Ammonium hydrogen phosphite is a hypothetical chemical compound with the possible formula $({\text{NH}}_4{)}_2{\text{HPO}}_3$. Below is a detailed analysis of this compound:

1. Chemical Structure and Existence

• Properties of Phosphorous Acid: Phosphorous acid (${\text{H}}_3{\text{PO}}_3$) is a dibasic acid with one non-dissociable hydrogen atom directly bonded to the phosphorus atom, leaving two acidic hydroxyl groups (pKa1 ≈ 1.3, pKa2 ≈ 6.7).

• Possible Salt Forms: Theoretically, phosphorous acid can form two ammonium salts:

  • Ammonium dihydrogen phosphite (${\text{NH}}_4{\text{H}}_2{\text{PO}}_3$): Neutralizes the first acidic hydroxyl group.

  • Ammonium hydrogen phosphite ($({\text{NH}}_4{)}_2{\text{HPO}}_3$): Neutralizes the second acidic hydroxyl group.

2. Synthesis and Stability

• Preparation: It may be synthesized by neutralizing phosphorous acid with aqueous ammonia in specific stoichiometric ratios, requiring precise pH control to favor the formation of the mono- or di-ammonium salt.

• Stability: Ammonium salts are generally thermally unstable and may decompose upon heating, releasing ammonia gas (${\text{NH}}_3$). Additionally, the reducing nature of phosphite ions (${\text{HPO}}_3^{2-}$) could contribute to instability under oxidative conditions.

3. Potential Applications

• Industrial Uses: Could serve as an intermediate in organic synthesis or specialized electroplating processes.

• Agriculture: Phosphite salts have been explored in some studies as plant disease resistance inducers, though their efficacy as phosphorus fertilizers is significantly weaker compared to phosphate salts.

4. Cautions and Common Confusions

• Differentiation from Phosphates: Ammonium hydrogen phosphate ($({\text{NH}}_4{)}_2{\text{HPO}}_4$) is a widely used fertilizer, whereas phosphites (oxidation state +3) differ fundamentally from phosphates (+5) in reactivity and applications.

• Existence in Literature: There is limited documented evidence for $({\text{NH}}_4{)}_2{\text{HPO}}_3$ in scientific literature, necessitating experimental validation of its synthesis and stability.

5. Summary

Ammonium hydrogen phosphite is theoretically plausible based on the chemistry of phosphorous acid and ammonium salts. However, its practical synthesis, stability, and applications require further research. For specific uses or experimental protocols, consult specialized literature or conduct laboratory verification. If the inquiry involves a naming confusion (e.g., mistaking phosphites for phosphates), clarify the requirements to ensure accurate information.