAS 32422-02-9, c-HEBMP) and water. The precise proportion of the two forms is dependent on pH, temperature and time, and under acidic or neutral conditions, the proportion of c-HEBMP in the multi-constituent substance may reach proportions as high as ≥50% w/w. Spectroscopic evidence from 31P-NMR analysis suggests that in the pH range ca. 1 – 7 a high proportion (50-75% w/w) is present as the cyclised form. The two forms exist in equilibrium therefore it is extremely difficult to separate and purify both forms. The properties of the whole substance, in which both forms are present at representative levels, are used in the chemical safety assessment.