China
Africa
Explore chapters and articles related to this topic
Conjugation and Reactions of Conjugated Compounds
Published in Michael B. Smith, A Q&A Approach to Organic Chemistry, 2020
Frontier molecular orbital theory is a model that approximates reactivity by looking at the frontier orbitals, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). This theory is based on three main observations: occupied orbitals of different molecules repel each other; positive charges of one molecule attract the negative charges of the other; occupied orbitals of one molecule interact and attract the unoccupied orbitals of the other. What are frontier molecular orbitals?
Theoretical study into structure-properties relationship on energetic derivatives coupling by nitroimidazoles and polynitrobenzenes
Published in Molecular Physics, 2023
According to frontier molecular orbital theory, HOMO is the highest electron occupied orbital of nucleophilic reagents, and LUMO is the lowest orbital of an electrophilic reagent that is not occupied by electrons. Therefore, EHOMO tends to indicate the tendency of electronic donation, while ELUMO is the corresponding HOMO tendency to accept electrons. On one hand, horizontal observation of the same series of A1, A2 and A4, it is not difficult to detect that when the number of -NO2 in the substituent rises, the HOMO and LUMO energy of the derivative will decrease. The energy range ΔEHOMO-LUMO will elevate, indicating that when the number of -NO2 increases, the electronic absorption spectrum of the derivative will move to high frequency. On the other hand, taking A2, B2 and C2 as a group of research objects, it can be discovered that HOMO energy and LUMO energy of the derivatives improve with the enhance of the quantity of substituent -NH2. This reveals that different substituents have various effects on the HOMO and LUMO energies of their substituted derivatives. The energy range ΔEHOMO-LUMO descends, showing that when the number of -NH2 adds, the electronic absorption spectrum of the derivative will move to a low frequency.
Experimental Study on the Inhibitory Effect of Organic Phosphonic Acid Compound on Coal Spontaneous Combustion
Published in Combustion Science and Technology, 2023
Jiantao Wang, Fusheng Wang, Xiaoxing Zhong, Meng Sun, Lei Li
Based on the frontier molecular orbital theory, the Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) between reactants attract each other and undergo electron transfer, which leads to a chemical reaction (Deng et al. 2020). The bonding property of chemical reactions depends on the energy level of the frontline molecular orbitals. As can be seen from Table 7, EHOMO and ELUMO of Fe(III)[HEDP]2− are both smaller compared to those of Fe(III)[HPAA]2−, indicating that Fe(III)[HEDP]2− is more stable. Besides, the molecule with a larger energy gap (△E) between the LUMO and HOMO has a weaker reactivity. The ∆E of Fe(III)[HEDP]2− is 0.0058 hartree larger than that of Fe(III)[HPAA]2−, which indicates the greater stability of the chelate formed by HEDP with iron ion. In summary, the reasons for the superiority of HEDP over HPAA in inhibiting CSC are revealed.
Gum Arabic as corrosion inhibitor in the oil industry: experimental and theoretical studies
Published in Corrosion Engineering, Science and Technology, 2019
Chen Shen, Victor Alvarez, Josh D. B. Koenig, Jing-Li Luo
All geometry optimizations and quantum calculations were performed for the study of chemical reactivity and selectivity in terms of frontier molecular orbital theory. The quantum chemical calculations were used to understand the sugar residues in GA response of providing corrosion inhibition. The most favourable configuration of the studied sugar residues in GA and Fe (111) surface were simulated using a molecular dynamics approach. The quantum chemical calculations were carried out with the aid of Material Studio 7.0 (MS) software suite from Accelrys [36]. One part of the monomeric structure of GA was used as the representative structure of the corresponding GA biopolymer for computational studies. The initial molecular structures and geometries were obtained with the aid of ChemDraw Ultra 12.0 from Cambridge Soft [37]. The initial geometry structure was optimised with Forcite module and the more stable molecular structure was obtained by Corformers tool module. For the optimizations, the Condensed-phase Optimised Molecular Potentials for Atomistic Simulation Studies (COMPASS) forcefield and Edwall summation method were used.