Three-membered Ring Structure Research Articles

Microwave-induced Facile Synthesis of Highly Strained Three-membered Ring Compounds and Some of Their Reactions

Abstract:Compounds with three membered rings experience greater strain than those with other ring systems. In general, the synthesis of small ring compounds, particularly three-membered molecules, faces major challenges because of the severe strain in this system. Moreover, microwaveassisted method creates a higher temperature due to the heat and radiation of a reaction mixture more rapidly than conventional methods. This paper reports the successful synthesis of threemembered heterocyclic compounds via microwave-assisted reactions. Microwaves have assisted in making three-membered compounds while inducing high energy to the reaction mixtures. No reviews have reported the synthesis of these types of molecules either by microwave or conventional procedure. In addition, the reaction of a few three-membered ring compounds to other products through the ring rupture method is also included. On this basis of the chemistry (formation and breakage) of three-membered compounds described here, this report can be considered novel, timely, and highly significant. This review may help numerous researchers for further study in this field as the synthesis and cleavage of three-membered ring structures using a microwave is a challenging objective.

Theoretical study on the quick thermal decomposition pathways for MTNI(1-Methyl-2,4,5-Trinitroimidazole)

In this study, we investigated the initial and subsequent decomposition mechanisms for MTNI(1-Methyl-2,4,5-trinitroimidazole) by DFT calculations. In the second stage of the nitro isomerization, a stable loose intermediate –ONO isomer is not generated but an unstable tight three-membered ring structure is generated, resulting in the direct production of NO. In the initial and subsequent process of H transfer, under certain conditions, a synergistic reaction occurs. The occurrence of the synergistic reaction is determined by the orientation of the –OH group on the hydroxymethyl group. Compared with the common decomposition mechanism, less energy is needed absorbed in above reaction.

Global Isomeric Survey of Elusive Cyclopropanetrione: Unknown but Viable Isomers.

Despite the great interest in energy storage application, stable neutral CnOn (n > 1) structures either in thermodynamics or kinetics have yet been largely limited due to the rather high tendency to release the very stable CO molecule. The neutral cyclopropanetrione (C3O3) cluster has long remained elusive since no isomer with sufficient kinetic stability has been found either experimentally or theoretically. In this work, we constructed the first global potential energy surface of singlet C3O3 at the CCSD(T)/aug-cc-pVTZ//B3LYP/aug-cc-pVTZ level, from which the kinetic stability of a wide range of C3O3 isomers can be determined by investigating their isomerization and fragmentation pathways. Amongst, a three-membered ring structure 01 is the global C3O3 isomer with a barrier of 10.6 kcal/mol at the sophisticated W1BD level. In particular, two carbene-type isomers 02 and 04 possess appreciable destruction barriers of 20.3 and 24.7 kcal/mol at W1BD, respectively. Thus, 02 and 04 can be useful building blocks for constructing larger high-energy density carbon-oxygen clusters. Moreover, with the carbene center, both might effectively functionalize various nano-materials while retaining the electrochemical active carbonyl and epoxyl moieties that are very desirable in alkali metal-ion batteries.

Synthesis of a multifunctional hard monomer from rosin: the relationship of allyl structure in maleopimarate and UV-curing property

Rosin is an important forestry resource with a specific three-membered phenanthrene ring structure, which can improve the mechanical resistance of polymer coatings. In this paper, a high purity rosin monomer, tri-allyl maleopimarate containing three allyl groups has been synthesized. The yield of the monomer product was 93.2% with the purity of 96.1%. The structure of the synthesized monomer was characterized through gas chromatography (GC), mass spectrometry (MS), hydrogen nuclear magnetic resonance spectroscopy (1H NMR), carbon nuclear magnetic resonance spectroscopy (13C NMR) and elemental analysis. Additionally, we present new experimental results regarding the polymerization reaction under ultraviolet (UV) irradiation. The cured film of tri-allyl maleopimarate exhibited good mechanical properties. The films were also characterized through thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses and a mechanism for polymerization was proposed. Overall, a facile catalytic process for the valorization of rosin in the field of UV polymerization is reported.

The addition reactions of germylenoid H2GeAlCl3 with ethylene: a theoretical investigation.

Theoretical calculations using the M062X and QCISD methods were performed on the addition reactions of the aluminum germylenoid H2GeAlCl3 with ethylene. The most two stable structures of germylenoid H2GeAlCl3, i.e., the p-complex and three-membered ring structures, respectively, were employed as reactants. The calculated results indicate that, for the p-complex, H2GeAlCl3 there are two pathways, I and II, of which path I involves just one transition state, while path II involves two transition states between reactants and products. Comparing the reaction barrier heights of path I (44.6kJmol-1) and II (37.6kJmol-1), the two pathways are competitive, with similar barriers under the same conditions, while for the three-membered ring structure, another two pathways, III and IV, also exist. Path III has one transition state; however, in path IV, two transition states exist. By comparing their barrier heights, path III (barrier height 39.2kJmol-1) could occur more easily than path IV (barrier height 92.8kJmol-1). Considering solvent effects on these addition reactions, the PCM model and CH2Cl2 solvent were used in calculations, and the calculated results demonstrate that CH2Cl2 solvent is unfavorable for the reactions, except for path II. In CH2Cl2 solvent, paths II and III are more favorable than paths I and IV.

Reaction mechanism and product branching ratios of the CH + C3H4 reactions: a theoretical study.

Two ground-state CH radical reactions with the C3H4 isomers allene and methylacetylene occurring along the C4H5 potential energy surface (PES) were studied to probe the reaction mechanisms and final product distributions. The calculations were performed using a CCSD(T)-F12//B2PLYPD3 PES in combination with the 1-D chemical master equation. The reaction between the CH radical and allene was found to lead to exclusive "funneling" of the energized C4H5 intermediates into linear C4H5 configurations before reaching the exit channels, regardless of the specific nature of the initial bimolecular reactive encounter. In the case of the CH radical reaction with methylacetylene, energized C4H5 three-membered ring structures underwent H loss in significant amounts resulting in the production of a cyclic C4H4 methylenecyclopropene product, in accordance with experiments. The theoretical product distribution at room temperature for methylacetylene + CH was ∼35% methylenecyclopropene, ∼36% vinylacetylene, and ∼28% 1,2,3-butatriene, which is in agreement with the available experimental data. The distribution for allene + CH was ∼93% vinylacetylene, ∼4% 1,2,3-butatriene and ∼3% acetylene + vinyl, which overestimates the experimental yield of vinylacetylene and underestimates that of 1,2,3-butatriene by ∼10%. The possible reasons for this slight quantitative deviation of the theoretical results obtained within statistical treatment from the experiment are discussed.

Homolytic Cleavage of Both Heme-Bound Hydrogen Peroxide and Hydrogen Sulfide Leads to the Formation of Sulfheme.

Many heme-containing proteins with a histidine in the distal E7 (HisE7) position can form sulfheme in the presence of hydrogen sulfide (H2S) and a reactive oxygen species such as hydrogen peroxide. For reasons unknown, sulfheme derivatives are formed specifically on solvent-excluded heme pyrrole B. Sulfhemes severely decrease the oxygen-binding affinity in hemoglobin (Hb) and myoglobin (Mb). Here, use of hybrid quantum mechanical/molecular mechanical methods has permitted characterization of the entire process of sulfheme formation in the HisE7 mutant of hemoglobin I (HbI) from Lucina pectinata. This process includes a mechanism for H2S to enter the solvent-excluded active site through a hydrophobic channel to ultimately form a hydrogen bond with H2O2 bound to Fe(III). Proton transfer from H2O2 to His64 to form compound (Cpd) 0, followed by hydrogen transfer from H2S to the Fe(III)-H2O2 complex, results in homolytic cleavage of the O-O and S-H bonds to form a reactive thiyl radical (HS(•)), ferryl heme Cpd II, and a water molecule. Subsequently, the addition of HS(•) to Cpd II, followed by three proton transfer reactions, results in the formation of a three-membered ring ferric sulfheme that avoids migration of the radical to the protein matrix, in contrast to that in other peroxidative reactions. The transformation of this three-membered episulfide ring structure to the five-membered thiochlorin ring structure occurs through a significant potential energy barrier, although both structures are nearly isoenergetic. Both three- and five-membered ring structures reveal longer NB-Fe(III) bonds compared with other pyrrole nitrogen-Fe(III) bonds, which would lead to decreased oxygen binding. Overall, these results are in agreement with a wide range of experimental data and provide fertile ground for further investigations of sulfheme formation in other heme proteins and additional effects of H2S on cell signaling and reactivity.

Chemical functionalization of graphene by carbene cycloaddition: A density functional theory study

Abstract In this work, we have systematically studied the structural, energetic and electronic properties of graphene functionalized with carbene groups by using density functional theory. Introducing a low concentration of CCl 2 group in graphene was studied in detail by DFT, and closed cyclopropane-like three-membered ring structure was formed, meanwhile, the potential candidate carbene groups CR 2 (R = H, F, CH 3 , CN, NO 2 , OCH 3 , CCH, C 6 H 5 ) were added to graphene sheet, and CR 2 (R = H, NO 2 , CH 3 ) groups were expected to be good reactive species to covalently modify graphene. The graphene functionalization with carbene groups above can open graphene's band gap. More CCl 2 molecules were added to graphene, and different concentrations of CCl 2 group can tune graphene's band gap. In addition, the addition of CCl 2 group to graphene edges was investigated, and the stronger binding energy was found. Multiple CCl 2 molecules preferred to be bound with the same edge of graphene nanoribbon. This work provides an insight into the detailed molecular mechanism of graphene functionalization with carbene groups.

Large increase in refractive index inside silica glass after the movement of voids caused by femtosecond laser pulses

When a transparent material is irradiated by focused femtosecond laser pulses, various types of structural modification can occur inside the material. Recently, it has been reported that asymmetric structures, which are composed of two regions with positive and negative refractive index changes (Δn), can be inscribed by irradiation of multiple femtosecond laser pulses at high (∼MHz) repetition rates. Interestingly, the amount of positive Δn in this type of modification is larger than those in conventional structural modifications by one order of magnitude. However, the mechanisms underlying such modifications are still unclear. In this paper, we describe that similar asymmetric structures can be inscribed by using femtosecond laser pulses at a low repetition rate. Then, we examine the formation and spectroscopic characteristics of the asymmetric structures. The observation of the processed areas reveals that the asymmetric structures are formed after the movement of voids. Furthermore, micro-Raman spectroscopy suggests a large increase of three-membered ring structures in the region with positive Δn, which may account for the large Δn.

Further investigations of the effect of replacing lithium by sodium on lithium silicate scintillating glass efficiency

Ce3+ doped lithium (6Li) silicate glasses are thermal neutron detectors. Prior work showed that when sodium (Na) is substituted for Li the scintillation efficiency, under beta particle stimulation, increased and then decreased as the sodium (Na) content was increased. When all the 6Li was replaced by Na no scintillation was observed. Raman spectra, acquired using a visible excitation source, provided no evidence of anomalous behavior. SEM microscopy did show some phase separation, but there was no obvious correlation with the scintillation efficiency. We have reexamined these glass samples using deep UV Raman excitation which reduces fluorescence interference. The newly acquired spectra show evidence of phase separation in the glasses. Specifically we see a peak at 800cm−1 Raman shift which can be assigned to a vitreous silica moiety that results from phase separation. There is a strong correlation between this peak's area, the scintillation efficiency, and the Na content. The observed trend suggests that phase separation enhances scintillation and addition of Na reduces the amount of phase separation. We also see evidence of at least two defect structures that can be tentatively assigned to a three-membered ring structure and an oxygen vacancy. The latter is fairly strongly correlated with enhanced scintillation efficiency.

Small carbides of third-row main group elements: structure and bonding in C3X compounds (X = K–Br)

The molecular structures of third-row main group tricarbides C(3)X (X = K-Br) have been studied by quantum chemical methods. It is found that less electronegative elements (K, Ca, Ga, Ge) favor either fan or rhombic structures (resulting from side interactions with either linear or triangular C(3) units), whereas the more electronegative elements (As, Se, Br) favor linear or three-membered ring structures (resulting from σ-type interactions with either linear or triangular C(3) units). The predicted global minima are of fan type for C(3)K, rhombic for C(3)Ca, C(3)Ga, and C(3)Ge, linear for C(3)As and C(3)Se, and a three-membered ring for C(3)Br. In order to aid in their possible experimental identification the molecular geometries, vibrational frequencies, IR intensities, and dipole moments have been provided. The nature of the interactions has been characterized through an analysis of the electronic charge density. In addition, the relative stability of the different isomers has been also rationalized in terms of an energy decomposition analysis.

Theoretical study on the structures, isomerization, and stability of [Si, C, N, S] isomers

The structures, energies, spectral parameters, and stabilities of the doublet [Si, C, N, S] radical are explored at the density functional theory and ab initio levels. Eighteen isomers including chainlike, three-membered ring, four-membered ring and cagelike structures are located, connected by 25 interconversion transition states at the B3LYP/6-311G(d) level. The structures of the kinetically stable isomers and their relevant transition states are further optimized at the QCISD/6-311G(2d) level. At the CCSD(T)/6-311 + G(2d)//QCISD/6-311G(2d)+ZPVE level, the global lowest-lying isomer NCSiS 1 is a bent structure. Additionally, the chainlike isomers CNSiS 2, SiNCS 3, SiSCN 4, SiSNC 5, and SiCNS 6 also process considerable kinetic barriers (more than 10.0 kcal/mol). All the six isomers may be experimentally or astrophysically observable. The bonding natures of all the six isomers are analyzed seriously. The calculated results are compared with those of analogous molecules [Si, Si, N, S], [Si, C, P, S], and [Si, C, N, O]. Implications of the computational structures and spectroscopies are also discussed.

Mechanisms of norbornadiene dimerization to Binor‐S using cationic CoI, RhI, and IrI catalysts

We investigated the transition metal-catalyzed reaction mechanisms of NBD dimerization to Binor-S using cationic Co(I), Rh(I), and Ir(I) catalysts, using mPW1PW91, mPW1K, and B3LYP density functional methods. Our results indicate that the monomeric metal center has the ability to bind with four double bonds of two NBD molecules with a syn spatial geometry to form a penta-coordinated complex. We designed three possible pathways, but found two of them blocked. The favored pathway involves three steps from the reactant precursor to the product precursor: the first step is the formation of a single bond to connect two NBD units, the second is the alkene insertion leading to the formation of the three-membered ring structure, and the final step is the formation of the final product precursor. Orbital analysis showed metal...C-C sigma agostic interaction in the product precursor, which is in agreement with the previous experimental findings. In addition, we found that the solvent and counter-ions had significant effects on the dimerization reactions.

The isomeric structures and stability of pentacoordinate silylenoid PhCH 2(OH)CH 3SiLiF

The structures and stability of pentacoordinate silylenoid PhCH 2(OH)CH 3SiLiF were studied by density functional theory. Two equilibrium structures, the three-membered ring and the p-complex structures, were located. The three-membered ring structure has the lowest energy both in vacuum and in solvents (ether, THF and acetone). The Si–O coordination energy is 13.5 kJ/mol in the three-membered ring structure of pentacoordinate PhCH 2(OH)CH 3SiLiF at the B3LYP/6-311+G(d, p) level. The substitution barrier of the three-membered ring structure with CH 3F is only 1.7 kJ/mol lower than that of PhCH 3CH 3SiLiF at the B3LYP/6-31G(d) level, showing that the pentacoordinate silylenoid PhCH 2(OH)CH 3SiLiF has almost the same stability as the corresponding tetracoordinate silylenoid PhCH 3CH 3SiLiF.

Theoretical study on the structures and stability of Si 2PS isomers

The structures, energetics, spectroscopies, and stabilities of the doublet Si 2PS radical are explored at the density functional theory and ab initio levels. Fifteen minima including the chainlike, three-membered ring, four-membered ring, and cagelike structures are located connected by 24 interconversion transition states. The structures of the stable isomers and their relevant transition states are further optimized at the QCISD/6-311G(2d) level. At the CCSD(T)/6-311+G(2df)//DFT/B3LYP/6-311G(d)+ZPVE level, the global minimum is found to be a four-membered-ring cPSiSSi 10 (0.0 kcal/mol) with a 2A′′ electronic state, whereas the cagelike isomer cagePSiSiS 15 (3.5 kcal/mol), the three-membered-ring isomers S-cSiPSi 4 (12.1 kcal/mol), and P-cSiSiS 5 (27.6 kcal/mol) also possess considerable kinetic stabilities (more than 10.0 kcal/mol). The bonding natures and structures of the four isomers 4, 5, 10, and 15 are analyzed. The calculated results are compared with those of the analogous molecules C 2PS and SiCPS.

In situ measurements of the D1 and D2 Raman band intensities of vitreous and molten silica in the 77–2150 K temperaturerange

In situ quantitative Raman spectra of vitreous and molten silica were measured fromLN2 temperatures up to above melting and used to calculate the intensities of the two ‘defect peaks’D1 andD2 associated with the corresponding four- and three-membered ring structures. TheD1 intensity decreases with increasing temperature while theD2 intensity appears to be invariant to temperature. The data are in disagreement with thequenching/fictive temperature experiments and show definitely no abrupt intensity changesat any temperature.

Boron nitride nanotubes functionalized by a series of carbenes

We systematically studied the structural, energetic and electronic properties of zigzag boron nitride nanotubes (BNNTs) functionalized by a class of substituted carbenes (CR(2)) where R = H, F, Cl, CH(3), CN and NO(2) on different absorption sites using density functional theory. For R = H, F and Cl, the open structure is preferred with a BNNT sidewall bond cleavage, while for R = CH(3) and CN, a competition between the open and closed cyclopropane-like three-membered ring (3MR) structure occurs. Interestingly, for R = NO(2) we find a novel double five-membered ring (5MR) structure with high reaction stability. This new structure cannot be found in BNNTs' alternative carbon nanotubes (CNTs). In addition, the electronic properties of BNNTs functionalized with carbenes are hardly changed for R = H, F, Cl, CH(3) and CN, but are significantly affected when R = NO(2) due to the heterocyclic double 5MR structure.

Ab initioStudy on Structures and Isomerization of Magnesium Fluorosilylenoid H2SiFMgF

The structures and isomerization of magnesium fluorosilylenoid H2SiFMgF were investigated by ab initio molecular orbital theory. Four equilibrium structures and three isomeric transition states were located and fully optimized at the B3LYP/6-31G(d,p) and G3MP2B3 levels, respectively. Based on the B3LYP/6-31G(d,p) optimized geometries, harmonic frequencies of various structures were obtained and 29Si chemical shifts were calculated. The solvent effects were investigated by means of the polarizable continuum model using THF as a solvent at B3LYP/6-31G(d,p) level. Isomerization paths for isomers were confirmed by intrinsic reaction coordinate calculations. The calculated results show that tetrahedral structure has the lowest energy and is the most stable; tetrahedral, three-membered ring, and p-complex structures are suggested to be the experimentally detectable ones; and -complex structure has the highest energy and will not exist.

First-principles analysis of optical absorption edge in pure and fluorine-doped SiO2 glass

We have carried out a “band-resolved” analysis of the optical absorption spectra of pure and fluorine-doped SiO2 glass by using the first-principles method, where dominant orbitals involved in the absorption spectra can be analyzed. We found that heavily strained bonds in three-membered ring structures affect the fundamental absorption edge and that the heavy strain is released by opening a ring structure with fluorine doping.

First-principles analysis of the optical properties of structural disorder inSiO2glass

We have carried out a band-resolved analysis of the optical absorption spectra of structural disorder in ${\text{SiO}}_{2}$ glass by using a first-principles method, where dominant orbitals involved in the absorption spectra can be analyzed. We provided a strong theoretical support to a model where heavily strained bonds in three-membered ring structures affect the fundamental absorption edge. We found that the main absorption peak induced by an oxygen vacancy can be ascribed to a transition between the occupied and unoccupied defect states consisting of Si-Si and neighboring O orbitals due to the structural disorder. The present scheme is effective for analyzing the relationship between microscopic atomic structures and macroscopic optical properties.