Energy levels in the carbon monoxide molecule

Fig. 1.15. Energy levels in the carbon monoxide molecule. (Adapted from H. B. Gray and G. P. Haight, Basic Principles of Chemistry, W.

A part of the energy-level diagram for carbon monoxide is shown in Figure VII-4. The energy levels have been obtained by analysis of the observed frequencies of the lines in the emission and absorption spectra of the molecule. 

The molecules must be predominantly in their ground state vibrational level, i.e., h(oec/KT < 1, where c is the velocity of light and energy separation of successive levels in wave numbers. For carbon monoxide at68°K with p = 0.8558 g/ccand a>e = 2.170 x 103 cm-1,45 the above factors are 2 x 10"1, 5 x 10 2, and 5 x 101, respectively. Therefore, to a first approximation real liquid carbon monoxide at this temperature and density behaves classically, and our comparisons will be justified. 

This is a noncyclic pathway that also results in the fixation of two molecules of C02 to form acetyl-CoA. It was elucidated by Wood, Ljungdahl, Thauer and others as a pathway which is used by acetogenic bacteria to synthesize acetate from C02 in their energy metabolism [21]. The acetyl-CoA pathway resembles the Monsanto process of acetate synthesis from CO and methanol, with one molecule of C02 being reduced to the level of methyltetrahydropterin, while another C02 molecule is reduced to the level of carbon monoxide in the reaction catalyzed by the nickel-dependent carbon monoxide dehydrogenase (Figure 3.3). 

Fig. 5.20 Energy level diagram for the molecular orbitals of carbon monoxide. Note that upon bond formation electrons occupy orbitals that are more oxygen-like than carbon-like. Note carefully the bond order The Icr and la MOs are essentially nonbonding. The bond order, as in the N2 molecule is three.

The presence of hydrocarbon impurities has been shown to affect the oxidation of carbon monoxide [22] and the decomposition of carbon dioxide [23]. It has been reported that the dissociations of ethane [24] and butane [25] at the elevated temperatures and typical densities of shock tube experiments are in the low pressure region with activation energies that are much less than their respective high pressure limit values. The reaction of p.p.m. levels of hydrogen atoms with the molecule under investigation can result in a low apparent energy for dissociation due to the increased importance of abstraction steps. 

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