Quantum-chemical calculation of molecule of 1-[2-(о-acetylmethyl)-3-о-acetyl2-ethyl]-methyldichlorinephosphite (I) and components of its synthesis [4] for the first time is executed by method AB INITIO in basis 6-311G**. The optimized geometrical and electronic structures of these compounds are received. Their acid force is theorized. All these compounds concern to a class of very weak С-Н-acids (рКа > 14, where рКа is the universal parameter of acidity). Dependence between acid force of components of synthesis рКа (II) and рКа (III) and acid force рКа (I)

1-[2-(о-Acetylmethyl)-3-о-acetyl-2-ethyl]-methyldichlorinephosphite (I) is intermediate substance for reception of a medical product from hepatitis. It possesses interesting and probably unique properties.