The Theoretical Research of Constitutive Property, Reactivity and FTIR of Chitosan

2010 ◽  
Vol 658 ◽  
pp. 177-180
Author(s):  
Juan Qin Xue ◽  
Dan Dan Wen ◽  
Li Hua Yu ◽  
Yu Jie Wang ◽  
Jun Zhu
Keyword(s):  
Molecular Orbital ◽  
Active Sites ◽  
Density Functional ◽  
Basis Set ◽  
Theoretical Research ◽  
Rotational Isomers ◽  
B3lyp Method ◽  
Stability Order ◽  
The Stability ◽  
Experimental Values

The structural optimization and the frequency for chitosan monomer, chitobiose and chitotriose with the quantum chemistry abinitio HF and the density functional B3LYP method by choosing 6-311 + G (d, p) as the basis set were calculated and studied. For its three rotational isomers, gauche-trans (gt), gauche - gauche (gg), and trans-gauche (tg), the calculations comparatively were performed respectively. The charge distribution and frontier molecular orbit were analyzed by using the method of natural bond orbital (NBO). The calculated IR spectrum was compared with the experimental data. The results showed that the three rotational isomers gt, gg, and tg can stably existed in chitosan with the stability order gg﹥gt﹥tg. Its highest occupied molecular orbital (HOMO) was provided primarily by nitrogen atom and its lowest unoccupied molecular orbital (LUMO) was provided mainly by the oxygen atom; Its reaction active sites were concentrated in -NH2 and –OH. The calculated infrared spectra were in good agreement with the experimental values.

Molecular Structural and Vibrational Spectroscopic Assignments of n5-(4-Methoxyphenyl)-3-(1-methylindol-3-yl)-isoxazole using DFT Theory Calculations

2019 ◽  
Vol 4 (3) ◽  
pp. 147-151
Author(s):  
J. Jani Matilda ◽  
T.F. Abbs Fen Reji
Keyword(s):  
Molecular Orbital ◽  
Density Functional ◽  
Population Analysis ◽  
Nbo Analysis ◽  
Basis Set ◽  
Atomic Charges ◽  
Dft Methods ◽  
Mulliken Population ◽  
B3lyp Method ◽  
Experimental Values

In an effort to evaluate and design fast, accurate density functional theory (DFT) methods for 5-(4- methoxyphenyl)-3-(1-methylindol-3yl)isoxazole compound was done using Gaussion’ 09 program package using B3LYP method with the 6-31G basis set, which has been successfully applied in order to derive the optimized geometry, bonding features, harmonic vibrational wave numbers, NBO analysis and Mulliken population analysis on atomic charges in the ground state. Optimized geometries of the molecule have been described and collate with the experimental values. The experimental atomic charges demonstrates adequate concurrence with the theoretical prediction from DFT. The theoretical spectra values have been interpreted and compared with the FT-IR spectra. The calculated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy gaps also confirm that charge transfer takes place within the molecule.

scholarly journals Molecular Structure and Vibrational Analysis of 1-Bromo-2-Chlorobenzene Using ab initio HF and Density Functional Theory (B3LYP) Calculations

2011 ◽  
Vol 2011 ◽  
pp. 1-10 ◽  
Author(s):  
G. Shakila ◽  
S. Periandy ◽  
S. Ramalingam
Keyword(s):  
Density Functional ◽  
Vibrational Analysis ◽  
Vibrational Frequencies ◽  
Basis Set ◽  
Geometrical Parameters ◽  
B3lyp Method ◽  
B3lyp Calculations ◽  
Ft Ir ◽  
Experimental Values ◽  
Ft Raman

The FT-Raman and FT-IR spectra for 1-bromo-2-chlorobenzene (1B2CB) have been recorded in the region 4000–100 cm−1 and compared with the harmonic vibrational frequencies calculated using HF/DFT (B3LYP) method by employing 6-31+G (d, p) and 6-311++G (d, p) basis set with appropriate scale factors. IR intensities and Raman activities are also calculated by HF and DFT (B3LYP) methods. Optimized geometries of the molecule have been interpreted and compared with the reported experimental values of some substituted benzene. The experimental geometrical parameters show satisfactory agreement with the theoretical prediction from HF and DFT. The scaled vibrational frequencies at B3LYP/6-311++G (d, p) seem to coincide with the experimentally observed values with acceptable deviations. The theoretical spectrograms (IR and Raman) have been constructed and compared with the experimental FT-IR and FT-Raman spectra. Some of the vibrational frequencies of the benzene are affected upon profusely with the halogen substitutions in comparison to benzene, and these differences are interpreted.

scholarly journals Crystallographic and DFT Studies on Pyrrolo[1,2-c]imidazole Scaffolds

2014 ◽  
Vol 2014 ◽  
pp. 1-8
Author(s):  
Manikandan Jayaraman ◽  
Rajarathinam Balakrishnan ◽  
Kannan Muthu ◽  
Manivel Panneerselvam ◽  
Vasuki Gnanasambandam ◽  
...  
Keyword(s):  
Density Functional ◽  
Crystal Packing ◽  
Stable State ◽  
Chair Conformation ◽  
Unit Cell ◽  
Basis Set ◽  
Monoclinic Space Group ◽  
Cell Parameters ◽  
B3lyp Method ◽  
The Stability

The crystal structures of the compounds C15H14N4O2 (1) and C16H16N4O4 (2) are reported and analyzed by single crystal X-ray diffraction technique. Compounds (1) and (2) crystallized in monoclinic space group P21/c and Cc with four molecules in the unit cell, respectively. The unit cell parameters for compound (1) are a = 11.4501(15) Å, b = 9.7869(11) Å, c = 12.3653(15) Å, β = 90.997(11)°, and Volume = 1385.5(3) Å3 and for compound (2) are a = 13.865(2) Å, b = 6.9538(8) Å, c = 16.841(2) Å, β = 98.602(11)°, and Volume = 1605.4(4) Å3. In both compounds (1) and (2), the pyrrolidine ring adopts half-chair conformation. Moreover, both inter- and intramolecular N–H⋯O hydrogen bonds stabilize the crystal structure and play a crucial role in crystal packing. This intermolecular interaction alone constructs C11 chain motif in both compounds. It is also supported by weak intermolecular π-π interaction which is essential for the stability of the crystal packing. Further, the Density Functional Theory (B3LYP) method with standard 6-31G basis set was used in the calculation and calculated geometrical parameter is correlated with the corresponding experimental data. The obtained HOMO and LUMO energies are in negative values indicating that the compounds are in stable state.

scholarly journals Synthesis, characterization, DFT, and TD-DFT studies of (E)-5-((4,6-dichloro-1,3,5-triazin-2-yl)amino)-4-hydroxy-3-(phenyldiazenyl)naphthalene-2,7-diylbis(hydrogen sulfite)

2021 ◽  
Vol 3 (7) ◽  
Author(s):  
Hitler Louis ◽  
Obieze C. Enudi ◽  
Joseph O. Odey ◽  
Izubundu B. Onyebuenyi ◽  
Azuaga T. Igbalagh ◽  
...  
Keyword(s):  
Molecular Orbital ◽  
Density Functional ◽  
Energy Gap ◽  
Nbo Analysis ◽  
Basis Set ◽  
Orbital Interactions ◽  
B3lyp Method ◽  
Td Dft ◽  
Donor Acceptor ◽  
Molecular Orbital Analysis

AbstractIn this study, (E)-5-((4,6-dichloro-1,3,5-triazin-2-yl)amino)-4-hydroxy-3-(phenyldiazenyl)naphthalene-2,7-diylbis(hydrogen sulfite), a cyanurated H-acid (CHA) azo dye, was synthesized and characterized using FT-IR spectrophotometer and GC-MS spectroscopy. A density functional theory (DFT) based B3LYP and CAM-B3LYP method with 6–311 + G (d,p) basis set analysis was computed for HOMO-LUMO, natural bonding orbitals (NBO), UV-Vis absorptions and excitation interactions, in order to understand its molecular orbital excitation properties. A low Energy gap (Eg) of 2.947 eV was obtained from the molecular orbital analysis, which showed that HOMO to LUMO transition is highly feasible; hence CHA is adequate for diverse electronic and optic applications. Studies of the first five excitations (S0 → S1/S2/S3/S4/S5) of CHA revealed that S0 → S1 and S0 → S3 are π → π* type local excitations distributed around the –N=N– group; S0 → S2, a Rydberg type local excitation; S0 → S4, a highly localized π → π* excitation; while S0 → S5 is an n → π* charge transfer from a benzene ring to –N=N– group. From NBO analysis, we obtained the various donor–acceptor orbital interactions contributing to the stabilization of the studied compound. Most significantly, some strong hyper-conjugations (n → n*) within fragments, and non-bondingand anti-bonding intermolecular (n → n*/π* and π → n*/π*) interactions were observed to contribute appreciable energies. This study is valuable for understanding the molecular properties of the azo dyes compounds and for synthesizing new ones in the future.

Theoretical Studies on the Chemical Structure of Carboxymethyl Chitosan

2010 ◽  
Vol 160-162 ◽  
pp. 1822-1827
Author(s):  
Xi Lu ◽  
Juan Qin Xue ◽  
Yu Jie Wang ◽  
Wei Bo Mao ◽  
Ming Wu ◽  
...  
Keyword(s):  
Active Sites ◽  
Density Functional ◽  
Carboxymethyl Chitosan ◽  
Water Soluble ◽  
Functional Theory ◽  
Molecular Orbit ◽  
The Density Functional Theory ◽  
Stability Order ◽  
The Stability ◽  
The One

The density functional theory (DFT) calculations explored the structural optimization and the frequency of N-carboxymethyl chitosan (N-CMCS) and O-carboxymethyl chitosan (O-CMCS). For the isomers, the calculations comparatively were performed. The charge distribution and frontier molecular orbit were analyzed by using the natural bond orbital (NBO) method. The results showed: the two rotational isomers a and b can stably exist, with the stability order a>b; N-carboxymethyl chitosan reaction active sites are concentrated in -OH and -NHCH2COOH, while O-carboxymethyl chitosan reaction active sites are concentrated in -NH2 and -CH2COOH; The water-soluble mechanism of carboxymethyl chitosan was investigated deeply, on the one hand, the presence of carboxymethyl of carboxymethyl chitosan had a tendency to ionize H+, on the other hand the carboxymethyl increased the distance and weakened the hydrogen bonds between molecules, even though Einstein shift H-bond is formed in the carboxymethyl chitosan molecules.

MOLECULAR STRUCTURE, VIBRATIONAL ASSIGNMENTS, CONFORMATIONAL STABILITY, GROUND AND EXCITED STATE HYDROGEN-BONDING ANALYSIS OF 2-NITROSO VINYL AMINE

2013 ◽  
Vol 12 (07) ◽  
pp. 1350072 ◽  
Author(s):  
FARIBA MOLLANIA ◽  
HEIDAR RAISSI
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Bonding ◽  
Excited State ◽  
Molecular Orbital ◽  
Density Functional ◽  
Dominant Factor ◽  
Potential Energy Distribution ◽  
Functional Theory ◽  
Stability Order ◽  
The Stability

In the present work, a detailed conformational study is performed using several computational methods, including density functional theory (DFT) (B3LYP), MP2 and G2MP2 on 2-Nitroso vinyl amine (NVA) in order to determine the stability order of conformers and the various possibilities of intramolecular hydrogen bonding (HB) formation. Four conformers exhibit HB . This feature, although not being the dominant factor in energetic terms, appears to be of foremost importance to define the geometry of the molecule. According to our theoretical results, oximimine conformers are more stable than the corresponding nitrosoamine and nitrosoimine analogues. Theoretical calculations show the following order for intramolecular HB strength in the conformers of title compound: [Formula: see text] The nature of intramolecular HB has been investigated by means of the Bader theory of atoms in molecules (AIM) and natural bond orbital (NBO) analysis. Also, Harmonic Oscillator Model of Aromaticity (HOMA) index as a geometrical indicator of a local aromaticity are investigated. The influence of the solvent on the stability order of conformers and the strength of intramolecular HB is considered using the Onsager reaction field model. The calculated highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energies confirm that charge transfer occur within the molecule. Further verification of the obtained transition state structures were implemented via intrinsic reaction coordinate (IRC) analysis. Calculations of the 1 H NMR chemical shift at GIAO/B3LYP/6–311++G** levels of theory are also presented. The excited-state properties of intramolecular HB in H -bonded systems have been investigated theoretically using the time-dependent density functional theory (TD-DFT) method. The complete vibrational assignment for three H -bonded conformers has been made on the basis of the calculated potential energy distribution (PED).

scholarly journals Structure, MESP and HOMO-LUMO study of 10-Acetyl- 10H-phenothiazine 5-oxide using vibrational spectroscopy and quantum chemical methods

BIBECHANA ◽  
2012 ◽  
Vol 9 ◽  
pp. 38-49
Author(s):  
Bhawani Datt Joshi ◽  
Poonam Tandon ◽  
Sudha Jain
Keyword(s):  
Molecular Orbital ◽  
Density Functional ◽  
Energy Gap ◽  
Geometry Optimization ◽  
Basis Set ◽  
Orbital Energy ◽  
Potential Energy Distribution ◽  
Hartree Fock ◽  
Quantum Chemical Methods ◽  
B3lyp Method

In this communication, we have presented the geometry optimization, complete vibrational study with potential energy distribution (PED) and frontier orbital energy gap for the 10-Acetyl-10H-phenothiazine 5-oxide (APTZ) molecule using ab initio Hartree-Fock (HF) and density functional theory (DFT/B3LYP) method employing 6-311++G(d,p) basis set. The calculated IR and Raman spectra with their intensities, molecular electrostatic potential (MESP) surface and highest occupied molecular orbital (HOMO) - lowest unoccupied molecular orbital (LUMO) plot have been given. DOI: http://dx.doi.org/10.3126/bibechana.v9i0.7151 BIBECHANA 9 (2013) 38-49

scholarly journals Normal Modes, Molecular Orbitals and Thermochemical Analyses of 2,4 and 3,4 Dichloro Substituted Phenyl-N-(1,3-thiazol-2-yl)acetamides: DFT Study and FTIR Spectra

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Ambrish K. Srivastava ◽  
Anoop K. Pandey ◽  
B. Narayana ◽  
B. K. Sarojini ◽  
Prakash S. Nayak ◽  
...  
Keyword(s):  
Density Functional ◽  
Normal Modes ◽  
Basis Set ◽  
Potential Energy Distribution ◽  
Vibrational Modes ◽  
Perfect Agreement ◽  
B3lyp Method ◽  
Functional Scheme ◽  
Experimental Values ◽  
Homo Lumo

A detailed spectroscopic analysis of two dichloro substituted phenyl-N-(1,3-thiazol-2-yl)acetamides at 2,4 and 3,4 positions of the phenyl ring has been carried out by using B3LYP method with 6-31+G(d, p) basis set within density functional scheme. The scaled theoretical wave numbers are in perfect agreement with the experimental values and the vibrational modes are interpreted in terms of potential energy distribution (PED). The internal coordinates are optimized repeatedly to maximize the PED contributions. The molecular HOMO-LUMO surfaces, their respective energy gaps, and MESP surfaces have also been drawn to explain the chemical activity of both molecules. Various thermodynamic parameters are presented at the same level of theory.

Quantum Mechanical Investigation of Geometrical Structure and Dynamic Behavior of h-BNNT (9,9-5) and h-AlNNT (9,9-5)Single-Walled Nanotubes: NBO Analysis

2019 ◽  
Vol 16 (9) ◽  
pp. 705-717
Author(s):  
Mehrnoosh Khaleghian ◽  
Fatemeh Azarakhshi
Keyword(s):  
Carbon Nanotubes ◽  
Density Functional ◽  
Structural Parameters ◽  
Energy Levels ◽  
Nbo Analysis ◽  
Electronic Energy ◽  
Boron Nitride Nanotubes ◽  
Basis Set ◽  
B3lyp Method ◽  
Mechanical Investigation

In the present research, B45H36N45 Born Nitride (9,9) nanotube (BNNT) and Al45H36N45 Aluminum nitride (9,9) nanotube (AlNNT) have been studied, both having the same length of 5 angstroms. The main reason for choosing boron nitride nanotubes is their interesting properties compared with carbon nanotubes. For example, resistance to oxidation at high temperatures, chemical and thermal stability higher rather than carbon nanotubes and conductivity in these nanotubes, unlike carbon nanotubes, does not depend on the type of nanotube chirality. The method used in this study is the density functional theory (DFT) at Becke3, Lee-Yang-Parr (B3LYP) method and 6-31G* basis set for all the calculations. At first, the samples were simulated and then the optimized structure was obtained using Gaussian 09 software. The structural parameters of each nanotube were determined in 5 layers. Frequency calculations in order to extract the thermodynamic parameters and natural bond orbital (NBO) calculations have been performed to evaluate the electron density and electrostatic environment of different layers, energy levels and related parameters, such as ionization energy and electronic energy, bond gap energy and the share of hybrid orbitals of different layers.

AlN Nanotubes: A DFT Study of Al-27 and N-14 Electric Field Gradient Tensors

2007 ◽  
Vol 62 (12) ◽  
pp. 711-715 ◽  
Author(s):  
Ahmad Seif ◽  
Mahmoud Mirzaei ◽  
Mehran Aghaie ◽  
Asadollah Boshra
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Density Functional ◽  
Quadrupole Coupling Constant ◽  
Basis Set ◽  
Basis Sets ◽  
B3lyp Method ◽  
Package Program ◽  
Nqr Parameters

Density functional theory (DFT) calculations were performed to calculate the electric field gradient (EFG) tensors at the sites of aliminium (27Al) and nitrogen (14N) nuclei in an 1 nm of length (6,0) single-walled aliminium nitride nanotube (AlNNT) in three forms of the tubes, i. e. hydrogencapped, aliminium-terminated and nitrogen-terminated as representatives of zigzag AlNNTs. At first, each form was optimized at the level of the Becke3,Lee-Yang-Parr (B3LYP) method, 6-311G∗∗ basis set. After, the EFG tensors were calculated at the level of the B3LYP method, 6-311++G∗∗ and individual gauge for localized orbitals (IGLO-II and IGLO-III) types of basis sets in each of the three optimized forms and were converted to experimentally measurable nuclear quadrupole resonance (NQR) parameters, i. e. quadrupole coupling constant (qcc) and asymmetry parameter (ηQ). The evaluated NQR parameters revealed that the considered model of AlNNT can be divided into four equivalent layers with similar electrostatic properties.With the exception of Al-1, all of the three other Al layers have almost the same properties, however, N layers show significant differences in the magnitudes of the NQR parameters in the length of the nanotube. Furthermore, the evaluated NQR parameters of Al-1 in the Al-terminated form and N-1 in the N-terminated form revealed the different roles of Al (base agent) and of N (acid agent) in AlNNT. All the calculations were carried out using the GAUSSIAN 98 package program.

Sign in / Sign up

Export Citation Format

Share Document