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Chemistry LibreTexts

17.3: Use of the Reaction With Bio Derived Molecules

  • Page ID
    306560
  • Synthesis of S-Methyl L-Cysteine from L-Cysteine

    Figure \(\PageIndex{1}\): Synthesis of S-methyl L-Cysteine from L-Cysteine

     

    Figure 1 shows the synthesis of S-Methyl L-Cysteine from L-Cysteine and Methyl Iodide.

    Example of Use with a Bio-based Molecule:


    There is an article called “The Species- and Site-Specific Acid–Base Properties of Biological Thiols and their Homodisulfides” by Béla Noszál and Arash Mirzahosseini. The purpose of this study was to determine the basicity of a few thiols and their respective sulfides that they form. In this case, the reaction being looked at is the synthesis of S-methyl-L-cysteine from L-cysteine (a bio-based molecule) and methyl iodide. 

    The results show that 0.24 g L-cysteine produced 0.22 g product, which is an 82% yield. As for basicity, cysteine has macroscopic protonation constants of log K1 = 10.39, log K2 = 8.52, and log K3 = 2.02. Meanwhile, S-methyl cysteine has protonation constants of log K1 = 8.84 and log K2 = 2.02.³

    Sources:

    ³Mirzahosseini, A.; Noszál, B. The Species- and Site-Specific Acid–Base Properties of Biological Thiols and Their Homodisulfides. Journal of Pharmaceutical and Biomedical Analysis 2014, 95, 184–192.