3-hydroxypropionate

3-hydroxypropionate is the conjugate base formed when the carboxyl group of 3-hydroxypropionic acid loses a proton. Its structure isThe primary ChEBI record gives formula ${\mathrm{C}}_3{\mathrm{H}}_5{\mathrm{O}}_3$, net charge $-1$ and the systematic name 3-hydroxypropanoate. The terminal hydroxyl group remains present; the acid-to-base change occurs at the carboxyl group, not by moving that hydroxyl or removing the carbon skeleton.^[ref]

The acid–base pair can be represented asIn a dilute-solution approximation with activity coefficients treated as equal, the Henderson-Hasselbalch equation givesAt a pH one unit above the relevant $\mathrm{p}{K}_a$, the ratio is $10:1$, so about $10/11$ of the acid-plus-conjugate-base pool is anionic in that model. This is an illustrative equilibrium calculation; no numerical $\mathrm{p}{K}_a$ for this compound is being supplied.

Speciation and total amount answer different analytical questions. If no other reactions occur, changing pH can redistribute $[\mathrm{HA}]$ and $[{\mathrm{A}}^{-}]$ while preserving their sum. A negatively charged 3-hydroxypropionate ion in a bulk solution is accompanied by compensating positive charge elsewhere; it is not the same molecular species as the neutral acid or a complete named salt.

The record’s average mass of $89.070g/mol$ applies to the anion’s composition. Reporting a concentration as acid equivalents instead uses the acid’s reference mass, while reporting a particular salt requires the salt’s complete composition. This distinction matters when comparing metabolic engineering measurements that use an acid name for a total analytical product pool.^[ref]