Sains Malaysiana 40(9)(2011): 973–976

Synthesis of Dipeptide Benzoylalanylglycine Methyl Ester and Corrosion

Inhibitor Evaluation by Tafel Equation

(Sintesis Ester Metil Dipeptida Benzoilalanilglisin dan Penilaian Penghalang Pengaratan Menggunakan Persamaan Tafel)

Juniarti Abdurrahman*, Deana Wahyuningrum, Sadijah Achmad & Bunbun Bundjali

Chemistry Study Program, Faculty of Mathematics and Natural Sciences, Bandung Institute of Technology, Jl. Ganesha 10, Bandung 40132, Indonesia

Received: 16 June 2010 / Accepted: 3 January 2011

ABSTRACT

Corrosion is one of the major problems in petroleum mining and processing industry. The pipelines used to transport crude oil from reservoir to the processing installation were made from carbon steel that is susceptible towards corrosion. One of the best methods to prevent corrosion that occurred at the inner parts of carbon steel pipelines is to use organic corrosion inhibitor. One of the potent organic corrosion inhibitors is amino acids derivatives. In this study, dipeptide compound namely benzoylalanylglycine methyl ester and benzoylalanylglycine have been synthesized. The structure elucidation of the products was performed by IR, MS and NMR spectroscopy. The determination of corrosion inhibition activity utilized the Tafel method. The corrosion inhibition efficiency of glycine methyl ester, benzoylalanine, dipeptide benzoylalanylglycine methyl ester and dipeptide benzoylalanylglycine were 63.34%, 35.86%, 68.40% and 27.72%, respectively. These results showed that the formation of dipeptide benzoylalanylglycine methyl ester, derived from carboxylic protected glycine and amine protected alanine, increased the corrosion inhibition activity due to the loss of acidity center in the structure of glicine and L-alanine that would induce the corrosive environment towards carbon steel.

Keywords: Benzoylalanylglycine methyl ester; carbon steel; corrosion inhibitor; dipeptide synthesis; Tafel method

ABSTRAK

Kakisan merupakan salah satu masalah utama dalam industri perlombongan dan pemprosesan petroleum. Paip yang digunakan untuk menyalurkan minyak mentah dari sumber ke bahagian pemprosesan yang dibuat daripada bahan aloi karbon mudah terdedah kepada kakisan. Salah satu cara terbaik dalam mencegah kakisan yang terjadi pada bahagian dalam paip aloi karbon adalah dengan menggunakan penebat kakisan organik. Salah satu penghalang kakisan organik yang berpotensi adalah terbitan asid amino. Dalam kajian ini, sebatian dipeptida iaitu ester metil benzoilalanilglisin dan benzoilalanilglisin telah disintesis. Penentuan struktur produk dilakukan dengan pengukuran spektroskopi IR, MS dan NMR. Penentuan keaktifan penghalang pengaratan dilakukan dengan kaedah Tafel. Kecekapan penebat kakisan glisin metil ester, benzoilalanin, dipeptida benzoilalanilglisin metil ester dan dipeptida benzoilalanilglisin, secara berturut-turut adalah 63.34%, 35.86%, 68.40% dan 27.72%. Hasil menunjukkan bahawa pembentukan dipeptida benzoilalanilglisin metil ester, yang berasal daripada glisin dengan kumpulan karboksilik dan alanin dengan kumpulan amina, meningkatkan keaktifan penebat kakisannya akibat kehilangan pusat keasidan dalam struktur glisin dan alanin yang boleh mendorong keadaan pengaratan terhadap aloi karbon.

Kata kunci: Aloi karbon; benzoilalanilglisin metil ester; kaedah Tafel; penebat pengaratan; sintesis dipeptida

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Chemistry Study Program

Faculty of Mathematics and Natural Sciences

Bandung Institute of Technology

Jl. Ganesha 10, Bandung 40132

Indonesia

*Corresponding author; email: juniartiabdurrahman@yahoo.co.id