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Juan Andres - One of the best experts on this subject based on the ideXlab platform.

  • electronic fluxes during diels alder reactions involving 1 2 benzoquinones mechanistic insights from the analysis of electron localization function and Catastrophe Theory
    Journal of Computational Chemistry, 2012
    Co-Authors: Patricio Gonzaleznavarrete, Juan Andres, Slawomir Berski, Luis R Domingo, Bernard Silvi
    Abstract:

    By means of the joint use of electron localization function (ELF) and Thom's Catastrophe Theory, a theoretical analysis of the energy profile for the hetero-Diels-Alder reaction of 4-methoxy-1,2-benzoquinone 1 and methoxyethylene 2 has been carried out. The 12 different structural stability domains obtained by the bonding evolution Theory have been identified as well as the bifurcation Catastrophes (fold and cusp) responsible for the changes in the topology of the system. This analysis permits finding a relationship between the ELF topology and the evolution of the bond breaking/forming processes and electron pair rearrangements through the reaction progress in terms of the different ways of pairing up the electrons. The reaction mechanism corresponds to an asynchronous electronic flux; first, the O1C5 bond is formed by the nucleophilic attack of the C5 carbon of the electron rich ethylene 2 on the most electrophilically activated carbonyl O1 oxygen of 1, and once the σ bond has been completed, the formation process of the second O4C6 bond takes place. In addition, the values of the local electrophilicity and local nucleophilcity indices in the framework of conceptual density functional Theory accounts for the asychronicity of the process as well as for the observed regioselectivity. © 2012 Wiley Periodicals, Inc.

  • nature of the ring closure process along the rearrangement of octa 1 3 5 7 tetraene to cycloocta 1 3 5 triene from the perspective of the electron localization function and Catastrophe Theory
    Journal of Computational Chemistry, 2012
    Co-Authors: Juan Andres, Slawomir Berski, Luis R Domingo, Patricio Gonzaleznavarrete
    Abstract:

    We analyze the behavior of the energy profile of the ring-closure process for the transformation of (3Z,5Z)-octa-1,3,5,7-tetraene 5 to (1Z,3Z,5Z)-cycloocta-1,3,5-triene 6 through a combination of electron localization function (ELF) and Catastrophe Theory (CT). From this analysis, concepts such as bond breaking/forming processes, formation/annihilation of lone pairs, and other electron pair rearrangements arise naturally through the reaction progress simply in terms of the different ways of pairing up the electrons. A relationship between the topology and the nature of the bond breaking/forming processes along this rearrangement is reported. The different domains of structural stability of the ELF occurring along the intrinsic reaction path have been identified. The reaction mechanism consists of six steps separated by fold and cusp Catastrophes. The transition structure is observed in the third step, d(C1C8) = 2.342 A, where all bonds have topological signature of single bonds (CC). The “new” C1C8 single bond is not formed in transition state and respective Catastrophe of the ELF field (cusp) is localized in the last step, d(C1C8) ≈ 1.97 A, where the two monosynaptic nonbonding basins V(C1) and V(C8) are joined into single disynaptic bonding basin V(C1,C8). The V(C1,C8) basin corresponds to classical picture of the C1C8 bond in the Lewis formula. In cycloocta-1,3,5-triene 6 the single C1C8 bond is characterized by relatively small basin population 1.72e, which is much smaller than other single bonds with 2.03 and 2.26e. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011

  • olefin epoxidation by molybdenum peroxo compound molecular mechanism characterized by the electron localization function and Catastrophe Theory
    Journal of Physical Chemistry A, 2011
    Co-Authors: Slawomir Berski, Juan Andres, Victor Polo, Fabricio R Sensato, V S Safont
    Abstract:

    The oxygen atom transfer reaction from the Mimoun-type complex MoO(η2-O2)2OPH3 to ethylene C2H4 affording oxirane C2H4O has been investigated within the framework of the Bonding Evolution Theory in which the corresponding molecular mechanism is characterized by the topological analysis of the electron localization function (ELF) and Thom’s Catastrophe Theory (CT). Topological analysis of ELF and electron density analysis reveals that all Mo−O bonds in MoO(η2-O2)2OPH3 and MoO2(η2-O2)OPH3 belong to closed-shell type interactions though negative values of total energy densities Ee(rBCP) imply some covalent contribution. The peroxo Oi—Oj bonds are characterized as charge-shift or protocovalent species in which pairs of monosynaptic basins V3(Oi), V3(Oj) with a small electron population of ∼0.25e each, are localized between core basins C(Oi), C(Oj). The oxygen transfer reaction from molybdenum diperoxo complex MoO(η2-O2)2OPH3 to C2H4 system can be described by the following consecutive chemical events: (a) pro...

  • understanding reaction mechanisms in organic chemistry from Catastrophe Theory applied to the electron localization function topology
    Journal of Physical Chemistry A, 2008
    Co-Authors: Victor Polo, Juan Andres, Slawomir Berski, Luis R Domingo, Bernard Silvi
    Abstract:

    Thomʼs Catastrophe Theory applied to the evolution of the topology of the electron localization function (ELF) gradient field constitutes a way to rationalize the reorganization of electron pairing and a powerful tool for the unambiguous determination of the molecular mechanisms of a given chemical reaction. The identification of the turning points connecting the ELF structural stability domains along the reaction pathway allows a rigorous characterization of the sequence of electron pair rearrangements taking place during a chemical transformation, such as multiple bond forming/breaking processes, ring closure processes, creation/annihilation of lone pairs, transformations of C−C multiple bonds into single ones. The reaction mechanism of some relevant organic reactions: Diels−Alder, 1,3-dipolar cycloaddition and Cope rearrangement are reviewed to illustrate the potential of the present approach.

  • an electron localization function and Catastrophe Theory analysis on the molecular mechanism of gas phase identity sn2 reactions
    Theoretical Chemistry Accounts, 2008
    Co-Authors: Victor Polo, Bernard Silvi, Patricio Gonzaleznavarrete, Juan Andres
    Abstract:

    A set of four reactions, XCH3+X− (X=F, Cl, Br) and ClSiH3+Cl−, is investigated by means of the joint use of the electron localization function (ELF) and Catastrophe Theory (CT) analysis in order to obtain new insights into the bond breaking/forming processes for identity SN2 gas-phase reactions. Using DFT calculations at the OLYP/6-311++G(d,p) level, the effect of nucleophile (F, Cl, and Br anions) and the role of reacting centers (C or Si) on the reaction mechanisms are investigated. The charge-shift character of carbon–halogen bonds is studied by determination of the weights of the Lewis resonance structures. In all SN2 reactions at the carbon atom, there is a progressive reduction on the covalent character of the C–X bond from the reactant complex (0.41, 0.57, 0.58 for F, Cl, and Br, respectively) until the bond-breaking process, occurring before the transition structure is reached. On the other hand, the Si–Cl bond maintains its degree of covalent character (0.51) from the isolated fragments to the formation of a stable transition complex, presenting two silicon–chlorine charge-shifted bonds. The analysis of the ELF topology along the reaction path reveals that all reactions proceed via the same turning points of fold-type but the order is inverted for reactions taking place at C or Si atoms.

Patricio Gonzaleznavarrete - One of the best experts on this subject based on the ideXlab platform.

  • electronic fluxes during diels alder reactions involving 1 2 benzoquinones mechanistic insights from the analysis of electron localization function and Catastrophe Theory
    Journal of Computational Chemistry, 2012
    Co-Authors: Patricio Gonzaleznavarrete, Juan Andres, Slawomir Berski, Luis R Domingo, Bernard Silvi
    Abstract:

    By means of the joint use of electron localization function (ELF) and Thom's Catastrophe Theory, a theoretical analysis of the energy profile for the hetero-Diels-Alder reaction of 4-methoxy-1,2-benzoquinone 1 and methoxyethylene 2 has been carried out. The 12 different structural stability domains obtained by the bonding evolution Theory have been identified as well as the bifurcation Catastrophes (fold and cusp) responsible for the changes in the topology of the system. This analysis permits finding a relationship between the ELF topology and the evolution of the bond breaking/forming processes and electron pair rearrangements through the reaction progress in terms of the different ways of pairing up the electrons. The reaction mechanism corresponds to an asynchronous electronic flux; first, the O1C5 bond is formed by the nucleophilic attack of the C5 carbon of the electron rich ethylene 2 on the most electrophilically activated carbonyl O1 oxygen of 1, and once the σ bond has been completed, the formation process of the second O4C6 bond takes place. In addition, the values of the local electrophilicity and local nucleophilcity indices in the framework of conceptual density functional Theory accounts for the asychronicity of the process as well as for the observed regioselectivity. © 2012 Wiley Periodicals, Inc.

  • nature of the ring closure process along the rearrangement of octa 1 3 5 7 tetraene to cycloocta 1 3 5 triene from the perspective of the electron localization function and Catastrophe Theory
    Journal of Computational Chemistry, 2012
    Co-Authors: Juan Andres, Slawomir Berski, Luis R Domingo, Patricio Gonzaleznavarrete
    Abstract:

    We analyze the behavior of the energy profile of the ring-closure process for the transformation of (3Z,5Z)-octa-1,3,5,7-tetraene 5 to (1Z,3Z,5Z)-cycloocta-1,3,5-triene 6 through a combination of electron localization function (ELF) and Catastrophe Theory (CT). From this analysis, concepts such as bond breaking/forming processes, formation/annihilation of lone pairs, and other electron pair rearrangements arise naturally through the reaction progress simply in terms of the different ways of pairing up the electrons. A relationship between the topology and the nature of the bond breaking/forming processes along this rearrangement is reported. The different domains of structural stability of the ELF occurring along the intrinsic reaction path have been identified. The reaction mechanism consists of six steps separated by fold and cusp Catastrophes. The transition structure is observed in the third step, d(C1C8) = 2.342 A, where all bonds have topological signature of single bonds (CC). The “new” C1C8 single bond is not formed in transition state and respective Catastrophe of the ELF field (cusp) is localized in the last step, d(C1C8) ≈ 1.97 A, where the two monosynaptic nonbonding basins V(C1) and V(C8) are joined into single disynaptic bonding basin V(C1,C8). The V(C1,C8) basin corresponds to classical picture of the C1C8 bond in the Lewis formula. In cycloocta-1,3,5-triene 6 the single C1C8 bond is characterized by relatively small basin population 1.72e, which is much smaller than other single bonds with 2.03 and 2.26e. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011

  • an electron localization function and Catastrophe Theory analysis on the molecular mechanism of gas phase identity sn2 reactions
    Theoretical Chemistry Accounts, 2008
    Co-Authors: Victor Polo, Bernard Silvi, Patricio Gonzaleznavarrete, Juan Andres
    Abstract:

    A set of four reactions, XCH3+X− (X=F, Cl, Br) and ClSiH3+Cl−, is investigated by means of the joint use of the electron localization function (ELF) and Catastrophe Theory (CT) analysis in order to obtain new insights into the bond breaking/forming processes for identity SN2 gas-phase reactions. Using DFT calculations at the OLYP/6-311++G(d,p) level, the effect of nucleophile (F, Cl, and Br anions) and the role of reacting centers (C or Si) on the reaction mechanisms are investigated. The charge-shift character of carbon–halogen bonds is studied by determination of the weights of the Lewis resonance structures. In all SN2 reactions at the carbon atom, there is a progressive reduction on the covalent character of the C–X bond from the reactant complex (0.41, 0.57, 0.58 for F, Cl, and Br, respectively) until the bond-breaking process, occurring before the transition structure is reached. On the other hand, the Si–Cl bond maintains its degree of covalent character (0.51) from the isolated fragments to the formation of a stable transition complex, presenting two silicon–chlorine charge-shifted bonds. The analysis of the ELF topology along the reaction path reveals that all reactions proceed via the same turning points of fold-type but the order is inverted for reactions taking place at C or Si atoms.

Slawomir Berski - One of the best experts on this subject based on the ideXlab platform.

  • electronic fluxes during diels alder reactions involving 1 2 benzoquinones mechanistic insights from the analysis of electron localization function and Catastrophe Theory
    Journal of Computational Chemistry, 2012
    Co-Authors: Patricio Gonzaleznavarrete, Juan Andres, Slawomir Berski, Luis R Domingo, Bernard Silvi
    Abstract:

    By means of the joint use of electron localization function (ELF) and Thom's Catastrophe Theory, a theoretical analysis of the energy profile for the hetero-Diels-Alder reaction of 4-methoxy-1,2-benzoquinone 1 and methoxyethylene 2 has been carried out. The 12 different structural stability domains obtained by the bonding evolution Theory have been identified as well as the bifurcation Catastrophes (fold and cusp) responsible for the changes in the topology of the system. This analysis permits finding a relationship between the ELF topology and the evolution of the bond breaking/forming processes and electron pair rearrangements through the reaction progress in terms of the different ways of pairing up the electrons. The reaction mechanism corresponds to an asynchronous electronic flux; first, the O1C5 bond is formed by the nucleophilic attack of the C5 carbon of the electron rich ethylene 2 on the most electrophilically activated carbonyl O1 oxygen of 1, and once the σ bond has been completed, the formation process of the second O4C6 bond takes place. In addition, the values of the local electrophilicity and local nucleophilcity indices in the framework of conceptual density functional Theory accounts for the asychronicity of the process as well as for the observed regioselectivity. © 2012 Wiley Periodicals, Inc.

  • nature of the ring closure process along the rearrangement of octa 1 3 5 7 tetraene to cycloocta 1 3 5 triene from the perspective of the electron localization function and Catastrophe Theory
    Journal of Computational Chemistry, 2012
    Co-Authors: Juan Andres, Slawomir Berski, Luis R Domingo, Patricio Gonzaleznavarrete
    Abstract:

    We analyze the behavior of the energy profile of the ring-closure process for the transformation of (3Z,5Z)-octa-1,3,5,7-tetraene 5 to (1Z,3Z,5Z)-cycloocta-1,3,5-triene 6 through a combination of electron localization function (ELF) and Catastrophe Theory (CT). From this analysis, concepts such as bond breaking/forming processes, formation/annihilation of lone pairs, and other electron pair rearrangements arise naturally through the reaction progress simply in terms of the different ways of pairing up the electrons. A relationship between the topology and the nature of the bond breaking/forming processes along this rearrangement is reported. The different domains of structural stability of the ELF occurring along the intrinsic reaction path have been identified. The reaction mechanism consists of six steps separated by fold and cusp Catastrophes. The transition structure is observed in the third step, d(C1C8) = 2.342 A, where all bonds have topological signature of single bonds (CC). The “new” C1C8 single bond is not formed in transition state and respective Catastrophe of the ELF field (cusp) is localized in the last step, d(C1C8) ≈ 1.97 A, where the two monosynaptic nonbonding basins V(C1) and V(C8) are joined into single disynaptic bonding basin V(C1,C8). The V(C1,C8) basin corresponds to classical picture of the C1C8 bond in the Lewis formula. In cycloocta-1,3,5-triene 6 the single C1C8 bond is characterized by relatively small basin population 1.72e, which is much smaller than other single bonds with 2.03 and 2.26e. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011

  • olefin epoxidation by molybdenum peroxo compound molecular mechanism characterized by the electron localization function and Catastrophe Theory
    Journal of Physical Chemistry A, 2011
    Co-Authors: Slawomir Berski, Juan Andres, Victor Polo, Fabricio R Sensato, V S Safont
    Abstract:

    The oxygen atom transfer reaction from the Mimoun-type complex MoO(η2-O2)2OPH3 to ethylene C2H4 affording oxirane C2H4O has been investigated within the framework of the Bonding Evolution Theory in which the corresponding molecular mechanism is characterized by the topological analysis of the electron localization function (ELF) and Thom’s Catastrophe Theory (CT). Topological analysis of ELF and electron density analysis reveals that all Mo−O bonds in MoO(η2-O2)2OPH3 and MoO2(η2-O2)OPH3 belong to closed-shell type interactions though negative values of total energy densities Ee(rBCP) imply some covalent contribution. The peroxo Oi—Oj bonds are characterized as charge-shift or protocovalent species in which pairs of monosynaptic basins V3(Oi), V3(Oj) with a small electron population of ∼0.25e each, are localized between core basins C(Oi), C(Oj). The oxygen transfer reaction from molybdenum diperoxo complex MoO(η2-O2)2OPH3 to C2H4 system can be described by the following consecutive chemical events: (a) pro...

  • understanding reaction mechanisms in organic chemistry from Catastrophe Theory applied to the electron localization function topology
    Journal of Physical Chemistry A, 2008
    Co-Authors: Victor Polo, Juan Andres, Slawomir Berski, Luis R Domingo, Bernard Silvi
    Abstract:

    Thomʼs Catastrophe Theory applied to the evolution of the topology of the electron localization function (ELF) gradient field constitutes a way to rationalize the reorganization of electron pairing and a powerful tool for the unambiguous determination of the molecular mechanisms of a given chemical reaction. The identification of the turning points connecting the ELF structural stability domains along the reaction pathway allows a rigorous characterization of the sequence of electron pair rearrangements taking place during a chemical transformation, such as multiple bond forming/breaking processes, ring closure processes, creation/annihilation of lone pairs, transformations of C−C multiple bonds into single ones. The reaction mechanism of some relevant organic reactions: Diels−Alder, 1,3-dipolar cycloaddition and Cope rearrangement are reviewed to illustrate the potential of the present approach.

  • the joint use of Catastrophe Theory and electron localization function to characterize molecular mechanisms a density functional study of the diels alder reaction between ethylene and 1 3 butadiene
    Journal of Physical Chemistry A, 2003
    Co-Authors: Slawomir Berski, Juan Andres, And Bernard Silvi, Luis R Domingo
    Abstract:

    The Catastrophe Theory has been used to investigate the reorganization of the localization basins, within the electron localization function formalism, along the intrinsic reaction coordinate associated with the reaction pathway of the Diels−Alder reaction between ethylene and 1,3-butadiene. There are distinguished seven phases (I−VII) characterized by a decay and formation of the double bonds, an accumulation of the nonbonding electron density on the C atoms involved in the formation of two sigma bonds and a ring closure processes. During the reaction 10 Catastrophes occur belonging to two elementary types:  fold and cusp. The transition structure is located in phase III, being determined by a “reduction” of the double CC bond of ethylene to the single bond, and it is not associated with any special event on the intrinsic reaction coordinate path. For the first time, it is shown that formation of two new sigma C−C bonds between ethylene and 1,3-butadiene begins in phase VI at 2.044A.

Luis R Domingo - One of the best experts on this subject based on the ideXlab platform.

  • electronic fluxes during diels alder reactions involving 1 2 benzoquinones mechanistic insights from the analysis of electron localization function and Catastrophe Theory
    Journal of Computational Chemistry, 2012
    Co-Authors: Patricio Gonzaleznavarrete, Juan Andres, Slawomir Berski, Luis R Domingo, Bernard Silvi
    Abstract:

    By means of the joint use of electron localization function (ELF) and Thom's Catastrophe Theory, a theoretical analysis of the energy profile for the hetero-Diels-Alder reaction of 4-methoxy-1,2-benzoquinone 1 and methoxyethylene 2 has been carried out. The 12 different structural stability domains obtained by the bonding evolution Theory have been identified as well as the bifurcation Catastrophes (fold and cusp) responsible for the changes in the topology of the system. This analysis permits finding a relationship between the ELF topology and the evolution of the bond breaking/forming processes and electron pair rearrangements through the reaction progress in terms of the different ways of pairing up the electrons. The reaction mechanism corresponds to an asynchronous electronic flux; first, the O1C5 bond is formed by the nucleophilic attack of the C5 carbon of the electron rich ethylene 2 on the most electrophilically activated carbonyl O1 oxygen of 1, and once the σ bond has been completed, the formation process of the second O4C6 bond takes place. In addition, the values of the local electrophilicity and local nucleophilcity indices in the framework of conceptual density functional Theory accounts for the asychronicity of the process as well as for the observed regioselectivity. © 2012 Wiley Periodicals, Inc.

  • nature of the ring closure process along the rearrangement of octa 1 3 5 7 tetraene to cycloocta 1 3 5 triene from the perspective of the electron localization function and Catastrophe Theory
    Journal of Computational Chemistry, 2012
    Co-Authors: Juan Andres, Slawomir Berski, Luis R Domingo, Patricio Gonzaleznavarrete
    Abstract:

    We analyze the behavior of the energy profile of the ring-closure process for the transformation of (3Z,5Z)-octa-1,3,5,7-tetraene 5 to (1Z,3Z,5Z)-cycloocta-1,3,5-triene 6 through a combination of electron localization function (ELF) and Catastrophe Theory (CT). From this analysis, concepts such as bond breaking/forming processes, formation/annihilation of lone pairs, and other electron pair rearrangements arise naturally through the reaction progress simply in terms of the different ways of pairing up the electrons. A relationship between the topology and the nature of the bond breaking/forming processes along this rearrangement is reported. The different domains of structural stability of the ELF occurring along the intrinsic reaction path have been identified. The reaction mechanism consists of six steps separated by fold and cusp Catastrophes. The transition structure is observed in the third step, d(C1C8) = 2.342 A, where all bonds have topological signature of single bonds (CC). The “new” C1C8 single bond is not formed in transition state and respective Catastrophe of the ELF field (cusp) is localized in the last step, d(C1C8) ≈ 1.97 A, where the two monosynaptic nonbonding basins V(C1) and V(C8) are joined into single disynaptic bonding basin V(C1,C8). The V(C1,C8) basin corresponds to classical picture of the C1C8 bond in the Lewis formula. In cycloocta-1,3,5-triene 6 the single C1C8 bond is characterized by relatively small basin population 1.72e, which is much smaller than other single bonds with 2.03 and 2.26e. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011

  • understanding reaction mechanisms in organic chemistry from Catastrophe Theory applied to the electron localization function topology
    Journal of Physical Chemistry A, 2008
    Co-Authors: Victor Polo, Juan Andres, Slawomir Berski, Luis R Domingo, Bernard Silvi
    Abstract:

    Thomʼs Catastrophe Theory applied to the evolution of the topology of the electron localization function (ELF) gradient field constitutes a way to rationalize the reorganization of electron pairing and a powerful tool for the unambiguous determination of the molecular mechanisms of a given chemical reaction. The identification of the turning points connecting the ELF structural stability domains along the reaction pathway allows a rigorous characterization of the sequence of electron pair rearrangements taking place during a chemical transformation, such as multiple bond forming/breaking processes, ring closure processes, creation/annihilation of lone pairs, transformations of C−C multiple bonds into single ones. The reaction mechanism of some relevant organic reactions: Diels−Alder, 1,3-dipolar cycloaddition and Cope rearrangement are reviewed to illustrate the potential of the present approach.

  • the joint use of Catastrophe Theory and electron localization function to characterize molecular mechanisms a density functional study of the diels alder reaction between ethylene and 1 3 butadiene
    Journal of Physical Chemistry A, 2003
    Co-Authors: Slawomir Berski, Juan Andres, And Bernard Silvi, Luis R Domingo
    Abstract:

    The Catastrophe Theory has been used to investigate the reorganization of the localization basins, within the electron localization function formalism, along the intrinsic reaction coordinate associated with the reaction pathway of the Diels−Alder reaction between ethylene and 1,3-butadiene. There are distinguished seven phases (I−VII) characterized by a decay and formation of the double bonds, an accumulation of the nonbonding electron density on the C atoms involved in the formation of two sigma bonds and a ring closure processes. During the reaction 10 Catastrophes occur belonging to two elementary types:  fold and cusp. The transition structure is located in phase III, being determined by a “reduction” of the double CC bond of ethylene to the single bond, and it is not associated with any special event on the intrinsic reaction coordinate path. For the first time, it is shown that formation of two new sigma C−C bonds between ethylene and 1,3-butadiene begins in phase VI at 2.044A.

Victor Polo - One of the best experts on this subject based on the ideXlab platform.

  • olefin epoxidation by molybdenum peroxo compound molecular mechanism characterized by the electron localization function and Catastrophe Theory
    Journal of Physical Chemistry A, 2011
    Co-Authors: Slawomir Berski, Juan Andres, Victor Polo, Fabricio R Sensato, V S Safont
    Abstract:

    The oxygen atom transfer reaction from the Mimoun-type complex MoO(η2-O2)2OPH3 to ethylene C2H4 affording oxirane C2H4O has been investigated within the framework of the Bonding Evolution Theory in which the corresponding molecular mechanism is characterized by the topological analysis of the electron localization function (ELF) and Thom’s Catastrophe Theory (CT). Topological analysis of ELF and electron density analysis reveals that all Mo−O bonds in MoO(η2-O2)2OPH3 and MoO2(η2-O2)OPH3 belong to closed-shell type interactions though negative values of total energy densities Ee(rBCP) imply some covalent contribution. The peroxo Oi—Oj bonds are characterized as charge-shift or protocovalent species in which pairs of monosynaptic basins V3(Oi), V3(Oj) with a small electron population of ∼0.25e each, are localized between core basins C(Oi), C(Oj). The oxygen transfer reaction from molybdenum diperoxo complex MoO(η2-O2)2OPH3 to C2H4 system can be described by the following consecutive chemical events: (a) pro...

  • understanding reaction mechanisms in organic chemistry from Catastrophe Theory applied to the electron localization function topology
    Journal of Physical Chemistry A, 2008
    Co-Authors: Victor Polo, Juan Andres, Slawomir Berski, Luis R Domingo, Bernard Silvi
    Abstract:

    Thomʼs Catastrophe Theory applied to the evolution of the topology of the electron localization function (ELF) gradient field constitutes a way to rationalize the reorganization of electron pairing and a powerful tool for the unambiguous determination of the molecular mechanisms of a given chemical reaction. The identification of the turning points connecting the ELF structural stability domains along the reaction pathway allows a rigorous characterization of the sequence of electron pair rearrangements taking place during a chemical transformation, such as multiple bond forming/breaking processes, ring closure processes, creation/annihilation of lone pairs, transformations of C−C multiple bonds into single ones. The reaction mechanism of some relevant organic reactions: Diels−Alder, 1,3-dipolar cycloaddition and Cope rearrangement are reviewed to illustrate the potential of the present approach.

  • an electron localization function and Catastrophe Theory analysis on the molecular mechanism of gas phase identity sn2 reactions
    Theoretical Chemistry Accounts, 2008
    Co-Authors: Victor Polo, Bernard Silvi, Patricio Gonzaleznavarrete, Juan Andres
    Abstract:

    A set of four reactions, XCH3+X− (X=F, Cl, Br) and ClSiH3+Cl−, is investigated by means of the joint use of the electron localization function (ELF) and Catastrophe Theory (CT) analysis in order to obtain new insights into the bond breaking/forming processes for identity SN2 gas-phase reactions. Using DFT calculations at the OLYP/6-311++G(d,p) level, the effect of nucleophile (F, Cl, and Br anions) and the role of reacting centers (C or Si) on the reaction mechanisms are investigated. The charge-shift character of carbon–halogen bonds is studied by determination of the weights of the Lewis resonance structures. In all SN2 reactions at the carbon atom, there is a progressive reduction on the covalent character of the C–X bond from the reactant complex (0.41, 0.57, 0.58 for F, Cl, and Br, respectively) until the bond-breaking process, occurring before the transition structure is reached. On the other hand, the Si–Cl bond maintains its degree of covalent character (0.51) from the isolated fragments to the formation of a stable transition complex, presenting two silicon–chlorine charge-shifted bonds. The analysis of the ELF topology along the reaction path reveals that all reactions proceed via the same turning points of fold-type but the order is inverted for reactions taking place at C or Si atoms.

  • lewis acid and substituent effects on the molecular mechanism for the nazarov reaction of penta 1 4 dien 3 one and derivatives a topological analysis based on the combined use of electron localization function and Catastrophe Theory
    Journal of Chemical Theory and Computation, 2007
    Co-Authors: Victor Polo, Juan Andres
    Abstract:

    The joint use of the topological analysis provided by the electron localization function (ELF) and Catastrophe Theory (CT), at the B3LYP/6-31G(d) calculation level, allows us to examine the Lewis acid (protonation H(+) and presence of BH3) and the role of an electron donor substituent (-OCH3) at α and β positions along the course of the molecular mechanism for the Nazarov rearrangement of penta-1,4-dien-3-one and eight derivatives. The progress of the reaction is monitored by the changes of the ELF structural stability domains (SSDs), each change being controlled by a turning point derived from CT. These SSDs and the corresponding turning points are associated with a sequence of elementary chemical steps. Along the cyclization path of penta-1,4-diene-3-one, four SSDs as well as three turning points (cusp1-fold1-cusp2) have been characterized. The first and second SSDs correspond to a polarization of the C-O bond and electronic redistribution among the C-C bonds, respectively, and they can be associated with the formation of an oxyallyl structure. The third and fourth SSDs can be assigned to the ring closure process. Protonation of the oxygen atom shifts the reactive directly into the second SSD, greatly reducing the activation and reaction energies. The electronic effects due to Lewis acids and electron donor substituents have been rationalized in terms of calculations of mesomeric structures from ELF basin populations. The combination of Lewis acids together with α and β -OCH3 substitutions renders a cooperative and competitive effect on activation and reaction free energies, respectively.

  • a joint study based on the electron localization function and Catastrophe Theory of the chameleonic and centauric models for the cope rearrangement of 1 5 hexadiene and its cyano derivatives
    Journal of Computational Chemistry, 2005
    Co-Authors: Victor Polo, Juan Andres
    Abstract:

    A novel interpretation of the chameleonic and centauric models for the Cope rearrangements of 1,5-hexadiene (A) and different cyano derivatives (B: 2,5-dicyano, C: 1,3,4,6-tetracyano, and D: 1,3,5-tricyano) is presented by using the topological analysis of the electron localization function (ELF) and Thom's Catastrophe Theory (CT) on the reaction paths calculated at the B3LYP/6-31G(d,p) level. The progress of the reaction is monitorized by the changes of the ELF structural stability domains (SSD), each being change controlled by a turning point derived from CT. The reaction mechanism of the parent reaction A is characterized by nine ELF SSDs. All processes occur in the vicinity of the transition structure and corresponding to a concerted formation/breaking of C1C6 and C3C4 bonds, respectively, together with an accumulation of charge density onto C2 and C5 atoms. Reaction B presents the same number of ELF SSDs as A, but a different order appears; the presence of 2,5-dicyano substituents favors the formation of C1C6 bonds over the breaking of C3C4 bond process, changing the reaction mechanism from a concerted towards a stepwise, via a cyclohexane biradical intermediate. On the other side, reaction C presents the same type of turning points but two ELF SSD less than A or B; there is an enhancement of the C3C4 bond breaking process at an earlier stage of the reaction by delocalizing the electrons from the C3C4 bond among the cyano groups. In the case of competitive effects of cyano subsituents on each moiety, as it is for reaction D, seven different ELF SSDs have been identified separated by eight turning points (two of them occur simultaneously). Both processes, formation/breaking of C1C6 and C3C4 bonds, are slightly favored with respect to the parent reaction (A), and the TS presents mixed electronic features of both B and C. The employed methodology provides theoretical support for the centauric nature (half-allyl, half-radical) for the TS of D. © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 1427–1437, 2005