FT-IR Studies on the Self-Association of N-methylpropionamide in Various Solvents

• Main Authors: Lin, Wei-Chi, 林偉智
• Other Authors: Chen, Jenn-Shing
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/18043221666240168827

碩士 === 國立交通大學 === 應用化學系碩博士班 === 99 === The hydrogen bond between amino acids in proteins plays a crucial role on its stability. In the past few decades the thermodynamic parameters for hydrogen bonding of amino acids and their derivatives have been endeavored to obtain. N-methylpropioamide, the derivatives of amino acids, is choosen for this study. In the very dilute solution, N-methylpropioamide exists trans monomer and linear dimer. And it becomes feasible to accurately study the self-association in various solvents at various temperatures. FT-IR has been employed to this purpose. Upon deconvolution of N-H stretching bands, the dimerization constant and the N-H stretching (N-H…O=C) molar absorptivity of the linear dimer N-H group can be obtained via fitting associated linear dimer N-H stretching (N-H…O=C) intergrated absorbance into equation (2-19). The enthalpy and entropy can be determined via a van’t Hoff plot from temperature-dependent dimeration constants. The N-H stretching molar absorptivities of the trans monomer N-H group and the end N-H group in linear dimer can be obtained via fitting trans monomer N-H stretching intergrated absorbances into equation (2-36). The linearity of dimer form has been confirmed by the plot of Am2/Ad against [B]0 , which appears to be linear with positive slope. Theoretical calculation (appendix A3) also indicates linearity of dimer form. Solvent effect in this study shows that as the dielectric constant of the solvent increases the dimerization constants, enthalpy and entropy will decrease.