Kinetic study for the hydroxymethylation of the rubeonic acid in alkaline medium and evaluation of Rubeonic and its derivatives as corrosion inhibitor for carbon steel by theoretical study.

Hydroxymethylation process for robeonic acid by the reaction of rubeonic acid with formalin solution 37% in alkaline medium of 10% NaOH has been studied at different temperature, i.e.,. 30,40,50, and 60°C respectively at constant time 3hours. The reaction prefer the conditions include the temperature 60°C and the time is 3hours. Thus, the energy of activation decreased as temperature increase , then the time of reaction was decreased. therefore; the consumption of formaldehyde molecules increased as the time of reaction increased at constant temperature. The efficiency of the rubeonic acid (RUA) and its derivatives that include MRU,DRU,N-DRU,TRU, and TERU as corrosion inhibitor for carbon steel was evaluated depending on theoretical calculations especially on the calculations of the EHOMO , ELUMO, and the energy gap AE, by using semi-empirical calculations. It was found that RUA has higher efficiency than their derivatives. Hence, the substitution of hydrogen atom by methylol group in RUA reduce the efficiency. Hence, the increasing of the methylol groups on RUA leads to decrease the efficiency, that corresponding to increase in the energy gap AE , and decrease the partial charge on N-atom on the products MRU to TREU compared with RUA, also the free energy of corrosion reaction AG was increasing as the substituted methylol groups increase on RUA, i.e., from MRU to TREU.