Shubhankar Bhattacharyya | RISE Research Institutes of Sweden (RISE) (original) (raw)
Papers by Shubhankar Bhattacharyya
Processes, 2020
A shift towards an economically viable biomass biorefinery concept requires the use of all biomas... more A shift towards an economically viable biomass biorefinery concept requires the use of all biomass fractions (cellulose, hemicellulose, and lignin) for the production of high added-value products. As lignin is often underutilized, the establishment of lignin valorization routes is highly important. In-house produced organosolv as well as commercial Kraft lignin were used in this study. The aim of the current work was to make a comparative study of thermoplastic biomaterials from two different types of lignins. Native lignins were alkylate with two different alkyl iodides to produce ether-functionalized lignins. Successful etherification was verified by FT-IR spectroscopy, changes in the molecular weight of lignin, as well as 13 C and 1 H Nuclear Magnetic Resonance (NMR). The thermal stability of etherified lignin samples was considerably improved with the T 2% of organosolv to increase from 143 • C to up to 213 • C and of Kraft lignin from 133 • C to up to 168 • C, and glass transition temperature was observed. The present study shows that etherification of both organosolv and Kraft lignin with alkyl halides can produce lignin thermoplastic biomaterials with low glass transition temperature. The length of the alkyl chain affects thermal stability as well as other thermal properties.
Journal of Molecular Liquids, 2019
CO 2 absorption and ion mobility are investigated in a series of 50/50 wt% aqueous solutions of c... more CO 2 absorption and ion mobility are investigated in a series of 50/50 wt% aqueous solutions of choline-based ionic liquids with different cations and anions: [N 1,1,4,2OH ][Threo], [N 1,1,5,2OH ][Threo], [N 1,1,6,2OH ][Threo], [N 1,1,5,2OH ][β-ala] and [N 1,1,5,2OH ][Tau]. The process of CO 2 absorption was completed in an hour reaching maximum of absorption capacity 0.07-0.10 wt% to ionic liquid (by 0.4-0.6 molar ratios). A rapid CO 2 absorption is observed by the formation of solid product as a result of reaction between CO 2 molecule and the ionic liquid. Diffusion coefficients of the cation and anion in the mixture are comparable while the diffusivity of water molecules is found to be quite different from the ions. In the process of CO 2 absorption, an increase in the diffusivity of ions is observed due to the precipitation of solid products and depletion of ions contents in the liquid phase of the system. 13 C NMR measurements of diffusivity of CO 2 enriched with 13 C isotope showed that a part of the absorbed CO 2 remained in the liquid phase being physically and chemically bound to ions. The ionic liquid is recycled by evaporating water and releasing CO 2 molecules using vacuum and temperature.
Journal of Molecular liquids, 2018
Thermal stability of different choline based amino acid ionic liquids were studied. Both short te... more Thermal stability of different choline based amino acid ionic liquids were studied. Both short term as well as long term thermal studies were carried out. Long term thermal studies of all ILs were carried out by isothermal TGA and short term thermal studies were measured by temperature ramped TGA. Isothermal TGA were studied at two different temperatures 100 °C and 150 °C for 500 min. Whereas, short term thermal stability represents as T 2% , T 5% and T 10% which are the temperature at which 2%, 5% and 10% mass loss of ILs were observed. The effect of alkyl side chain on the cation, etherification of the cation as well structural variation of anion on the thermal stability of choline based ILs were investigated. It was observed that thermal characteristics of ILs towards temperature ramped TGA were different compared to isothermal TGA.
Computational inside of Banert cascade reaction for triazole formation is studied with B3LYP/6-31... more Computational inside of Banert cascade reaction for triazole formation is studied with B3LYP/6-31G(d,p) level of theory. The reaction proceeds mainly by SN2 initial chloride displacement rather than SN2-type attack. Furthermore, according to the rate of reaction calculation, SN2 displacement is much faster than SN2 displacement in the order of 8. The [3,3]-sigmatropic rearrangement for the conversion of propargyl azide into triazafulvene has been proved as the rate-determining step having highest activation energy parameter. Solvent effect on total course of reaction has been found negligible. Furthermore, effects of different density functional theory functionals and functional groups on activation energies of [3,3]-sigmatropic rearrangement of propargyl azide were also studied. BHHLYP, ωB97XD, M062X and BMK calculated G ‡ are consistent with B3LYP.
The effect of CO 2 absorption on the aromaticity and hydrogen bonding in ionic liquids is investi... more The effect of CO 2 absorption on the aromaticity and hydrogen bonding in ionic liquids is investigated. Five different ionic liquids with choline based cations and aprotic N-heterocyclic anions were synthesized. Purity and structures of the synthesized ionic liquids were characterized by 1 H and 13 C NMR spectroscopy. CO 2 capture performance was studied at 20 1C and 40 1C under three different pressures (1, 3, 6 bar). The IL [N 1,1,6,2OH ][4-Triz] showed the highest CO 2 capture capacity (28.6 wt%, 1.57 mol of CO 2 per mol of the IL, 6.48 mol of CO 2 per kg of the ionic liquid) at 20 1C and 1 bar. The high CO 2 capture capacity of the [N 1,1,6,2OH ][4-Triz] IL is due to the formation of carbonic acid (–OCO 2 H) together with carbamate by participation of the –OH group of the [N 1,1,6,2OH ] + cation in the CO 2 capture process. The structure of the adduct formed by CO 2 reaction with the IL [N 1,1,6,2OH ][4-Triz] was probed by using IR, 13 C NMR and 1 H– 13 C HMBC NMR experiments utilizing 13 C labeled CO 2 gas. 1 H and 13 C PFG NMR studies were performed before and after CO 2 absorption to explore the effect of cation–anion structures on the microscopic ion dynamics in ILs. The ionic mobility was significantly increased after CO 2 reaction due to lowering of aromaticity in the case of ILs with aromatic N-heterocyclic anions.
We used 1 H pulsed field gradient nuclear magnetic resonance to study the self-diffusion of polye... more We used 1 H pulsed field gradient nuclear magnetic resonance to study the self-diffusion of polyethylene glycol (PEG) with average molecular mass of 200 and ions in mixtures of PEG with imidazolium bis(mandelato)borate (BMB) and imidazolium bis(oxalato)bo-rate ionic liquids (ILs). The IL was mixed with PEG in the concentration range of 0–100 wt%. Within the temperature range of 295 to 353 K, the diffusion coefficient of BMB is slower than that of the imidazolium cation. The diffusion coefficients of PEG, as well as the imidazolium cation and BMB anions, differ under all experimental conditions tested. This demonstrates that the IL in the mixture is present in at least a partially dissociated state. Generally, increasing the concentration of PEG leads to an increase in the diffusion coefficients of PEG and both the ions and decreases their activation energy for diffusion. Nuclear magnetic resonance chemical shift alteration analysis showed that the presence of PEG changes the chemical shifts of both ions but in different directions. Impedance spectroscopy was used to measure the ionic conductivity of the ILs mixed with PEG.
We investigate a comparative effect of CO 2 absorption on the ionic mobility of two choline based... more We investigate a comparative effect of CO 2 absorption on the ionic mobility of two choline based ionic liquids comprising two different anions such as threonine and imidazole. The synthesized ionic liquids were characterized using 1 H and 13 C NMR and other spectroscopic techniques. By keeping a common cation and changing the anion from threonine to imidazole both the viscosity and density reduced drastically. We found that [N 1,1,6,2OH ][Imi] exhibits the highest CO 2 capture capacity at 20 1C of 5.27 mol of CO 2 per kg of ionic liquid (1.27 mol of CO 2 per mol of ionic liquid, 23.26 wt% of CO 2) whereas [N 1,1,6,2OH ][Threo] exhibits 3.6 mol of CO 2 per kg of ionic liquid (1.05 mol of CO 2 per mol of ionic liquid, 15.87 wt% of CO 2). The activation energy for diffusion is calculated using the Vogel-Fulcher-Tamman (VFT) equation in the form of diffusivity. It was found that the activation energy for the diffusion of [N 1,1,6,2OH ][Threo] is B10 times higher than that of [N 1,1,6,2OH ][Imi]. 1 H diffusion NMR data revealed that the diffusivity of [N 1,1,6,2OH ][Imi] is increased after CO 2 absorption whereas a decrease in diffusivity was observed in the case of [N 1,1,6,2OH ][Threo]. This anomalous behavior of [N 1,1,6,2OH ][Imi] was further explained by using DFT calculations.
Amino acid ionic liquids (ILs) are the most interesting and effective for CO2 capture due to thei... more Amino acid ionic liquids (ILs) are the most interesting and effective for CO2 capture due to their low toxicity, biodegradability, and fast reactivity toward CO2. The ionic nature of amino acid ILs can raise an environmental issue if the cation counterpart becomes toxic to the aquatic ecosystems, and they can become potential atmospheric pollutants. In this regard, choline based ILs are known to be promising scaffolds for the development of less toxic amino acid ILs. However, the existing choline amino acid ILs are highly viscous, limiting their applicability as solvents. Ether functionalized choline based amino acid ILs with a novel series of less toxic green ILs were explored with reduced viscosity and high CO2 capture capacity. A simple, economic, clean, and environmentally benign method was utilized for the synthesis of novel choline based amino acid ILs using a commercially available and economical starting material, 2-(dimethylamino)ethanol (deanol, a human dietary food supplement). These ILs have low viscosity with high CO2 capture capacity (1.62 mol of CO2 /mol of IL, 4.31 mol of CO2/kg of IL, 19.02 wt % of CO2). The mechanism of [N1,1,6,2O4][Lys] + CO2 reaction and adduct structure was proposed by using DFT calculations, and IR and NMR spectroscopic techniques.
N-(ω-Bromoalkyl)dichlorothiophosphoramidates have been designed as a new class of reagent for the... more N-(ω-Bromoalkyl)dichlorothiophosphoramidates have been
designed as a new class of reagent for the single-reagent-driven multistep preparation of 2-substituted thiazolines and 1,3-thiazines from
aldoximes, nitriles, or carboxylic acids. A wide range of substrates both aromatic as well as aliphatic were investigated and found suitable for the developed protocol.
Green …, Jan 1, 2011
This is the first report of a facile synthesis of thiazolines and thiazines from a self-catalyze... more This is the first report of a facile synthesis of thiazolines
and thiazines from a self-catalyzed, water assisted
tandem S-alkylation-cyclodeamination reaction of
thioamides/haloamines. The reaction is clean and efficient
with simple product work-up, and is applicable to a variety
of substrates.
An efficient method for amidation and esterification of aldehydes utilizing hydrogen peroxide as... more An efficient method for amidation and esterification of
aldehydes utilizing hydrogen peroxide as an oxidant has
been revealed. Cyclic amines and primary alcohols
selectively reacted under mild conditions with aromatic
aldehydes to yield corresponding amides and esters.
A mechanistically unprecedented approach for the formation of tertiary amides from N,N-dialkylchl... more A mechanistically unprecedented approach for the formation of tertiary amides from N,N-dialkylchlorothiophosphoramidates and aldehydes has been developed. The reaction occurred via the activation of aldehydes with N,N-dialkylchlorothiophosphoramidates followed by amidation with dialkylamine pendent of the same phosphoramidate.
The present DFT investigation supports a previous conclusion of Dean et al. that hydroxylation oc... more The present DFT investigation supports a previous conclusion of Dean et al. that hydroxylation occurs without epoxide intermediate at room temperature due to a strong electrostatic interaction of peroxide ions with π electrons of C[double bond, length as m-dash]C bonds of chalcone, and 3-hydroxyflavone has been found to be the major product. The calculated activation energy difference (ΔG#) of initial enolization followed by hydroxylation or simultaneous cyclization and hydroxylation has been found to be negligible ([similar]4 kcal mol−1). On the other hand, epoxide formation requires significant activation energy, which is supposed to occur at high temperatures. In addition, if epoxide is formed, the ring opens by an attack of phenolic oxygen, occurring preferentially at α position via a five-member transition state due to a low activation barrier height (19.82 kcal mol−1 in the gas phase and 19.55 kcal mol−1 in ethanol) compared to that of a six-member transition state (44.41 kcal mol−1 at B3LYP in the gas phase and 38.55 kcal mol−1 in ethanol). It is also observed that the solvation study does not affect the main conclusion of the paper. These findings also support the previous observation of Dean et al. Predicted ΔG# in different DFT functionals are consistent, although the total energy is significantly different.
RSC Advances, Apr 8, 2014
Monoalkylation of primary amines using amine hydrobromides and alkyl bromides has been carried ou... more Monoalkylation of primary amines using amine hydrobromides and alkyl bromides has been carried out. Under controlled reaction conditions the reactant primary amine was selectively deprotonated and made available for reaction, while the newly generated secondary amine remained protonated, and did not participate in alkylation further. Reaction was carried out under mild reaction conditions and was applicable to a wide range of primary amines and alkyl bromides.
Primary thioamides have been utilised directly in water, without any derivatisation, to selective... more Primary thioamides have been utilised directly in water, without any derivatisation, to selectively thioacylate primary amines. By employing 2-hydroxyethylamines, the reaction can be extended to the preparation of 2-thiazolines via formation of β-hydroxythioamides.
Processes, 2020
A shift towards an economically viable biomass biorefinery concept requires the use of all biomas... more A shift towards an economically viable biomass biorefinery concept requires the use of all biomass fractions (cellulose, hemicellulose, and lignin) for the production of high added-value products. As lignin is often underutilized, the establishment of lignin valorization routes is highly important. In-house produced organosolv as well as commercial Kraft lignin were used in this study. The aim of the current work was to make a comparative study of thermoplastic biomaterials from two different types of lignins. Native lignins were alkylate with two different alkyl iodides to produce ether-functionalized lignins. Successful etherification was verified by FT-IR spectroscopy, changes in the molecular weight of lignin, as well as 13 C and 1 H Nuclear Magnetic Resonance (NMR). The thermal stability of etherified lignin samples was considerably improved with the T 2% of organosolv to increase from 143 • C to up to 213 • C and of Kraft lignin from 133 • C to up to 168 • C, and glass transition temperature was observed. The present study shows that etherification of both organosolv and Kraft lignin with alkyl halides can produce lignin thermoplastic biomaterials with low glass transition temperature. The length of the alkyl chain affects thermal stability as well as other thermal properties.
Journal of Molecular Liquids, 2019
CO 2 absorption and ion mobility are investigated in a series of 50/50 wt% aqueous solutions of c... more CO 2 absorption and ion mobility are investigated in a series of 50/50 wt% aqueous solutions of choline-based ionic liquids with different cations and anions: [N 1,1,4,2OH ][Threo], [N 1,1,5,2OH ][Threo], [N 1,1,6,2OH ][Threo], [N 1,1,5,2OH ][β-ala] and [N 1,1,5,2OH ][Tau]. The process of CO 2 absorption was completed in an hour reaching maximum of absorption capacity 0.07-0.10 wt% to ionic liquid (by 0.4-0.6 molar ratios). A rapid CO 2 absorption is observed by the formation of solid product as a result of reaction between CO 2 molecule and the ionic liquid. Diffusion coefficients of the cation and anion in the mixture are comparable while the diffusivity of water molecules is found to be quite different from the ions. In the process of CO 2 absorption, an increase in the diffusivity of ions is observed due to the precipitation of solid products and depletion of ions contents in the liquid phase of the system. 13 C NMR measurements of diffusivity of CO 2 enriched with 13 C isotope showed that a part of the absorbed CO 2 remained in the liquid phase being physically and chemically bound to ions. The ionic liquid is recycled by evaporating water and releasing CO 2 molecules using vacuum and temperature.
Journal of Molecular liquids, 2018
Thermal stability of different choline based amino acid ionic liquids were studied. Both short te... more Thermal stability of different choline based amino acid ionic liquids were studied. Both short term as well as long term thermal studies were carried out. Long term thermal studies of all ILs were carried out by isothermal TGA and short term thermal studies were measured by temperature ramped TGA. Isothermal TGA were studied at two different temperatures 100 °C and 150 °C for 500 min. Whereas, short term thermal stability represents as T 2% , T 5% and T 10% which are the temperature at which 2%, 5% and 10% mass loss of ILs were observed. The effect of alkyl side chain on the cation, etherification of the cation as well structural variation of anion on the thermal stability of choline based ILs were investigated. It was observed that thermal characteristics of ILs towards temperature ramped TGA were different compared to isothermal TGA.
Computational inside of Banert cascade reaction for triazole formation is studied with B3LYP/6-31... more Computational inside of Banert cascade reaction for triazole formation is studied with B3LYP/6-31G(d,p) level of theory. The reaction proceeds mainly by SN2 initial chloride displacement rather than SN2-type attack. Furthermore, according to the rate of reaction calculation, SN2 displacement is much faster than SN2 displacement in the order of 8. The [3,3]-sigmatropic rearrangement for the conversion of propargyl azide into triazafulvene has been proved as the rate-determining step having highest activation energy parameter. Solvent effect on total course of reaction has been found negligible. Furthermore, effects of different density functional theory functionals and functional groups on activation energies of [3,3]-sigmatropic rearrangement of propargyl azide were also studied. BHHLYP, ωB97XD, M062X and BMK calculated G ‡ are consistent with B3LYP.
The effect of CO 2 absorption on the aromaticity and hydrogen bonding in ionic liquids is investi... more The effect of CO 2 absorption on the aromaticity and hydrogen bonding in ionic liquids is investigated. Five different ionic liquids with choline based cations and aprotic N-heterocyclic anions were synthesized. Purity and structures of the synthesized ionic liquids were characterized by 1 H and 13 C NMR spectroscopy. CO 2 capture performance was studied at 20 1C and 40 1C under three different pressures (1, 3, 6 bar). The IL [N 1,1,6,2OH ][4-Triz] showed the highest CO 2 capture capacity (28.6 wt%, 1.57 mol of CO 2 per mol of the IL, 6.48 mol of CO 2 per kg of the ionic liquid) at 20 1C and 1 bar. The high CO 2 capture capacity of the [N 1,1,6,2OH ][4-Triz] IL is due to the formation of carbonic acid (–OCO 2 H) together with carbamate by participation of the –OH group of the [N 1,1,6,2OH ] + cation in the CO 2 capture process. The structure of the adduct formed by CO 2 reaction with the IL [N 1,1,6,2OH ][4-Triz] was probed by using IR, 13 C NMR and 1 H– 13 C HMBC NMR experiments utilizing 13 C labeled CO 2 gas. 1 H and 13 C PFG NMR studies were performed before and after CO 2 absorption to explore the effect of cation–anion structures on the microscopic ion dynamics in ILs. The ionic mobility was significantly increased after CO 2 reaction due to lowering of aromaticity in the case of ILs with aromatic N-heterocyclic anions.
We used 1 H pulsed field gradient nuclear magnetic resonance to study the self-diffusion of polye... more We used 1 H pulsed field gradient nuclear magnetic resonance to study the self-diffusion of polyethylene glycol (PEG) with average molecular mass of 200 and ions in mixtures of PEG with imidazolium bis(mandelato)borate (BMB) and imidazolium bis(oxalato)bo-rate ionic liquids (ILs). The IL was mixed with PEG in the concentration range of 0–100 wt%. Within the temperature range of 295 to 353 K, the diffusion coefficient of BMB is slower than that of the imidazolium cation. The diffusion coefficients of PEG, as well as the imidazolium cation and BMB anions, differ under all experimental conditions tested. This demonstrates that the IL in the mixture is present in at least a partially dissociated state. Generally, increasing the concentration of PEG leads to an increase in the diffusion coefficients of PEG and both the ions and decreases their activation energy for diffusion. Nuclear magnetic resonance chemical shift alteration analysis showed that the presence of PEG changes the chemical shifts of both ions but in different directions. Impedance spectroscopy was used to measure the ionic conductivity of the ILs mixed with PEG.
We investigate a comparative effect of CO 2 absorption on the ionic mobility of two choline based... more We investigate a comparative effect of CO 2 absorption on the ionic mobility of two choline based ionic liquids comprising two different anions such as threonine and imidazole. The synthesized ionic liquids were characterized using 1 H and 13 C NMR and other spectroscopic techniques. By keeping a common cation and changing the anion from threonine to imidazole both the viscosity and density reduced drastically. We found that [N 1,1,6,2OH ][Imi] exhibits the highest CO 2 capture capacity at 20 1C of 5.27 mol of CO 2 per kg of ionic liquid (1.27 mol of CO 2 per mol of ionic liquid, 23.26 wt% of CO 2) whereas [N 1,1,6,2OH ][Threo] exhibits 3.6 mol of CO 2 per kg of ionic liquid (1.05 mol of CO 2 per mol of ionic liquid, 15.87 wt% of CO 2). The activation energy for diffusion is calculated using the Vogel-Fulcher-Tamman (VFT) equation in the form of diffusivity. It was found that the activation energy for the diffusion of [N 1,1,6,2OH ][Threo] is B10 times higher than that of [N 1,1,6,2OH ][Imi]. 1 H diffusion NMR data revealed that the diffusivity of [N 1,1,6,2OH ][Imi] is increased after CO 2 absorption whereas a decrease in diffusivity was observed in the case of [N 1,1,6,2OH ][Threo]. This anomalous behavior of [N 1,1,6,2OH ][Imi] was further explained by using DFT calculations.
Amino acid ionic liquids (ILs) are the most interesting and effective for CO2 capture due to thei... more Amino acid ionic liquids (ILs) are the most interesting and effective for CO2 capture due to their low toxicity, biodegradability, and fast reactivity toward CO2. The ionic nature of amino acid ILs can raise an environmental issue if the cation counterpart becomes toxic to the aquatic ecosystems, and they can become potential atmospheric pollutants. In this regard, choline based ILs are known to be promising scaffolds for the development of less toxic amino acid ILs. However, the existing choline amino acid ILs are highly viscous, limiting their applicability as solvents. Ether functionalized choline based amino acid ILs with a novel series of less toxic green ILs were explored with reduced viscosity and high CO2 capture capacity. A simple, economic, clean, and environmentally benign method was utilized for the synthesis of novel choline based amino acid ILs using a commercially available and economical starting material, 2-(dimethylamino)ethanol (deanol, a human dietary food supplement). These ILs have low viscosity with high CO2 capture capacity (1.62 mol of CO2 /mol of IL, 4.31 mol of CO2/kg of IL, 19.02 wt % of CO2). The mechanism of [N1,1,6,2O4][Lys] + CO2 reaction and adduct structure was proposed by using DFT calculations, and IR and NMR spectroscopic techniques.
N-(ω-Bromoalkyl)dichlorothiophosphoramidates have been designed as a new class of reagent for the... more N-(ω-Bromoalkyl)dichlorothiophosphoramidates have been
designed as a new class of reagent for the single-reagent-driven multistep preparation of 2-substituted thiazolines and 1,3-thiazines from
aldoximes, nitriles, or carboxylic acids. A wide range of substrates both aromatic as well as aliphatic were investigated and found suitable for the developed protocol.
Green …, Jan 1, 2011
This is the first report of a facile synthesis of thiazolines and thiazines from a self-catalyze... more This is the first report of a facile synthesis of thiazolines
and thiazines from a self-catalyzed, water assisted
tandem S-alkylation-cyclodeamination reaction of
thioamides/haloamines. The reaction is clean and efficient
with simple product work-up, and is applicable to a variety
of substrates.
An efficient method for amidation and esterification of aldehydes utilizing hydrogen peroxide as... more An efficient method for amidation and esterification of
aldehydes utilizing hydrogen peroxide as an oxidant has
been revealed. Cyclic amines and primary alcohols
selectively reacted under mild conditions with aromatic
aldehydes to yield corresponding amides and esters.
A mechanistically unprecedented approach for the formation of tertiary amides from N,N-dialkylchl... more A mechanistically unprecedented approach for the formation of tertiary amides from N,N-dialkylchlorothiophosphoramidates and aldehydes has been developed. The reaction occurred via the activation of aldehydes with N,N-dialkylchlorothiophosphoramidates followed by amidation with dialkylamine pendent of the same phosphoramidate.
The present DFT investigation supports a previous conclusion of Dean et al. that hydroxylation oc... more The present DFT investigation supports a previous conclusion of Dean et al. that hydroxylation occurs without epoxide intermediate at room temperature due to a strong electrostatic interaction of peroxide ions with π electrons of C[double bond, length as m-dash]C bonds of chalcone, and 3-hydroxyflavone has been found to be the major product. The calculated activation energy difference (ΔG#) of initial enolization followed by hydroxylation or simultaneous cyclization and hydroxylation has been found to be negligible ([similar]4 kcal mol−1). On the other hand, epoxide formation requires significant activation energy, which is supposed to occur at high temperatures. In addition, if epoxide is formed, the ring opens by an attack of phenolic oxygen, occurring preferentially at α position via a five-member transition state due to a low activation barrier height (19.82 kcal mol−1 in the gas phase and 19.55 kcal mol−1 in ethanol) compared to that of a six-member transition state (44.41 kcal mol−1 at B3LYP in the gas phase and 38.55 kcal mol−1 in ethanol). It is also observed that the solvation study does not affect the main conclusion of the paper. These findings also support the previous observation of Dean et al. Predicted ΔG# in different DFT functionals are consistent, although the total energy is significantly different.
RSC Advances, Apr 8, 2014
Monoalkylation of primary amines using amine hydrobromides and alkyl bromides has been carried ou... more Monoalkylation of primary amines using amine hydrobromides and alkyl bromides has been carried out. Under controlled reaction conditions the reactant primary amine was selectively deprotonated and made available for reaction, while the newly generated secondary amine remained protonated, and did not participate in alkylation further. Reaction was carried out under mild reaction conditions and was applicable to a wide range of primary amines and alkyl bromides.
Primary thioamides have been utilised directly in water, without any derivatisation, to selective... more Primary thioamides have been utilised directly in water, without any derivatisation, to selectively thioacylate primary amines. By employing 2-hydroxyethylamines, the reaction can be extended to the preparation of 2-thiazolines via formation of β-hydroxythioamides.