Balvant Singh - Profile on Academia.edu (original) (raw)
Papers by Balvant Singh
Ultrasonics Sonochemistry, 2013
The present paper deals with the synthesis of aminooxazole derivatives via thermal and ultrasonic... more The present paper deals with the synthesis of aminooxazole derivatives via thermal and ultrasonic methods using deep eutectic solvent as medium. It was observed that ultrasound-assisted method gave 90% yield in just 8 min as against 3.5 h required to get 69% yield by thermal method. One of the compounds 4-(4-nitrophenyl)-1,3-oxazol-2-amine synthesized by both methods were subjected to material characterization study via XRD, TGA and SEM analysis. It was observed that use of ultrasound not only increased the rate of reaction but also improved the quality of product obtained. The crystallinity of the product from ultrasound method was 21.12% whereas thermal method fetched only 8.33% crystallinity thereby improving crystallinity by almost 60%. In addition, sonochemical synthesis also saved more than 70% energy as depicted by energy calculations.
Ultrasonics Sonochemistry, 2013
The present work deals with the synthesis of novel oxazole compounds by using effective combinati... more The present work deals with the synthesis of novel oxazole compounds by using effective combination of ultrasound (US) and deep eutectic solvent (DES). The reaction was also conducted by thermal method (NUS) and the comparative studies are provided. It was observed that applying ultrasound not only improved yields and reduced reaction times but also saved more than 85% energy as shown by energy consumption calculations. The advantages of using DES as reaction medium is highlighted from the fact that it is biodegradable , non-toxic, recyclable and could be easily prepared using inexpensive raw materials. The recyclability for DES was studied wherein it was found that ultrasound has no negative effects on DES even up to four runs. In addition, the present work is the first report on the combinative use of DES and US in organic synthesis.
Optical Materials, 2013
Organic push-pull chromophoric system containing thiazole Schiff bases were synthesized from amin... more Organic push-pull chromophoric system containing thiazole Schiff bases were synthesized from aminothiazole intermediate. These novel chromophores possessed excellent thermal and optical properties with complete transparency in the visible spectral region. Thermogravimetric analysis revealed that all dyes were thermally stable at temperatures above 300°C. The third-order nonlinear optical studies, performed using the Z-scan technique with $2 ps pulses, revealed excellent three photon absorption coefficients/cross-sections combined with reasonably high values of nonlinear refractive index (n 2). The solute n 2 was of opposite sign compared to that of solvents. To the best of our knowledge, this is the first report of three-photon absorption studies in Schiff base compounds.
Green Chemistry Letters and Reviews, 2012
Chemistry - A European Journal, 2014
We report the synthesis, characterization, and optical and electrochemical properties of two stru... more We report the synthesis, characterization, and optical and electrochemical properties of two structurally similar coumarin dyes (C1 and C2). These dyes have been deployed as sensitizers in TiO 2 nanoparticles and thin films, and the effect of molecular structure on interfacial electron-transfer dynamics has been studied. Steady-state optical absorption, emission, and time-resolved emission studies on both C1 and C2, varying the polarity of the solvent and the solution pH, suggest that both photoexcited dyes exist in a locally excited (LE) state in solvents of low polarity. In highly polar solvents, however, C1 exists in an intramolecular chargetransfer (ICT) state, whereas C2 exists in both ICT and twisted intramolecular charge-transfer (TICT) states, their populations depending on the degree of polarity of the solvent and the pH of the solution. We have employed femtosecond transient absorption spectroscopy to monitor the charge-transfer dynamics in C1-and C2-sensitized TiO 2 nanoparticles and thin films. Electron injection has been confirmed by direct detection of electrons in the conduction band of TiO 2 nanoparticles and of radical cations of the dyes in the visible and near-IR regions of the transient absorption spectra. Electron injection in both the C1/TiO 2 and C2/TiO 2 systems has been found to be pulse-width limited (< 100 fs); however, backelectron-transfer (BET) dynamics has been found to be slower in the C2/TiO 2 system than in the C1/TiO 2 system. The involvement of TICT states in C2 is solely responsible for the higher electron injection yield as well as the slower BET process compared to those in the C1/TiO 2 system. Further pH-dependent experiments on C1-and C2-sensitized TiO 2 thin films have corroborated the participation of the TICT state in the slower BET process in the C2/TiO 2 system.
Catalysis Letters, 2012
Lipase bio-catalyst or ammonium based deep eutectic mixture efficiently catalyzed aqueous phase s... more Lipase bio-catalyst or ammonium based deep eutectic mixture efficiently catalyzed aqueous phase synthesis of methyl-thiazole and amino-thiazole derivatives. The simple ammonium deep eutectic catalyst, easily synthesized from choline chloride and urea, is inexpensive, recyclable and biodegradable , making it suitable for industrial applications.
Selective N-Alkylation of Aromatic Primary Amines Catalyzed by Bio-catalyst or Deep Eutectic Solvent
Catalysis Letters, 2010
Abstract Biocatalysts or deep eutectic solvents (DES) are effective for selective N-alkylation o... more Abstract Biocatalysts or deep eutectic solvents (DES) are effective for selective N-alkylation of various aromatic primary amines. These methods avoided complexity of multiple alkylations giving products in good yields. Both DES and lipase can be recycled and re-used at least five times. In addition, these catalysts are biodegradable, non-toxic and cost-effective. Graphical Abstract
Choline chloride based eutectic solvents: Magical catalytic system for carbon–carbon bond formation in the rapid synthesis of β-hydroxy functionalized derivatives
Catalysis Communications, 2012
ABSTRACT Significant β-hydroxy functionalized derivatives including nitroaldols, β-hydroxy nitril... more ABSTRACT Significant β-hydroxy functionalized derivatives including nitroaldols, β-hydroxy nitriles and β-hydroxy carboxylic acids were successfully prepared, for the first time, by catalytic use of deep eutectic solvents (DES). This paper explores the versatility and effectiveness of DES as catalyst in three different carbon–carbon bond formation reactions. The uniqueness of this catalyst lies in its simplicity since it avoids expensive catalysts and multi-step synthesis as reported in literature. The compounds, which are potent intermediates for innumerable useful products, were synthesized in excellent yields within very short reaction times. The catalyst prepared from choline chloride and urea, is biodegradable, non-toxic, cost-effective and recyclable.
Bio-compatible eutectic mixture for multi-component synthesis: A valuable acidic catalyst for synthesis of novel 2,3-dihydroquinazolin-4(1H)-one derivatives
Catalysis Communications, 2012
ABSTRACT Novel derivatives of quinazolin-4(1H)-one derivatives were effectively synthesized via o... more ABSTRACT Novel derivatives of quinazolin-4(1H)-one derivatives were effectively synthesized via one-pot multi-component reaction of isatoic anhydride, aldehyde and aromatic amines using acidic catalyst in methanol. The catalyst, being a deep eutectic mixture of choline chloride and malonic acid, gave better results than several reported catalysts. Moreover, such eutectic mixtures are cost-effective, recyclable, non-toxic and bio-degradable. The methodology was successfully used for incorporating significant phenyl and heterocyclic substitutions at 2,3-positions of quinazolinone core. In addition, studies related to catalyst screening, substrate variation, recyclability and plausible mechanism of reaction are also described.
Ultrasound-assisted intensification of bio-catalyzed synthesis of mono-N-alkyl aromatic amines
Biochemical Engineering Journal, 2013
ABSTRACT Bio-catalyzed process for mono-N-alkylation of primary aromatic amines was considerably ... more ABSTRACT Bio-catalyzed process for mono-N-alkylation of primary aromatic amines was considerably improved by the use of sonochemical energy. The optimized method exhibited good tolerance toward various aromatic primary amines as well alkylating agents. A comparative study was done by carrying out the bio-catalyzed reaction in the presence of ultrasound and non-ultrasound conditions both at room temperature and elevated temperature. The results showed that ultrasonication gave enhanced yields in shorter reaction times. The optimization studies also included variation in organic solvents, amount of catalyst and reaction temperature. These studies conclusively suggest that ultrasound technique improved the activity of catalyst thereby saving time and energy, improving the selectivity and yield of the product. In addition, the bio-degradable and non-toxic bio-catalyst was easily recycled till five consecutive runs.
Ultrasonics Sonochemistry, 2013
The present paper deals with the synthesis of aminooxazole derivatives via thermal and ultrasonic... more The present paper deals with the synthesis of aminooxazole derivatives via thermal and ultrasonic methods using deep eutectic solvent as medium. It was observed that ultrasound-assisted method gave 90% yield in just 8 min as against 3.5 h required to get 69% yield by thermal method. One of the compounds 4-(4-nitrophenyl)-1,3-oxazol-2-amine synthesized by both methods were subjected to material characterization study via XRD, TGA and SEM analysis. It was observed that use of ultrasound not only increased the rate of reaction but also improved the quality of product obtained. The crystallinity of the product from ultrasound method was 21.12% whereas thermal method fetched only 8.33% crystallinity thereby improving crystallinity by almost 60%. In addition, sonochemical synthesis also saved more than 70% energy as depicted by energy calculations.
Ultrasonics Sonochemistry, 2013
The present work deals with the synthesis of novel oxazole compounds by using effective combinati... more The present work deals with the synthesis of novel oxazole compounds by using effective combination of ultrasound (US) and deep eutectic solvent (DES). The reaction was also conducted by thermal method (NUS) and the comparative studies are provided. It was observed that applying ultrasound not only improved yields and reduced reaction times but also saved more than 85% energy as shown by energy consumption calculations. The advantages of using DES as reaction medium is highlighted from the fact that it is biodegradable , non-toxic, recyclable and could be easily prepared using inexpensive raw materials. The recyclability for DES was studied wherein it was found that ultrasound has no negative effects on DES even up to four runs. In addition, the present work is the first report on the combinative use of DES and US in organic synthesis.
Optical Materials, 2013
Organic push-pull chromophoric system containing thiazole Schiff bases were synthesized from amin... more Organic push-pull chromophoric system containing thiazole Schiff bases were synthesized from aminothiazole intermediate. These novel chromophores possessed excellent thermal and optical properties with complete transparency in the visible spectral region. Thermogravimetric analysis revealed that all dyes were thermally stable at temperatures above 300°C. The third-order nonlinear optical studies, performed using the Z-scan technique with $2 ps pulses, revealed excellent three photon absorption coefficients/cross-sections combined with reasonably high values of nonlinear refractive index (n 2). The solute n 2 was of opposite sign compared to that of solvents. To the best of our knowledge, this is the first report of three-photon absorption studies in Schiff base compounds.
Green Chemistry Letters and Reviews, 2012
Chemistry - A European Journal, 2014
We report the synthesis, characterization, and optical and electrochemical properties of two stru... more We report the synthesis, characterization, and optical and electrochemical properties of two structurally similar coumarin dyes (C1 and C2). These dyes have been deployed as sensitizers in TiO 2 nanoparticles and thin films, and the effect of molecular structure on interfacial electron-transfer dynamics has been studied. Steady-state optical absorption, emission, and time-resolved emission studies on both C1 and C2, varying the polarity of the solvent and the solution pH, suggest that both photoexcited dyes exist in a locally excited (LE) state in solvents of low polarity. In highly polar solvents, however, C1 exists in an intramolecular chargetransfer (ICT) state, whereas C2 exists in both ICT and twisted intramolecular charge-transfer (TICT) states, their populations depending on the degree of polarity of the solvent and the pH of the solution. We have employed femtosecond transient absorption spectroscopy to monitor the charge-transfer dynamics in C1-and C2-sensitized TiO 2 nanoparticles and thin films. Electron injection has been confirmed by direct detection of electrons in the conduction band of TiO 2 nanoparticles and of radical cations of the dyes in the visible and near-IR regions of the transient absorption spectra. Electron injection in both the C1/TiO 2 and C2/TiO 2 systems has been found to be pulse-width limited (< 100 fs); however, backelectron-transfer (BET) dynamics has been found to be slower in the C2/TiO 2 system than in the C1/TiO 2 system. The involvement of TICT states in C2 is solely responsible for the higher electron injection yield as well as the slower BET process compared to those in the C1/TiO 2 system. Further pH-dependent experiments on C1-and C2-sensitized TiO 2 thin films have corroborated the participation of the TICT state in the slower BET process in the C2/TiO 2 system.
Catalysis Letters, 2012
Lipase bio-catalyst or ammonium based deep eutectic mixture efficiently catalyzed aqueous phase s... more Lipase bio-catalyst or ammonium based deep eutectic mixture efficiently catalyzed aqueous phase synthesis of methyl-thiazole and amino-thiazole derivatives. The simple ammonium deep eutectic catalyst, easily synthesized from choline chloride and urea, is inexpensive, recyclable and biodegradable , making it suitable for industrial applications.
Selective N-Alkylation of Aromatic Primary Amines Catalyzed by Bio-catalyst or Deep Eutectic Solvent
Catalysis Letters, 2010
Abstract Biocatalysts or deep eutectic solvents (DES) are effective for selective N-alkylation o... more Abstract Biocatalysts or deep eutectic solvents (DES) are effective for selective N-alkylation of various aromatic primary amines. These methods avoided complexity of multiple alkylations giving products in good yields. Both DES and lipase can be recycled and re-used at least five times. In addition, these catalysts are biodegradable, non-toxic and cost-effective. Graphical Abstract
Choline chloride based eutectic solvents: Magical catalytic system for carbon–carbon bond formation in the rapid synthesis of β-hydroxy functionalized derivatives
Catalysis Communications, 2012
ABSTRACT Significant β-hydroxy functionalized derivatives including nitroaldols, β-hydroxy nitril... more ABSTRACT Significant β-hydroxy functionalized derivatives including nitroaldols, β-hydroxy nitriles and β-hydroxy carboxylic acids were successfully prepared, for the first time, by catalytic use of deep eutectic solvents (DES). This paper explores the versatility and effectiveness of DES as catalyst in three different carbon–carbon bond formation reactions. The uniqueness of this catalyst lies in its simplicity since it avoids expensive catalysts and multi-step synthesis as reported in literature. The compounds, which are potent intermediates for innumerable useful products, were synthesized in excellent yields within very short reaction times. The catalyst prepared from choline chloride and urea, is biodegradable, non-toxic, cost-effective and recyclable.
Bio-compatible eutectic mixture for multi-component synthesis: A valuable acidic catalyst for synthesis of novel 2,3-dihydroquinazolin-4(1H)-one derivatives
Catalysis Communications, 2012
ABSTRACT Novel derivatives of quinazolin-4(1H)-one derivatives were effectively synthesized via o... more ABSTRACT Novel derivatives of quinazolin-4(1H)-one derivatives were effectively synthesized via one-pot multi-component reaction of isatoic anhydride, aldehyde and aromatic amines using acidic catalyst in methanol. The catalyst, being a deep eutectic mixture of choline chloride and malonic acid, gave better results than several reported catalysts. Moreover, such eutectic mixtures are cost-effective, recyclable, non-toxic and bio-degradable. The methodology was successfully used for incorporating significant phenyl and heterocyclic substitutions at 2,3-positions of quinazolinone core. In addition, studies related to catalyst screening, substrate variation, recyclability and plausible mechanism of reaction are also described.
Ultrasound-assisted intensification of bio-catalyzed synthesis of mono-N-alkyl aromatic amines
Biochemical Engineering Journal, 2013
ABSTRACT Bio-catalyzed process for mono-N-alkylation of primary aromatic amines was considerably ... more ABSTRACT Bio-catalyzed process for mono-N-alkylation of primary aromatic amines was considerably improved by the use of sonochemical energy. The optimized method exhibited good tolerance toward various aromatic primary amines as well alkylating agents. A comparative study was done by carrying out the bio-catalyzed reaction in the presence of ultrasound and non-ultrasound conditions both at room temperature and elevated temperature. The results showed that ultrasonication gave enhanced yields in shorter reaction times. The optimization studies also included variation in organic solvents, amount of catalyst and reaction temperature. These studies conclusively suggest that ultrasound technique improved the activity of catalyst thereby saving time and energy, improving the selectivity and yield of the product. In addition, the bio-degradable and non-toxic bio-catalyst was easily recycled till five consecutive runs.