Supplementary data from: Are natural-based isothiocyanate derivatives alternative antioxidant additives used in petrochemical products?

Synthetic additives used in petrochemical products, such as plastics, rubbers, resins, and polymers, can enter the environment as contaminants and pollute the aquatic and soil environment. Thus, using natural-based alternative compounds has excellent potential to reduce the negative impact. In this study, the role of natural-based isothiocyanate derivatives Cp1-Cp4, i.e., allylisothiocyanate, 1-isothiocyanate-3-methylbutane, 4-methylphenyl isothiocyanate, and 2-phenylethyl isothiocyanate in use as primary antioxidant additives was studied via their HOꞏ-radical scavenging activity. Formal hydrogen transfer, radical adduct formation, and single electron transfer mechanisms were investigated in water and pentyl ethanoate (PEA) using Density Functional Theory at M06-2X/6-311++G(3df,3pd)//M06-2X/6-311++G(d,p) level of theory. The results illustrated the high HOꞏ-scavenging activity of the isothiocyanate compounds with rate constants of about 108 - 109 M-1s-1. Allylisothiocyanate Cp1 represents the most efficient HOꞏ-scavenger with koverallof5.20 × 109 M-1s-1 in water and 1.85 × 109 M-1s-1 in PEA. These results allow us to enrich the data on effective antioxidant additives from natural sources to reduce HOꞏ-radicals-induced oxidation processes in different environmental conditions.

Methods
All DFT calculations were performed by Gaussian 16 Rev. C.01 package. The Gaussian Post Processor (GPOP) program was used to calculate the rate constant for chemical reactions.