The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Rudraksha N Bhattacharya - One of the best experts on this subject based on the ideXlab platform.
-
an unexpected rearrangement Hydration Reaction sequence of 2h chromenes to dihydrochalcones under catalysis of haucl4
ChemInform, 2013Co-Authors: Gourhari Maiti, Utpal Kayal, Rajiv Karmakar, Rudraksha N BhattacharyaAbstract:A simple protocol is developed for the conversion of various substrates into highly functionalized propanone frameworks.
-
an unexpected rearrangement Hydration Reaction sequence of 2h chromenes to dihydrochalcones under catalysis of haucl4
Tetrahedron Letters, 2012Co-Authors: Gourhari Maiti, Utpal Kayal, Rajiv Karmakar, Rudraksha N BhattacharyaAbstract:Abstract 2-Aryl-2H-chromenes in aqueous DCM medium under catalysis of HAuCl4 are converted into 3-(2-hydroxyaryl)-1-arylpropan-1-ones through Hydration-rearrangement Reaction sequence in very good yield. The key step probably involves the [1,5] hydride shift followed by the hydrolysis under the Reaction condition. The notable advantages of this method are operational simplicity and ease of isolation of products and also provide a pathway to convert the chalcone into DHCs with the transposition of carbonyl group.
Francesca Ridi - One of the best experts on this subject based on the ideXlab platform.
-
Effect of phosphate additives on the Hydration process of magnesium silicate cements
Journal of Thermal Analysis and Calorimetry, 2019Co-Authors: Monica Tonelli, Lucia Calucci, Marco Geppi, Silvia Borsacchi, Alessio Milanesi, Francesca De Martini, Francesca RidiAbstract:The role of phosphate additives on the Hydration process of magnesium silicate cement pastes was investigated through a multi-technique approach. A MgO/SiO_2 mixture was hydrated for 28 days either in the absence or in the presence of sodium hexametaphosphate, trimetaphosphate or orthophosphate. Information on the kinetics of the Hydration Reaction was acquired by monitoring the free water index by means of differential scanning calorimetry, while the Hydration products were thoroughly investigated by X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, scanning electron microscopy and ^29Si solid-state nuclear magnetic resonance spectroscopy. The overall results provide new insight into the effect of phosphates on the Hydration Reaction and on the structure of magnesium silicate hydrate cements. All additives showed a plasticizing effect and promoted the formation of the binding phase magnesium silicate hydrate (M–S–H), without significantly altering its structure. Sodium orthophosphate was found to be by far the best-performing additive, even better than sodium hexametaphosphate, which is commonly used in these cementitious formulations. For the first time, ^31P solid-state NMR investigation allowed orthophosphate ion to be identified as the effective species.
-
Influence of acrylic superplasticizer and cellulose-ether on the kinetics of tricalcium silicate Hydration Reaction.
Journal of Colloid and Interface Science, 2013Co-Authors: Francesca Ridi, Roberta Alfani, Emiliano Fratini, Piero BaglioniAbstract:Abstract This paper reports on the analysis of the Hydration kinetics of a tricalcium silicate paste cured in presence of polymers industrially used in the extrusion process of mortars. In particular, we investigated the effect of a rheology-modifying additive (a methyl hydroxy ethyl cellulose) and a superplasticizer (a polyacrylic polymer). These polymers have been added to tricalcium silicate paste, both separately and together, to understand their distinct influence on the tricalcium silicate Hydration and their possible synergies. The kinetic curves have been monitored from 10 to 40 °C by means of Differential Scanning Calorimetry and fitted using the generalized Boundary Nucleation and Growth Model combined to a diffusion-limited model, to extract: induction times, Reaction rates, activation energies and diffusion coefficients. As a main result, this paper contributes to the advancement of the knowledge in the field of the extrusion process of cementitious materials, providing a thermodynamic support to the empirical evaluations of the additives performances.
-
tricalcium silicate Hydration Reaction in the presence of comb shaped superplasticizers boundary nucleation and growth model applied to polymer modified pastes
Journal of Physical Chemistry C, 2012Co-Authors: Francesca Ridi, Emiliano Fratini, Paola Luciani, Frank Winnefeld, Piero BaglioniAbstract:The Boundary Nucleation and Growth Model (BNGM), developed for the analysis of the Hydration Reaction of tricalcium silicate, has been applied to study the kinetic behavior of pastes containing chemical admixtures. Four comb-shaped polycarboxylate ether (PCE) superplasticizers with well-known molecular structures have been added to tricalcium silicate. The BNGM analysis performed on this series of additives allows insights into the effect of the molecular architecture of the PCEs on the induction time and rate constants. The results show that decreasing the length of the polyethylene oxide side chains of the PCE molecules increases the induction time. Also, the side chain density, which highly influences the adsorption of the polymer to the C3S unreacted grains, is shown to significantly affect the duration of the induction period: in particular, molecules with low side chain density delay the setting of the paste to a greater extent than molecules with denser side chains. Moreover, the chemical admixture...
Piero Baglioni - One of the best experts on this subject based on the ideXlab platform.
-
Influence of acrylic superplasticizer and cellulose-ether on the kinetics of tricalcium silicate Hydration Reaction.
Journal of Colloid and Interface Science, 2013Co-Authors: Francesca Ridi, Roberta Alfani, Emiliano Fratini, Piero BaglioniAbstract:Abstract This paper reports on the analysis of the Hydration kinetics of a tricalcium silicate paste cured in presence of polymers industrially used in the extrusion process of mortars. In particular, we investigated the effect of a rheology-modifying additive (a methyl hydroxy ethyl cellulose) and a superplasticizer (a polyacrylic polymer). These polymers have been added to tricalcium silicate paste, both separately and together, to understand their distinct influence on the tricalcium silicate Hydration and their possible synergies. The kinetic curves have been monitored from 10 to 40 °C by means of Differential Scanning Calorimetry and fitted using the generalized Boundary Nucleation and Growth Model combined to a diffusion-limited model, to extract: induction times, Reaction rates, activation energies and diffusion coefficients. As a main result, this paper contributes to the advancement of the knowledge in the field of the extrusion process of cementitious materials, providing a thermodynamic support to the empirical evaluations of the additives performances.
-
tricalcium silicate Hydration Reaction in the presence of comb shaped superplasticizers boundary nucleation and growth model applied to polymer modified pastes
Journal of Physical Chemistry C, 2012Co-Authors: Francesca Ridi, Emiliano Fratini, Paola Luciani, Frank Winnefeld, Piero BaglioniAbstract:The Boundary Nucleation and Growth Model (BNGM), developed for the analysis of the Hydration Reaction of tricalcium silicate, has been applied to study the kinetic behavior of pastes containing chemical admixtures. Four comb-shaped polycarboxylate ether (PCE) superplasticizers with well-known molecular structures have been added to tricalcium silicate. The BNGM analysis performed on this series of additives allows insights into the effect of the molecular architecture of the PCEs on the induction time and rate constants. The results show that decreasing the length of the polyethylene oxide side chains of the PCE molecules increases the induction time. Also, the side chain density, which highly influences the adsorption of the polymer to the C3S unreacted grains, is shown to significantly affect the duration of the induction period: in particular, molecules with low side chain density delay the setting of the paste to a greater extent than molecules with denser side chains. Moreover, the chemical admixture...
Gourhari Maiti - One of the best experts on this subject based on the ideXlab platform.
-
an unexpected rearrangement Hydration Reaction sequence of 2h chromenes to dihydrochalcones under catalysis of haucl4
ChemInform, 2013Co-Authors: Gourhari Maiti, Utpal Kayal, Rajiv Karmakar, Rudraksha N BhattacharyaAbstract:A simple protocol is developed for the conversion of various substrates into highly functionalized propanone frameworks.
-
an unexpected rearrangement Hydration Reaction sequence of 2h chromenes to dihydrochalcones under catalysis of haucl4
Tetrahedron Letters, 2012Co-Authors: Gourhari Maiti, Utpal Kayal, Rajiv Karmakar, Rudraksha N BhattacharyaAbstract:Abstract 2-Aryl-2H-chromenes in aqueous DCM medium under catalysis of HAuCl4 are converted into 3-(2-hydroxyaryl)-1-arylpropan-1-ones through Hydration-rearrangement Reaction sequence in very good yield. The key step probably involves the [1,5] hydride shift followed by the hydrolysis under the Reaction condition. The notable advantages of this method are operational simplicity and ease of isolation of products and also provide a pathway to convert the chalcone into DHCs with the transposition of carbonyl group.
Utpal Kayal - One of the best experts on this subject based on the ideXlab platform.
-
an unexpected rearrangement Hydration Reaction sequence of 2h chromenes to dihydrochalcones under catalysis of haucl4
ChemInform, 2013Co-Authors: Gourhari Maiti, Utpal Kayal, Rajiv Karmakar, Rudraksha N BhattacharyaAbstract:A simple protocol is developed for the conversion of various substrates into highly functionalized propanone frameworks.
-
an unexpected rearrangement Hydration Reaction sequence of 2h chromenes to dihydrochalcones under catalysis of haucl4
Tetrahedron Letters, 2012Co-Authors: Gourhari Maiti, Utpal Kayal, Rajiv Karmakar, Rudraksha N BhattacharyaAbstract:Abstract 2-Aryl-2H-chromenes in aqueous DCM medium under catalysis of HAuCl4 are converted into 3-(2-hydroxyaryl)-1-arylpropan-1-ones through Hydration-rearrangement Reaction sequence in very good yield. The key step probably involves the [1,5] hydride shift followed by the hydrolysis under the Reaction condition. The notable advantages of this method are operational simplicity and ease of isolation of products and also provide a pathway to convert the chalcone into DHCs with the transposition of carbonyl group.
