Rapid prediction of the hydrogen bond cooperativity in N-methylacetamide chains.
A method is proposed to rapidly predict the hydrogen bond cooperativity in N-methylacetamide chains. The parameters needed are obtained from the fittings to the hydrogen bonding energies in the formamide chains containing 2 to 8 monomeric units. The scheme is then used to calculate the individual hydrogen bonding energies in N-methylacetamide chains containing 2 to 7 monomeric units. The cooperativity predicted is in good agreement with those obtained from MP2/6-31+G** calculations by including the BSSE correction. Our scheme is further employed to predict the individual hydrogen bonding energies in larger N-methylacetamide chains containing up to 200 monomeric N-methylacetamide units, to which the MP2 method cannot be applied. Based on our scheme, a cooperative effect of over 170% of the dimer hydrogen bonding energy in long N-methylacetamide chains is predicted. The method is also applied to heterogeneous chains containing formamide, acetamide, N-methylformamide, and N-methylacetamide. The individual hydrogen bonding energies in these heterogeneous chains are also in good agreement with those obtained from MP2 calculations with the BSSE correction, further demonstrating that our method is reasonable.
Jiang
Xiao-Nan
XN
School of Chemistry and Chemical Engineering, Liaoning Normal University, Dalian 116029, People's Republic of China.
Wang
Chang-Sheng
CS
D000081:Acetamides / Q000737:chemistry*; D000465:Algorithms; D006860:Hydrogen Bonding; D013816:Thermodynamics
D000081:Acetamides; C018595:N-methylacetamide