Because of their availability, lower cost, biodegradability, respect for health, environmental standards and their extremely high efficiency [Benmessaoud Left D, Zertoubi M, Irhzo A, Azzi M, Revue: Huiles et extraits de plantes comme inhibiteurs de corrosion pour différents métaux et alliages dans le milieu acide chlorhydrique, J Mater Environ Sci 4:855–866, 2013], the green corrosion inhibitors are currently the most sought after candidates. The ultimate aim of this work is to study the selectivity and reactivity of a series of three molecules, namely Cytisine, Dehydro-Cytisine and N-methyl Cytisine which are the major constituents of Retama monosperma seeds alkaloid extract (AERS) as eco-friendly inhibitors of corrosion of carbon steel in acidic medium HCl (1M), using the density functional theory (DFT) at B3LYP/aug-cc-pvdz levels. Indeed, this alkaloid extract AERS has proven experimentally its corrosion inhibitory power for carbon steel in 1 M HCl even at lower concentration (94.42% at 400[Formula: see text]mg/L). Besides, its adsorption on the steel surface in 1 M HCl solution followed Langmuir’s isotherm [El Hamdani N, Fdil R, Tourabi M, Jama C, Bentiss F, Alkaloids extract of Retama monosperma (L.) Boiss. seeds used as novel eco-friendly inhibitor for carbon steel corrosion in 1 M HCl solution: Electrochemical and surface studies, Appl Surf Sci 357:1294–1305, 2015, doi: 10.1016/j.apsusc.2015.09.159; El Hamdani N, Contribution a la valorisation des parties aériennes de Retama Monosperma, phytochimie, activités antimicrobiennes et propriétés anticorrosives, Universite Chouaib Doukkali Faculte des sciences El jadida, 2015]. Herein, the major aim of this work is to investigate the likelihood of the carbon steel corrosion being inhibited by the protonated species in the aqueous acidic solution. For this purpose, after proving that the most favorable protonation site for protonation was N9, we have evaluated the structural, global and local reactivity descriptors, partial atomic charge in terms of Natural bond orbital (NBO) of the three protonated inhibitors at the level of N9, which are the most stable in the aqueous acidic solution. NBO analysis and the thermodynamic properties such as entropy, enthalpy, heat capacity and Gibbs free energy were also done. In conclusion, it was observed that three protonated molecules showed a high propensity to adsorb to the mild steel surface with a priority of the molecule d-CytN9H+.

中文翻译：

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对 Retama monosperma (L.) Boiss 的生物碱提取物 Cytisine 衍生物的理论理解。种子，作为酸性 1M HCl 溶液中碳钢腐蚀的环保抑制剂

由于它们的可用性、成本更低、可生物降解、尊重健康、环境标准和极高的效率 [Benmessaoud Left D、Zertoubi M、Irhzo A、Azzi M、Revue：Huiles et extraits de plantes comme inhibitors de Corrosion pour différents métaux et alliages dans le milieu acide chlorhydrique, J Mater Environ Sci 4:855–866, 2013]，绿色缓蚀剂是目前最受追捧的候选者。这项工作的最终目的是研究一系列三种分子的选择性和反应性，即 Cytisine、Dehydro-Cytisine 和 N-methyl Cytisine，它们是 Retama monosperma 种子生物碱提取物 (AERS) 的主要成分作为环保抑制剂使用密度泛函理论 (DFT) 在 B3LYP/aug-cc-pvdz 水平下对酸性介质 HCl (1M) 中碳钢的腐蚀进行了研究。确实，这种生物碱提取物 AERS 已通过实验证明其在 1 M HCl 中即使在较低浓度下（94.42% 在 400[公式：见正文]mg/L）下对碳钢的腐蚀抑制能力。此外，它在 1 M HCl 溶液中对钢表面的吸附遵循 Langmuir 等温线 [El Hamdani N, Fdil R, Tourabi M, Jama C, Bentiss F, Retama monosperma (L.) Boiss 的生物碱提取物。种子用作 1 M HCl 溶液中碳钢腐蚀的新型环保抑制剂：电化学和表面研究，Appl Surf Sci 357:1294–1305, 2015, doi: 10.1016/j.apsusc.2015.09.159；El Hamdani N, Contribution a la valorisation desparty aériennes de Retama Monosperma, phytochimie, activités antimicrobiennes et propriétés anticorrupts, Universite Chouaib Doukkali Faculte des Sciences El jadida, 2015]。在此处，这项工作的主要目的是研究酸性水溶液中质子化物质抑制碳钢腐蚀的可能性。为此，在证明最有利于质子化的质子化位点是 N9 之后，我们在N9 在酸性水溶液中最稳定。还进行了NBO分析和熵、焓、热容量和吉布斯自由能等热力学性质。总之，观察到三个质子化分子显示出较高的吸附到低碳钢表面的倾向，优先考虑分子 d-CytN9H+。