Acetamide hydrogen bonding

Next, the authors explored the 02 mechanism. In this case, the largest model used (15) involved two methylammonium ions and two formate ions to mimic the Lys-Asp-Lys-Asp tetrad, and an acetamide hydrogen-bonded to a water, which interacts with 02, to mimic a glutamine-water bridge found in the Wu-Pai crystal structure.22... 

Cieplak, P., Caldwell, J. W., Kollman, P. A., Molecular mechanical models for organic and biological systems going beyond the atom centered two body additive approximation aqueous solution free energies of methanol and IV-methyl acetamide, nucleic acid base, and amide hydrogen bonding and chloroform/water partition coefficients of the nucleic acid bases, J. Comput. Chem. 2001, 22, 1048-1057... 

Figure 5.64 Hydrogen-bonded and fully protonated acetamide complexes, showing the optimized pseudo-civ conformer for each species.

Tests of the best hydrogen bonding agents in ether-alcohol showed the following compds trimethyl-, trimethallyl-, tributyl phosphates, isophorone, dimethyl acetamide, and dibutyl tartrate were superior to dibutyl phthalate or triacetin in the amts reqd for gelatinization and in the viscosities of the resulting solns... 

Primary amides (except acetamide, whose C=0 bond absorbs at 1694 cm-1) have a strong amide I band in the region of 1650 cm-1 when examined in the solid phase. When the amide is examined in dilute solution, the absorption is observed at a higher frequency, near 1690 cm-1. In more concentrated solutions, the C=0 frequency is observed at some intermediate value, depending on the degree of hydrogen bonding. 

The solvents used for electroanalytical determinations vary widely in their physical properties liquid ranges (e.g., acetamide, N-methyl-acetamide and sulfolane are liquid only above ambient temperatures), vapour pressures (Table 3.1), relative permittivities (Table 3.5), viscosities (Table 3.9), and chemical properties, such as electron pair and hydrogen bond donicities (Table 4.3), dissolving ability of the required supporting electrolyte to provide adequate conductivity, and electrochemical potential windows (Table 4.8). A suitable solvent can therefore generally be found among them that fits the electroanalytical problem to be solved. 

Similar shortening of the C-N bond and lengthening of the C=0 bond is found when the structures of acetamide [376, 377], fluoroacetamide [299], and thioacetamide [204] in the hydrogen-bonded crystals are compared with ab-initio molecular orbital calculations for the isolated molecule, as shown in Thble 5.4. 

Table 5.4. Hydrogen-bonding effects on the covalent-bond lengths in formamide, acetamide, fluoroacetamide and thioacetamide. A (A) refers to differences between values from the neutron diffraction analysis (corrected to rest structure) and the theoretical value for the isolated molecule (at rest) at the HF/3 - 210 level...

Mechanical Models for Organic and Biological Systems Going Beyond the Atom Centered Two Body Additive Approximation Aqueous Solution Free Energies of Methanol and N-Methyl Acetamide, Nucleic Acid Base, and Amide Hydrogen Hydrogen Bonding and Chloroform/Water Partition Coefficients of the Nucleic Acid Bases. 

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