Alkyl Length Research Articles

Oleochemical carbonates: A comprehensive characterization of an emerging class of organic compounds

Dialkyl carbonates (DAC) with short-medium alkyl length - oleochemical carbonates – are attracting attention because of their appealing properties, including low viscosity, flammability, toxicity, environmental impact and wide range of applications: lubricants, personal care, fuel additives etc. However, not much is known concerning their chemical physical properties and, more importantly, on the nature of microscopic correlations that eventually determine bulk performances. In view of this paucity, we present a large exploration of a series of chemical physical properties of a set of DACs ranging from dimethyl up to didodecyl carbonate. This study extends previously determined databases, thus providing a complete picture of the temperature dependence of chemical physical properties around room temperature. Furthermore, we explored the microscopic morphology of DACs, by synergic exploitation of X-ray scattering and Molecular Dynamics techniques. These tools allow detecting the existence of a distinct degree of mesoscopic spatial segregation between polar carbonate moieties and apolar alkyl chains domains. The role of first neighbour carbonate moieties in driving the corresponding molecules towards weak hydrogen bonding interactions and alkyl chain alignment is described. Such an effect is related to the overall mesoscopic segregation of alkyl tails that isolate small droplets formed by stacked carbonate groups. Such a highly compartmentalised morphology can explain and potentially suggest applications of DACs in fields as relevant as separation, catalysis, lubrication etc.

Facile Synthesis of Liquid Crystal Dimers Bridged with a Phosphonic Group.

Liquid crystal (LC) dimers with well-defined composition and structure arouse broad attentions for their exhibiting LC properties beyond conventional low molar mass mesogens and serving as fascinating model compounds for LC polymers. Here in this work, a series of LC dimers bridged with a phosphonic group have been synthesized through a facile free radical mediated addition reaction between hypophosphorous acid and vinyl terminated cyanobiphenyl mesogens with variant length alkyl spacers. In addition, two esterified derivatives and a group of mono-addition homologues with a terminal phosphonic acid group have also been prepared for comparison study. All the newly synthesized compounds exhibit monotropic nematic (N) phase with typical schlieren textures except for the LC dimer with the longest eleven-methylene spacer, which surprisingly shows twist-bend nematic (NTB ) phase directly from the isotropic state upon cooling. Moreover, the thermal transition properties such as the nematic-isotropic transition temperatures and associated entropy changes of the series LC dimers display a modest odd-even effect. Furthermore, both the LC dimers and the mono-addition homologues in N phase are quite easy to achieve homeotropic alignment upon annealing thanks to the supramolecular interactions between the introduced phosphonic acid group and the hydroxylated glass surface. This work thus provides a novel synthesis strategy for a class of LC materials bridged with a phosphonic acid group prone to further functionalization, which may serve as promising vertical alignment agents and pave the way for developing a new kind of functionalized LC materials of NTB phase.

The effect of extended alkyl length on molecular orientation of nonfullerene acceptor: A case study in as-cast polymer solar cells

In this work, the effective electronic coupling on the indacenodithiophene (IDT)-based nonfullerene core was investigated by changing the length of the linear alkyl side chain. Extended linear alkyl side chain reduces the extinction coefficient in thin films and promotes the tendency of nonfullerene molecules to edge-on orientation. The theoretical calculation illustrates that the enhanced electronic coupling stem from short alkyl side chain could be beneficial for face-on orientation and charge transport. For the as-cast solar cells, the devices based on IDIC with the short alkyl side chain possessed the best efficiency. Our result manifests that the linear alkyl chain on the core of nonfullerene acceptor dominates molecular packing mode, light absorption, bulk heterojunction size, charge carrier transport and recombination dynamics.

Optimal structure of acidic ionic liquids for synthesis of tetraphenylporphyrins

The structure of the most optimal acidic ionic liquids for the tetraphenylporphyrin synthesis was investigated, focusing on the cationic structure of ionic liquids. The investigation in [[Formula: see text]im][CF3CO2] ([Formula: see text]=1-12) with different lengths of alkyl groups at the N(1) position of imidazolium showed that the highest yield of tetraphenylporphyrin (20%) was obtained when the alkyl chain length was C8, which indicated that [HC8im][CF3CO2] is the optimal ionic liquid for the tetraphenylporphyrin synthesis. In addition, we also investigated the influence of electron-withdrawing and electron-donating substituents at the C(2), C(4), and C(5) positions of the imidazolium cation of the acidic ionic liquids on the synthesis of tetraphenylporphyrins. The highest tetraphenylporphyrin yields were obtained in [HC8mim][CF3CO2], which suggested that the imidazolium cation with an octyl group at the N(1) position and a methyl group at the C(2) position was the optimal structure.

Difference in the hydration state of water at the hydrophobic interface of structural isomers of propanol investigated by U.V visible absorption and Raman spectroscopic study

In this work, the nature of hydration shell water around hydrophobic groups of alcohol has been investigated by studying the U.V visible absorption energy shift of p-nitro-aniline upon interaction with water-alcohol mixture in different proportion. Analysis shows that, at low mole fraction of alcohol the absorption energy shift with composition of alcohol-water mixture originates from the interaction of hydrophobically modified water with PNA. It is further observed that, the absorption energy changes nonlinearly with the chain length of alkyl group of alcohol. From Raman studies it is apparent that, the absorption energy shift originates from the changing population of dangling OH interacting with PNA. The central part of the study has been to investigate the difference in the hydrophobic environment due to variation in the arrangement of hydrophobic groups in propanol. The U.V visible absorption studies of PNA in 1-propanol and 2-propanol water mixture show that 1-propanol bears higher population of dangling OH compared to 2-propanol. In addition, we have also performed Raman spectroscopic studies in the region of OH stretch. The spectra of hydration shell water are extracted by RD-SCF method. The characteristic peak due to dangling OH was analyzed and it also shows 1-propanol to possess relatively higher amount of dangling OH compared to 2-propanol. This joint study confirms that arrangement of hydrophobic moiety in small molecules can affect the water hydrogen bonding of water at the hydrophobic interface.

Revealing the roles of hydrogen bond and Al2Cl7− anion species and kinetics for ionic liquid catalyzed transesterification of ethylene carbonate with methanol

The co-production of dimethyl carbonate (DMC) and ethylene glycol (EG) from the transesterification of ethylene carbonate (EC), which is synthesized from CO2 and ethylene oxide, with methanol has received researchers’ attention. Herein, this transformative process catalyzed with metal chloride-based ionic liquids (ILs) was investigated by employing spectroscopic characterizations in combination with kinetic studies. The interaction between cation and methanol via hydrogen bond and activation of carbonyl group in EC (or 2-hydroxyethyl methyl carbonate, HEMC) by metal chloride-contained anion were identified to show synergistic effects on catalytic transesterification. The chain length of alkyl group substituted at the 1-position N atom in imidazole ring affected the reaction rates due to the steric hindrance effect. Not AlCl4− but Al2Cl7− anion species in AlCl3-based IL exhibited activity in this transesterification, and the content of Al2Cl7− species was observed to show linear relationship with the transformative rates of both EC and HEMC. The kinetic studies also elucidated that the rates of both EC (or HEMC) and methanol are first-order dependent on their concentrations, and the formation of HEMC intermediate was the kinetic-relevant step with the activation barrier of 92 kJ/mol. As a result, the yield and selectivity of DMC (or EG) could reach up to around 95 % and 97 % with catalysis of [MDMIM]Cl/AlCl3 with AlCl3 molar fraction of 0.67 after 12 h reaction at 140 °C, which showed higher performance than any other tested metal chloride-based IL. Besides, no decay in catalytic activity and selectivity of this IL was observed after 10 times’ recycling.

MCM-41 supported S-alkyl/aryl-substituted 2-mercaptobenzothiazolium-based ionic liquids: synthesis, characterization, and application in the fuel desulfurization

Supported ionic liquids (SILs), synthesized by immobilization of ionic liquids (ILs) onto solid support materials, have played an effective role in several applications like fuel desulfurization, organic catalysis, gas separations, biofuel synthesis, etc., in comparison to pure ILs which suffer from many drawbacks like difficult recovery, high cost, mass transfer issue owing to large viscosity, toxic nature, complications in product purifications and fixed bed reactor technology. In this study, a series of new SILs (MCM-41@[S-RBTh][Cl]; R = aryl/alkyl groups) were synthesized via immobilization of different S-alkyl/aryl-substituted 2-mercaptobenzothiazolium-based ILs onto MCM-41 silica support. Structure elucidation of SILs was achieved through SEM, EDS, SAXS, NMR, BET, and FT-IR spectroscopy. Further, the synthesized SILs and MCM-41 were investigated for the removal of sulfur-containing aromatic species from model gasoline and real gasoline. MCM-41@[S-BzBTh][Cl] (0.5 g) removed maximum sulfur content with the percentage of 57.5 % (at 35 °C), 58.7 % (at 40 °C), and 63.4 % (at 45 °C) of TS, TN, and DBT respectively, from model gasoline (5 g) of sulfur concentration of 200 ppm under shaking conditions for 140 min. The impact of the aryl group and different lengths of alkyl groups of supported benzothiazolium-based ILs on their adsorption performance was also studied.

Injectable amphiphilic hydrogel systems from the self-assembly of partially alkylated poly(2-dimethyl aminoethyl) methacrylate with inherent antimicrobial property and sustained release behaviour

Inability to encapsulate hydrophobic guest molecules and excessive water swelling by an injectable hydrogel system restrict its application in sustained delivery. Herein, we report the injectable hydrogel system with inherent antimicrobial property for sustained release of hydrophobic/hydrophilic therapeutics. The design of the injectable hydrogel system is based on in situ reaction between the self-assembly of partially alkylated poly(2-dimethyl aminoethyl) methacrylate (QPDMA) and activated halide bearing poly(ethylene glycol). The effect of degree of alkylation (Dalkylation) of PDMA and the chain length of alkyl on the antimicrobial activity, loading of hydrophobic/hydrophilic guest molecules, degradation behaviour and modulus of the resultant hydrogels have been evaluated. Hydrogel formed by the QPDMA bearing long alkyl group (C12) exhibits superior antimicrobial property, loading of hydrophobic guest molecules (pyrene loading = 1 % w/w) and modulus (22 kPa) than that when the alkyl chain length (C1-C8) is relatively shorter (pyrene loading = 0–0.6 % w/w and modulus 1–12 kPa). The C12 alkyl bearing hydrogels exhibit sustained release of hydrophobic (pyrene and prednisolone acetate) and hydrophilic (ornidazole and methotrexate) guest molecules for extended time at pH 7.4 and the triggered release at pH 5. The hydrogels formed by the self-assemblies of long-chain alkylated PDMA show promises in the biological area.

Hydrophobicity modulation on a ferriporphyrin-based metal–organic framework for enhanced ambient electrocatalytic nitrogen fixation

Electrocatalytic N2 fixation represents an energy-efficient and long-term sustainable approach, which can convert N2 to NO3– or NH3 via the electrochemical N2 oxidation reaction (NOR) or N2 reduction reaction (NRR). However, the inert N2 molecule, low activity of electrocatalysts, and predisposed competitive reactions result in the poor yields and Faradaic efficiencies of N2 fixation reactions, which greatly restrict the application of such green synthesis technology. In this work, a molecular-level post-modification strategy has been explored to integrate diverse alkyl chains on a ferriporphyrin-based metal–organic framework (MOF) PCN-222(Fe), which provides adjustable hydrophobicity and highly dispersed active sites. The increased lengths of alkyl groups can gradually improve the hydrophobicity of decorated MOFs, which effectively suppress the competitive reactions and boost the electrocatalytic NOR and NRR performances. Significantly, the highest Faradaic efficiency of 70.7% so far and a state-of-the-art NO3− yield of 110.9 μg h–1 mgcat.–1 can be achieved for NOR, which are attributed to the synergistic effect of FeN4 active sites, high porosity, and strong hydrophobicity for n-octadecylphosphonic acid (OPA) decorated PCN-222(Fe).

Prediction of the corrosion inhibition efficiency and antibacterial activity of 1,2,4-oxadiazole derivatives using DFT and docking analysis: effect of alkoxy chain length

Synthesis of newly organic corrosion inhibitors may be costly and needs an experimental procedure to evaluate the inhibition efficiency. Therefore, pre-designing and theoretical calculations may be a powerful tool for initial inhibition performance. In the present work, the Density Functional Theory (DFT), Hartree-Fock (HF), and docking were performed on twelve new substituted oxadiazole derivatives. The calculated quantum chemical parameters were correlated to the inhibition efficiency. In addition, some physical values are studied, such as heat of formation and total energy. It is seen that disruption of electron density occurred due to increasing the alkyl length. Among the twelve studied inhibitors, the compound (12) named (4-(5-(p-tolyl)-1, 2, 4-oxadiazol-3-yl) phenyl-4-(dodecyloxy)benzoate) was recorded as an inhibitor against corrosion, while the compound 1 named (4-(5-(p-tolyl)-1, 2, 4-oxadiazol-3-yl) phenyl-4-methoxybenzoate) showed opposite effect towards bacterial and autodock calculations where it was better than other derivatives.

Development of Organogels for Live Yarrowia lipolytica Encapsulation

Encapsulation of cells/microorganisms attracts great attention in many applications, but current studies mainly focus on hydrophilic encapsulation materials. Herein, we develop a new class of hydrophobic and lipophilic organogels for highly efficient encapsulation of Yarrowia lipolytica, an oleaginous yeast, by a mild and nonsolvent photopolymerization method. The organogels allow free diffusion of hydrophobic molecules that oleaginous yeasts require to survive and function. Moreover, they are mechanically robust and possess favorable biocompatibility, thus providing a free-standing platform and an ideal survival environment for oleaginous Y. lipolytica encapsulation. By tuning monomer structures and cross-linking densities, the optimized organogel, Gel12-1.5%, achieves the highest viability of ∼96%. Furthermore, organogels can inhibit the cryoinjuries to oleaginous yeasts in cryopreservation, exhibiting the potential for long-term storage. It is also found that with varying alkyl lengths, the organogels show different temperature-dependent phase transition properties, which enable the rapid selection of targeted yeasts for steganography. Findings in this work provide guidance for designing biocompatible, hydrophobic, and lipophilic encapsulation materials.

Chiral Transcription from Chiral Au Nanowires to Self-Assembled Monolayers of Achiral Azobenzene Derivatives

Abstract Chiral transcription from chiral inorganic nanoobjects to achiral organic molecules is a fascinating topic. In this study, chiral transcription was demonstrated using helically controlled Au nanowires (NWs) and achiral azobenzene derivatives with thiol moieties as the terminal group. The azobenzene derivatives mAZonSH can form a self-assembled monolayer on helical Au NWs through thiol-Au bonding. UV-Vis spectroscopy revealed that mAZonSH in the self-assembled monolayer forms H-aggregates. The self-assembled monolayers on the right- and left-handed Au NWs showed opposing circular dichroism (CD) signals derived from the azobenzene chromophore. This result indicates that chiral transcription from the helical Au NWs to the azobenzene derivatives was successfully accomplished by the self-assembly of achiral mAZonSH. Furthermore, we demonstrated that the CD responses of mAZonSH are independent of the tail (m) and spacer (n) alkyl lengths.

Controlled Synthesis of Luminescent Xanthene Dyes and Use of Ionic Liquid in Thermochromic Reaction.

In this study, we demonstrate six novel xanthene derivatives and their spectroscopic and chemical properties. The presented synthesis examination allowed us to obtain two different compounds during one step, with open and closed lactone rings substituted with different length alkyl chains. Increasing the reaction efficiency to 77% was obtained using the microwave-assisted method. Moreover, the modification of O-alkylation synthesis in an ecofriendly way using a ball mill led to achieving exclusively one opened ring product. All of the synthesized compounds showed different spectroscopic behaviors in comparison with the different organic dyes; the typical concentration quenching of luminescence was not observed. The relationship between the length of the alkyl chain and the time of luminescence decay is presented. Synthetized closed forms of dyes turned out to be promising leuco dyes. For the first time, an ionic liquid was used as a developer of synthesized xanthene derivatives (as leuco dyes), which led to obtaining an irreversible thermochromic marker.

Dicationic Bis-Pyridinium Hydrazone-Based Amphiphiles Encompassing Fluorinated Counteranions: Synthesis, Characterization, TGA-DSC, and DFT Investigations.

Quaternization and metathesis approaches were used to successfully design and synthesize the targeted dicationic bis-dipyridinium hydrazones carrying long alkyl side chain extending from C8 to C18 as countercation, and attracted to halide (I-) or fluorinated ion (PF6-, BF4-, CF3COO-) as counteranion. Spectroscopic characterization using NMR and mass spectroscopy was used to establish the structures of the formed compounds. In addition, their thermal properties were investigated utilizing thermogravimetric analyses (TGA), and differential scanning calorimetry (DSC). The thermal study illustrated that regardless of the alkyl group length (Cn) or the attracted anions, the thermograms of the tested derivatives are composed of three stages. The mode of thermal decomposition demonstrates the important roles of both anion and alkyl chain length. Longer chain length results in greater van der Waals forces; meanwhile, with anions of low nucleophilicity, it could also decrease the intramolecular electrostatic interaction, which leads to an overall interaction decrease and lower thermal stability. The DFT theoretical calculations have been carried out to investigate the thermal stability in terms of the Tonset. The results revealed that the type of the counteranion and chain length had a substantial impact on thermal stability, which was presumably related to the degree of intermolecular interactions. However, the DFT results illustrated that there is no dominant parameter affecting the thermal stability, but rather a cumulative effect of many factors of different extents.

Binary mixtures of homologous room-temperature ionic liquids: Nanoscale structure evolution with alkyl lengths’ difference

The nanoscale structure of equimolar binary mixtures [C12mim]0.5[Cnmim]0.5[NTf2] was studied by small-angle X-ray scattering for n=1-22 and T=293-373 K. All mixtures exhibit local layering and layer-normal thermal contraction with increasing T, as found for the pure components. The layer-parallel spacings of the polar headgroups and of the alkyl chains vary minimally with n over the full n range. The layer-normal spacing dI at high n follows closely, with a 1–1.5 Å downshift, the increasing trend of the pure longer component’s dI, indicating its dominance of the layering. At low n,dI at n=1 greatly exceeds dI of the pure longer component, n=12, and decreases sharply with increasing n, indicating a structure akin to lipid bilayer solutions. At intermediate n,dI is roughly constant, lying 1–1.5 Å below dI of n=12. Our layer spacings provide a near-unique opportunity to study the evolution over a wide n-range of the normalized dI’s molecular-scale deviation from ideality, yielding a linear dependence on the normalized n-difference squared. This may be related to the same-dependence interchange energy due to chain length mismatch, dominating binary alkane and alcohol mixtures. Finally, our dI also show the power P of the modified Vegard’s Law to be linear in the mixtures’ normalized n-mismatch, albeit with different low- and high-n slopes.

The Unexpected Importance of the Primary Structure of the Hydrophobic Part of One-Component Ionizable Amphiphilic Janus Dendrimers in Targeted mRNA Delivery Activity.

Viral and synthetic vectors for delivery of nucleic acids impacted genetic nanomedicine by aiding the rapid development of the extraordinarily efficient Covid-19 vaccines. Access to targeted delivery of nucleic acids is expected to expand the field of nanomedicine beyond most expectations. Both viral and synthetic vectors have advantages and disadvantages. The major advantage of the synthetic vectors is their unlimited synthetic capability. The four-component lipid nanoparticles (LNPs) are the leading nonviral vector for mRNA used by Pfizer and Moderna in Covid-19 vaccines. Their synthetic capacity inspired us to develop a one-component multifunctional sequence-defined ionizable amphiphilic Janus dendrimer (IAJD) delivery system for mRNA. The first experiments on IAJDs provided, through a rational-library design combined with orthogonal-modular accelerated synthesis and sequence control in their hydrophilic part, some of the most active synthetic vectors for the delivery of mRNA to lung. The second experiments employed a similar strategy, generating, by a less complex hydrophilic structure, a library of IAJDs targeting spleen, liver, and lung. Here, we report preliminary studies designing the hydrophobic region of IAJDs by using dissimilar alkyl lengths and demonstrate the unexpectedly important role of the primary structure of the hydrophobic part of IAJDs by increasing up to 90.2-fold the activity of targeted delivery of mRNA to spleen, lymph nodes, liver, and lung. The principles of the design strategy reported here and in previous publications indicate that IAJDs could have a profound impact on the future of genetic nanomedicine.

Linear cross-linkers enabling photothermally cured hole transport layer for high-performance quantum dots light-emitting diodes with ultralow efficiency roll-off

In quantum-dot light-emitting diodes (QLEDs), poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt(4,4′-(N-(4-butylphenyl))] (TFB) has been one of the most widely used hole-transport layer (HTL) materials. However, for solution-processed especially ink-jet printed QLEDs, TFB normally suffers from low glass-transition temperature and inter-layer erosions hindering to achieve both high device efficiency and stability. In the present work, three novel linear bis-benzophenone cross-linkers (BPO4, BPO6 and BPO8) were carefully designed and synthesized for constructing compact HTL with ∼ 100 % solvent resistance. Under a mild photothermal curing condition of 120 °C and 365 nm UV with a power of 16 mW cm−2, the introduction of these cross-linkers into TFB film, even at a low weight concentration of 3.33 %, not only resulted in the HTL with reduced free film volumes and hence compact three-dimensional networks in QLEDs, but also enhanced the hole transport ability, so that better charge balance in QDs layer and improved overall QLED performance could be achieved. In the BPO series which have varying alky lengths, the BPO6 with a medium central alkyl length showed the best thin film state, and thus enabled to improve the QLED device performance with the highest EQE of 16.77 % (20.22 lm W−1, 22.72 cd A-1), which is 20% higher than that of pristine TFB based device. From the peak EQE to the EQE at 20000 cd m−2, an ultra-low deviation of 1.73 % was observed in the TFB:BPO6 based red QLEDs. The T50 lifetime of TFB:BPO6 based QLEDs is almost twice of that of the pristine TFB based device. Our strategy demonstrates that developing linear cross-linkers for polymer HTL can facilitate forming compact and dense HTL, achieving simultaneous improvements in QLEDs device efficiency and stability.

Synthesis and liquid crystal properties of benzoates containing 1,2,3-triazole

Two series of benzoates containing 1,2,3-triazole heterocyclic were prepared. The molecules containing alkyl chains of 12 ∼ 14 carbon atoms and with benzene ring as the central core show liquid crystal behaviors. After replacing benzene ring with cyclohexane, the compounds with short or long alkyl chains or ferrocene terminal group have no mesomorphic behavior. However, the compounds with medium length alkyl chain have lower melting point and wider mesomorphic domain than those with benzene ring as the central core containing the same length alkyl chain. This study adds new members to liquid crystal whose central core is a flexible ring.

A UV–visible and conductometric studies on the analyses of valine and ninhydrin reaction in aqueous-surfactant solutions of dicationic geminis (n-s-n type)

The influence of surfactants (represent the respective length of alkyl and tail chain referred to as gemini) was investigated on rate constant (kψ) of valine (Val) and ninhydrin. Also, the effect of other experimental parameters that includes reactant’s concentration (Val and ninhydrin), pH and temperature was performed and examined. Via UV–visible method, the absorbance of different solutions was recorded at fixed time intermissions and kψ was estimated by employing a computer-based procedure. The values ofkψ obtained at varied concentrations of gemini n-s-n (n = 16; s = 4–6) surfactants show an infrequent behavior (plotted askψvs. [gemini]). In the plot, kψ data rises gently at surfactant concentration far smaller related to cmc-value (Segment I) and formerly attains virtually unaffected behavior (Segment II, up to 400 × 10-5 mol dm−3). To end, we perceive a quick variation in kψ beyond 400 × 10-5 mol dm−3 (Segment III). Dicationic geminis improve the study, excellently, at [n-s-n] slighter than cmc over monomeric CTAB. However, quantitative treatment of such results achieved in dicationic gemini surfactant solutions was made by an appropriate model of micellar activity recognized as pseudo phase. Critical micelle concentration (cmc) of dicationic geminis (n-s-n type) with reactants has been determined at two different temperatures 303 K and 353 K using conductometric analysis. A reasonable reaction mechanism concerning the present study is provided. Additionally, some other reaction factors (binding and rate constants) were evaluated and discussed.

Alkylimidazolium Protic Ionic Liquids: Structural Features and Physicochemical Properties.

We focus on a series of protic ionic liquids (PILs) with imidazolium and alkylimidazolium (1R3HIm, R=methyl, ethyl, propyl, and butyl) cations. Using the literature data and our experimental results on the thermal and transport properties, we analyze the effects of the anion nature and the alkyl radical length in the cation structure on the above properties. DFT calculations in gas and solvent phase provide further microscopic insights into the structure and cation-anion binding in these PILs. We show that the higher thermodynamic stability of an ion pair raises the PIL decomposition temperature. The melting points of the salts with the same cation decrease as the hydrocarbon radical in the cation becomes longer, which correlates with the weaker ion-ion interaction inthe ion pairs. A comparative analysis of the protic ILs and corresponding ILs (1R3MeIm) with the same radical (R) in the cation structure and the same anion has been performed. The lower melting points of the ILs with 1R3MeIm cations are assumed to result from the weakening of both the ion-ion interaction and the hydrogen bond.