Molecular Self-Assembling of -Methylacetamide in Solvents

Hideyuki Minami,Makio Iwahashi

doi:10.1155/2011/640121

Abstract

The self-association of -methylacetamide (NMA), which is one of the most simple compound having a peptide bond, in various solvents such as carbon tetrachloride (CCl4), chloroform, dichloromethane, and acetonitrile was studied through the near-infrared (NIR) spectroscopic observation at various temperatures and concentrations. An analysis assuming a successive association processes for the NMA molecules was applied to the sharp 1470-nm band (the first-overtone band of NH stretching vibration mode attributed to free NH group of NMA monomer and partly to the free, terminal NH group of NMA aggregate); the mean association number for NMA in CCl4 increases with increasing concentration and decreases with increasing temperature. Comparisons of the association number of NMA in various solvents indicate that the degree of association is in the following order: chloroform ≒ dichloromethane acetonitrile. Interestingly, the association number of NMA in CCl4 is thought to be larger than that in its pure liquid.

Highlights

Near-infrared (NIR) spectroscopy is a useful analytical method for practical materials [1] and has been applied to various industrial and agricultural problems [2, 3]
International Journal of Spectroscopy of CH3OD at 40◦C, and by the distillation of the alcohol
The densities for the samples of pure liquid and the CCl4 solution of NMA were measured on a vibration-type densimeter (Anton Paar Model DMA 58) over temperature range of 10.0–65.0 ± 0.05◦C

Summary

Introduction

Near-infrared (NIR) spectroscopy is a useful analytical method for practical materials [1] and has been applied to various industrial and agricultural problems [2, 3]. NIR spectroscopy has such important technical merits that a liquid quartz cell with the path length of 10 mm or more can be used, remote spectroscopy is applicable, and so on. To make full use of the advantages, it is absolutely important to utilize the analytical information which NIR absorptions possess. Hydrogen-bonding interactions are known to be important in determining the structural properties of proteins. Among the forces that contribute to the stabilization of configuration of protein molecules in solution, intramolecular hydrogen bonds have often been assigned a key role. We measured the NIR spectroscopy of NMA in various solvents such as CCl4, CHCl3, CH2Cl2, and CH3CN and calculated the aggregation number by assuming a successive association processes for NMA molecules

Experimental

Results and Discussion

Conclusions