Carbon Atom Of CO Research Articles

Microwave Fourier Transform Spectrum of the Water-Carbon Disulfide Complex

The microwave spectrum of the water-carbon disulfide complex has been observed with a pulsed-beam, Fabry-Perot cavity, Fourier transform microwave spectrometer. In addition to the normal isotopic form, we have also observed the spectrum of H2O-34SCS, HDO-CS2, HDO-34SCS, D2O-CS2, and D2O-34SCS. The rotational constants are B = 1030.1109(6) MHz and C = 1026.2912(6) MHz for H2O-C52; B = 1028.4595(8) MHz and C = 1024.6511(8) MHz for HDO-SC34S; (B + C)/2 = 990.5359(8) MHz for HDO-CS2 (B + C)/2 = 989.2168(2) MHz for HDO-34SCS; B = 959.3024(8) MHz and C = 953.5587(8) MHz for D2O-CS2; and B = 958.2422(6) MHz and C = 952.5114(6) MHz for D2O-34SCS, respectively, with uncertainties of two standard deviations shown in parentheses. Stark effect measurements for H2O-CS2 give a dipole moment of 6.931(34) × 10−30 Cm [2.078(10) D]. The most probable structure of H2O-CS2 is C2v planar with the sulfur atom of carbon disultide bonded to the oxygen atom of water. The oxygen-sulfur van der Waals bond length is calculated to be 3.20 Å. The structure of H2O-SCS is unusual because the structure of the isoelectronic molecule, H2O-CO2 is known to be T-shaped with an OC van der Waals bond, i.e., the oxygen atom of water bonded to the carbon atom of CO2.

Ab initio MO calculations on the stable conformations and their binding energies of the ion-molecule complexes: Ion = H+, Li+, Na+, K+ Be2+, and molecule = CO and N2

Abstract The most stable conformation of ion-molecule complexes involving a CO molecule were surveyed by the use of Hartree-Fock (HF) MO and third-order Moller-Plesset perturbation (MP3) methods with a 6–31G* basis set ion = H + , Li + , Na + , K + , Bc 2+ , Mg 2+ , and Ca 2+ . The MP3 level of theory reveals the ion-CO conformation in which the ion bonds to a carbon atom of CO to be the most stable; these MP3 results are contrary to the HF ones. Binding energies of ion-molecule complexes involving CO and N 2 were computed; MP3 energies are in good agreement with the experimental ones. The computed binding energies of cation-N 2 are about one-third of cation-NH 3 due to the absence of dipole moment and the smaller polarizability of N 2 . The decrease in binding energy in cation-CO and -N 2 complexes, with increasing cation size, is mainly caused by the decrease of the electrostatic and polarization stabilizations.

Theoretical study of the relative stabilities of H+(X)2 and H+(X)3 conformers and their clustering energies: X  CO and N2

AbstractThird‐order Møller–Plesset perturbation theory (MP3) with a 6‐31G** basis set was applied to study the relative stabilities of H+(X)2 conformations (X  CO and N2) and their clustering energies. The effect of both basis set extensions and electron correlation is not negligible on the relative stabilities of the H+(CO)2 clusters. The most stable conformation of H+(CO)2 is found to be a C∞v structure in which a carbon atom of CO bonds to the proton of H+(CO), whereas that of H+(N2)2 is a symmetry D∞h structure. The second lowest energy conformations of H+(CO)2 and H+(N2)2 lie within 2 kcal/mol above the energies of the most stable structures. Clustering energies computed using MP3 method with the 6‐31G** basis set are in good agreement with the experimental findings of Hiraoka, Saluja, and Kebarle. The low‐lying singlet conformations of H+(X)3 (X  CO and N2) have been studied by the use of the Hartree–Fock MO method with the 6‐31G** basis set and second‐order Møller–Plesset perturbation theory with a 4‐31G basis set. The most stable structure is a T‐shaped structure in which a carbon atom of CO (or a nitrogen atom of N2) attacks the proton of the most stable conformation of H+(X)2 clusters.

Is the oxygen atom of carbon monoxide coordinated to the copper of hemocyanin?

The carbon monoxide binding site of hemocyanins was studied by comparing the isotope shift of the CO-stretching frequencies in CO-hemocyanins with that of carbon monoxide diethylenetriaminecopper(I)tetraphenylboron in which the carbon atom of CO is coordinated to the copper. Coordination by the carbon atom of CO in CO-hemocyanin is suggested.

An infrared study of carbon monoxide complexes of hemocyanins

A vibrational analysis was carried out showing that the infrared experimental data of 13C and 18O carbon monoxide complexes of hemocyanin of Fager and Alben (Biochemistry 11 (1972) 4786) are consistent with a coordination of the carbon atom of CO to one of the two copper ions in the active site. This conclusion contradicts the original interpretation of Fager and Alben in which oxygen-coordination to copper was suggested. This vibrational analysis can also be applied to the study of Alben and Caughey (Biochemistry 7 (1968) 175) with 13C and 18O carbonyl hemoglobin, in which oxygen-coordination to iron was suggested. Carbonyl hemocyanins from several sources have also been studied by infrared spectroscopy. The single stretching vibration of CO bound to arthropodal (Cancer magister) hernocyanin (nu(co)) is at 2042.5 cm(-1), while nu(CO) for gastropod (Helix pomatia of the phylum Mollusca) alpha and beta hemocyanin is at 2064.5 cm(-1)and 2062.5 cm(-1), respectively. The intensities of the CO stretching bands were all around 1.5 X 10(4) M(-1) cm(-2). Calculations show that with the present attainable accuracy it is impossible to detect hydrogen bonding of exchangeable protons to small molecules bound to proteins (for example CO), by comparing its stretching frequencies in H2O and D2O buffers.