الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The calculations showed that, the Keto form is the most stable form in the gas phase. The ability to form dimer, trimer and tetramer was investigated concerning the energetical changes; dipole moments using the RHF/6-31G(d) level of computation. The thermodynamic parameters at different temperatures were studied.The results showed that, there is a high interconversion process between the cyclic and open dimer. Also, the probability to form higher association forms is presumably rare. At room temperature 2- pyrrolidinone only could exist in a dimer form in equilibrium with the monomer. The ability of 1-methyl-2-pyrrolidinones (NMP) to form dimer was investigated using the B3LYP/6-311G(d,p) level of computation. The thermodynamic parameters at different temperatures for the association process of 1-methyl-2-pyrrolidinones (NMP) to form dimer were studied using the PM3 semiemperical method. the results of theoretical investigation of the ground state geometry of 2-pyrrolidinone (2-py) and its 1-methyl-2- pyrrolidinones (NMP) derivative using different levels of computation. Results indicated that the 2-py and the NMP molecules exist in a twist C1 conformation, where the other possible five membered ring conformer, the envelope form, was not found to be a stable form. The planar form was found to be a transition state in both molecules with a barrier to planarity 0.97 Kcal/mol in the 2-py molecule and with 0.77 kcal/mol in the NMP molecule. The ring puckering of both molecules were theoretically discussed. The structural parameters of the two dimeric forms of the 2-py molecule (cyclic and open dimer) were theoretically determined and compared to that of the 2-py in the monomer form. Also, the structural parameters of the possible dimeric form of the NMP molecule were obtained theoretically and compared to that of the monomer NMP structural parameters. results of normal coordinate calculations using the GF-Matrix method for 2-pyrrolidinone (2-py) and its 1-methyl-2-pyrrolidinone (NMP) derivative. All observed vibrational wave numbers in the infrared and Raman spectra of these molecules were assigned to fundamental modes of vibration on the basis of the PED’s obtained from the normal coordinate analysis, as well as their corresponding theoretically calculated values using the B3LYP/6-31G(d) level of calculation. A good agreement was found between the computed and the experimentally wave numbers.