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Journal of Applied Sciences
  Year: 2020 | Volume: 20 | Issue: 1 | Page No.: 26-34
DOI: 10.3923/jas.2020.26.34
 
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Protonation of Carbonyl Sulfide: Ab initio Study
Emmanuel Edet Etim , Chrysanthus Andrew, Usman Lawal, Ifeoma Sandra Udegbunam and Etiowo George Ukpong

Abstract:
Background and Objectives: Computational studies have gained popularity nowadays as a means of studying simple and complex chemical systems with a view to complement experimental techniques. Hence the objective of this work was to use different computational methods to study the protonation of carbonyl sulphide, its possible protonated analogues and determine the best site for its protonation which will correspond with the experimentally determined proton affinity. Materials and Methods: In this study, quantum chemical calculations were carried out using GAUSSIAN 09 suite of programs using 5 different levels of theory and two basis sets. Bond lengths and angles, vibrational frequencies, dipole moments and proton affinity (PA) are among parameters of interest that have been calculated for OCS and its protonated analogues. In other to evaluate the best computational method, the difference between the calculated value and the reported experimental data is used as a benchmark. Results: CCSD method along with 6-311++G** gives the best prediction for the bond length in the neutral molecule. G4 predicts best the rotational constants and dipole moments for HOCS+ and OCS respectively. The proton affinity values calculated in this work reveals that the protonation of OCS is more favoured via sulphur atom than via oxygen atom. Thus proton affinity corresponds to the most stable protonated analogue with the proton attached to the site of less electron density hence electronegativity is not a good criterion for predicting the protonation site of a molecule. Conclusion: Optimization of OCS molecule and its protonated analogues was performed. We have shown that the protonation of a molecule can be determined by considering electron density rather than electronegativity.
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How to cite this article:

Emmanuel Edet Etim, Chrysanthus Andrew, Usman Lawal, Ifeoma Sandra Udegbunam and Etiowo George Ukpong, 2020. Protonation of Carbonyl Sulfide: Ab initio Study. Journal of Applied Sciences, 20: 26-34.

DOI: 10.3923/jas.2020.26.34

URL: https://scialert.net/abstract/?doi=jas.2020.26.34

 
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