Bond distances formic acid

Table 2.37 Optimized interoxygen distance and thermodynamics of H-bond between formic acid and water or CH NH, calculated with 6-3IG basis set"". Energetics not corrected for BSSE,...

This isotopic difference is small and has been scarcely measured. A difference of -0.02 A for O- O distances in the H-bonds and D-bonds of formic acid dimers in the gas phase has been measured by electron diffraction (1) as covered in Ch. 3. These dimers are excellent models of H-bonds. Their strnctnre is drawn in Figures 1.6 and 4.4. From the analysis of the shape of their bands, developed in Ch. 5 and from which the equations developed in the appendix of this chapter are dednced, a value for the dimensionless parameter b that characterizes the anharmonic coupling between and intermonomer modes and is proportional to dcoldQ, following the eqnation... 

The formation of hydrocarbons from thermal decomposition of formic acid at room pressure and high temperature (1696 K) has been reported by Muller et al. [142]. In our study we also find evidence of hydrocarbons and note how their spectral features depend on reaction conditions. At 3 GPa and room temperature, the nature of O-H bonds from formic acid become more covalent-like with increasing temperature. Once a reaction occurs the long-range order of the O-H network in crystalline formic acid becomes disrupted with bond distances increasing to a more hydrogen-like bond length centered at frequency of approximately 3500 cm" . 

Contrary to all other reactions with acids the behaviour of the zwitterion towards vapours of formic acid is intriguing, since no proton transfer is observed. The formic acid vapour uptake generates a material composed of pairs of zwitterion molecules, linked by O-H- - O bonds between the protonated -COOH and the deprotonated -COO() groups [0---0 separation 2.526(4) A] residing on the organometallic moiety. The zwitterion dimers interact with two formic acid molecules via 0-H---0 and C-H---0 hydrogen bonds [0---0 distance 2.541(4),... 

Quantum-chemical calculations of the formic acid dimer structure were carried out by Graf et al. [1981] and Meier et al. [1982]. The bond lengths and angles in the ground and transition states are listed in Table 6.3. Hydrogen transfer in two OH----O fragments occurs when the distance... 

Table 9 Selected optimized bond distances of formic acid monomers, dimer, and chains as obtained with an ST0-3G basis. All values in bohr.

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