Evaluation of the chemical reactivity in lignin precursors using the Fukui function

Martinez, C.; Rivera, Juan; Herrera, Rafael; Rico, José Luis; Flores, N; Rutiaga, J.G.; López, Pablo

doi:10.1007/s00894-007-0253-0

Cited by 42 publications

(35 citation statements)

References 23 publications

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“…Lignin is an aromatic heteropolymer that is mainly found in the secondary wall of wood cells 1. As per Goring findings,2 lignin is a random three‐dimensional network polymer that is placed in the true middle lamella of wood and composed of phenylpropane monomers 3…”

Section: Introductionmentioning

confidence: 84%

Spectroscopic studies and evaluation of thermorheological properties of softwood and hardwood lignin

Awal¹,

Sain²

2011

J of Applied Polymer Sci

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Fourier transform infrared spectroscopy (FTIR) was used to determine characteristic absorption peaks of softwood kraft lignin and soda hardwood lignin. Remarkable spectral differences were noticed between the different lignins due to their various chemical structures. Proton nuclear magnetic resonance spectrometry ( 1 H NMR) was employed to analyze the structure of lignin. Matrix-assisted laser desorption/ionization time-offlight mass spectrometry (MALDI-TOF) provided important data regarding the molecular weight distribution of lignin. Thermal stability of softwood lignin was found to be remarkably higher than that of hardwood lignin. Softening temperature and glass transition temperature of lignin were measured by differential scanning calorimetry (DSC) which was useful in selecting an optimal temperature profile during extrusion process. Rheological studies provided valuable information about the viscosity of lignins. V C 2011 Wiley Periodicals, Inc. J Appl Polym Sci 122: [956][957][958][959][960][961][962][963] 2011

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Section: Introductionmentioning

confidence: 84%

Spectroscopic studies and evaluation of thermorheological properties of softwood and hardwood lignin

Awal¹,

Sain²

2011

J of Applied Polymer Sci

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“…The S, C3 atoms in IsRd, the O, C3 atoms in Rd, and the C1, C2 atoms in DMm (cis, trans) were considered. The Fukui function is widely used in the prediction of reactive sites in molecules [38][39][40]. The values of the f + (r), f − (r), and f 0 (r) functions, which can be interpreted as indicators of the preferred place of the nucleophilic, electrophilic, and radical attack in molecules, are presented in Table 8.…”

Section: Resultsmentioning

confidence: 99%

Why are rhodanines less efficient reagents in Diels–Alder reactions than isorhodanines? A quantum chemical study

et al. 2019

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The reactivity of the 5-arylidenerhodanine and 5-arylideneisorhodanine derivatives in reactions with dimethyl maleate was computationally studied at the DFT(M06-2X)/6-311+G(d,p) theory level. Eight stereoisomers of the reaction products were considered. The effect of the solvent was taken into account by means of the continuous and discrete models for acetic acid (PCM and three CH 3 COOH molecules). Aromatic stabilization of the transition states was documented by the values of HOMA, NICS(0), and NICS(1) indices. The higher reactivity of the isorhodanine derivative was associated with a relatively low activation energy, ΔE a (15.2-22.3 kcal mol -1 ), which is needed to cross the TS. For the rhodanine derivative, higher values of ΔE a (34.1-36.1 kcal mol -1 ) were obtained. The reactivity was also studied from the perspective of the frontier molecular orbitals, the energy gaps between the HOMO and LUMO, the flux of electron density, the Fukui functions, f + (r), f − (r), and f 0 (r), and the global indexes defined in the conceptual DFT, i.e., the electronic chemical potential, chemical hardness, global electrophilicity, and empirical nucleophilicity index.

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“…The reactivity analyses will be helpful for determining which BPFs or which sites of the BPFs are vulnerable to HO· attack. The main basis of this part are: (i) During the initial stage of hydrogen abstraction or free radical addition reactions, the free radical is firstly attracted by the electrostatic potential; (ii) Frontier orbitals match well is the prerequisite for the title reactions; (iii) When the radicals and target group are close enough, the electron population began to overlap and Fukui function will be more precise to present the reactivity of functional groups …”

Section: Resultsmentioning

confidence: 99%

Initial reaction mechanism between HO· and bisphenol‐F: Conformational dependence and the role of nonbond interactions

Bian

Wang

et al. 2017

Int J of Quantum Chemistry

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Hydroxyl radical (HO·) plays an important role in the initial pyrolysis of hydroxyl-containing polymers, such as phenolic resin (PR). In this study, the reaction mechanism between HO· and bisphenol-F (BPF) or tetra-methyl substituted BPFs, which were taken as the model molecules of PR, was studied with the density functional theory approach. The results based on the Fukui function and reduced density gradient function showed that, both the hydroxyls and the carbon atoms in the phenolic groups are the reactive sites for HO· attack. The hydroxyls are most likely to be attacked by HO· owing to the strong electrostatic potential around the hydroxyls and the low reaction barriers, especially for cis-o-o' type BPF. The strong pAp (CHAp and OHAp) interaction between the phenolic rings in BPF leads to decreased conjugative effect of the phenolic rings, which further lead to decreased addition barriers and reaction rate constant. K E Y W O R D S bisphenol-F, conformation, density functional theory, hydroxyl radical, reaction mechanism 1 | I N T R O D U C T I O N Bis(hydroxyphenyl)methanes, also named as bisphenol-Fs or BPFs, are a group of chemical compounds with two hydroxyphenyl functionalities bridged by one methylene group ( Figure 1). Owing to the structurally similarity to bisphenol-A, BPFs are desirable materials with many attractive applications paralleling bisphenol-A in use, such as the primary raw materials of epoxy, polycarbonate, or phenolic resins, but considerably lower toxicity than bisphenol-A. [1] However, the widespread application of BPFs also leads to considerable environmental problems. [2] A detailed investigation on the thermal decomposition mechanism of BPFs will be conducive to guiding the application and degradation of BPFs in reasonable ways. In particular, BPFs can also be regarded as the basic structural units or model compounds for phenolic resins (PRs), which are generally made from phenol and formaldehyde. [3] Hence, the elucidation of the thermal decomposition mechanism of BPF will be helpful for understanding the relationship of structural-thermal stability of PRs.The constitutional and conformational isomerism of BPFs lead to multiple structural characteristics of BPFs. There are three constitutional BPF isomers, 2,2 0 -bis(hydroxyphenyl)methane, 2,4 0 -bis(hydroxyphenyl)methane, and 4,4 0 -bis(hydroxyphenyl)methane (Figure 1), and this is also the primary reason for the rather complex crosslinked structure of PR. Wang et al.'s computational results [4] showed that there are more than 24 stable conformers of o-o' type BPF. Pillsbury et al. [5] stated that owing to the hydrogen bonds and OHAp interaction formation, the conformers with hydroxyls paralleled or perpendicular to each other are the dominant structures. Gruber et al. [6] proved that a p-p 0 type BPF conformer with the C 2 symmetry has the lowest energy, leading to a strong crystallinity of p-p 0 type BPF. In the highly crosslinked network of cured PR, most of the BPF-like structures are four methylene substituted BPFs, this fu...

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Evaluation of the chemical reactivity in lignin precursors using the Fukui function

Cited by 42 publications

References 23 publications

Spectroscopic studies and evaluation of thermorheological properties of softwood and hardwood lignin

Spectroscopic studies and evaluation of thermorheological properties of softwood and hardwood lignin

Why are rhodanines less efficient reagents in Diels–Alder reactions than isorhodanines? A quantum chemical study

Initial reaction mechanism between HO· and bisphenol‐F: Conformational dependence and the role of nonbond interactions

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