We report the molecular design of antiscaling chemicals based on carboxylic acids and sulfonate random copolymers focused in avoiding the formation of CaCO3 particles to be applied in oil fields having high salinity and high hardness such as those of Mexican reservoirs. Density functional theory calculations reveal that the studied antiscaling chemicals inhibit the growth of calcite particles, undo the previously formed ones, and capture the CaCl2 salt units. This functionality is due to antiscaling chemicals having a marked trend for reacting with CaCO3 units to form bicarbonate anions. In particular, the random copolymer whose backbone contains itaconic acids and sodium vinyl sulfonates in a 4:1 molar ratio is a better antiscaling chemical than the one having a 1:1 molar ratio because adjacent itaconic acids’ carboxylic heads act together to form chelating bindings with the formed bicarbonates. Likewise, these random copolymers overcome the scale-inhibiting performance of commercial products based on phosphonates. The experimental static and dynamical antiscaling tests, as well as the scanning electron microscopy images confirm the theoretical predictions.