Esterification Of Alcohols Research Articles

Regulation of the Co–Nx Active Sites of MOF-Templated Co@NC Catalysts via Au Doping for Boosting Oxidative Esterification of Alcohols

The Co–Nx active sites play a critical role over the Co@NC catalyst in the heterogeneous catalysis. However, the effective methods for the regulation of the content and electronic structure of Co–Nx active sites to enhance the catalytic efficiency of heterogeneous catalysts are still insufficient. Herein, a nitrogen-doped porous carbon-encapsulated Au-doped Co nanoparticle catalysts with abundant and electron-rich Co–Nx sites in the outer carbon layer was designed by a Au doping strategy through pyrolysis of the HAuCl4-modified ZIF-67 metal organic framework precursor. The optimal catalyst exhibits improved catalytic performance in alcohol selective oxidative esterification. The linear relationship between the ester yield and Co–Nx species content, combined with a series of control experiments, indicated that the Co–Nx active sites are crucial for achieving the excellent catalytic activity (yield: 99.9%). In situ diffuse reflectance infrared Fourier transform spectroscopy, O2-temperature-programed desorption characterizations, active oxygen species quenching experiments together with density functional theory calculations results indicate that Au doping in the Co nanoparticle core increases the content and the electron density of Co–Nx species on the outer carbon shell, which enhanced the chemical adsorption and activation of molecular O2 for producing reactive O2•– species. This study demonstrated a novel Co–Nx active site regulation strategy for the efficient selective oxidative esterification of alcohols under mild reaction conditions.

Phase behavior and extraction mechanism of ethanol in alcohol ester mixture separated by deep eutectic solvents

The production of diclofenac salt involves an azeotropic system consisting of ethanol and isopropyl acetate (IPAc). Owing to their simple preparation, low cost, and non-volatility, deep eutectic solvents (DESs) have attracted considerable attention in the field of azeotrope separation. The σ profiles were constructed using a conductor-like shielding model, and the hydrogen-bonding ability between several common hydrogen-bond acceptors (HBAs) and hetero-azeotropic systems was analyzed. To prepare the three types of DESs, choline chloride (ChCl) was selected as the HBA, while ethylene glycol, urea, and glycerol were selected as the hydrogen-bond donors (HBDs). The liquid–liquid equilibrium (LLE) experimental data of the IPAc, ethanol, and synthetic DES systems were then measured at 101.3 kPa and 298.15 K. The accuracy of the experimental data was verified by correlating the data with the Othmer–Tobias and Hand equations, and the NRTL model was used to fit the experimental results. According to the distribution (D) and selectivity (S) coefficients, ethanol had the highest affinity for the ChCl–ethylene glycol DES, and the experimental data and the molecular dynamics (MD) simulations data were well correlated. The interaction energy, spatial distribution functions (SDFs), radial distribution functions (RDFs), and self-diffusion coefficients were calculated using MD simulations to elucidate the extraction mechanism. The MD simulation results showed that the interaction between the HBA in the DESs and ethanol was dominant in the separation, whereas the interaction of the HBD in the DESs with ethanol played an auxiliary role. Based on the experimental and simulation results, the feasibility and effectiveness of the azeotropic system for the DES separation of ethanol and IPAc were verified, which is important for the sustainable utilization of resources.

Refining lipid for aviation biofuel at the molecular level

For improving aviation biofuel in quantity and quality, main precursor compounds have been investigated on the hydrotreating mechanism, including triglycerides by lipid extraction, fatty acid methyl/ethyl esters by transesterification, and fatty acids by hydrothermal liquefaction. Hydrotreating tests have been conducted on the effects of temperature, pressure, catalyst loading, and reaction time at molecular level. Fatty acid methyl/ethyl esters are the most desirable hydrotreating compounds for their highest biofuel yield and mildest upgrading conditions(≥290 °C, ≥10% catalyst loading). At the proper conditions of 290 °C and 30% catalyst loading, methyl stearate can yield 61.6% biofuel with 100% selectivity to alkanes. Fatty acids are the most difficult compounds to upgrade and should be hydrotreated above 310 °C and at least 30% catalyst loading, otherwise there are unconverted fatty acids, fatty aldehydes and fatty alcohols in the products. C30+ heavy esters are commonly found in the undesirable products and suppose to be derived from esterification of fatty acids and fatty alcohols under low temperature. Enhancing carbon number and unsaturation of the precursors promote the generation of olefins and oxygenates.

AERIAL PART FERULA TENUISECTA ALTERNATIVE INDUSTRIAL RAW MATERIAL FOR THE PRODUCTION OF TEFESTROL SUBSTANCE

The main losses of tefestrol have been identified and the advantages and disadvantages of the existing technology in the production of the substance from the aerial parts of Ferula tenuisecta have been established. It was found that the final product obtained by the existing technology has a green color that does not meet the requirements of the Pharmacopoeia article. The stage proposed of extraction of the sum of esters of sesquiterpene alcohols from the aerial part of Ferula tenuisecta and purification of the obtained extract, allowing to subsequent obtain the substance of tefestrol without green color. It has been shown that the use of activated carbon makes it possible to remove the green color of the extract. To purify tefestrol from other esters of sesquiterpene alcohols and accompanying substances, a chromatographic separation on silica gel is proposed under the following conditions: the ratio of the amount introduced into the column and the sorbent is 1 : 20; the ratio of the height of the sorption layer to the column diameter is 4 : 1; elution rate 35 l/h.m2. To obtain the pharmacopoeial substance of tefestrol is proposed, crystallization of a technical product from a mixture of ethyl acetate with hexane in a volume ratio of 1 : 3. Based on the results obtained, technology has been developed for obtaining the tefestrol substance from the aerial part of Ferula tenuisecta. Using this technology 70.96% of the substance of tefestrol is obtained from the content in the raw material, according to the existing technology 33.9%.

"Synthesis of Pine-Apple Flavor by Celite-Immobilized Lipase "

Alkaline-thermotolerant lipase from Bacillus licheniformis MTCC-10498 was purified and immobilized on Celite-545 matrix. The matrix shows a binding efficiency of 80% for lipase of B. licheniformis with a specific activity 1.02 U/mg of protein. The immobilized lipase shows 50% activity up to 70°C. This immobilized lipase was checked for its efficacy in the synthesis of butyl butyrate, a flavor ester. The formation of ester was highest when butyric acid and butyl alcohol were as in an equimolar ratio (100 mM each) in n-hexane under continuous shaking (120 rpm) along with 20 mg celite-bound lipase at 45°C in 5 h. The addition of molecular sieves (50 mg) to the reaction cocktail promoted the ester yield. The immobilized lipase was reused up to 8 th cycle. The immobilized lipase when used for the esterification of butyl alcohol and butyric acid under above-optimized conditions resulted in butyl butyrate (91.6%) conversion in n-hexane.

Beating neat fuels by dedicated blending: Performance analysis of bio-hybrid fuel blends on a spark-ignition engine for passenger car applications

The alcohol fuel ethanol is well known for its favorable engine performance in terms of both high net indicated efficiency and low nitrogen oxide emissions. Other alternative neat fuels such as 2-butanone were not able to outperform ethanol in its engine performance. In addition, ethanol has lower production costs compared to 2-butanone, which makes ethanol even more attractive. To compete with neat fuels, model-based fuel design was introduced to tailor fuels by means of dedicated blending of neat alternative components. First, a blend consisting of ethanol, 2-butanone, cyclopentane, and cyclopentanone (EBCC) was defined. Second, a ketone–ester–alcohol–alkane (KEAA) blend consisting of methyl isopropyl ketone, methyl acetate, ethyl acetate, ethanol, methanol, and pentane was developed. Both blends were optimized regarding their production costs while simultaneously considering fuel properties such as the octane number, the oxygen content, and the enthalpy of vaporization. Although both blends showed promising fuel properties, their performance in an internal combustion engine was not evaluated in the fuel design process. This study presents investigations of both blends on a thermodynamic spark-ignition single-cylinder engine for passenger car applications with a compression ratio of 16.4. In particular, a variation of the engine load at an engine speed of 2000 1/min and two variations of the relative air/fuel ratio at the same engine speed and net indicated mean effective pressures of 6 bar and 15 bar were performed. The combustion behavior of the two blends was compared to that of neat ethanol, neat 2-butanone, and conventional gasoline pump fuel. In addition, 0D/1D simulations were performed to evaluate the efficiency losses during the combustion. EBCC achieved a maximum net indicated efficiency of 46.9% at a net indicated mean effective pressure of 15 bar and a relative air/fuel ratio of 1.7, exceeding ethanol’s maximum net indicated efficiency of 46.0% in the same operating point. KEAA achieved a lower net indicated efficiency than ethanol and was on the same level as neat 2-butanone, resulting in a maximum net indicated efficiency of 45.0% in the same operating point. This work shows that the combustion performance in an internal combustion engine should be considered in the fuel design process to better predict promising fuel candidates from an engine perspective.

Determination of three oryzanols in rice by mixed-mode solid-phase extraction coupled with high performance liquid chromatography-tandem mass spectrometry

建立了利用高效液相色谱-串联质谱结合混合型阴离子交换固相萃取柱测定稻米中3种谷维素(环木菠萝烯醇阿魏酸酯(CA-FA)、24-亚甲基环木菠萝烯醇阿魏酸酯(24MCA-FA)和菜油甾醇阿魏酸酯(Camp-FA))含量的分析方法。实验通过优化3种谷维素的多反应监测(MRM)质谱参数,比较了在不同流动相中的分离度以及响应强度,同时考察了不同提取条件、净化条件对3种谷维素提取率和净化效果的影响,再结合外标法定量,实现了对稻米中3种谷维素的定量分析。实验结果表明,采用5 mmol/L乙酸铵水溶液为流动相A,甲醇∶乙腈=1∶1(v/v)为流动相B,梯度洗脱,3种谷维素在Agilent Eclipse XDB-C8色谱柱(150 mm×2.1 mm, 3.5 μm)上基本分离且响应强度和峰形最佳;提取条件经正交实验优化后可得:料液比为1∶20(g/mL)、提取溶剂为甲醇、浸泡时间为12 h、超声温度为40 ℃以及超声时间为20 min时,3种谷维素提取率最高;对混合型阴离子交换固相萃取柱的上样溶剂以及洗脱溶剂优化后,样品基质效应为1.6%~10.8%。在各优化条件下,3种谷维素在各自的线性范围内线性良好,相关系数(r2)均≥0.9983,检出限(LOD)为0.5~1.0 μg/L,定量限(LOQ)为2.0~3.5 μg/L。在稻米样品本底浓度2、5和10倍的加标水平下3种谷维素的平均回收率为86.1%~110.6%,相对标准偏差(RSD)为0.9%~3.2%。该方法可快速准确测定稻米中3种谷维素的含量,为后续稻米中谷维素类化合物测定及鉴定奠定基础。

Dual Activation of Carboxylic Acid Functionality by Protic Ionic Liquid: Solvent and Metal Free Strategy for Selective Esterification of Alcohols and Acylation of Aromatic Amines

AbstractHighly efficient and chemoselective esterification of alcohols and acylation of aromatic amines with carboxylic acids using imidazolium based protic ionic liquid, 1‐butyl‐imidazolium trifluoroacetate ([HBIm]TFA) as activator has been realized under organic volatile solvent free condition. The protic ionic liquid played dual role for activation of carboxylic acid which was proved by NMR study. A very interesting aspect of the present protocol is the acylation of less basic aromatic amines than the more reactive aliphatic amines as the later one forms salt with carboxylic acid. Our methodology offers several advantages like high yield, fast, efficient, chemo‐selectivity, metal and other coupling agent free procedure, recyclability of ionic liquid used and formation of water as the only by‐product.

Integration of morphological, physiological and multi-omics analysis reveals a comprehensive mechanism for cuticular wax during development of greasiness in postharvest apples

Skin greasiness is a common postharvest disorder of apple (Malus × domestica). However, the molecular mechanism of skin greasiness is unclear. In this study, fruits of ‘Golden Delicious’ (GD), ‘Granny Smith’, and ‘Fuji’ with distinct characteristics of greasiness were used for greasiness scoring, wax morphology, wax metabolite, and RNA-seq analyses. Additionally, GD fruit were treated with 1-methylcyclopropene (1-MCP), which repressed greasiness. A partial least squares discriminant analysis (PLS-DA) revealed that wax esters were the critical wax fraction for skin greasiness. Among these wax esters, liquid linoleate esters of short-chain alcohols (C4–C6) and farnesol showed increased contents with increasing greasiness. Their concentrations were significantly correlated with greasiness score. To identify the genes encoding key enzymes for the synthesis of liquid linoleate esters, a weighted gene co-expression network analysis was conducted. MdDCR1, encoding an acyltransferase (defective in cuticular ridges, DCR), was selected as a candidate gene. MdDCR1 was significantly upregulated in greasy skin, and significantly suppressed by 1-MCP treatment. MdDCR1 silencing suppressed the accumulation of liquid linoleate esters of short-chain alcohols, including butyl linoleate, pentyl linoleate, and hexyl linoleate, in GD skin. These results provide insights into the molecular mechanisms of cuticular wax metabolism related to skin greasiness in apple. Our results show that transcriptional regulation of MdDCR1, encoding an acyltransferase that catalyzes the biosynthesis of liquid linoleate esters of short-chain alcohols (C4–C6) via an independent side branch of the C18:2 CoA pathway, regulates the formation of greasiness.

Gold Nanoparticles Supported on Poly(2,6‐dimethyl‐1,4‐phenylene oxide) as Robust, Selective and Cost‐Effective Catalyst for Aerobic Oxidation and Direct Oxidative Esterification of Alcohols

AbstractA new catalytic system based on gold nanoparticles (AuNPs) incarcerated in poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) matrix has been synthesized and successfully tested in aerobic oxidation of alkyl alcohols. PPO is a cheap and commercially available polymer, showing nanoporous morphology, high glass transition temperature (Tg =220 °C), semi‐crystallinity, excellent thermal stability, and interesting chemo‐physical properties. The synthesis of the AuNPs‐PPO catalyst is simple, cost‐effective and allows a fine control of the gold concentration, as well as an optimal dispersion of 7–8 nm sized AuNPs in the polymer matrix. AuNPs‐PPO is an efficient, robust and selective catalyst active in the aerobic oxidation and oxidative esterification of alcohols in water under mild reaction conditions (35 °C, atmospheric pressure of oxygen). The testing of AuNPs‐PPO in aerobic oxidation of 1‐phenylethanol to acetophenone, as a benchmark reaction, highlighted that this gold catalyst exhibits activity values among the highest so far reported for polymer‐supported AuNPs under mild reaction conditions. The oxidation of primary alcohols, such as benzyl and cinnamyl alcohols, could be addressed to the corresponding aldehyde or carboxylate derivatives. Alkyl cinnamates were obtained with efficiency in the one‐pot aerobic oxidation of cinnamyl alcohol in the presence of alkyl alcohols, such as n‐butanol or n‐hexanol. The role of the polymer matrix and the reaction conditions on both activity and selectivity of the AuNPs‐PPO catalyst were also investigated and discussed.

Ketoreductase-Catalyzed Access to Axially Chiral 2,6-Disubstituted Spiro[3.3]heptane Derivatives.

The desymmetrization of a prochiral 6-oxaspiro[3.3]heptane-2-carboxylic acid derivative via biocatalytic ketoreductase-mediated reduction has provided access to both enantiomers in high ee. The axially chiral alcohol was converted to the corresponding ester alcohol, amino acid, and amino alcohol building blocks while high enantiopurity was maintained.

Palladium(II)-Catalyzed Enantioselective Hydrooxygenation of Unactivated Terminal Alkenes.

A novel Pd(II)-catalyzed enantioselective Markovnikov hydrooxygenation of unactivated terminal alkenes using a substituted pyridinyl oxazoline (Pyox) ligand has been developed. Herein it was discovered that the (EtO)2MeSiH/BQ redox system is vital for the highly selective and efficient hydrooxygenation, where the alkylpalladium(II) species generated from enantioselective oxypalladation step is reduced by silane. This method provides efficient access to optically pure alcohol esters from easily available alkenes with excellent enantioselectivities and features a broad substrate scope.

Solvent-free oxidative esterification of furfural to 2-methyl furoate using novel copper-exchanged tungstophosphoric acid supported on montmorillonite K-10 catalyst

The valorization of bio-based chemicals using green processes plays a vital role in the up-gradation of biofuels that are useful to reduce the demand for fossil feedstock. Furfural is a promising renewable biomass-based platform chemical, which can be catalyically transformed into many value-added chemicals. Oxidative esterification of furfural produces 2-methyl furoate, which is used as flavour and fragrance in fine chemical industries. There lies a challenge to find a cheaper and efficient catalyst for one-pot oxidative esterification of furfural. Supported heteropolyacids (HPAs) are useful for many biomass transformation reactions owing to their strong Bronsted acidity as well as high surface area, which both help promote catalytic surface reaction. In the present work, we have synthesized Cu exchanged tungstophosphoric acid (TPA) with different supports, viz. SiO2, ZrO2, and montmorillonite K-10 clay (K10) which were prepared by incipient wetness impregnation. Oxidative esterification of furfural with methyl alcohol was investigated using the aforesaid catalysts and tert-butyl hydroperoxide (TBHP) as an oxidant. 20% w/w Cu substituted TPA (abbreviated as Cu-TK10) catalyst is green, stable, active, selective, reusable, and cheaper. It was observed that the higher acidic strength and good surface area are responsible for oxidative esterification of furfural and methyl alcohol with higher selectivity. In this work, 91% conversion with 100% selectivity was achieved in 5 h at 120 °C using 1:3 molar ratio of furfural and TBHP with a catalyst loading of 0.01 g/cm3. The synthesized catalysts were analyzed by various characterization techniques such as SEM, XRD, FT-IR, BET surface area analyser, and NH3-TPD, before and after use. This is an interesting example of valorization of furfural.

Thermochemical liquefaction of wheat straw in sub- and supercritical tetralin

The present work investigates the thermochemical conversion of wheat straw biomass in a suband supercritical tetralin medium. The experiment was carried out in a batch reactor at 285, 330, 380, 420 and 460 °C for 10 minutes. The process of straw liquefaction in subcritical tetralin was characterised by relatively high efficiency. At 420 °C, the biomass conversion rate amounted to 98.2% a.d.m. The maximum yield of liquid products during liquefaction (81.6% a.d.m.) was obtained at 380 °C. The liquid products were fractionated by successive extraction with hexane, water and ethanol. According to GC-MS data, the liquefaction products soluble in hexane comprised a mixture of low-molecular weight degradation products of straw components and tetralin derivatives, including methyl esters of fatty acids, aromatic compounds, alkanes and minor alcohols and ketones. When the process temperature increased, the content of esters diminished, followed by an increment in the proportion of aromatic compounds up to 50% rel. No esters and phenolic compounds were present in the liquefaction products soluble in hexane obtained at 460 °C. Dehydrogenation, alkylation and isomerisation of tetralin with the formation of naphthalene, 1,4-dihydronaphthalene and alkyl derivatives of tetralin, naphthalene and indane occurred under the given conditions. The conducted comparative analysis of infrared spectra for straw and solid products of liquefaction suggested that, at temperatures of up to 330 °C, the process of polysaccharide fragmentation is more pronounced in the straw biomass, while, at higher temperatures, the process of lignin fragmentation prevails. As a result, the IR-spectrum of the solid product obtained at 380 °C revealed weakly pronounced absorption bands of alkylaromatic structural fragments. At the same time, only the absorption bands of mineral components in straw ash and adsorbed water were observed in the IR-spectrum of the solid product obtained at 420 °C.

Biocatalytic Synthesis of Terpene Esters and their Biological Activity in Human Glioma Cells

Gliomas are highly malignant brain tumours with high resistance to chemotherapy. Therefore, investigations of new therapeutic molecules with high anti-glioma activity are of great importance. In this work, biocatalytic esterification of terpene alcohols with proven anti-cancer activity was performed to enhance their potency to induce cell death in human glioblastoma multiforme T98G and anaplastic astrocytoma MOGGCCM cell lines in vitro. We used primary terpene alcohols and carboxylic acids with a length of two to nine carbon atoms. The structure of the alcohols had an influence on the esterification efficiency, which decreased in the following order: monocyclic > linear > bicyclic. Terpene alcohols and their esters only induced apoptotic cell death, which is highly desirable from a therapeutic point of view, but did not induce autophagy and necrosis. The esterification of perillyl alcohol with butyric acid caused a 4-fold increase in cell death induction in the T98G line. Citronellol valerate, caprylate, and pelargonate and myrtenol butyrate, caprylate and pelargonate also showed higher activity than their alcohol precursors. We have herein shown that esterification of natural alcohols by biocatalysis can be used for improving the activity of other compounds investigated for their anti-glioma activity.

Electrospinning NH2-MIL-101/PAN nanofiber mats: A promising catalyst with Lewis acidic and basic bifunctional sites for organic transformation reactions

Because of their distinctive characteristics, like great surface area and capability of structure modifications, Metal-organic frameworks (MOFs) were endorsed as outstanding candidates for catalysis purposes. The incorporation of MOF into an organic polymer frameworks is thought to be a promising approach to enhance the catalysts performance, however, a facile and low-cost approach to prepare such catalysts is currently missing. Herein, a direct approach for integration the MOF into nanofibers with improved catalytic organic transformation reactions without film rupture is reported. The electrospun NH2-MIL-101 @polyacrylonitrile (PAN) catalyst nanofibers with varied MOF to PAN mass ratio was fabricated by a facile electrospinning approach and used as integrated catalyst for Friedel–Crafts acylation of anisole, esterification of amyl alcohol, and Knoveonagel condensation reaction of aldehydes. The fabricated MOF-catalysts nanofibers NH2-MIL-101 @PAN show effective anisole acylation, ester production, and Knoveonagel condensation reaction. The anisole acylation, ester production, and Knoveonagel condensation efficiency boosted to 90%, 79%, and 98% after incorporating NH2-MIL-101 nanocrystals into the elctrospun PAN nanofibers. The great surface area, available active centers in the pore architecture, and unsaturated Cr3+ Lewis acid centers are responsible for this exceptional performance. Because of its adaptability, our approach offers a cutting-edge and intriguing platform for the future tailoring of MOF fabrics with a wide range of practical uses.

GSH/enzyme-responsive 2-sulfonyl-1-methylimidazole prodrug for enhanced transdermal drug delivery and therapeutic efficacy against hyperthyroidis

Novel GSH/enzyme-responsive anti-hyperthyroidism prodrugs designed for transdermal delivery of 2-sulfonyl-1- methylimidazole (MMI) were synthesized by a Michael addition reaction of MMI with propiolic acid (PA) followed by esterification with three long chain fatty alcohols and their structures were characterized by 1H NMR, 13C NMR and mass spectrometry. Their maximum steady state flux through rat skin in the PG/W solution was found to be more than 37-times faster than that of MMI. The result may be attributed to the improved lipophilicity of prodrug and rapid bioconversion. The prodrugs were hydrolyzed by esterase on passing through the skin and appeared mainly as intermediate MMI-PA in the receiver compartment and accompanied by a small amount of MMI and intact prodrug. The prodrugs did not release any MMI in the media without GSH or with 100 µM GSH, while the obvious MMI release could be observed within 6.4 h in the media containing 2 mM and 10 mM GSH, and their maximum cumulative release rates reached 95.07% for lauryl alcohol ester prodrug (MMI-PA-OLa). MMI-PA-OLa exhibited a significant inhibition effect on lactoperoxidase (LPO) after being incubated in millimolar GSH media, whose inhibition rate was very similar to that of free MMI with an equivalent dose. These results suggested that MMI-PA-OLa could pass efficiently through the skin and release MMI in response to the intracellular environment.

Scientific Opinion on Flavouring Group Evaluation 7, Revision 6 (FGE.07Rev6): saturated and unsaturated aliphatic secondary alcohols, ketones and esters of secondary alcohols and saturated linear or branched-chain carboxylic acids from chemical group 5.

The EFSA Panel on Food Additives and Flavourings was requested to evaluate 55 flavouring substances assigned to the Flavouring Group Evaluation 07 (FGE.07), using the Procedure as outlined in the Commission Regulation (EC) No 1565/2000. Fifty‐three substances have already been considered in FGE.07 and its revisions. This revision 6 includes two additional substances which have been cleared with respect to genotoxicity in FGE.201Rev2 (4‐methyl‐3‐hepten‐5‐one [FL‐no: 07.261]) and FGE.204Rev1 (non‐2‐en‐4‐one, [FL‐no: 07.187]). The substances were evaluated through a stepwise approach that integrates information on the structure–activity relationships, intake from current uses, toxicological threshold of concern (TTC) and available data on metabolism and toxicity. The Panel concluded that none of the 55 substances gives rise to safety concerns at their levels of dietary intake, when estimated on the basis of the ‘Maximised Survey‐derived Daily Intake’ (MSDI) approach. Besides the safety assessment of the flavouring substances, the specifications for the materials of commerce have also been considered and found adequate. Normal and maximum use levels were available for all flavouring substances. For 52 substances, including the newly included substances [FL‐no: 07.187 and 07.261], their ‘modified Theoretical Added Maximum Daily Intakes’ (mTAMDIs) estimates were above the TTC for their structural classes (I and II). Therefore, for these 52 flavouring substances, more detailed data on uses and use levels should be provided to finalise their safety evaluations.

Mechanochemical Palladium-Catalyzed Oxidative Esterification of Alcohols

A mechanochemical palladium-catalyzed oxidative esterification of alcohols has been developed. The protocol allows a solvent-free synthesis of symmetric and unsymmetric esters from liquid and solid benzylic and aliphatic alcohols in up to excellent yields. Various green metrics for the developed protocol have been calculated and compared with those of solution-based protocols, highlighting the benefits of the mechanochemical approach.

A review on performance, combustion and emissions utilizing alternative fuels

The present work is an effort towards the review of literature of performance, combustion and emissions of unmodified compression ignition engine utilizing different alternative fuels. This study is established on the published work of eminent researchers between 2005 and 2021. The fast depletion of fossil fuels necessitates an alternative fuel and biodiesel may be deliberated as potential substitute fuel for CI engines to accomplish the global energy requirement. The various researchers and scientists conducted the experiments, using different alternative fuels viz. esters of edible oils, non-edible oils, alcohols and ethers and their mixing with diesel fuel. These studies showed the acceptable outcomes of performance, combustion and emission characteristics when they utilized biodiesel. Some of the researchers observed subsequent enhancement in performance and reduction in emissions with use of different additives.