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Physical & Chemical properties

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Description of key information

Physical appearance (HEBMP-H): liquid (aqueous solution)

Key value for chemical safety assessment

Physical state at 20°C and 1013 hPa:
liquid

Additional information

The anhydrous form of the substance is a solid under ambient conditions, however, the commercial samples as supplied in Europe are typically manufactured in situ as an aqueous solutions (liquid). Thus, the substance is not marketed or used in the solid state.

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.