N, N-dimethyl Formamide / Alcohol System Spectroscopic Studies And Association Model For Theoretical Research

Investigation of the association phenomenon in solution system, is always the object chemists pay attention to, because the conclusion association phenomena resulted from molecules reciprocity all play a pivotal role for chemical or physical properties of both organism system and abiological system. The paper studies the system N,N-Dimethylformamide with alcohol using spectroscopy and quantum chemistry.We study the association model of the system, DMF/alcohol, using IR spectrum and NMR. The finding indicates: following the increase by degrees of alcohol mole fraction, the hydrogen bond formed by association becomes of stronger, hydroxyl proton IR vibrational wave number shows "blue shift", and the chemical shifts increase gradually. We bring forword the concept of excess IR vibrational wave number on the basis of excess chemical shift, and find when the highest excess chemical shift appears with the hightest of excess IR vibrational wave number, indicating that both of them are well in agreement.Adopting quantum chemistry computational methods we compute the binding energy of the association and IR vibrational wave number between different number of methanol molecules and single DMF molecule. As a result, methanol molecules first associate with a carbonyl, then the unassociated methanol molecules can self-associate with the associated methanol molecules. Along with DMF concentration increasing, the carbonyls that associate different numbers methanol molecules IR vibrational wave number also increase, appear red shift, which is in good agreement with experiment result. Their bond length increase gradually, which shows the formed hydrogen bond weaker and weaker.