Linear Aliphatic Amines Research Articles

Remote Alkynylation of Aliphatic Amines.

Advancements in transition metal catalyzed C-H activation/functionalization cascades have allowed the synthetic chemist's toolbox to be significantly expanded. Despite this, protocols for the remote alkynylation of linear aliphatic amines still remain limited. Herein, a palladium-catalyzed directing-group approach to alkynylation of aliphatic amines is disclosed. The synthetic utility was demonstrated with a gram-scale reaction and a functional group compatibility test.

Yttrium‐Catalyzed Intermolecular Hydroamination of Norbornene with Simple Amines

AbstractThe intermolecular hydroamination of norbornene with simple amines was achieved using silyl‐substituted ortho‐terphenoxide yttrium complexes. Excellent conversion was obtained for both benzylic and aliphatic amines. For benzyl and linear aliphatic amines, the highest activity was observed for the sterically more encumbered methyldiphenylsilyl‐substituted complex, whereas the trimethylsilyl‐substituted complex was more active for sterically encumbered primary amines.

Unveiling the Quantitative Relationships between Electron Distribution and Steric Hindrance of Organic Amines and Their Reaction Rates with Carbonyl Sulfur: A Theoretical Calculation Investigation.

The removal of carbonyl sulfide (COS) commonly contained in natural gas is of great significance but still very challenging via a widely employed absorption process due to its low reactivity and solubility in various commercial solvents. Artificial intelligence (AI) is playing an increasingly important role in the exploration of desulfurization solvents. However, practically feasible AI models still lack a thorough understanding of the reaction mechanisms. Machine learning (ML) models established on chemical mechanisms exhibit enhanced chemical interpretability and prediction performance. In this study, we constructed a series of solvent molecules with varying functional groups, including linear aliphatic amines, cyclic aliphatic amines, and aromatic amines and proposed a three-step reaction pathway to dissect the effects of charge and steric hindrance of different substituents on their reaction rates with COS. Chemical descriptors, based on electrostatic potential (ESP), average local ionization energy (ALIE) theory, Hirshfeld charges, and Fukui functions, were used to correlate and predict the electrophilic reactivity of amine groups with COS. Substituents influence the reaction rate by changing the attraction interaction of amine groups to COS molecules and the electron rearrangement in the electrophilic reaction. Furthermore, they have more pronounced steric effects on the reaction rate in the linear amines. The descriptors N_ALIE and q(N) were found to be crucial in predicting the reactivity of amine groups with COS. Present study provides a comprehensive understanding of the reaction mechanisms of COS with amine compounds, offers specific chemical principles for the development of chemistry-driven ML models, sheds light on other types of electrophilic reactions occurring on amine and phosphine groups, and guides the development of chemical solvents in gas absorption processes.

Flexible covalent organic framework membranes with linear aliphatic amines for enhanced organic solvent nanofiltration

COF membranes were synthesized using aliphatic diamines with tunable pore size for precise separation, solvent permeance, and fouling resistance. These membranes showed good operational stability and potential for various filtration applications.

Orthogonal Access to α-/β-Branched/Linear Aliphatic Amines by Catalyst-Tuned Regiodivergent Hydroalkylations.

Linear, α-branched, and β-branched aliphatic amines are widespread in pharmaceuticals, agrochemicals, and fine chemicals. Thus, the development of direct and efficient methods to these structures in a tunable manner is highly desirable yet challenging. Herein, a catalyst-controlled synthesis of α-branched, β-branched and linear aliphatic amines from Ni/Co-catalyzed regio- and site-selective hydroalkylations of alkenyl amines with alkyl halides is developed. This catalytic protocol features the reliable prediction and control of the coupling position of alkylation to provide orthogonal access to α-branched, β-branched and linear alkyl amines from identical starting materials. This platform unlocks orthogonal reactivity and selectivity of nickel hydride and cobalt hydride chemistry to catalytically repurpose three types of alkyl amines under mild conditions.

Orthogonal Access to α‐/β‐Branched/Linear Aliphatic Amines by Catalyst‐Tuned Regiodivergent Hydroalkylations

AbstractLinear, α‐branched, and β‐branched aliphatic amines are widespread in pharmaceuticals, agrochemicals, and fine chemicals. Thus, the development of direct and efficient methods to these structures in a tunable manner is highly desirable yet challenging. Herein, a catalyst‐controlled synthesis of α‐branched, β‐branched and linear aliphatic amines from Ni/Co‐catalyzed regio‐ and site‐selective hydroalkylations of alkenyl amines with alkyl halides is developed. This catalytic protocol features the reliable prediction and control of the coupling position of alkylation to provide orthogonal access to α‐branched, β‐branched and linear alkyl amines from identical starting materials. This platform unlocks orthogonal reactivity and selectivity of nickel hydride and cobalt hydride chemistry to catalytically repurpose three types of alkyl amines under mild conditions.

Atomistic Modeling of Dual-Cured Thermosets Based on Glycidyl Methacrylate and Hardeners with Various Architecture and Functionality

We report a versatile computational procedure for making and testing dual-cured thermosets based on a sequential chain-growth polymerization mechanism and step-growth polymerization mechanism, applicable to the generation of dual-cured thermosets with tunable macroscopic properties. The first stage involves a chain-growth polymerization of glycidyl methacrylate (GMA) monomers in the presence of hardeners, and the second stage is based on the step-growth polymerization of the epoxide bearing side chains of the polymerized GMA, p(GMA), with amine groups of the hardeners with various architecture and functionality, namely diethylenetriamine (DETA), isophoronediamine (IPDA), tris(2-aminoethyl)amine (TREN), and diethyltoluenediamine (DETDA). The mobility of the hardener in the once-cured samples determined the final density of the dual-cured samples. The faster the hardener is in the sample, the higher is the density of the dual-cured sample. Mechanical properties of the dual-cured samples showed a dependence on the architecture of hardener. The samples cured with linear aliphatic amines (DETA and TREN) obtained smaller Young’s modulus values compared with the samples cured with cyclic (aliphatic or aromatic) amines (IPDA and DETDA).

Pd-Catalyzed γ-C(sp3)-H Fluorination of Free Amines.

The first example of free amine γ-C(sp3)-H fluorination is realized using 2-hydroxynicotinaldehyde as the transient directing group. A wide range of cyclohexyl and linear aliphatic amines could be fluorinated selectively at the γ-methyl and methylene positions. Electron withdrawing 3,5-disubstituted pyridone ligands were identified to facilitate this reaction. Computational studies suggest that the turnover determining step is likely the oxidative addition step for methylene fluorination, while it is likely the C-H activation step for methyl fluorination. The explicit participation of Ag results in a lower energetic span for methylene fluorination and a higher energetic span for methyl fluorination, which is consistent with the experimental observation that the addition of silver salt is desirable for methylene but not for methyl fluorination. Kinetic studies on methyl fluorination suggest that the substrate and PdL are involved in the rate-determining step, indicating that the C-H activation step may be partially rate-determining. Importantly, an energetically preferred pathway has identified an interesting pyridone-assisted bimetallic transition state for the oxidative addition step in methylene fluorination, thus uncovering a potential new role of the pyridone ligand.

Silanization Efficiency of Silica/Silane in Dependence of Amines in Natural Rubber-based Tire Compounds

Silica-silane technology for low rolling resistance tire compounds requires efficient bridging between the silica surface and rubber molecules through silanization and coupling reactions. The presence of diphenylguanidine (DPG) as secondary vulcanization accelerator is also needed to catalyze the silanization reaction between the alkoxy groups of silane coupling agents and the silanol groups on the silica surface. However, DPG can liberate toxic aniline under high mixing temperatures and therefore safer alternatives are required. This study investigates the influence of amines with different structures, i.e. hexylamine (HEX), octadecylamine (OCT), cyclohexylamine (CYC) and dicyclohexylamine (DIC) on the primary silanization reaction rate constant in a model system, and on interfacial compatibility of practical silica-reinforced NR compounds. Compared to the system without, the amines clearly increase the reaction rate constant for which linear aliphatic amines work better than cyclic ones. This is due to better accessibility of the amines towards the silica surface, in agreement with the values of Payne effect as observed in the rubber compounds, except for the OCT case. The lowest Payne effect of the OCT-containing rubber compound is attributed to the additional shielding effect obtained from the long alkyl-chain that leads to more hydrophobicity, resulting in good physical interaction between silica and rubber. The presence of all amines improves the cure properties in which the linear aliphatic amines give shorter cure times than the cyclic aliphatic ones. As a result of good interfacial compatibility, the OCT-containing compound which shows lowest filler-filler interaction gives good mechanical properties that are closest to the reference compound with DPG.

Enhancing the Silanization Reaction of the Silica-Silane System by Different Amines in Model and Practical Silica-Filled Natural Rubber Compounds.

Diphenyl guanidine (DPG) is an essential ingredient in silica-reinforced rubber compounds for low rolling resistance tires, as it not only acts as a secondary accelerator, but also as a catalyst for the silanization reaction. However, because of concern over the toxicity of DPG that liberates aniline during high-temperature processing, safe alternatives are required. The present work studies several amines as potential alternatives for DPG. Different amines (i.e., hexylamine, decylamine, octadecylamine, cyclohexylamine, dicyclohexylamine, and quinuclidine) are investigated in a model system, as well as in a practical rubber compound by taking the ones with DPG and without amine as references. The kinetics of the silanization reaction of the silica/silane mixtures are evaluated using model compounds. The mixtures with amines show up to 3.7 times higher rate constants of the primary silanization reaction compared to the compound without amine. Linear aliphatic amines promote the rate constant of the primary silanization reaction to a greater extent compared to amines with a cyclic structure. The amines with short-alkyl chains that provide better accessibility towards the silica surface, enhance the primary silanization reaction more than the ones with long-alkyl chains. The different amines have no significant influence on the rate constant of the secondary silanization reaction. The amine types that give a higher primary silanization reaction rate constant show a lower flocculation rate in the practical compounds. For the systems with a bit lower primary silanization reaction rate, but higher extent of shielding or physical adsorption that still promotes higher interfacial compatibility between the elastomer and the filler surface, the rubber compounds show a lower Payne effect which would indicate lower filler-filler interaction. However, the flocculation rate constant remained high.

REINFORCEMENT OF NATURAL RUBBER BY SILICA/SILANE IN DEPENDENCE OF DIFFERENT AMINE TYPES

ABSTRACT Diphenyl guanidine (DPG) is the most commonly used secondary accelerator in silica-reinforced rubber compounds because of its additional positive effect on the silanization reaction and deactivation of free silanol groups that are left over after the silanization. However, because of health and safety concerns about the use of DPG, which decomposes to give highly toxic aniline during high processing temperature, safe alternatives are required. This work investigates the effect of various types of aliphatic amines having alkyl or cyclic structures and similar pKa (i.e., hexylamine [HEX], decylamine [DEC], octadecylamine [OCT], cyclohexylamine [CYC], dicyclohexylamine [DIC], and quinuclidine [QUI]) on the properties of silica-reinforced natural rubber (NR) compounds by taking the ones with DPG and without amine as references. When compared with the compound without amine, the use of all amine types reduces filler–filler interaction (i.e., the Payne effect) and enhances filler–rubber interaction, as indicated by bound rubber content and decreased heat capacity increment. The amines with alkyl chains can reduce the Payne effect and enhance cure rate to a greater extent compared with the amines with cyclic rings as a result of better accessibility toward the silica surface and a shielding effect because of less steric hindrance. The longer carbon tails on linear aliphatic amines ranging from HEX, DEC, to OCT lead to a lower Payne effect, lower heat capacity increment, higher bound rubber content, and higher modulus as well as tensile strength. Overall, the use of OCT provides silica-reinforced NR compounds with properties closest to the reference one with DPG and can act as a potential alternative for DPG.

Development of structure/property relation based on surface thermodynamic properties of alkyl-pyridine and aliphatic amines

In this article, available experimental surface entropy, surface energy, and surface tension values were used to study the structure/property relation in pyridine, its alkyl derivatives, and linear aliphatic amines. Dipole moment was employed as molecular descriptor. Density functional theory and polarizable continuum model were used to calculate dipole moments in gas and in liquid states, respectively. Surface entropies importantly conform to dipole moments and to the trend characteristics of molecular structures. The decrease of surface entropy with alkyl chain length indicates more aggregation and alignment of surface molecules; similarly the decrease in surface tension suggests the non-polar part exposing more to the vapor side of the interface. Applying these to amines substantiates structure/property relation based on surface properties and dipole moment. Møller–Plesset theory and density functional theory were used to calculate the dipole moment and both correlate adequately with surface properties. These results suggest treatment of surface energy and surface entropy as part of usual qualitative prediction of solvation capability of liquids.

Mechanical properties of epoxy networks based on DGEBA and aliphatic amines

AbstractThe mechanical properties of epoxy networks based on diglycidyl ether of bisphenol A epoxy resin cured with various linear aliphatic amines, such as ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and cyclic amines such as 1‐(2‐aminoethyl)piperazine and isophorone diamine, were studied. General characteristics such as Tg, density, and packing density, were determined and related to the structure and funcionality of the curing agent. Dynamic mechanical spectra were used to study both the α and β relaxations. Tensile and the flexural tests were used to determine the Young's and flexural modulus, and fracture strength all in the glassy state. Furthermore, linear elastic fracture mechanics was used to determine KIC. As a rule, isophorone diamine network presented the higher tensile and flexure modulus while 1‐(2‐aminoethyl)piperazine gave the highest toughness properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Guest Selectivity in Complexation of β-Chitin

Guest selectivity in complexation of β-chitin with small molecules was studied. Since amines are strong agents for β-chitin complexation, selectivity for various amines was studied first. Of three isomers of phenylenediamine, the para isomer formed a complex, while ortho and meta isomers did not. The selectivity for linear aliphatic amines was examined for equimolar mixtures of various combinations, i.e., primary−secondary−tertiary amines of C6 main chain; C5 diamine and C6 monoamine; and C6 monoamine and C8 monoamine. The results showed a clear selectivity for primary amine over secondary and tertiary, diamine over monoamine, and longer alkyl chain over a shorter one. On the basis of such selectivity, complexation by guest incorporation from solution was established. This procedure allowed β-chitin complexation with high melting point compounds, to which pure liquid treatment was not applicable. By the solution treatment, complexes with acrylamide, p-aminobenzoic acid, and d-glucose were successfully prepared. In this method, even low-solubility combinations such as acrylamide/benzene (0.3% (w/w)) were found effective, presumably because of high chemical potential of solutes in the solution. The wide variety of guest species thus attained is expected to be useful in applications such as drug delivery or composite material preparation.

Effects of Chemistries of Trifunctional Amines on Mechanisms of Michael Addition Polymerizations with Diacrylates

The mechanisms of the Michael addition polymerizations of different trifunctional amines with an equimolar 1,4-butanediol diacrylate (BDA) were investigated by using 1H and 13C NMR to in situ monitor the polymerization processes. The trifunctional amine monomers adopted were 1-(2-aminoethyl)piperazine (AEPZ) and 4-(aminomethyl)piperidine (AMPD) and linear aliphatic amines with different steric hindrance on the 2° amines (original), i.e., N-methylethylenediamine (MEDA), N-ethylethylenediamine (EEDA), and N-hexylethylenediamine (HEDA). For AEPZ, AMPD, and MEDA with low steric hindrance on the 2° amines (original), the reactivity sequence of the three types of amines was 2° amines (original) > 1° amines ≫ 2° amines (formed) and linear poly(amino ester)s were formed via AB-type intermediates due to the 2° amines (formed) being kept out of the reaction. However, AB-type intermediates were only formed from the 2° amines (original) for AEPZ and AMPD, but from both the 2° amines (original) and 1° amines due to th...

Inclusion complex of beta-chitin and aliphatic amines.

Inclusion complexation of beta-chitin with linear aliphatic amines was studied by X-ray diffraction. All tested amines, C3 to C8 monoamines and C2 to C7 diamines with terminal amino groups, reversibly formed crystalline complexes with beta-chitin by immersion of dry chitin in pure liquid. Complex formation caused linear increase in the 010 sheet spacing of beta-chitin depending on the carbon number of amine. The complexes could be classified as type I and type II according to the increment of sheet spacing against carbon number. All monoamines formed type II complexes. In dry conditions, diamine formed a type I complex though the type of diamine complex differed for guest species in wet conditions. Based on the unit cell dimension and thermogravimetry, type II and type I are likely to correspond to guest-host (amine-chitobiose) ratios of 2:1 and 1:1, respectively. These differences seem to arise from varied interactions between functional groups of chitin and amines.

Structural and Electrical Characterization of Polymeric Haloplumbate(II) Systems

The synthesis and the structural, thermal, and electrical characterization of haloplumbate(II) systems are described. The counterions are diprotonated linear aliphatic amines, such as the 2-methylpentane-1,5-diamine (2meptH2) and propane-1,3-diamine (pnH2) dications. The (2meptH2)[PbCl4] and (2meptH2)[PbBr4] are isostructural, space group Cc, with a = 24.140(4) Å, b = 7.720(2) Å, c = 7.795(2) Å, β = 98.1(1)°, Z = 4 for the chlorine compound and a = 24.539(4) Å, b = 8.031(2) Å, c = 8.198(2) Å, β = 99.6(1)°, Z = 4 for the bromine compound; the (2meptH2)[Pb1.5I5] crystallizes in the triclinic P1̄ space group, with a = 11.803(3) Å, b = 12.565(3) Å, c = 8.494(8) Å, α = 106.2(1)°, β = 100.5(1)°, γ = 117.4(1)°, Z = 2; the crystals of (pnH2)[PbCl4] are orthorhombic, space group P212121, a = 19.247(4) Å, b = 7.862(2) Å, c = 7.581(2) Å, Z = 4; the (pnH2)2[Pb1.5Br7]·H2O crystallizes in the triclinic P1̄ space group, with a = 11.517(3) Å, b = 14.122(3) Å, c = 8.149(2) Å, α = 104.1(1)°, β = 109.8(1)°, γ = 77.5(1)°, Z = 2. Three different types of polymeric haloplumbate(II) systems were obtained: strictly monodimensional, (2meptH2)[Pb1.5I5], ribbonlike, (pnH2)2[Pb1.5Br7]·H2O, and perovskite-like structures, (pnH2)[PbCl4] and (2meptH2)[PbX4] (X = Cl, Br). Worthy of note is the presence of organic dications in their extended form, intercalated between the inorganic anions, which are at different distances, depending on the amine length. The nitrogen atoms of the ammonium cations interact with the inorganic anions forming a network of hydrogen bonds, which contribute to the crystal packing.

Acylanthranils. 7. Influence of the end group on selectivity in the reaction of .omega.-substituted linear aliphatic amines with acetylanthranil

Acylanthranils. 7. Influence of the end group on selectivity in the reaction of .omega.-substituted linear aliphatic amines with acetylanthranil

Acylanthranils. 8. Question of Newman steric hindrance in the reaction of linear aliphatic amines with acetylanthranil

Acylanthranils. 8. Question of Newman steric hindrance in the reaction of linear aliphatic amines with acetylanthranil