Kinetic Study and NBO Analysis of the Dehydrogenation Mechanism of Five‐membered Ring Heterocyclic 2,5‐Dihydro‐[furan, thiophene, selenophene | Zendy

Shiroudi Abolfazl | Zendy; Zahedi Ehsan | Zendy

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Kinetic Study and NBO Analysis of the Dehydrogenation Mechanism of Five‐membered Ring Heterocyclic 2,5‐Dihydro‐[furan, thiophene, selenophene

Author(s) -

Shiroudi Abolfazl,

Zahedi Ehsan

Publication year - 2011

Publication title -

chinese journal of chemistry

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 1.28

H-Index - 41

eISSN - 1614-7065

pISSN - 1001-604X

DOI - 10.1002/cjoc.201180388

Subject(s) - natural bond orbital , chemistry , antibonding molecular orbital , computational chemistry , delocalized electron , thiophene , crystallography , density functional theory , dehydrogenation , molecular orbital , furan , non bonding orbital , molecular orbital diagram , atomic orbital , molecule , organic chemistry , linear combination of atomic orbitals , basis set , physics , quantum mechanics , electron , catalysis

The theoretical study of the dehydrogenation of 2,5‐dihydro‐[furan ( 1 ), thiophene ( 2 ), and selenophene ( 3 )] was carried out using ab initio molecular orbital (MO) and density functional theory (DFT) methods at the B3LYP/6‐311G**//B3LYP/6‐311G** and MP2/6‐311G**//B3LYP/6‐311G** levels of theory. Among the used methods in this study, the obtained results show that B3LYP/6‐311G** method is in good agreement with the available experimental values. Based on the optimized ground state geometries using B3LYP/6‐311G** method, the natural bond orbital (NBO) analysis of donor‐acceptor (bond‐antibond) interactions revealed that the stabilization energies associated with the electronic delocalization from non‐bonding lone‐pair orbitals [LP(e) X3 ] to δ* C(1) H(2) antibonding orbital, decrease from compounds 1 to 3 . The LP(e) X3 →δ* C(1) H(2) resonance energies for compounds 1 – 3 are 23.37, 16.05 and 12.46 kJ/mol, respectively. Also, the LP(e) X3 →δ* C(1) H(2) delocalizations could fairly explain the decrease of occupancies of LP(e) X3 non‐bonding orbitals in ring of compounds 1 – 3 ( 3 > 2 > 1 ). The electronic delocalization from LP(e) X3 non‐bonding orbitals to δ* C(1) H(2) antibonding orbital increases the ground state structure stability, Therefore, the decrease of LP(e) X3 →δ* C(1) H(2) delocalizations could fairly explain the kinetic of the dehydrogenation reactions of compounds 1 – 3 ( k 1 > k 2 > k 3 ). Also, the donor‐acceptor interactions, as obtained from NBO analysis, revealed that the ( C(4)C(7) →δ* C(1) H(2) resonance energies decrease from compounds 1 to 3 . Further, the results showed that the energy gaps between ( C(4)C(7) bonding and δ* C(1) H(2) antibonding orbitals decrease from compounds 1 to 3 . The results suggest also that in compounds 1 – 3 , the hydrogen eliminations are controlled by LP(e)→δ* resonance energies. Analysis of bond order, natural bond orbital charges, bond indexes, synchronicity parameters, and IRC calculations indicate that these reactions are occurring through a concerted and synchronous six‐membered cyclic transition state type of mechanism.

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