Mixed Solvent Chemistry through Synergistic Solvation: Structure,Property and Function of <Emphasis Type="Italic">t</Emphasis>-Butanol—Dichloromethane Binary Solvent Mixtures

The present study elucidates the synergetic solvation behavior of t-butanol–dichloromethane (t-BuOH–DCM) binary solvent mixtures. UV–visible absorption, emission and ¹H-NMR spectroscopy along with analytical modelling were used to ascertain the nature of interactions present, which are found to be maximum at X _t-BuOH = 0.40, leading to a super solvation environment. The increased polarity of the t-BuOH–DCM binary solvent mixtures through interactive solvent association is believed provide a unique reaction medium that can alter the fate of chemical processes involving a polar species. This idea has been demonstrated by the transformation of merocyanine to 1′,3′-dihydro-,1′,3′,3′-trimethyl-6-nitropiro[2H-1-benzopyran-2,2′-(2H)-indole] and the oxidation of cholestanol to cholestanone.     

Kinetics and Mechanism of Monomolecular Heterolysis of Commercial Organohalogen Compounds: XLII. Effect of Aprotic Solvent on the Rate of 3-Methyl-3-chloro-1-butene Dehydrochlorination. Correlation Analysis of Solvation Effects

The kinetics of 3-methyl-3-chloro-1-butene dehydrochlorination in propylene carbonate, γ-butyrolactone, sulfolane, acetone, MeCN, PhNO₂, PhCN, PhCOMe, MeCOEt, cyclohexanone, o-dichlorobenzene, PhCl, PhBr, 1,2-dichloroethane, dioxane, and AcOEt were studied; v = k[C₅H₉Cl], E1 mechanism. The reaction rate is satisfactorily described by the parameters of the polarity, electrophilicity, and cohesion of the solvent; the solvent nucleophilicity and polarizability exert no effect on the reaction rate.     

Generation and properties of hydrogenation catalysts based on palladium bisacetylacetonate and lithium alkoxyhydroaluminates

Generation and properties of a catalytic system for hydrogenation, based on Pd(acac)₂ and LiAlH₄ and modified with n-BuOH and t-BuOH, were studied. The promoting and inhibiting effects of the alcohols were revealed, and their causes were discussed.     

Transformations of <Emphasis Type="Italic">N</Emphasis>-(2-acylaryl)benzamides and their analogs under the Camps cyclization conditions

N-(2-Acylaryl)benzamides and analogous N-substituted furan-2-, thiophene-2-, and cyclopropane-carboxamides in the systems EtONa–EtOH, EtONa–THF, and t-BuOK–t-BuOH undergo Camps cyclization to 2-aryl-, 2-hetaryl-, and 2-cyclopropylquinolin-4(1H)-ones with high yields. The same substrates in the system t-BuOK (5 equiv)–THF are converted mainly to the corresponding N-(2-hydroxyaryl) amides as a result of oxidative transformation of the acyl fragment into hydroxy group.     

Kinetics and mechanism of monomolecular heterolysis of commercial organohalogen compounds: XLIII. Solvent effect on activation parameters of dehydrochlorination of 3-chloro-3-methylbut-1-ene. Correlation analysis of solvation effects

The influence of temperature on the rate of dehydrochlorination of 3-chloro-3-methylbut-1-ene in 17 aprotic and 13 protic solvents, ν = k[C₅H₉Cl], was studied by the verdazyl method. In aprotic solvents, the electrophilicity, ionizing power, and cohesion of solvents decrease ΔG ^≠ by increasing ΔS ^≠. The nucleophilicity and polarizability increase both ΔH ^≠ and ΔS ^≠ to equal extent and therefore do not affect ΔG ^≠. In protic solvents, the solvent nucleophilicity increases ΔH ^≠ to a greater extent than ΔS ^≠, and the overall effect of the nucleophilic solvation is small and negative.     

Structural studies of nickel(II) complexes with 1-<Emphasis Type="Italic">tert</Emphasis>-butylimidazole-2-thione and 3-phenyl-5-methyl-pyrazole ligands

The nickel(II) complexes dichlorobis(1-tert-butylimidazole-2-thione)nickel(II) [Ni(tm ^t-Bu)₂Cl₂] (1), dinitratobis(1-tert-butylimidazole-2-thione)nickel(II) [Ni(tm ^t-Bu)₂(NO₃)₂] (2), dichloro-bis(3-phenyl-5-methyl-pyrazole)(1-tert-butylimidazole-2-thione)nickel(II) [Ni(pz^Ph,MeH)₂(tm ^t-Bu)Cl₂] (3) and dinitratobis(3-phenyl-5-methyl-pyrazole)(1-tert-butylimidazole-2-thione)nickel(II) [Ni(pz^Ph,MeH)₂(tm ^t-Bu)(NO₃)₂] (4) have been synthesized and studied. The single crystal X-ray diffraction analysis was carried out for 1 and 4 {Bruker Kappa Apex-II CCD diffractometer, MoK _α radiation}. Crystal data for 1: monoclinic C2/c, a = 16.949(2) Å, b = 8.6647(10) Å, c = 15.461(3) Å, β = 117.662(4)°, V = 2011.1(5) ų, Z = 4, D _calc = 1.460 g/cm³. Crystal data for 4: triclinic P-1, a = 9.9775(7) Å, b = 11.2254(8) Å, c = 14.8068(10) Å, α = 75.401(4)°, β = 87.422(4)°, γ = 74.874(4)°, V = 1548.86(19) ų, Z = 2, D _calc = 1.405 g/cm³. Coordination core of complex 1 adopts distorted tetrahedral geometry whereas core 4 has distorted octahedral geometry. The bonded nitrates are of two types coordinating as monodentate and bidentate ligands.     

<Emphasis Type="Italic">Tetra</Emphasis>-EDOT substituted 3D electrochromic polymers with lower band gaps

A couple of novel electrochromic materials poly(2,3,4,5-tetrakis(2,3-hydrothieno[3,4-b]dixin-5-yl)-1-methyl-1H-pyrrole) (P(t-EDOT-mPy)) and poly(5,5′,5′′,5′′′-(thiophene-2,3,4,5-tetrayl)tetrakis(2,3-dihydrothieno[3,4-b][1,4]dioxine)) (P(t-EDOT-Th)) are electrodeposited via multi-position polymerization of their tetra-EDOT substituted monomers t-EDOT-mPy and t-EDOT-Th, respectively. Compared with the linear 2D structured poly(thiophene) (E _g=2.2 eV) and poly(2,5-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)thiophene) (E _g=1.7 eV), P(t-EDOT-Th) (E _g=1.62 eV) has the lowest band gap. Hence, we speculate that the band gaps of the two polymers, having 3D structures, are decreased in contrast to non-substituted polymers or bi-EDOT substituted polymers, thiophene and 1-methyl-1H-pyrrole. The results indicated that P(t-EDOT-Th) thin films are more stable and show higher transmittance amid two polymers, which may find their utilization in organic optoelectronics.     

Relationship between the internal pressure and cohesive energy density of a liquid nonelectrolyte. Consequences of application of Dack’s concept

Dack’s concept that correlates internal pressure with cohesive energy density of a liquid system is shown to be applicable to identification of energy and structural changes in series of alkanols: MeOH, EtOH, n-PrOH, (i-PrOH), and n-BuOH, (t-BuOH). The side chain of methyl groups that appears in the molecule loosens the structural packing of the alkanol, creating additional steric hindrances for stable hydrogen bonds in alcohol media.     

Aromaticity of Bare Iridium Trimers and Ir3M0/+ and $$\rm{Ir}_3M_2^{+/3+}$$ (M = Li,Na, K,and Be,Ca) Bimetallic Clusters

The structural stabilities, bonding nature, electronic properties, and aromaticity of bare iridium trimers \(\rm{Ir}_3^{+/-}\) with different geometries and spin multiplicities are studied at the DFT/B3LYP level of theory. The ground state of the \(\rm{Ir}_3^{+}\) cation is found to be the ³A₂ (C_2v) triplet state and the ground state of the \(\rm{Ir}_3^{-}\) anion the ⁵A₂ (C_2v) quintet state. A detailed molecular orbital (MO) analysis indicates that the ground-state \(\rm{Ir}_3^{+}\) ion (C_2v, ³A₂) possesses double (σ and partial δ) aromaticity as well as the ground-state \(\rm{Ir}_3^{-}\) ion (C_2v, ⁵A₂). The multiple d-orbital aromaticity is responsible for the totally delocalized three-center metal-metal bond of the triangular Ir₃ framework. \(\rm{Ir}_3^{-}\) (C_2v, ¹A₁) structure motif is perfectly preserved in pyramidal Ir₃M^0/+ (C_s, ¹A′) and bipyramidal \(\rm{Ir}_3M_2^{+/3+}\) (C_2v, ¹A₁) (M = Li, Na, K and Be, Ca) bimetallic clusters which also possess the corresponding d-orbital aromatic characters.     

Vinyl Ethers Containing an Epoxy Group: XXII. Synthesis and Base-Catalyzed Transformations of 1-(Allyloxy)- and 1-[2-(Vinyloxy)ethoxy]-3-(2-propynyloxy)propan-2-ols

Reactions of 2-(allyloxymethyl)- and 2-[2-(vinyloxy)ethoxy]methyloxiranes with 2-propynol (～3 wt % of t-BuOK, 75–85°C, 5–10 h) lead to formation of new 1-organyloxy-3-(2-propynyloxy)propan-2-ols (yield 65–95%). On heating to 45–100°C in the presence of bases (KOH, t-BuOK), 1-allyloxy- and 1-[2-(vinyloxy)ethoxy]-3-(2-propynyloxy)propan-2-ols are transformed into the corresponding 2-vinyl-1,3-dioxolane, 6-methyl-2,3-dihydro-1,4-dioxine, 6-methylene-1,4-dioxane, and 2,3-dihydro-5H-1,4-dioxepine derivatives, whose yield and ratio strongly depend on the solvent nature, catalyst, and substituent at the hydroxy group. 2-Vinyl-1,3-dioxolane and 6-methyl-2,3-dihydro-1,4-dioxine derivatives are formed as the major products (yield 70–99%) in the presence of t-BuOK in aprotic media (toluene, THF, DMSO) or in the absence of a solvent as a result of prototropic isomerization followed by intramolecular heterocyclization. Intramolecular nucleophilic cyclization of 3-(2-propynyloxy)propan-2-ols to 6-methylene-1,4-dioxane is the predominant process in water in the presence of KOH. In all cases, the fraction of 2,3-dihydro-5H-1,4-dioxepine derivatives among the cyclization products ranges from 0 to 5% (KOH) or to 14% (t-BuOK).     

Solvent,substituent, and dimerization effects on the ring-opening mechanisms of monosilacyclopropylidenoids: a theoretical study

Density functional theory and ab initio computations elucidated the ring-opening of substituted (R = –CF₃, –CN, –CH₃, –H, –NH₂, –OCH₃, –OH, –SiH₃) 1-bromo–1-lithiosilirane 1 and 2-bromo–2-lithiosilirane 2 to LiBr complexes of 2-silaallene and 1-silaallene, respectively. Formally, two competitive pathways can be considered. The ring-opening reaction can take place through a concerted manner via TS3. Alternatively, the reaction may proceed in a stepwise fashion with the intermediacy of a free silacyclopropylidene–LiBr complex 7. In both cases, the position of the substituents determines the kinetic of the reactions. The structures with an electron-donating group are generally unstable, whereas the silacyclopropylidenoids bearing electron-withdrawing substituents are particularly stable species. Here, we propose the ring-opening of 5a–h to corresponding LiBr complexes of 2-silaallenes can proceed in both concerted and stepwise mechanism except for –H, –CH₃, and –SiH₃. The obtained activation energies for the ring-openings of 5a–h to related 2-silaallenes are too high for a reaction at room temperature with up to 61.4 kcal/mol. In contrast, the activation energy barriers for the isomerization of 6a–h to the LiBr complexes of 1-silaallenes was determined to be relatively low at the B3LYP/6-31+G(d,p), M06/6-31+G(d,p), and MP2/6-31+G(d,p) levels. Moreover, we have also investigated the solvent effect on the unsubstituted models using both implicit and explicit solvation models. The energy barriers of the solvated models are found to be slightly higher than the results of gas phase calculations. Additionally, the ring-opening of dimer 6 (6–Dim) is also calculated for the ring-opening mechanism with the energy barrier of 3.7 kcal/mol at B3LYP/6-31+G(d,p) level of theory.     

Enantioseparation of Phenylsuccinic Acid Enantiomers by Solvent Sublation with Collaborative Selectors

A new solvent sublation (SS) system for chiral separation is introduced by using phenylsuccinic acid (H₂A) as the model enantiomers. The experiments were carried out in a traditional SS apparatus but with collaborative chiral selectors: dibenzoyl-L-tartaric acid (L-DBTA) in the organic phase and hydroxypropyl-β-cyclodextrin (HP-β-CD) in the aqueous phase. The chiral recognition abilities of the two selectors are opposite for the H₂A enantiomers. Several important parameters were investigated. The results demonstrate that enantioselective sublation and partitioning behavior are mainly dependent on the pH of the solution, the concentrations of chiral selectors and H₂A. Furthermore, the flow rate of air and flotation time also have some effects on the enantioseparation. Under the optimized conditions, the enantioselectivity expressed by the separation factor (β) and enantiomer excess (e.e.%) are 2.47 and 29.50%, and the yields of R-H₂A and S-H₂A are 0.23 and 0.13 g·L^?1, respectively. Compared with the SS system with the single selector HP-β-CD in the aqueous phase (or L-DBTA in the organic phase), the increased values of β and e.e.% in the new SS system with collaborative selectors are 1.31 (or 1.38) and 5.90% (or 13.82%), respectively.     

Titanium tetra-<Emphasis Type="Italic">tert</Emphasis>-butoxide-<Emphasis Type="Italic">tert</Emphasis>-butyl hydroperoxide oxidizing system: Physicochemical and chemical aspects

The reaction of titanium tetra-tert-butoxide with tert-butyl hydroperoxide (1: 2) (C₆H₆, 20 C) involves the steps of formation of the titanium-containing peroxide (t-BuO)₃TiOOBu-t and peroxytrioxide (t-BuO)₃TiOOOBu-t. The latter decomposes with the release of oxygen, often in the singlet form, and also homolytically with cleavage of both peroxy bonds. The corresponding alkoxy and peroxy radicals were identified by ESR using spin traps. The title system oxidizes organic substrates under mild conditions. Depending on the substrate structure, the active oxidant species can be titanium-containing peroxide, peroxytrioxide, and oxygen generated by the system.     

Polarization of the contact between fluorine-conducting solid electrolyte and metal alloys

The kinetics of low-sized phase formation on polarization of the interface between LaF₃:Eu²⁺ and Pb–Sn, Sn–Bi, and Sb–Bi alloys is studied by the potentiostatic and linear voltammetry methods. The analysis of anodic transients shows that the new phase formation involving fluoride ions from the solid electrolyte proceeds by the mechanism of instantaneous two-dimensional or three-dimensional nucleation. Comparison of calculated and experimental transients describing the instantaneous nucleation with either two-dimensional growth on the I/I _m vs. t/t _m coordinates or three-dimensional growth on the I ²/I _m ² vs. t/t _m coordinates shows adequate agreement between the model and the initial regions of experimental curves. The properties of phases formed depend on the alloy composition and the polarization conditions as well as on the energy of interaction between components in the alloy and in the new phase.     

The use of recurrent equations in chromatography

Recurrent equations A(x + k) = aA(x) + b were shown to be applicable to the approximation not only of virtually arbitrary properties of organic compounds (A) in homologous series (A = n _C, k = 1 or 2) but also of the dependences of chromatographic retention parameters on the number of carbon atoms in homologue molecules (A = t _R). The same equations described the temperature dependences of retention times of arbitrary compounds under isothermal separation conditions in gas chromatography (x = T, k = ΔT = const) and the dependences of retention times on the concentration of an organic solvent as an eluent component (x = C, k = ΔC = const) under isocratic separation conditions in high performance liquid chromatography.     

Crystal structures of 1,1,1-trifluoro-4-hydroxy-4-phenyl-but-3-en-2-one, 2,2,6,6-tetramethyl-3-hydroxy-hept-3-en-5-one, 2,2,6,6-tetramethyl-3-methylamino-hept-3-en-5-one and a study of the ability of these ligands to complex formation with metals

Crystal structures are determined (Bruker Nonius X8 Apex, 4K CCD-detector, λMoK _α, graphite monochromator, T 150 K and 293 K) for two β-diketones F₃CC(O)CH₂C(O)Ph (1) (space group P2₁/c, a = 7.0713(3)Å, b = 11.5190(6)Å, c = 11.3602(6) Å, β = 99.405(2)°, V = 912.90(8) ų, Z = 4), (CH₃)₃CC(O)CH₂C(O)C(CH₃)₃ (2) (space group Pbca, a = 11.5536(8) Å, b = 11.5796(10) Å, c = 17.2523(13) Å, V = 2308.1(3) ų, Z = 8) and a ketoimine (CH₃)₃CC(NCH₃)CH₂C(O)C(CH₃)₃ (3) (space group I4₁/a, a = 18.7687(6) Å, b = 18.7687(6) Å, c = 14.5182(6) Å, V = 5114.2(3) ų, Z = 16). All structures are molecular and comprise isolated molecules joined by van der Walls interactions. The substitution energy of a Na atom for a hydrogen atom in free ligands is calculated by the hybrid B3LYP quantum chemical method. A successful preparation of Na(I) chelates with ligands 1, 2 and failed attempts to prepare a complex with ligand 3 are in accordance with the calculations. Geometrical simulation of a copper(II) complex with ligand 3 reveals the overlap of CH₃ groups which hinders the complexation.     

RAFT polymerization of linear ABC triblock copolymer P<Emphasis Type="Italic">t</Emphasis>BA-<Emphasis Type="Italic">b</Emphasis>-PS-<Emphasis Type="Italic">b</Emphasis>-P2VP and regulation of its hierarchical self-assembly structure in solution

Linear ABC triblock copolymer PtBA₁₅₄-b-PS₃₀₀-b-P2VP₂₄₀ was successfully synthesized by RAFT polymerization. Block copolymer micelles were prepared by the two-step hierarchical self-assembly process. Size exclusion chromatography and ¹H NMR were used to characterize the structure of samples. Morphologies and size of micelles were determined by transmission electron microscope. The results showed that the densely dispersed spherical micelles of PtBA₁₅₄-b-PS₃₀₀-b-P2VP₂₄₀ were obtained in the first step of the hierarchical self-assembly process. In the second step, core-compartmentalized micelle strings with different lengths and distribution densities were obtained when the primary self-assembled solution was dialyzed in distilled water with pH ≈ 3. When distilled water with pH ≈ 3 was added drop-wise to this solution, uniformly dispersed spherical core-compartmentalized micelles of PtBA₁₅₄-b-PS₃₀₀-b-P2VP₂₄₀ were prepared. Thus, hierarchical self-assembly structure of linear ABC triblock copolymer was obtained successfully and the preparation of uniformly dispersed spherical micelles of triblock copolymers was realized simply by changing the secondary self-assembly methods.     

Rheological study on the cure kinetics of two-component addition cured silicone rubber

The cure kinetics for two-component silicone rubber formed by addition reaction was studied by the rheological method. The influence of reaction temperature (T) on the cure kinetics was explored in detail. It was observed that the data of gel time (t _gel, i.e. the time when the reaction reaches the gel point) or a specific reaction time (t _nc) (defined as the reaction time before which time the influence of confinement of network on the diffusion of reaction components can be neglected) versus T obey certain functional relationship, which was well explained by the cure kinetics model of thermoset network. The cure kinetics for the two-component silicone rubber can be well fitted by the Kamal-Sourour(autocatalyst) reaction model rather than Kissinger model. When the reaction time was before or equal to t _nc, the reaction order obtained by the Kamal-Sourour reaction model was 2, which was consistent with the reaction order inferred from the two components chemical reaction when the diffusion of reaction components was not influenced by the formed cross-linked polymer network. When the reaction time was larger than t _nc, such as to the end of reaction (t _e), the influence of confinement of network on the diffusion of reaction components cannot be neglected, and the reaction order obtained by the Kamal-Sourour reaction model was larger than 2. It was concluded that the confinement effect of network had a greater influence on the cure kinetics of the silicone rubber. The reaction rate constants (k _r) under different temperatures were also determined by Kamal-Sourour reaction model. The activation energy (E) for the two-component silicone rubber was also calculated from the results of lnt _gel, lnt _nc, and lnk _r versus 1/T, respectively. The three values of E were close, which indicated that above analyses were self-consistent.     

Steric structure of alkyl 2-aryl(hetaryl)hydrazono-3-fluoroalkyl-3-oxopropionates

Steric structure of fluorinated 2-arylhydrazono-3-oxo esters was studied by ¹H, ¹⁹F, and ¹³C NMR spectroscopy and X-ray analysis. It was found that these compounds in the crystalline state and in solutions in acetone-d ₆, DMSO-d ₆, and CDCl₃ exist as Z isomers with the ester fragment involved in intramolecular hydrogen bond with the hydrazone NH proton. Exceptions are alkyl 2-arylhydrazono-4,4-difluoro-3-oxobutanoates which exist in acetone-d ₆ as mixtures of Z and E isomers, the former prevailing. Unlike fluorinated analogs, ethyl 2-(4-methylphenyl)hydrazono-3-oxobutanoate in crystal has the structure of E isomer in which intramolecular hydrogen bond is formed between the NH proton and acetyl carbonyl group. The same compound in acetone-d ₆, DMSO-d ₆, and CDCl₃ gives rise to a mixture of Z and E isomers, the latter prevailing.     

Effect of solvent nature on the photoreduction kinetics of substituted benzoquinones

Effect of the solvent nature on the kinetics of photoreduction of substituted benzoquinones in the presence of hydrogen donors has been studied. It has been found that the effective photoreduction rate constant (k_H) for quinones decreases with an increase in solvent polarity. For the 3,6-di-tert-butylbenzoquinone–1,2-N,N-dimethylaniline pair, the dependence of ln k_H on the difference of the reciprocals of optical and static solvent permitivities (1/ε _∞–1/ε₀) is stepwise with a break point corresponding to CH₂Cl₂. A similar relationship lnk_H = f(1/ε _∞–1/ε₀) is observed for the p-chloranil–mesitylene pair. In the study of the photoreduction kinetics for a series of seven o-benzoquinones in the presence of p-derivatives of N,N-dimethylaniline in CH₂Cl₂, it has been found that the dependence of k_H on the free energy of electron transfer (ΔG_e) has a maximum for the 3,6-di-tert-butylquinone-1,2–N,N-dimethylaniline pair at ΔG_e = 0.11 eV.