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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 19, Number 1
BKCSDE 19(1)
January 20, 1998 

Basicity of Urea: Near-Infrared Spectroscopic and Theoretical Studies on the Hydrogen Bonding Ability of TMU and DMDPU
Ho-Jin Lee, Jeunghee Park, Chang-Ju Yoon, Young Sang Choi*
The hydrogen-bonding interactions between thioacetamide (TA) and urea derivatives such as tetramethylurea (TMU) and dimethyldiphenylurea (DMDPU) have been studied using near-infrared absorption spectroscopy. Thermodynamic parameters for the interactions between TA and urea derivatives were determined by analyzing the νasN-H + Amide Ⅱ combination band of TA at 1970 nm. The ΔH°values, indicating the intrinsic strength of hydrogen bonding, are - 23.0 kJ/mole and - 19.8 kJ/mol for TMU and DMDPU, respectively. This is well explained by the inductive effects of substituents. Ab initio molecular orbital calculations for the proton affinity of TMU, N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMA) in gas phase have been carried out at HF/3-21G ad HF/6-31G(d) levels, showing that the proton affinity of TMU is larger than that of DMA, which agrees well the experimental results.
110 - 114
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