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163 KiB

Open AccessEditorial

Renewable Green Platform Chemicals for Polymers

by Parijat Ray, Craig Smith, George P. Simon and Kei Saito

Molecules 2017, 22(3), 376; https://doi.org/10.3390/molecules22030376 - 28 Feb 2017

Cited by 17 | Viewed by 4475

Abstract

This Special Issue covered topics in the field of Green Chemistry.[...] Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

Research

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915 KiB

Open AccessArticle

Poly(N-4-vinylbenzyl-1,4,7-triazacyclononane) Copper Complex Grafted Solid Catalyst for Oxidative Polymerization of 2,6-Dimethylphenol

by Kei Saito, Koji Miyamoto, Sepa Nanayakkara, Hirotaka Ihara and Milton T. W. Hearn

Molecules 2016, 21(2), 146; https://doi.org/10.3390/molecules21020146 - 26 Jan 2016

Cited by 2 | Viewed by 5216

Abstract

A new solid phase catalyst, poly(N-4-vinylbenzyl-1,4,7-triazacyclononane) copper(I) complex, grafted onto polystyrene particles, has been employed for the oxidative polymerization of 2,6-dimethylphenol using an aqueous biphasic (water/toluene) solvent system. The solid catalyst was synthesized by first grafting N-(4-vinylbenzyl)-1,4,7-triaza-cyclononane onto polystyrene particles [...] Read more.

A new solid phase catalyst, poly(N-4-vinylbenzyl-1,4,7-triazacyclononane) copper(I) complex, grafted onto polystyrene particles, has been employed for the oxidative polymerization of 2,6-dimethylphenol using an aqueous biphasic (water/toluene) solvent system. The solid catalyst was synthesized by first grafting N-(4-vinylbenzyl)-1,4,7-triaza-cyclononane onto polystyrene particles using a radical mediated polymerization method and next by creating the polymer-metal complex of copper-triazacyclononane with these modified particles. Poly(2,6-dimethyl-1,4-phenylene oxide) was successfully obtained from the polymerization of 2,6-dimethylphenol using this new metal-organic solid phase catalyst. Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

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1837 KiB

Open AccessArticle

Green Synthesis of Novel Polyaniline Nanofibers: Application in pH Sensing

by Shivani Tanwar and Ja-an Annie Ho

Molecules 2015, 20(10), 18585-18596; https://doi.org/10.3390/molecules201018585 - 13 Oct 2015

Cited by 29 | Viewed by 8285

Abstract

An optically active polyaniline nanomaterial (PANI-Nap), doped with (S)-naproxen, was developed and evaluated as a potent pH sensor. We synthesized the material in one pot by the addition of the dopant, (S)-naproxen, prior to polymerization, followed by the addition [...] Read more.

An optically active polyaniline nanomaterial (PANI-Nap), doped with (S)-naproxen, was developed and evaluated as a potent pH sensor. We synthesized the material in one pot by the addition of the dopant, (S)-naproxen, prior to polymerization, followed by the addition of the oxidizing agent (ammonium persulfate) that causes polymerization of the aniline. This green chemistry approach allowed us to take only 1 h to produce a water-soluble and stable nanomaterial. UV-visible spectroscopy, fluorescence spectroscopy, FT-IR spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize the designed nanomaterial. This nanomaterial exhibited excellent pH sensing properties and showed long term stability (up to one month) without loss of sensor performance. Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

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733 KiB

Open AccessArticle

The Application of Template Selectophores for the Preparation of Molecularly Imprinted Polymers

by Basil Danylec, Lachlan J. Schwarz, Simon J. Harris, Reinhard I. Boysen and Milton T. W. Hearn

Molecules 2015, 20(9), 17601-17613; https://doi.org/10.3390/molecules200917601 - 23 Sep 2015

Cited by 17 | Viewed by 7335

Abstract

Molecularly imprinted polymers are versatile materials with wide application scope for the detection, capture and separation of specific compounds present in complex feed stocks. A major challenge associated with their preparation has been the need to sacrifice one mole equivalent of the template [...] Read more.

Molecularly imprinted polymers are versatile materials with wide application scope for the detection, capture and separation of specific compounds present in complex feed stocks. A major challenge associated with their preparation has been the need to sacrifice one mole equivalent of the template molecule to generate the complementary polymer cavities that selectively bind the target molecule. Moreover, template molecules can often be difficult to synthesise, expensive or lack stability. In this study, we describe a new approach, directed at the use of synthetic selectophores, chosen as readily prepared and low cost structural analogues with recognition groups in similar three-dimensional arrangements as found in the target molecule. To validate the approach, a comparative study of selectophores related to the polyphenolic compound (E)-resveratrol has been undertaken using traditional and green chemical synthetic approaches. These molecular mimic compounds were employed as polymer templates and also as binding analytes to interrogate the recognition sites associated with the molecularly imprinted polymers. Importantly, the study confirms that the use of selectophores has the potential to confer practical advantages, including access to more efficient methods for selection and preparation of suitable template molecules with a broader range of molecular diversity, as well as delivering imprinted polymers capable of recognizing the target compound and structurally related products. Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

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798 KiB

Open AccessArticle

Addition of CFCl₃ to Aromatic Aldehydes via in Situ Grignard Reaction

by Balaka Barkakaty, Bandana Talukdar and Bradley S. Lokitz

Molecules 2015, 20(8), 15098-15107; https://doi.org/10.3390/molecules200815098 - 18 Aug 2015

Cited by 1 | Viewed by 7982

Abstract

Synthetic modification of trichlorofluoromethane (CFCl₃) to non-volatile and useful fluorinated precursors is a cost-effective and an environmentally benign strategy for the safe consumption/destruction of the ozone depleting potential of the reagent. In this report, we present a novel method for in [...] Read more.

Synthetic modification of trichlorofluoromethane (CFCl₃) to non-volatile and useful fluorinated precursors is a cost-effective and an environmentally benign strategy for the safe consumption/destruction of the ozone depleting potential of the reagent. In this report, we present a novel method for in situ Grignard reaction using magnesium powder and CFCl₃ for synthesis of dichlorofluoromethyl aromatic alcohols. Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

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1074 KiB

Open AccessArticle

Iminoiodane- and Brønsted Base-Mediated Cross Dehydrogenative Coupling of Cyclic Ethers with 1,3-Dicarbonyl Compounds

by Ciputra Tejo, Xiao Rong Sim, Bo Ra Lee, Benjamin James Ayers, Chung-Hang Leung, Dik-Lung Ma and Philip Wai Hong Chan

Molecules 2015, 20(7), 13336-13353; https://doi.org/10.3390/molecules200713336 - 22 Jul 2015

Cited by 8 | Viewed by 9392

Abstract

A one-pot, two-step approach to prepare 2-tetrahydrofuran and -pyran substituted 1,3-dicarbonyl compounds by PhI=NTs-mediated amination/Brønsted base-catalyzed cross dehydrogenative coupling (CDC) reaction of the cyclic ether and 1,3-dicarbonyl derivative under mild conditions is reported. The reaction is compatible with a variety of cyclic ethers [...] Read more.

A one-pot, two-step approach to prepare 2-tetrahydrofuran and -pyran substituted 1,3-dicarbonyl compounds by PhI=NTs-mediated amination/Brønsted base-catalyzed cross dehydrogenative coupling (CDC) reaction of the cyclic ether and 1,3-dicarbonyl derivative under mild conditions is reported. The reaction is compatible with a variety of cyclic ethers and 1,3-dicarbonyl compounds, affording the corresponding coupled products in moderate to good yields of up to 80% over two steps. Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

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1492 KiB

Open AccessArticle

Cu and Boron Doped Carbon Nitride for Highly Selective Oxidation of Toluene to Benzaldehyde

by Hongling Han, Guodong Ding, Tianbin Wu, Dexin Yang, Tao Jiang and Buxing Han

Molecules 2015, 20(7), 12686-12697; https://doi.org/10.3390/molecules200712686 - 13 Jul 2015

Cited by 41 | Viewed by 8301

Abstract

A novel Cu and boron doped graphitic carbon nitride catalyst (Cu-CNB) was synthesized using cheap precursors and systematically characterized. The selective oxidation of toluene proceeded very smoothly over the catalyst at 70 °C using tert-butyl hydroperoxide (TBHP) as the oxidant to exclusively afford [...] Read more.

A novel Cu and boron doped graphitic carbon nitride catalyst (Cu-CNB) was synthesized using cheap precursors and systematically characterized. The selective oxidation of toluene proceeded very smoothly over the catalyst at 70 °C using tert-butyl hydroperoxide (TBHP) as the oxidant to exclusively afford benzaldehyde. The catalyst can be used for at least five cycles without decrease in activity and selectivity. Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

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790 KiB

Open AccessArticle

Synthesis of (E)-2-Styrylchromones and Flavones by Base-Catalyzed Cyclodehydration of the Appropriate β-Diketones Using Water as Solvent

by Joana Pinto, Vera L. M. Silva, Ana M. G. Silva and Artur M. S. Silva

Molecules 2015, 20(6), 11418-11431; https://doi.org/10.3390/molecules200611418 - 22 Jun 2015

Cited by 19 | Viewed by 8025

Abstract

A low cost, safe, clean and environmentally benign base-catalyzed cyclodehydration of appropriate β-diketones affording (E)-2-styrylchromones and flavones in good yields is disclosed. Water was used as solvent and the reactions were heated using classical and microwave heating methods, under open and [...] Read more.

A low cost, safe, clean and environmentally benign base-catalyzed cyclodehydration of appropriate β-diketones affording (E)-2-styrylchromones and flavones in good yields is disclosed. Water was used as solvent and the reactions were heated using classical and microwave heating methods, under open and closed vessel conditions. β-Diketones having electron-donating and withdrawing substituents were used to evaluate the reaction scope. The reaction products were isolated in high purity by simple filtration and recrystallization from ethanol, when using 800 mg of the starting diketone under classical reflux heating conditions. Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

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412 KiB

Open AccessArticle

An Efficient Synthesis of 3,4-Dihydropyrimidin-2(1H)-Ones and Thiones Catalyzed by a Novel Brønsted Acidic Ionic Liquid under Solvent-Free Conditions

by Yonghong Zhang, Bin Wang, Xiaomei Zhang, Jianbin Huang and Chenjiang Liu

Molecules 2015, 20(3), 3811-3820; https://doi.org/10.3390/molecules20033811 - 26 Feb 2015

Cited by 80 | Viewed by 9003

Abstract

We report here an efficient and green method for Biginelli condensation reaction of aldehydes, β-ketoesters and urea or thiourea catalyzed by Brønsted acidic ionic liquid [Btto][p-TSA] under solvent-free conditions. Compared to the classical Biginelli reaction conditions, the present method has the [...] Read more.

We report here an efficient and green method for Biginelli condensation reaction of aldehydes, β-ketoesters and urea or thiourea catalyzed by Brønsted acidic ionic liquid [Btto][p-TSA] under solvent-free conditions. Compared to the classical Biginelli reaction conditions, the present method has the advantages of giving good yields, short reaction times, near room temperature conditions and the avoidance of the use of organic solvents and metal catalyst. Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

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1466 KiB

Open AccessArticle

Selective C–C Coupling Reaction of Dimethylphenol to Tetramethyldiphenoquinone Using Molecular Oxygen Catalyzed by Cu Complexes Immobilized in Nanospaces of Structurally-Ordered Materials

by Zen Maeno, Takato Mitsudome, Tomoo Mizugaki, Koichiro Jitsukawa and Kiyotomi Kaneda

Molecules 2015, 20(2), 3089-3106; https://doi.org/10.3390/molecules20023089 - 12 Feb 2015

Cited by 8 | Viewed by 10218

Abstract

Two high-performance Cu catalysts were successfully developed by immobilization of Cu ions in the nanospaces of poly(propylene imine) (PPI) dendrimer and magadiite for the selective C–C coupling of 2,6-dimethylphenol (DMP) to 3,3',5,5'-tetramethyldiphenoquinone (DPQ) with O₂ as a green oxidant. The PPI dendrimer [...] Read more.

Two high-performance Cu catalysts were successfully developed by immobilization of Cu ions in the nanospaces of poly(propylene imine) (PPI) dendrimer and magadiite for the selective C–C coupling of 2,6-dimethylphenol (DMP) to 3,3',5,5'-tetramethyldiphenoquinone (DPQ) with O₂ as a green oxidant. The PPI dendrimer encapsulated Cu ions in the internal nanovoids to form adjacent Cu species, which exhibited significantly high catalytic activity for the regioselective coupling reaction of DMP compared to previously reported enzyme and metal complex catalysts. The magadiite-immobilized Cu complex acted as a selective heterogeneous catalyst for the oxidative C–C coupling of DMP to DPQ. This heterogeneous catalyst was recoverable from the reaction mixture by simple filtration, reusable without loss of efficiency, and applicable to a continuous flow reactor system. Detailed characterization using ultraviolet-visible (UV-vis), Fourier transform infrared (FTIR), electronic spin resonance (ESR), and X-ray absorption fine structure (XAFS) spectroscopies and the reaction mechanism investigation revealed that the high catalytic performances of these Cu catalysts were ascribed to the adjacent Cu species generated within the nanospaces of the PPI dendrimer and magadiite. Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

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Review

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1825 KiB

Open AccessReview

Recent Developments in Chemical Synthesis with Biocatalysts in Ionic Liquids

by Mahesh K. Potdar, Geoffrey F. Kelso, Lachlan Schwarz, Chunfang Zhang and Milton T. W. Hearn

Molecules 2015, 20(9), 16788-16816; https://doi.org/10.3390/molecules200916788 - 15 Sep 2015

Cited by 84 | Viewed by 13406

Abstract

Over the past decade, a variety of ionic liquids have emerged as greener solvents for use in the chemical manufacturing industries. Their unique properties have attracted the interest of chemists worldwide to employ them as replacement for conventional solvents in a diverse range [...] Read more.

Over the past decade, a variety of ionic liquids have emerged as greener solvents for use in the chemical manufacturing industries. Their unique properties have attracted the interest of chemists worldwide to employ them as replacement for conventional solvents in a diverse range of chemical transformations including biotransformations. Biocatalysts are often regarded as green catalysts compared to conventional chemical catalysts in organic synthesis owing to their properties of low toxicity, biodegradability, excellent selectivity and good catalytic performance under mild reaction conditions. Similarly, a selected number of specific ionic liquids can be considered as greener solvents superior to organic solvents owing to their negligible vapor pressure, low flammability, low toxicity and ability to dissolve a wide range of organic and biological substances, including proteins. A combination of biocatalysts and ionic liquids thus appears to be a logical and promising opportunity for industrial use as an alternative to conventional organic chemistry processes employing organic solvents. This article provides an overview of recent developments in this field with special emphasis on the application of more sustainable enzyme-catalyzed reactions and separation processes employing ionic liquids, driven by advances in fundamental knowledge, process optimization and industrial deployment. Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

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695 KiB

Open AccessReview

Non-Covalent Derivatives: Cocrystals and Eutectics

by Emily Stoler and John C. Warner

Molecules 2015, 20(8), 14833-14848; https://doi.org/10.3390/molecules200814833 - 14 Aug 2015

Cited by 81 | Viewed by 11611

Abstract

Non-covalent derivatives (NCDs) are formed by incorporating one (or more) coformer molecule(s) into the matrix of a parent molecule via non-covalent forces. These forces can include ionic forces, Van der Waals forces, hydrogen bonding, lipophilic-lipophilic interactions and pi-pi interactions. NCDs, in both cocrystal [...] Read more.

Non-covalent derivatives (NCDs) are formed by incorporating one (or more) coformer molecule(s) into the matrix of a parent molecule via non-covalent forces. These forces can include ionic forces, Van der Waals forces, hydrogen bonding, lipophilic-lipophilic interactions and pi-pi interactions. NCDs, in both cocrystal and eutectic forms, possess properties that are unique to their supramolecular matrix. These properties include critical product performance factors such as solubility, stability and bioavailability. NCDs have been used to tailor materials for a variety of applications and have the potential to be used in an even broader range of materials and processes. NCDs can be prepared using little or no solvent and none of the reagents typical to synthetic modifications. Thus, NCDs represent a powerfully versatile, environmentally-friendly and cost-effective opportunity. Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

4063 KiB

Open AccessReview

Graphene-Based Nanomaterials as Efficient Peroxidase Mimetic Catalysts for Biosensing Applications: An Overview

by Bhaskar Garg, Tanuja Bisht and Yong-Chien Ling

Molecules 2015, 20(8), 14155-14190; https://doi.org/10.3390/molecules200814155 - 4 Aug 2015

Cited by 132 | Viewed by 15051

Abstract

“Artificial enzymes”, a term coined by Breslow for enzyme mimics is an exciting and promising branch of biomimetic chemistry aiming to imitate the general and essential principles of natural enzymes using a variety of alternative materials including heterogeneous catalysts. Peroxidase enzymes represent a [...] Read more.

“Artificial enzymes”, a term coined by Breslow for enzyme mimics is an exciting and promising branch of biomimetic chemistry aiming to imitate the general and essential principles of natural enzymes using a variety of alternative materials including heterogeneous catalysts. Peroxidase enzymes represent a large family of oxidoreductases that typically catalyze biological reactions with high substrate affinity and specificity under relatively mild conditions and thus offer a wide range of practical applications in many areas of science. The increasing understanding of general principles as well as intrinsic drawbacks such as low operational stability, high cost, difficulty in purification and storage, and sensitivity of catalytic activity towards atmospheric conditions of peroxidases has triggered a dynamic field in nanotechnology, biochemical, and material science that aims at joining the better of three worlds by combining the concept adapted from nature with the processability of catalytically active graphene-based nanomaterials (G-NMs) as excellent peroxidase mimetic catalysts. This comprehensive review discusses an up-to-date synthesis, kinetics, mechanisms, and biosensing applications of a variety of G-NMs that have been explored as promising catalysts to mimic natural peroxidases. Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

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1263 KiB

Open AccessReview

Green Chemistry Metrics with Special Reference to Green Analytical Chemistry

by Marek Tobiszewski, Mariusz Marć, Agnieszka Gałuszka and Jacek Namieśnik

Molecules 2015, 20(6), 10928-10946; https://doi.org/10.3390/molecules200610928 - 12 Jun 2015

Cited by 384 | Viewed by 19724

Abstract

The concept of green chemistry is widely recognized in chemical laboratories. To properly measure an environmental impact of chemical processes, dedicated assessment tools are required. This paper summarizes the current state of knowledge in the field of development of green chemistry and green [...] Read more.

The concept of green chemistry is widely recognized in chemical laboratories. To properly measure an environmental impact of chemical processes, dedicated assessment tools are required. This paper summarizes the current state of knowledge in the field of development of green chemistry and green analytical chemistry metrics. The diverse methods used for evaluation of the greenness of organic synthesis, such as eco-footprint, E-Factor, EATOS, and Eco-Scale are described. Both the well-established and recently developed green analytical chemistry metrics, including NEMI labeling and analytical Eco-scale, are presented. Additionally, this paper focuses on the possibility of the use of multivariate statistics in evaluation of environmental impact of analytical procedures. All the above metrics are compared and discussed in terms of their advantages and disadvantages. The current needs and future perspectives in green chemistry metrics are also discussed. Full article

(This article belongs to the Special Issue Frontier in Green Chemistry Approaches)

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