Dye Intermediates Research Articles

Advancements in Primary Alcohol Oxidation Leading to Carboxylic Acids: A Detailed Review

This review article explores the direct oxidation of primary alcohols into carboxylic acids, highlighting its importance in organic synthesis for producing valuable chemicals in a sustainable and efficient manner. Carboxylic acids are widely employed in a wide range of applications, encompassing food preservatives, insecticides, dye intermediates, coatings, plasticizers, spices, flavors, scents, and a variety of industries such as polymers, solvents, and medications. This review article covers recent advancements in catalytic systems, including catalysts based on transition metals, organocatalysts, nanocatalysts, and electrochemical methods. It examines the impact of reaction conditions such as solvents, temperature, and substrate scope on these processes. The review also delves into mechanistic insights and recent developments in tandem and cascade reactions, aiming to provide a comprehensive understanding of current strategies and future research directions in this field.

An efficient measure for controlling pollution in the dye industry: Experimental and DFT investigations on direct determination of 3-(N,N-diethylamino)acetanilide

The rapid expansion of the dye industry has led to severe environmental pollution. The lack of real-time direct determination methods for dye intermediates is a key factor in high pollution emissions and low product quality in the continuous synthesis of dyes. This study proposes an accessible, fast, and precise approach for the clean and direct determination of 3-(N,N-Diethylamino)acetanilide (DEAA), a dye intermediate used in the synthesis of the azo dye Disperse Violet 93:1. For precise DEAA quantification, we developed a multi-pathlength and multi-wavelength coupled differential photometric approach based on the absorption spectra characteristics of DEAA at various concentrations and optical pathlengths. A relatively stable analytical sensitivity (0.5671–66.2630) and a large concentration range of 0.01–11% were obtained. Compared to the traditional single-optical pathlength and single-wavelength quantification, this new method possessed 119 times higher sensitivity. The maximum quantitative relative error decreased from 9.17% to 2.44%. The orbital contribution and distinctive peak electronic excitation mechanism of DEAA were uncovered using TD-DFT. By comparing the oscillator strength and peak position variations between the target DEAA and coexisting sulfuric acid, the unique spectral behavior of DEAA, such as its high sensitivity and selectivity, was explained. In addition to providing a reference for real-time industrial dye and intermediate monitoring, this study lays the methodological groundwork for future research. In light of the new method's short time consumption and non-secondary pollution benefits, we further believe it will be crucial in controlling the industrial synthesis process in order to improve product quality, resource conversion efficiency, and effectively prevent excessive pollution generation.

Sequence-Defined Tertiary Amine-Based Oligomer Employing a Scalable, Support-Free, and Protection/Deprotection-Free Iterative Strategy.

Sequence-defined oligomers (SDOs) with their unique monomeric sequence and customizable nature are attracting the attention of researchers globally. The structural and functional diversity attainable in SDOs makes this platform promising, albeit with challenges in the synthesis. Herein, we report the design and synthesis of a novel class of SDO by incorporating tertiary amines into the backbone from commercially available inexpensive materials. Tertiary amines were selected due to their various material and biomedical applications. Even though the synthesis and purification of amine compounds are challenging, their various significant applications, such as pharmaceuticals, catalysts, surfactants, corrosion inhibitors, dye intermediates, polymer additives, rubber accelerators, gas treating agents, agriculture, and analytical chemistry, make them fascinating. The synthetic strategy that is designed here is extremely efficient and economical for the scalable synthesis of the SDO and is support-free, protection-deprotection chemistry-free, and catalyst/template-free. Most importantly, no extra design and synthesis of the monomer is required here. The key reactions employed for the SDO synthesis are (i) transformation of the hydroxy group to a halide and (ii) substitution of the halide by the secondary amine units. Including the purifying processes, the multigram synthesis of 4-mer was completed in 12-14 h. The synthetic strategy was established by synthesizing two different sequences of SDOs. The SDOs are characterized by 1H NMR and LC-MS. The tandem MS (MS/MS) experiment was conducted in order to validate the sequences over the SDO chain. Furthermore, the SDO platform was advanced in two ways: (i) by increasing the chain length via attaching a linker, which provides a rapid method for increasing the tertiary amine over the SDO chain, and (ii) postsynthetic modification of SDO with other functional groups, including guanidine for biological importance and a well-known fluorophore dansyl group for material significance.

Core-fluorinated dipyrromethanes and BODIPYs. Synthesis and study of photophysical properties

An efficient synthetic protocol for the preparation of novel 1,7-difluorinated BODIPYs was elaborated. A set of novel dipyrromethanes, which are key intermediates for the target dyes, was prepared by acid-catalyzed condensation of ethyl 3-aryl-4-fluoro-1H-pyrrole-2-carboxylates with aldehydes in up to quantitative yield. Subsequent oxidation and boron difluoride complexation under microwave irradiation afforded a family of novel core-fluorinated BODIPYs in up to 92 % yield. Their photophysical properties were studied by UV–visible and fluorescence spectroscopy. In addition, DFT calculations were performed to estimate 2,6-substituents effect. This revealed that the values of the absorption and emission maxima perfectly correlated with the energy gap between the frontier orbitals.

Prodigious catalytic activity towards reduction of 4-hydroxynitrobenzene sodium salt using one-pot synthesized ZnO-Pd nanobolts

4-Hydroxynitrobenzene sodium salt (4-HNBS) is primarily used to manufacture pesticides, p-aminophenol, paracetamol, and dye intermediates. However, it is released into aquatic systems, which can cause severe health issues in humans. Therefore, novel approaches for detoxifying excessive 4-HNBS must be devised using ultralow amounts of cost-effective catalysts with high reduction efficiencies. To that end, an innovative one-pot, sustainable, and cost-effective method was developed in this study to synthesize ZnO–Pd nanobolt catalysts. The nanobolts were characterized using UV–vis spectroscopy, dynamic light scattering analysis, X-ray diffractometry, field-emission scanning electron microscopy, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). TEM images indicated that the nanobolts were 13.8–66.6-nm-thick and that they had a 44.5-nm-diameter central hole. The EDS results suggested that the weight percentages of Zn, O, and Pd were 37.12 %, 23.63 %, and 39.24 %, respectively. This is the first report on the catalytic conversion of 4-HNBS into 4-hydroxyaniline sodium salt (4-HAS), whereas previous studies have mainly focused on converting small amounts of 4-hydroxynitrobenzene (4-HNB) into 4-HAS using high catalyst concentrations. Additionally, the reusability of the catalyst was studied to prevent the problems encountered in large-scale remediation. The synthesized nanobolts exhibited outstanding catalytic properties for converting 4-HNBS to 4-HAS. The rate constant k was estimated to be 0.068 min−1 from the linear plot of ln(C/C0) versus the conversion time. Notably, the nanobolts achieved 99 % reduction of 0.125 mM 4-HNBS after only 30 min of incubation.

Alkaline-thermal hydrolysate of waste activated sludge as a co-metabolic substrate enhances biodegradation of refractory dye reactive black 5

Aromatic azo dyes possess inherent resistance and are known to be carcinogenic, posing a significant threat to human and ecosystems. Enhancing the biodegradation of azo dyes usually requires the presence of co-metabolic substrates to optimize the process. In addressing the issue of excessive waste activated sludge (WAS) generation, this study explored the potential of utilizing alkaline-thermal hydrolysate of WAS as a co-metabolic substrate to boost the degradation of reactive black 5 (RB5) dyes. The acclimated microbial consortium, when supplemented with the WAS hydrolysate obtained at a hydrolysis temperature of 30 °C, achieved an impressive RB5 decolorization efficiency of 90.3% (pH = 7, 35 °C) with a corresponding COD removal efficiency of 45.0%. The addition of WAS hydrolysate as a co-substrate conferred the consortium with a remarkable tolerance to high dye concentration (1500 mg/L RB5) and salinity levels (4–5%), surpassing the performance of conventional co-metabolic sugars in RB5 degradation. 3D-EEM analysis revealed that protein-like substances rich in tyrosine and tryptophan, present in the WAS hydrolysate, played a crucial role in promoting RB5 biodegradation. Furthermore, the microbial consortium community exhibited an enrichment of dye-degrading species, including Acidovorax, Bordetella, Kerstersia, and Brevundimonas, which dominated the community. Notably, functional genes associated with dye degradation and intermediates were also enriched during the RB5 decolorization and biodegradation process. These findings present a practical strategy for the simultaneous treatment of dye-containing wastewater and recycling of WAS.

Refractory azo dye wastewater treatment by combined process of microbial electrolytic reactor and plant-microbial fuel cell

An innovative design of microbial electrolytic reactor (MER) coupled with Ipomoea aquaticaForsk. plant microbial fuel cell (IAF-PMFC) was developed for azo dye wastewater treatment and electricity generation. This study aims to assess the sequential degradation of azo dye and the feasibility of energy self-sufficiency in the MER/IAF-PMFC system. The decomposition of azo dye into aromatic amines and dye decolorization occurred in the MER at high hydraulic loading of 0.28 m3/(m2·d), while dye intermediates were mainly mineralized in the IAF-PMFC at low hydraulic loading of 0.06 m3/(m2·d). The final decolorization efficiency and COD removal of the combined system reached 99.64% and 92.06% respectively, even at influent dye concentration of 1000 mg/L. The effects of open/closed circuit conditions, presence/absence of aquatic plant and different cathode areas on the performance of the IAF-PMFC for treating the effluent of the MER were systematically tested, and the results showed that closed-circuit condition, plant involvement and larger cathode area were more beneficial to decolorization, detoxification and mineralization of dye wastewater, bioelectricity output, plant growth and photosynthetic rate. The power consumption by the MER was 0.0163 kWh/m3 of dye wastewater, while the highest power generation of the IAF-PMFC reached 0.0183 kWh/m3. The current efficiency of the MER for dye decolorization was as high as 942.83%, while the maximum coulombic efficiency of the IAF-PMFC for intermediates metabolism was only 6.30%, which still had much space of bioelectricity generation promotion. The MER/IAF-PMFC technology can simultaneously realize refractory wastewater treatment and balance of electricity production and consumption.

Sequential treatment of simulated textile wastewater using zero-valent aluminum under alkaline conditions and biodegradation

The azo dye reactive yellow 145 (RY145) is inherently recalcitrant due to the presence of azo, ethyl sulfone and monochlorotriazine groups. This study explored removal of RY145 using zero valent aluminum (ZVAl) treatment under alkaline conditions followed by aerobic degradation using the bacterial strains Pseudomonas aeruginosa (RS1) and Thiosphaera pantotropha. During pretreatment using 1 g L−1 ZVAl at pH 11, 59% decolorization was observed after 30 min for 50 mg L−1 dye. However, even after carbon source supplementation, the supernatant could not support microbial activity due to the high aluminum concentration in solution at pH 11. After pH adjustment to neutral and Al(OH)3 precipitation, complete decolorization occurred and subsequently microbial degradation of the intermediates could be achieved. ZVAl pretreatment followed by biological treatment could cause an overall TOC reduction of 65% within 96 h. Sorption of dye on the precipitate only contributed to 13% dye removal. The bacterial cultures could utilize nitrogen from the dye intermediates formed after alkaline ZVAl treatment. The sequential treatment also reduced the concentration of total amines and phytotoxicity to Vigna radiata seeds. When a simulated textile wastewater containing 200 mg L−1 of RY145 was subjected to this sequential treatment, complete dye decolorization and 99.2% overall TOC reduction was observed in 30.5 h. The other compounds present in the synthetic wastewater facilitated decolorization as well as mineralization of the dye.

Cleaner production through enhanced resource recovery and reuse in dye intermediates industry: Integration of Vinyl Sulphone with H-acid production

H-Acid (HA) and para-base ester Vinyl Sulphone (VS) are the significant raw materials for several industrially important dyes consumed worldwide. Owing to the toxicity and non-biodegradability of HA and VS as well as the associated by-products and hazardous wastes, most developed countries in the world have banned their production. Many states in the Union of India, too, have banned the production of HA. Due to the economic significance of the dye intermediates sector, especially in international trade, the regulatory agencies in India as well as the international importers of dye intermediates are demanding a transition to cleaner production through enhanced recycle and reuse of wastes and minimization of resource consumption. In this context, this study focuses on the ways for enhancing cleaner production as well as maximizing reuse and recycle in HA and VS production through: (i) enhancing resource recovery and internal reuse of recovered water, (ii) exploring possibilities of co-processing of wastes by linking unit operations and unit processes in HA and VS production, and (iii) balancing the scales of production of HA and VS to enhance the benefits of the so-called ‘Zero Liquid Discharge’ to potentially minimize operating costs, increase resource efficiency, and lower environmental footprint. In addition, this is the first study to address the resource intensity and pollution intensity in the production of VS. The two cleaner production opportunities identified and evaluated in this study are (1) Reuse of Spent Mixed Acid and (2) Recovery and reuse of Glauber's Salt. The optimum production quantities of HA and VS were determined to be 2256 MT HA and 5000 MT VS so that the complete reuse of Spent Mixed Acid (i.e. 0% emission) can be achieved. This balanced production of HA and VS will be able to achieve several production benefits such as: 37% reuse of Glauber's Salt (67% sold to other industries), reduced freshwater consumption (55% reduction in HA and 7.2% reduction in VS), and reduced acid consumption (45% reduction in HA and 26% reduction in VS). Further, the balanced production of HA and VS will be able to achieve environmental benefits such as a 26% reduction in wastewater generation and a 74% reduction in waste salt sent to engineered hazardous waste management facilities.

Comparative studies for the treatment of industrial effluents employing advanced processes: towards enhancement of environmental performance

The investigation was inspired by the declaration of critically polluted industrial zones in India. It was also reported that most of the Common Effluent Treatment Plants (CETPs) are non-compliant due to higher COD values in discharge than regulatory norms. Furthermore, most of the literature has not reported the efficacy of advanced wastewater technologies for real industrial effluent. Thus, this research focused on field trials of scalable advanced wastewater technologies in Vatva Industrial Estate (VIE), Ahmedabad. The potential of physico-chemical and advanced treatment processes are explored for applicability in industrial wastewater treatment. Thus, for this research, three industries from each sector, i.e., textile processing, dyes, and dye intermediates, a total of nine different industries were chosen. A sufficient volume of effluent was collected from each industry for detailed investigations. The initial COD loading observed was in the range of 68 to 7074, 30 to 896, and 100 to 1541 kg COD/day for textile processing, dyes, and dye intermediates, respectively, with significant variation in the qualitative profiles. The collected effluent was treated by electrocoagulation and Fenton's reagent in batch scale reactors. The batch scale reactors for both the technologies were of 1L size. The results of treatability studies represented that Fenton's reagent performed better than the electrocoagulation process for most of the industries selected in this study. This research provides insight for improvement in the environmental performance of the individual industries in general and CETPs in particular.

A Case Study of Dye Intermediate Production Wastewater Treatment Project

Dye intermediates are indispensable chemical raw materials and play an important role in global industrial production. In the production process of dye intermediates, a large amount of wastewater is produced, which will cause serious pollution to the environment, and ultimately harm human health. Dye intermediate production wastewater is characterized by high organic matter concentration, complicated pollutants and poor biodegradability. The traditional treatment process has limited ability to purify wastewater and can not effectively degrade the organic pollutants. In this project, a novel combined process of "ozone catalytic oxidation + biochemical degradation" was adopted to treat the dye intermediate production wastewater, and the process mechanism and treatment effect were analyzed. The results showed that the key process unit of this project was heterogeneous ozone catalytic oxidation. Due to the high activity, low cost, easy recovery and strong adsorption capacity of heterogeneous ozone catalysts, a large amount of organic matters in wastewater could be adsorbed on the surface to improve the treatment effect. Through the oxidation process, the biodegradability of wastewater was improved to facilitate subsequent advanced treatment. Ultimately, the effluent water quality could meet the three-level limit requirements in the "Integrated Wastewater Discharge Standard" (GB8978-1996), with the water index as follows: CODcr≤450 mg/L, BOD₅≤200 mg/L, SS≤200 mg/L, chromatic value≤32 times. This operational process was manifested to be economical and reliable, possessing a broad development prospect in wastewater treatment of dye intermediates related industries.

Sonochemical synthesis and characterization of Cu2HgI4 nanostructures photocatalyst with enhanced visible light photocatalytic ability

These days, an important concern in water contamination is the remaining dyes from various sources (for instance, dye and dye intermediates industries, pulp and paper industries, textile industries, craft bleaching industries, tannery, and pharmaceutical industries, etc.), and a broad range of persistent organic contamination has been entered to the wastewater treatment systems or natural water supplies. Indeed, it is extremely hazardous and toxic to the living organism. Therefore, it is necessary to remove these organic pollutants before releasing them into the environment. Photocatalysis is a quickly growing technology for sewage procedures. For this purpose, Cu2HgI4 nanostructures were prepared via facile, and cost-effective sonochemical method. The effect of varied circumstances, such as various surfactants, sonication power, and sonication time was considered on the crystallinity, structure, shape, and particle size of products. Cu2HgI4 possesses a suitable bandgap (2.2 eV) in the visible area. The photocatalytic performance of the Cu2HgI4 was surveyed for the elimination of various organic dyes under visible radiation and exposed that this compound could degrade and remove methyl orange about 94.2% in an acidic medium after 160 min under visible light. Besides, the result showed that various parameters, including, pH, dye concentration, types of dyes, catalyst dosages, and time of irradiation affected the photocatalytic efficiency.

Synthesis of reusable cyclodextrin polymers for removal of naphthol and naphthylamine from water.

As one group of important naphthalene derivatives, naphthol and naphthylamine are diffusely employed as dye intermediates. The presence of naphthol and naphthylamine in water systems may pose risks to the environment and public health due to their carcinogenicity. In this study, four mesoporous polymers prepared by β-cyclodextrin derivatives and tetrafluoroterephthalonitrile were obtained and applied to adsorbing 1-naphthylamine, 2-naphthylamine, 1-naphthol, and 2-naphthol from water. The impact of adsorption time, initial concentration of naphthol and naphthylamine, and temperature on the adsorption efficiency of the four polymers were explored separately. The four polymers present fast adsorption kinetics toward naphthol and naphthylamine, attaining 93 ~ 100% of adsorption equilibrium uptake for 1-naphthol, 1-naphthylamine, 2-naphthylamine in 15min, and 87 ~ 90% of equilibrium uptake for 2-naphthol in 15min. The kinetics could be depicted well by the pseudo-second-order kinetic model. The adsorption isotherms of the four polymers toward naphthol and naphthylamine accord with the Redlich-Peterson or Sips model. The maximum adsorption capacities of 1-naphthylamine, 2-naphthylamine, 1-naphthol, and 2-naphthol are 189.9mg/g, 82.8mg/g, 137.7mg/g, and 88.7mg/g, respectively. The adsorption ratio increases fast with reducing the initial concentration of naphthol and naphthylamine, and the adsorption ratio of naphthol and naphthylamine in 5mg/L can achieve over 95% in 25°C. In addition, the four polymers can be effortlessly regenerated by a gentle and simple washing procedure with little reduction in performance. The adsorption performance of the four polymers toward the four naphthalene derivatives can be improved by increasing the adsorption temperature. In conclusion, the prepared β-cyclodextrin polymers exhibit rapid water treatment in removing the four low-concentration naphthalene derivatives with convenient regeneration and good reusability.

Alkali-stable solid state fluorescent pyrazolo/pyrrolinone disperse dyes: Synthesis and application for dyeing polyester fabric

Six novel fluorescent disperse dyes were synthesized by diazo-coupling reaction. As dye intermediates, two diazo components having 5-amino-4-arylazo-3-methyl-1H-pyrazoles moieties were initially prepared, diazotized and coupled with three pyrrolinone esters (PES) derivatives to give azo-hydrazone pyrazolo/pyrrolinone derivatives. The dye structures were confirmed by FTIR, 1HNMR, mass spectroscopy and elemental analysis. The absorption spectra of the prepared dyes and its solvatochromic behavior were investigated. These dyes displayed significant emission spectra in polycrystalline (powder) form, but no fluorescence observed in solution. The dyes were applied on polyester fabric using conventional high temperature exhaustion dyeing method, exhibited high tinctorial strength and bright fluorescent orange to reddish violet colors on polyester fabric with dyeing stability under acidic, neutral and alkaline pH. The relationship among different dyeing pH and color difference effects for dyed fabrics were studied. It was found that disperse dyes containing phenylazo-pyrazolone structure showed better dyeing performance and alkali-stable dyeing properties on polyester fabrics than those containing nitrophenol derivatives. The color fastness to washing, perspiration, sublimation and light fastness were also investigated.

Environmental Impact of leather Industrial Pollution on Agricultural Production in Vellore District

Water plays a vital role on agricultural production and industrial process, but this valuable resource is gradually declining from the past few decades due to increasing industrial activities, irrigation, drinking and domestic usage etc. Leather and leather goods manufacturing industry is one of the traditional business in India. It requires huge amount of water and chemical, dye and dye intermediates, distilleries etc for leather process. The wastewater produces during the process which released into the lands and water sources. It leads to damage of crops and declining the agricultural productivity. The rate of environmental degradation was identified by the decline of agricultural productivity and the quality of surface and ground water has decline at very high rate. This study focused on impact of leather industrial pollution on agricultural production and to give the remedial measures for reducing water pollution. In order to obtain the objectives of this study, we used secondary data sources.

Environmental Impact of leather Industrial Pollution on Agricultural Production in Vellore District

Water plays a vital role on agricultural production and industrial process, but this valuable resource is gradually declining from the past few decades due to increasing industrial activities, irrigation, drinking and domestic usage etc. Leather and leather goods manufacturing industry is one of the traditional business in India. It requires huge amount of water and chemical, dye and dye intermediates, distilleries etc for leather process. The wastewater produces during the process which released into the lands and water sources. It leads to damage of crops and declining the agricultural productivity. The rate of environmental degradation was identified by the decline of agricultural productivity and the quality of surface and ground water has decline at very high rate. This study focused on impact of leather industrial pollution on agricultural production and to give the remedial measures for reducing water pollution. In order to obtain the objectives of this study, we used secondary data sources.

Environmental Impact of leather Industrial Pollution on Agricultural Production in Vellore District

Water plays a vital role on agricultural production and industrial process, but this valuable resource is gradually declining from the past few decades due to increasing industrial activities, irrigation, drinking and domestic usage etc. Leather and leather goods manufacturing industry is one of the traditional business in India. It requires huge amount of water and chemical, dye and dye intermediates, distilleries etc for leather process. The wastewater produces during the process which released into the lands and water sources. It leads to damage of crops and declining the agricultural productivity. The rate of environmental degradation was identified by the decline of agricultural productivity and the quality of surface and ground water has decline at very high rate. This study focused on impact of leather industrial pollution on agricultural production and to give the remedial measures for reducing water pollution. In order to obtain the objectives of this study, we used secondary data sources.

Constructed wetland–microbial fuel cell for azo dyes degradation and energy recovery: Influence of molecular structure, kinetics, mechanisms and degradation pathways

Complete degradation of azo dye has always been a challenge due to the refractory nature of azo dye. An innovative hybrid system, constructed wetland-microbial fuel cell (CW-MFC) was developed for simultaneous azo dye remediation and energy recovery. This study investigated the effect of circuit connection and the influence of azo dye molecular structures on the degradation rate of azo dye and bioelectricity generation. The closed circuit system exhibited higher chemical oxygen demand (COD) removal and decolourisation efficiencies compared to the open circuit system. The wastewater treatment performances of different operating systems were ranked in the decreasing order of CW-MFC (R1 planted-closed circuit) > MFC (R2 plant-free-closed circuit) > CW (R1 planted-open circuit) > bioreactor (R2 plant-free-open circuit). The highest decolourisation rate was achieved by Acid Red 18 (AR18), 96%, followed by Acid Orange 7 (AO7), 67% and Congo Red (CR), 60%. The voltage outputs of the three azo dyes were ranked in the decreasing order of AR18 > AO7 > CR. The results disclosed that the decolourisation performance was significantly influenced by the azo dye structure and the moieties at the proximity of azo bond; the naphthol type azo dye with a lower number of azo bond and more electron-withdrawing groups could cause azo bond to be more electrophilic and more reductive for decolourisation. Moreover, the degradation pathway of AR18, AO7 and CR were elucidated based on the respective dye intermediate products identified through UV–Vis spectrophotometry, high-performance liquid chromatography (HPLC), and gas chromatograph-mass spectrometer (GC–MS) analyses. The CW-MFC system demonstrated high capability of decolouring azo dyes at the anaerobic anodic region and further mineralising dye intermediates at the aerobic cathodic region to less harmful or non-toxic products.

Recent Advances in Radical Nitration Using tert-Butyl Nitrite

Nitro compounds serve as valuable intermediates for pharmaceuticals, agrochemicals, dyes, and polymers. In recent years, radical nitration using tert-butyl nitrite (t-BuONO) has attracted wide attention and desirable progress has been made. On the one hand, t-BuONO is a potential active nitro radical source and can react with various functional groups. On the other hand, as a green and novel nitration reagent, t-BuONO has relatively low price and can easily produce a radical under mild conditions, which undoubtedly provides a simple and efficient way for nitration reactions. To date, some important reviews are available that summarize the synthesis of nitro compounds. To the best of our knowledge, however, there is still no review that exclusively discusses the synthesis of nitro compounds using t-BuONO through a radical strategy. Therefore, this review aims to highlight the recent advances in radical nitration using t-BuONO as nitration reagent. The main progress in this area has been presented according to the type of reaction substrates. Special attention has been paid discussion of the reaction mechanisms and selected examples of substrates have been given. We hope this paper will be a useful reference and inspiration for those who are exploring the synthesis of nitro compounds using t-BuONO.1 Introduction2 Radical Nitration of Alkenes3 Radical Nitration of Aromatics4 Radical Nitration of Alkynes5 Radical Nitration of 1,n-Enynes6 Radical Nitration of Alkanes7 Summary and Perspective

Phosphoryl trichloride. Documentation of proposed values of occupational exposure limits (OELs)

Phosphoryl trichloride is a clear, colorless or yellowish liquid with an unpleasant, pungent odor. In contact with water or steam, it rapidly hydrolyses by releasing hydrogen chloride and phosphoric(V) acid. Phosphoryl trichloride is used in industry primarily for the production of alkyl and aryl triesters of phosphoric(V) acid. It is also used in the production of plasticizers, flame retardants, hydraulic fluids, insecticides, pharmaceuticals, gasoline additives and dye intermediates. Phosphoryl trichloride is also used as chlorinating agent, pH regulator, catalyst, solvent in cryoscopy, dopant for semiconductor grade silicon, and as reagent in laboratories. Phosphoryl trichloride is classified for acute toxicity as category 2 with inhalation (inhalation may lead to death) and as category 4 if swallowed (harmful if swallowed). In addition, it is classified as corrosive category 1A (causes severe skin burns and eye damage) and toxic to target organs due to repeated exposure, category 1 (causes damage to organs through prolonged or repeated exposure). Both in acute and chronic cases of inhalation exposure, the primary effect was irritating to the respiratory tract and eyes (burning eyes and throat, feeling of breathlessness, tearing, coughing, bronchospasm, pain behind the sternum, pleurisy). In exposed workers, deterioration of pulmonary spirometric parameters was observed. The late effects of exposure were asthmatic problems and obstructive respiratory disease. Available animal studies are poorly documented. Phosphoryl trichloride did not show any mutagenic effects. There is no information on the carcinogenic, embryotoxic or teratogenic effects of this substance in the available literature. The critical effect of the action of phosphoryl trichloride is a strong irritation on the mucous membranes of the eyes and upper respiratory tract. A concentration of 0.48 mg/m3 constituting the threshold for toxic effects of phosphoryl trichloride in studies in rats and guinea pigs was taken as the LOAEC value. After applying the uncertainty coefficients, the MAC value of phosphoryl trichloride calculated on this basis is 0.06 mg/m3. It is proposed to adopt the MAC value in accordance with the SCOEL and ACSH recommendation, i.e., 0.064 mg/m3. Phosphoryl trichloride is a strongly irritating substance, in order to prevent peak concentrations of this substance it is proposed to set the maximum allowable short-term concentration (MAC-STEL) at level 2 x MAC value, i.e., 0.13 mg/m3. There are no substantive foundations to determine the permissible biological exposure indices to phosphoryl trichloride (DSB). Due to the corrosive effect of phosphoryl chloride, it is proposed to label it with the letter "C" (a substance with a corrosive effect). This article discusses the problems of occupational safety and health, which are covered by health sciences and environmental engineering.