Mangalya Kar - Academia.edu (original) (raw)
Papers by Mangalya Kar
Data reduction, structure solution and refinement were carded out using SHELXTL-Plus (Sheldrick, ... more Data reduction, structure solution and refinement were carded out using SHELXTL-Plus (Sheldrick, 1991). Lists of structure factors, anisotropic displacement parameters and H-atom coordinates have been deposited with the IUCr (Reference: ABl148). Copies may be obtained through The Managing Editor,
The Journal of Physical Chemistry, 1994
The Diels-Alder dimerization of isoprene is an important reaction; dipentene (or racemic limonene... more The Diels-Alder dimerization of isoprene is an important reaction; dipentene (or racemic limonene), one of the products formed in this reaction, has major applications in the manufacture of polymers and adhesives.' Dipentene also has various uses in the food and pharmaceutical industries.' In the present work, the QCFF force field program2 was used to calculate gas-phase thermodynamic properties of the monomer (isoprene) and the dimers 1-methyl-5-(1-methylethenyl)cyclohexene (diprene) and 1-methyl-4-(1-methylethenyl)cyclohexene (dipentene) for the temperature range 298.15-1000 K. These QCFF-calculated thermodynamic values were compared, when possible, with corresponding values obtained experimentally or from other force field programs, and the agreement was found to be satisfactory. The QCFF values were further used to derive gas-phase equilibrium properties-AHO, ASo, AGO, and &-for the isoprene dimerization reaction at various temperatures. These computational results suggest that, based upon thermodynamics, diprene and dipentene are about equally favored dimerization products of isoprene and that reported experimental data reflect kinetic control of dipentene formation at lower temperatures. The equilibrium thermodynamics data for the isoprene dimerization reaction presented in this paper are felt to be sufficiently reliable that they can be utilized in the absence of any additional experimental data; the present work thus illustrates the power of predictive thermodynamic computational techniques in extending the thermochemical database.
Acta Crystallographica Section C Crystal Structure Communications, 1996
The title compound, C10H6O3, has been studied by both X-ray diffraction and molecular-mechanics c... more The title compound, C10H6O3, has been studied by both X-ray diffraction and molecular-mechanics calculations to determine the ring-ring dihedral angle. Calculated and observed values of 5.4 and 5.53 (6) Degrees for this dihedral angle in the crystal were found to be in ...
The Journal of Chemical Thermodynamics, 1992
ABSTRACT In the present experimental work, the energy of combustion of the crystalline Diels-Alde... more ABSTRACT In the present experimental work, the energy of combustion of the crystalline Diels-Alder adduct of anthracene and maleic anhydride: C18H12O3, was measured with a model 1241 Parr automatic calorimeter and a Parr model 1710 calorimeter controller. The standard molar enthalpy of combustion of the (anthracene + maleic anhydride) adduct at po = 0.1 MPa was determined to be ΔcHmo(C18H12O3, cr, 298.15 K) = −(8380.0±5.9) kJ·mol−1. The molar enthalpy of fusion of this adduct at its melting temperature (534.07 K), as measured by a 910 DuPont d.s.c. and a 9900 DuPont thermal (analyzer + digital computer), was found to be (36.3±4.2) kJ·mol−1. The other thermodynamic properties of the (anthracene + maleic anhydride) adduct derived from those measured properties are: ΔfHmo(C18H12O3, cr, 298.15 K) = −(418.2±6.4) kJ·mol−1 and ΔfHmo(C18H12O3, 1, 298.15 K) = −(389.7 ± 7.7) kJ·mol−1.
Journal of Computational Chemistry, 1994
The QCFF program originated by Warshel and Karplus4" was modified to compute accurate thermodynam... more The QCFF program originated by Warshel and Karplus4" was modified to compute accurate thermodynamic properties So, C;, (H;-Hi)/T, and AH; for various acyclic and cyclic alkenes and alkadienes. Modifications consisted of adjusted bond angle, dihedral angle, bond stretch, and bond energy parameters that improved calculated vibrational frequencies, zero point energies, and thermodynamic functions. Supplemental torsional potential energy functions that were added to existing torsional functions led to greatly improved relative conformer energies and AH! values. It was shown that inclusion of hindered internal rotation leads to significantly better agreement of calculated thermodynamic functions with observed values for acyclic alkenes at high temperatures. The calculated thermodynamic properties of the alkenes and alkadienes were deemed sufficiently accurate for calculation of standard enthalpies and Gibbs free energies of gas phase chemical reactions at various temperatures.
The Journal of Physical Chemistry, 1994
The Diels-Alder dimerization of isoprene is an important reaction; dipentene (or racemic limonene... more The Diels-Alder dimerization of isoprene is an important reaction; dipentene (or racemic limonene), one of the products formed in this reaction, has major applications in the manufacture of polymers and adhesives.' Dipentene also has various uses in the food and pharmaceutical industries.' In the present work, the QCFF force field program2 was used to calculate gas-phase thermodynamic properties of the monomer (isoprene) and the dimers 1-methyl-5-(1-methylethenyl)cyclohexene (diprene) and 1-methyl-4-(1-methylethenyl)cyclohexene (dipentene) for the temperature range 298.15-1000 K. These QCFF-calculated thermodynamic values were compared, when possible, with corresponding values obtained experimentally or from other force field programs, and the agreement was found to be satisfactory. The QCFF values were further used to derive gas-phase equilibrium properties-AHO, ASo, AGO, and &-for the isoprene dimerization reaction at various temperatures. These computational results suggest that, based upon thermodynamics, diprene and dipentene are about equally favored dimerization products of isoprene and that reported experimental data reflect kinetic control of dipentene formation at lower temperatures. The equilibrium thermodynamics data for the isoprene dimerization reaction presented in this paper are felt to be sufficiently reliable that they can be utilized in the absence of any additional experimental data; the present work thus illustrates the power of predictive thermodynamic computational techniques in extending the thermochemical database.
Acta Crystallographica Section C Crystal Structure Communications, 1996
The title compound, C10H6O3, has been studied by both X-ray diffraction and molecular-mechanics c... more The title compound, C10H6O3, has been studied by both X-ray diffraction and molecular-mechanics calculations to determine the ring-ring dihedral angle. Calculated and observed values of 5.4 and 5.53 (6) Degrees for this dihedral angle in the crystal were found to be in ...
The Journal of Chemical Thermodynamics, 1992
ABSTRACT In the present experimental work, the energy of combustion of the crystalline Diels-Alde... more ABSTRACT In the present experimental work, the energy of combustion of the crystalline Diels-Alder adduct of anthracene and maleic anhydride: C18H12O3, was measured with a model 1241 Parr automatic calorimeter and a Parr model 1710 calorimeter controller. The standard molar enthalpy of combustion of the (anthracene + maleic anhydride) adduct at po = 0.1 MPa was determined to be ΔcHmo(C18H12O3, cr, 298.15 K) = −(8380.0±5.9) kJ·mol−1. The molar enthalpy of fusion of this adduct at its melting temperature (534.07 K), as measured by a 910 DuPont d.s.c. and a 9900 DuPont thermal (analyzer + digital computer), was found to be (36.3±4.2) kJ·mol−1. The other thermodynamic properties of the (anthracene + maleic anhydride) adduct derived from those measured properties are: ΔfHmo(C18H12O3, cr, 298.15 K) = −(418.2±6.4) kJ·mol−1 and ΔfHmo(C18H12O3, 1, 298.15 K) = −(389.7 ± 7.7) kJ·mol−1.
Journal of Computational Chemistry, 1994
The QCFF program originated by Warshel and Karplus4" was modified to compute accurate thermodynam... more The QCFF program originated by Warshel and Karplus4" was modified to compute accurate thermodynamic properties So, C;, (H;-Hi)/T, and AH; for various acyclic and cyclic alkenes and alkadienes. Modifications consisted of adjusted bond angle, dihedral angle, bond stretch, and bond energy parameters that improved calculated vibrational frequencies, zero point energies, and thermodynamic functions. Supplemental torsional potential energy functions that were added to existing torsional functions led to greatly improved relative conformer energies and AH! values. It was shown that inclusion of hindered internal rotation leads to significantly better agreement of calculated thermodynamic functions with observed values for acyclic alkenes at high temperatures. The calculated thermodynamic properties of the alkenes and alkadienes were deemed sufficiently accurate for calculation of standard enthalpies and Gibbs free energies of gas phase chemical reactions at various temperatures.
Organic Process Research & Development, 1997
The large-scale preparation of the-alkynyl-amino acid ester (()-1,1-dimethylethyl 3-amino-5-(trim... more The large-scale preparation of the-alkynyl-amino acid ester (()-1,1-dimethylethyl 3-amino-5-(trimethylsilyl)-4-pentynoate (A) is discussed. It was discovered that addition of a catalytic amount of lithium bis(trimethylsilyl)amide (LHMDS) to a mixture of tert-butyl acetate and N,3-bis(trimethylsilyl)-2propyn-1-imine (B) initiated a self-perpetuating reaction and gave high yields of the-amino ester A upon quench. This one-pot procedure eliminated the need to prepare the unstable lithium tert-butyl acetate in a separate reactor and enabled the reaction to be scaled up and run at a more acceptable process temperature (-20°C) compared to the analogous two-pot reaction (-45°C). Addition of 3-(trimethylsilyl)-2-propynal to LHMDS in THF at-20°C followed by chlorotrimethylsilane formed the imine B in situ. tert-Butyl acetate (6 equiv) was added followed by a substoichiometric quantity (0.15-0.20 equiv) of LHMDS. After quenching with aqueous ammonium chloride the product A was obtained in a yield averaging 70%. Scheme 1
Data reduction, structure solution and refinement were carded out using SHELXTL-Plus (Sheldrick, ... more Data reduction, structure solution and refinement were carded out using SHELXTL-Plus (Sheldrick, 1991). Lists of structure factors, anisotropic displacement parameters and H-atom coordinates have been deposited with the IUCr (Reference: ABl148). Copies may be obtained through The Managing Editor,
The Journal of Physical Chemistry, 1994
The Diels-Alder dimerization of isoprene is an important reaction; dipentene (or racemic limonene... more The Diels-Alder dimerization of isoprene is an important reaction; dipentene (or racemic limonene), one of the products formed in this reaction, has major applications in the manufacture of polymers and adhesives.' Dipentene also has various uses in the food and pharmaceutical industries.' In the present work, the QCFF force field program2 was used to calculate gas-phase thermodynamic properties of the monomer (isoprene) and the dimers 1-methyl-5-(1-methylethenyl)cyclohexene (diprene) and 1-methyl-4-(1-methylethenyl)cyclohexene (dipentene) for the temperature range 298.15-1000 K. These QCFF-calculated thermodynamic values were compared, when possible, with corresponding values obtained experimentally or from other force field programs, and the agreement was found to be satisfactory. The QCFF values were further used to derive gas-phase equilibrium properties-AHO, ASo, AGO, and &-for the isoprene dimerization reaction at various temperatures. These computational results suggest that, based upon thermodynamics, diprene and dipentene are about equally favored dimerization products of isoprene and that reported experimental data reflect kinetic control of dipentene formation at lower temperatures. The equilibrium thermodynamics data for the isoprene dimerization reaction presented in this paper are felt to be sufficiently reliable that they can be utilized in the absence of any additional experimental data; the present work thus illustrates the power of predictive thermodynamic computational techniques in extending the thermochemical database.
Acta Crystallographica Section C Crystal Structure Communications, 1996
The title compound, C10H6O3, has been studied by both X-ray diffraction and molecular-mechanics c... more The title compound, C10H6O3, has been studied by both X-ray diffraction and molecular-mechanics calculations to determine the ring-ring dihedral angle. Calculated and observed values of 5.4 and 5.53 (6) Degrees for this dihedral angle in the crystal were found to be in ...
The Journal of Chemical Thermodynamics, 1992
ABSTRACT In the present experimental work, the energy of combustion of the crystalline Diels-Alde... more ABSTRACT In the present experimental work, the energy of combustion of the crystalline Diels-Alder adduct of anthracene and maleic anhydride: C18H12O3, was measured with a model 1241 Parr automatic calorimeter and a Parr model 1710 calorimeter controller. The standard molar enthalpy of combustion of the (anthracene + maleic anhydride) adduct at po = 0.1 MPa was determined to be ΔcHmo(C18H12O3, cr, 298.15 K) = −(8380.0±5.9) kJ·mol−1. The molar enthalpy of fusion of this adduct at its melting temperature (534.07 K), as measured by a 910 DuPont d.s.c. and a 9900 DuPont thermal (analyzer + digital computer), was found to be (36.3±4.2) kJ·mol−1. The other thermodynamic properties of the (anthracene + maleic anhydride) adduct derived from those measured properties are: ΔfHmo(C18H12O3, cr, 298.15 K) = −(418.2±6.4) kJ·mol−1 and ΔfHmo(C18H12O3, 1, 298.15 K) = −(389.7 ± 7.7) kJ·mol−1.
Journal of Computational Chemistry, 1994
The QCFF program originated by Warshel and Karplus4" was modified to compute accurate thermodynam... more The QCFF program originated by Warshel and Karplus4" was modified to compute accurate thermodynamic properties So, C;, (H;-Hi)/T, and AH; for various acyclic and cyclic alkenes and alkadienes. Modifications consisted of adjusted bond angle, dihedral angle, bond stretch, and bond energy parameters that improved calculated vibrational frequencies, zero point energies, and thermodynamic functions. Supplemental torsional potential energy functions that were added to existing torsional functions led to greatly improved relative conformer energies and AH! values. It was shown that inclusion of hindered internal rotation leads to significantly better agreement of calculated thermodynamic functions with observed values for acyclic alkenes at high temperatures. The calculated thermodynamic properties of the alkenes and alkadienes were deemed sufficiently accurate for calculation of standard enthalpies and Gibbs free energies of gas phase chemical reactions at various temperatures.
The Journal of Physical Chemistry, 1994
The Diels-Alder dimerization of isoprene is an important reaction; dipentene (or racemic limonene... more The Diels-Alder dimerization of isoprene is an important reaction; dipentene (or racemic limonene), one of the products formed in this reaction, has major applications in the manufacture of polymers and adhesives.' Dipentene also has various uses in the food and pharmaceutical industries.' In the present work, the QCFF force field program2 was used to calculate gas-phase thermodynamic properties of the monomer (isoprene) and the dimers 1-methyl-5-(1-methylethenyl)cyclohexene (diprene) and 1-methyl-4-(1-methylethenyl)cyclohexene (dipentene) for the temperature range 298.15-1000 K. These QCFF-calculated thermodynamic values were compared, when possible, with corresponding values obtained experimentally or from other force field programs, and the agreement was found to be satisfactory. The QCFF values were further used to derive gas-phase equilibrium properties-AHO, ASo, AGO, and &-for the isoprene dimerization reaction at various temperatures. These computational results suggest that, based upon thermodynamics, diprene and dipentene are about equally favored dimerization products of isoprene and that reported experimental data reflect kinetic control of dipentene formation at lower temperatures. The equilibrium thermodynamics data for the isoprene dimerization reaction presented in this paper are felt to be sufficiently reliable that they can be utilized in the absence of any additional experimental data; the present work thus illustrates the power of predictive thermodynamic computational techniques in extending the thermochemical database.
Acta Crystallographica Section C Crystal Structure Communications, 1996
The title compound, C10H6O3, has been studied by both X-ray diffraction and molecular-mechanics c... more The title compound, C10H6O3, has been studied by both X-ray diffraction and molecular-mechanics calculations to determine the ring-ring dihedral angle. Calculated and observed values of 5.4 and 5.53 (6) Degrees for this dihedral angle in the crystal were found to be in ...
The Journal of Chemical Thermodynamics, 1992
ABSTRACT In the present experimental work, the energy of combustion of the crystalline Diels-Alde... more ABSTRACT In the present experimental work, the energy of combustion of the crystalline Diels-Alder adduct of anthracene and maleic anhydride: C18H12O3, was measured with a model 1241 Parr automatic calorimeter and a Parr model 1710 calorimeter controller. The standard molar enthalpy of combustion of the (anthracene + maleic anhydride) adduct at po = 0.1 MPa was determined to be ΔcHmo(C18H12O3, cr, 298.15 K) = −(8380.0±5.9) kJ·mol−1. The molar enthalpy of fusion of this adduct at its melting temperature (534.07 K), as measured by a 910 DuPont d.s.c. and a 9900 DuPont thermal (analyzer + digital computer), was found to be (36.3±4.2) kJ·mol−1. The other thermodynamic properties of the (anthracene + maleic anhydride) adduct derived from those measured properties are: ΔfHmo(C18H12O3, cr, 298.15 K) = −(418.2±6.4) kJ·mol−1 and ΔfHmo(C18H12O3, 1, 298.15 K) = −(389.7 ± 7.7) kJ·mol−1.
Journal of Computational Chemistry, 1994
The QCFF program originated by Warshel and Karplus4" was modified to compute accurate thermodynam... more The QCFF program originated by Warshel and Karplus4" was modified to compute accurate thermodynamic properties So, C;, (H;-Hi)/T, and AH; for various acyclic and cyclic alkenes and alkadienes. Modifications consisted of adjusted bond angle, dihedral angle, bond stretch, and bond energy parameters that improved calculated vibrational frequencies, zero point energies, and thermodynamic functions. Supplemental torsional potential energy functions that were added to existing torsional functions led to greatly improved relative conformer energies and AH! values. It was shown that inclusion of hindered internal rotation leads to significantly better agreement of calculated thermodynamic functions with observed values for acyclic alkenes at high temperatures. The calculated thermodynamic properties of the alkenes and alkadienes were deemed sufficiently accurate for calculation of standard enthalpies and Gibbs free energies of gas phase chemical reactions at various temperatures.
Organic Process Research & Development, 1997
The large-scale preparation of the-alkynyl-amino acid ester (()-1,1-dimethylethyl 3-amino-5-(trim... more The large-scale preparation of the-alkynyl-amino acid ester (()-1,1-dimethylethyl 3-amino-5-(trimethylsilyl)-4-pentynoate (A) is discussed. It was discovered that addition of a catalytic amount of lithium bis(trimethylsilyl)amide (LHMDS) to a mixture of tert-butyl acetate and N,3-bis(trimethylsilyl)-2propyn-1-imine (B) initiated a self-perpetuating reaction and gave high yields of the-amino ester A upon quench. This one-pot procedure eliminated the need to prepare the unstable lithium tert-butyl acetate in a separate reactor and enabled the reaction to be scaled up and run at a more acceptable process temperature (-20°C) compared to the analogous two-pot reaction (-45°C). Addition of 3-(trimethylsilyl)-2-propynal to LHMDS in THF at-20°C followed by chlorotrimethylsilane formed the imine B in situ. tert-Butyl acetate (6 equiv) was added followed by a substoichiometric quantity (0.15-0.20 equiv) of LHMDS. After quenching with aqueous ammonium chloride the product A was obtained in a yield averaging 70%. Scheme 1