Density functional studies on the electronic structure, polarizability and thermal properties of eugenol and carvacrol
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Author:
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ANUPAM SHARMA, O. P. SINGH, A. K. SHARMA, ANIL K. SHARMA, ANIL KUMAR
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Abstract:
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Density functional theory (DFT) has been applied to compute atomization energy (AE), electron affinity (EA), and
ionization potential (IP) of eugenol and carvacrol compounds derived from Ocimum tenuiflorum (Tulsi). These
calculations have been carried out by using DFT(B3LYP)/6- 31G(d) geometries, zero point corrections and
DFT(B3LYP)/ 6-31+G(d,p) energies. It was observed that neutral form of eugenol possesses polarizability as
compared to carvacrol, which explain the dynamical response of eugenol to the external perturbations and provide
insight into their behaviour to different receptors inside human body. Redistribution of charges on carvacrol was
reported to be over larger range (-0.628e to 0.628e) but every ring H of eugenol had greater degree of positive
charge. Bond length of O-H in Eugenol was found to be 0.9626A0 which was greater than that of Carvacrol O-H.
Further bond lengths of methyl group of C11-H12, C11-H13, C11-H14 in Eugenol and C20-H21, C20-H22, C20-H23
of Carvacrol were compared. Bond lengths of methyl group was found to be greater in Carvacrol than Eugenol. This
led us to conclude that Eugenol displays higher reactivity than carvacrol. Quantum mechanical study of thermal
properties, electronic structure, polarizability and electorstatic potential surface study further suggests that eugenol
has greater reactive sites as compared to carvacrol. Further comparison of total energy from the ADMP calculations
with DFT(B3LYP) at 6-31G(d) level explains the greater stability of carvacrol.
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Keyword:
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Quantum chemical calculations; DFT; HF; electronic structure; dipole moment; polarizability; atomization energy; Ionization potential
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EOI:
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DOI:
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https://doi.org/10.31838/ijpr/2019.11.03.026
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