The Study of Formamide and N-Methylformamide Liquid Structure Based on their Experimental and Theoretically Simulated Raman Spectra

• Main Authors: LEE, JHENG-YI, 李政益
• Other Authors: LEE, YING-TE
• Format: Others
• Language: zh-TW
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/00550922874374381853

碩士 === 逢甲大學 === 光電學系 === 105 === We use the C=O bond Raman spectral asymmetry and Gaussian09 simulation to propose cluster structures of Formamide(F) and N-Methylformamide(MF) in pure, aqueous and methanol solutions. The revised C=O peak fitting of the previously studied F aqueous solution, and those of solutions mentioned above show that the spectral area of lower frequency is greater than that of high frequency. These cluster structures include F pure solution: dimer and tetramer; MF pure solution: dimer and monomer; F aqueous, methanol solution and MF aqueous solution: dimer with two solvent molecules (dimer+2) and monomer with one solvent molecule (monomer+1); MF methanol solution: dimer with one solvent molecule (dimer+1) and monomer with one solvent molecule (monomer+1). We use two peaks to fit the spectral same as the former research’s method. But in the F and MF pure solution, we use three peaks to fit the spectral different from former research. These fitting method can agree with the cluster structure above-mentioned. For example, the scaling factors calculated by the simulated Raman shifts of clusters and experimental Raman shifts are close to the values provided by National Institute of Standards and Technology (NIST). The simulated Raman activities of these clusters also agree with the experimental spectral area ratio of lower frequency band to the higher frequency band. Additionally, these spectral area ratio results also agree with the calculated hydrogen bonding energies of various clusters. We use Morse potential and Raman shifts form C=O spectral to find out the interaction relationship between solute and solvent molecules. The relationship in F solution is F+F > F+ water > F+ methanol; MF solution: MF+MF > MF+ water > MF+ methanol. The similar trends are also found in the simulated dipole moments of these “monomer+1” clusters corresponding to higher frequency C=O bond spectral. Since the order of hydrogen bonding energies of these clusters slightly deviate away from this trend, we expect that the dipolar interactions are playing greater roles than the hydrogen bonding in these solutions.