Formamide electrostatic potential

Momany F A 1978 Determination of partial atomic charges from ab initio molecular electrostatic potentials. Application to formamide, methanol and formic acid J. Phys. Chem. 82 592... 

CM Breneman, KB Wiberg. Determining atom-centered monopoles from molecular electrostatic potentials. The need for high sampling density m formamide conformational analysis. J Comput Chem 11 361-373, 1990. 

Examine the geometry of formamide. Is the CN bond shorter than expected for a normal single bond (in methylamine), and closer to that expected for a full double bond (in methyleneimine) Is the CO bond longer than that expected in a carbonyl compound (in formaldehyde), perhaps closer to that appropriate for a single bond (in methanol) Also, compare the electrostatic potential map for formamide with those of formaldehyde and methylamine. Is the CO bond in formamide more or less polar than that in formaldehyde Is the CN bond in formamide more or less polar than that in methylamine Draw whatever Lewis structures are needed to properly describe the geometry and charge distribution of formamide. 

Electrostatic potential map for formamide shows negatively-charged regions (in red) and positively-charged regions (in blue). 

It has been shown that the electrostatic potentials of formamide calculated at near-Hartree-Fock (HF/6-31G ) and post-Hartree-Fock (MP2/6-31G ) levels are qualitatively similar (Politzer and Murray 1991). Both computational approaches predict the oxygen to be the preferred site for electrophilic attack (Seminario, Murray, and Politzer 1991). It is further noteworthy that SCF results obtained with minimal basis sets (e.g., HF/STO-3G and HF/STO-5G) are also in good agreement with those calculated at the higher computational levels. 

Breneman, C. M. and K. B. Wiberg. 1990. Determining Atom-Centered Monopoles from Molecular Electrostatic Potentials. The Need for High Sampling Density in Formamide Computational Analysis. J. Comp. Chem. 11, 361. 

Ab Initio Molecular Electrostatic Potentials. Application to Formamide, Methanol, and Formic Acid. 

Centered Monopoles from Molecular Electrostatic Potentials. The Need for High Sampling Density in Formamide Conformational Analysis. 

Figure 4. The molecular electrostatic potential generated by the [Zn(NHs)sOH HCONH2]+ complex, simulating the interaction of the active site of carboxypep-tidase with a peptide substrate geometries are from (82). The plane is parallel to the molecular plane of formamide at a distance of 1 A. See legend to Figure 3 for computational details. (Q) 95.0 (Q) 100 (A) 110 ( ) 140 (X) 170 (0) 200 ...

Figure 14. Electrostatic potential isocontour maps for FD at equilibrium a, b) Isolated formamide monomers at the dimer geometry, (c) Dimer. Contours as in Fig. 13.

F. A. Momany, /. Phys. Chem., 82, 592 (1978). Determination of Partial Atomic Charges from Ab Initio Molecular Electrostatic Potentials. Application to Formamide, Methanol, and Formic Acid,... 

Figures 3 and 4 show the electrostatic potentials of formamide (21) calculated at near-Hartree-Fock (HF/6-31G ) and post-Hartree-Fock (MP2/ 6-31G ) computational levels, respectively. There is a distinct qualitative simi-...

Figure 3 Calculated HF/6-3JG electrostatic potential of formamide (21), in kcal/mol, in (a) the plane defined by C, N, and O, and (b) the plane perpendicular to the C, N, O plane passing through the C —N bond. The projections of nuclear positions not in these planes are shown by their atomic symbols. Dashed contours correspond to negative potentials. The positions of the most negative potentials are indicated the values are a) ) -65.9, ( ) -62.3 (b)(B) -32.5, ( ) -11.1,( ) -10.6.

Figure 4 Calculated MP2/6-31G" electrostatic potential of formamide (21), in kcal/mol, in the plane defined by C, N, and O. Dashed contours correspond to negative potentials. The positions of the most negative potentials are indicated the values are ( ) -54.7 ( ) -50.3.

Formamide (HCONH2) has a pA of approximately 25. Predict, based on the map of electrostatic potential for formamide shown here, which hydrogen atom(s) has this pA value. Support your conclusion with arguments having to do with the electronic structure of formamide. 

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