Formic acid Atomic charges

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... 

Figure 3 Adsorption energy of monodentate-B adsorbed formic acid on ZnO(lOlO) as a function of coverage. Calculated values (solid lines) are compared to a simple electrostatic model (dashed line) based on the atomic charges, lxn coverages refer to surface cells extended in the (000T) direction, and nxl to extensions in the (1120) direction, nxn cells have been extended in both the (0001) and the (1120) directions.

TABLE 3.8 Atomic Charges" of Formic Acid, Ethanol, and Their Conjugate Bases... 

S. Scheins, B. Dittrich, M. Messerschmidt, C. Pauhnaim and P. Luger, Atomic volumes and charges in a system with a strong hydrogen bond L-tryptophan formic acid, Acta Cryst. B60, 184-190 (2004). 

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,... 

In formic acid and its decomposition products, the directions of the valences or the charges on the atoms are fairly definitely known as definitely perhaps as in any compound. The formula for formic acid is given in the brackets as an equilibrium between the two tautomeric forms as discussed in some detail in Chapter II. It will be noticed that in both formulas, the state of oxidation of the carbon atom is the same, + 2. Formic acid is known to decompose in two ways (a) carbon monoxide and water are formed and... 

This analysis leads to a discussion of the important concept called resonance, which will be used in many places in this book. Reaction of formic acid (acetic acid) and a base gives a carboxylate anion (the formate anion, 79A) as the conjugate base. Note that the three atoms (0=C-0) are connected. One atom (O) has a negative charge, which can be viewed as a full p-orbital (a p-or-bital containing two electrons). In addition, there is an adjacent 7C-bond (C=0). In Figures 5.1-5.3, it is clear that two adjacent and parallel orbitals overlap and share electron density to form a 7C-bond. The concept that adjacent orbitals share electron density can be extended from two orbitals to three, four, or even more. All that is required is that the orbitals are on adjacent atoms and are parallel. Therefore, when three orbitals are on adjacent atoms and are parallel, electron density is shared between all three atoms. 

Comparison of partial atomic charges for methanol, and acetic and formic acid... 

Fig. 1. Variation of partial atomic charge with distance for the H4 and Ois atoms of methanol, and H4 and Oi7 atoms of formic acid Dashed lines follow the CNDO/2 (ON) charges (Reference 12), and the solid lines are empirical. (, Reference 39 A, Reference 40 +, Reference 38). The Aq value of O18 from Reference 38 occurs at a value —0.08 e.c.u. and is not shown.

Dipole moments (Debye) and Mulliken atomic charges (units of electron) for water, methanol, formic acid and formamide in the gas phase (gas) and in aqueous solution (sol)... 

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