Properties of 3-hydroxypropionaldehyde 3-phosphate.

Several modifications to the synthesis of the diethyl acetal of 3-hydroxypropionaldehyde-3-P (HPAP) are described. HPAP is liberated from its acetal by treatment with Dowex 50-H⁺ at 40 °C for 4 min, and longer time or higher temperature lower yields. Breakdown of the dianion of HPAP (pK 6.7) is self-catalyzed, with the phosphate acting as a general base to remove a proton from carbon 2 and allow elimination of phosphate to give acrolein. Monoanion breakdown is at least 400-fold slower. At 25 °C the dianion breaks down with k = 0.025 min^?1, and the activation energy for the process is 24 kcal/mol. Buffers have little effect on breakdown of HPAP, except for those containing primary or secondary amines. Thus morpholine enhances breakdown by forming a Schiff's base with a positively charged nitrogen, and Tris inhibits breakdown by forming one with an uncharged nitrogen. The aldehyde group of HPAP is 60% hydrated in water.