The Polyene Series - Revision history

Cmditradmin: /* Hexatriene */

2011-06-20T16:33:14Z

Hexatriene

← Older revision		Revision as of 09:33, 20 June 2011
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	=== Hexatriene ===		=== Hexatriene ===
	[[Image:hexatriene.JPG\|thumb\|left\|400px\|Hexatriene has three ethylene like sub units, 3 occupied levels and 3 unoccuppied pi * levels.]]		[[Image:hexatriene.JPG\|thumb\|left\|400px\|Hexatriene has three ethylene like sub units, 3 occupied levels and 3 unoccuppied pi * levels.]]
	[[Image:hexatriene_wavefunctions.JPG\|thumb\|~~300px~~\|Hexatriene wave functions. The wave functions for hexadiene can have 0, 1, or 2 nodes in the HOMO. The gap between the HOMO and LUMO is 4.7eV.]]		[[Image:hexatriene_wavefunctions.JPG\|thumb\|400px\|Hexatriene wave functions. The wave functions for hexadiene can have 0, 1, or 2 nodes in the HOMO. The gap between the HOMO and LUMO is 4.7eV.]]

Cmditradmin: /* Hexatriene */

2011-06-20T16:33:00Z

Hexatriene

← Older revision		Revision as of 09:33, 20 June 2011
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	=== Hexatriene ===		=== Hexatriene ===
	[[Image:hexatriene.JPG\|thumb\|left\|~~300px~~\|Hexatriene has three ethylene like sub units, 3 occupied levels and 3 unoccuppied pi * levels.]]		[[Image:hexatriene.JPG\|thumb\|left\|400px\|Hexatriene has three ethylene like sub units, 3 occupied levels and 3 unoccuppied pi * levels.]]
	[[Image:hexatriene_wavefunctions.JPG\|thumb\|300px\|Hexatriene wave functions. The wave functions for hexadiene can have 0, 1, or 2 nodes in the HOMO. The gap between the HOMO and LUMO is 4.7eV.]]		[[Image:hexatriene_wavefunctions.JPG\|thumb\|300px\|Hexatriene wave functions. The wave functions for hexadiene can have 0, 1, or 2 nodes in the HOMO. The gap between the HOMO and LUMO is 4.7eV.]]

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	<br clear='all'>		<br clear='all'>
	[[Image:H2wavecombined.JPG\|thumb\|~~300px~~\|The smoother the evolution of the wave function the smaller the kinetic energy term that is associated with it.]]		[[Image:H2wavecombined.JPG\|thumb\|400px\|The smoother the evolution of the wave function the smaller the kinetic energy term that is associated with it.]]
	The energy of the π MO’s goes UP as a function of the # of nodes this is related to the kinetic term in the Schrödinger equation.		The energy of the π MO’s goes UP as a function of the # of nodes this is related to the kinetic term in the Schrödinger equation.

Cmditradmin: /* External Links */

2010-08-10T20:34:29Z

External Links

← Older revision		Revision as of 13:34, 10 August 2010
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	== External Links ==		== External Links ==

	[http://138.253.125.24/~ng/external/orbitalsethene.htm MO orbital visualization of ethylene]		*[http://138.253.125.24/~ng/external/orbitalsethene.htm MO orbital visualization of ethylene]

	[http://www.jce.divched.org/JCEDLib/LivTexts/pChem/JCE2005p1880_2LTXT/QuantumStates/ Quantum States of Atoms and Molecules]		*[http://www.jce.divched.org/JCEDLib/LivTexts/pChem/JCE2005p1880_2LTXT/QuantumStates/ Quantum States of Atoms and Molecules]

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Cmditradmin: /* Electronic Band Structure of Polyacetylene and other Polymers */

2010-06-23T16:50:37Z

Electronic Band Structure of Polyacetylene and other Polymers

← Older revision		Revision as of 09:50, 23 June 2010
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	\|}		\|}
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	[[Image:Polyene_bandgaps.png\|thumb\|300px\|]]		[[Image:Polyene_bandgaps.png\|thumb\|300px\|Band gap for various polymers]]

	Effect of electron donating and electron withdrawing substituents:		Effect of electron donating and electron withdrawing substituents:

Cmditradmin at 19:31, 29 December 2009

2009-12-29T19:31:28Z

← Older revision		Revision as of 12:31, 29 December 2009
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	<br clear='all'>		<br clear='all'>
			[[category:electronic band structure]]
	<table id="toc" style="width: 100%">		<table id="toc" style="width: 100%">
	<tr>		<tr>

Cmditradmin: /* Geometry */

2009-12-22T21:55:17Z

Geometry

← Older revision		Revision as of 14:55, 22 December 2009
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	[[Image:hexatriene_geometry.JPG\|thumb\|300px\|]]		[[Image:hexatriene_geometry.JPG\|thumb\|300px\|]]
	Going the ground state geometry to the reduced state there is lesser degree of bond length alternation because double bonds will have lengthened and the single bonds will have shortened. When the molecule is oxidized(remove an electron) the electron is lost from the HOMO, that is from a bonding factor, it weakens the bonding characteristic and that bond will elongate. But if the electron is removed from an antibonding wave function, that allows the bond to shorten. As a consequence adding an electron on the LUMO (i.e. reduce the molecule) or removing an electron from HOMO (oxidize the molecule) the double bonds will elongate and the single bond will shorten. When going to the excited state (taking and electron from the HOMO to the LUMO) there should be longer double bonds and shorter single bonds compared to the ground state. This is because the π electron densities on the bonds changes the geometry of the molecule.		Going from the ground state geometry to the reduced state there is lesser degree of bond length alternation because double bonds will have lengthened and the single bonds will have shortened. When the molecule is oxidized(remove an electron) the electron is lost from the HOMO, that is from a bonding factor, it weakens the bonding characteristic and that bond will elongate. But if the electron is removed from an antibonding wave function, that allows the bond to shorten. As a consequence adding an electron on the LUMO (i.e. reduce the molecule) or removing an electron from HOMO (oxidize the molecule) the double bonds will elongate and the single bond will shorten. When going to the excited state (taking and electron from the HOMO to the LUMO) there should be longer double bonds and shorter single bonds compared to the ground state. This is because the π electron densities on the bonds changes the geometry of the molecule.

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Cmditradmin: /* Geometry */

2009-12-07T20:56:48Z

Geometry

← Older revision		Revision as of 13:56, 7 December 2009
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	]]		]]

	When π electrons are added they will be distributed unevenly over the bonds. The double bonds are shortened (1.34 Å). Even the single bond will be shorter (1.47 Å) than a single bond because of the π conjugated system. The HOMO ~~wavefunction~~ reflects the single double bond alternation in the ground state. If we add an electron to hexatriene (reduce it) this electron will go to the LUMO causing an antibonding factor between the first carbons. This will cause the first bond to lengthen. So a rule of thumb is that when an electron is added to an antibonding ~~wavefunction~~ the bond will elongate. If it is added to a bonding factor then it will shorten.		When π electrons are added they will be distributed unevenly over the bonds. The double bonds are shortened (1.34 Å). Even the single bond will be shorter (1.47 Å) than a single bond because of the π conjugated system. The HOMO wave function reflects the single double bond alternation in the ground state. If we add an electron to hexatriene (reduce it) this electron will go to the LUMO causing an antibonding factor between the first carbons. This will cause the first bond to lengthen. So a rule of thumb is that when an electron is added to an antibonding wave function the bond will elongate. If it is added to a bonding factor then it will shorten.
	<br clear='all'>		<br clear='all'>
	[[Image:hexatriene_geometry.JPG\|thumb\|300px\|]]		[[Image:hexatriene_geometry.JPG\|thumb\|300px\|]]
	Going the ground state geometry to the reduced state there is lesser degree of bond length alternation because double bonds will have lengthened and the single bonds will have shortened. When the molecule is oxidized(remove an electron) the electron is lost from the HOMO, that is from a bonding factor, it weakens the bonding characteristic and that bond will elongate. But if the electron is removed from an antibonding ~~wavefunction~~, that allows the bond to shorten. As a consequence adding an electron on the LUMO (i.e. reduce the molecule) or removing an electron from HOMO (oxidize the molecule) the double bonds will elongate and the single bond will shorten. When going to the excited state (taking and electron from the HOMO to the LUMO) there should be longer double bonds and shorter single bonds compared to the ground state. This is because the π electron densities on the bonds changes the geometry of the molecule.		Going the ground state geometry to the reduced state there is lesser degree of bond length alternation because double bonds will have lengthened and the single bonds will have shortened. When the molecule is oxidized(remove an electron) the electron is lost from the HOMO, that is from a bonding factor, it weakens the bonding characteristic and that bond will elongate. But if the electron is removed from an antibonding wave function, that allows the bond to shorten. As a consequence adding an electron on the LUMO (i.e. reduce the molecule) or removing an electron from HOMO (oxidize the molecule) the double bonds will elongate and the single bond will shorten. When going to the excited state (taking and electron from the HOMO to the LUMO) there should be longer double bonds and shorter single bonds compared to the ground state. This is because the π electron densities on the bonds changes the geometry of the molecule.

	<br clear='all'>		<br clear='all'>

Cmditradmin: /* Hexatriene */

2009-12-07T20:56:23Z

Hexatriene

← Older revision		Revision as of 13:56, 7 December 2009
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	=== Hexatriene ===		=== Hexatriene ===
	[[Image:hexatriene.JPG\|thumb\|left\|300px\|Hexatriene has three ethylene like sub units, 3 occupied levels and 3 unoccuppied pi * levels.]]		[[Image:hexatriene.JPG\|thumb\|left\|300px\|Hexatriene has three ethylene like sub units, 3 occupied levels and 3 unoccuppied pi * levels.]]
	[[Image:hexatriene_wavefunctions.JPG\|thumb\|300px\|Hexatriene ~~wavefunctions~~. The ~~wavefunctions~~ for hexadiene can have 0, 1, or 2 nodes in the HOMO. The gap between the HOMO and LUMO is 4.7eV.]]		[[Image:hexatriene_wavefunctions.JPG\|thumb\|300px\|Hexatriene wave functions. The wave functions for hexadiene can have 0, 1, or 2 nodes in the HOMO. The gap between the HOMO and LUMO is 4.7eV.]]

Cmditradmin: /* Hexatriene */

2009-12-07T20:55:47Z

Hexatriene

← Older revision		Revision as of 13:55, 7 December 2009
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	<br clear='all'>		<br clear='all'>
	[[Image:H2wavecombined.JPG\|thumb\|300px\|The smoother the evolution of the ~~wavefunction~~ the smaller the kinetic energy term that is associated with it.]]		[[Image:H2wavecombined.JPG\|thumb\|300px\|The smoother the evolution of the wave function the smaller the kinetic energy term that is associated with it.]]
	The energy of the π MO’s goes UP as a function of the # of nodes this is related to the kinetic term in the Schrödinger equation.		The energy of the π MO’s goes UP as a function of the # of nodes this is related to the kinetic term in the Schrödinger equation.

Cmditradmin: /* Butadiene */

2009-12-07T20:55:28Z

Butadiene

← Older revision		Revision as of 13:55, 7 December 2009
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	From the point of view of the π level butadiene corresponds to the interaction between two ethylene sub-units. The π homo level of one ethylene subunit interacts with the π homo level of the other subunit. There can be a positive combination and a negative combination, one leads to a level that is more stable one that is less stable. The same thing happens for the π* levels. The π * LUMO has come down while the π HOMO has increased. As a result the energy difference between HOMO and LUMO (the first optical transition ) has decreased to 5.4 eV.		From the point of view of the π level butadiene corresponds to the interaction between two ethylene sub-units. The π homo level of one ethylene subunit interacts with the π homo level of the other subunit. There can be a positive combination and a negative combination, one leads to a level that is more stable one that is less stable. The same thing happens for the π* levels. The π * LUMO has come down while the π HOMO has increased. As a result the energy difference between HOMO and LUMO (the first optical transition ) has decreased to 5.4 eV.
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	[[Image:butadienewave.JPG\|thumb\|300px\|Butadience ~~wavefunctions~~]]		[[Image:butadienewave.JPG\|thumb\|300px\|Butadience wave functions]]
	Considering the ~~wavefunction~~. The positive combination gives you all bonding for the lowest π bonding orbital. Then mixing two positive with two negative (++--) you fill the HOMO level resulting in a single node. In the π * orbitals the LUMO includes a negative combination (+--+) which results in bonding in the middle with 2 nodes. The fully antibonding molecular orbital has three nodes.		Considering the wave function. The positive combination gives you all bonding for the lowest π bonding orbital. Then mixing two positive with two negative (++--) you fill the HOMO level resulting in a single node. In the π * orbitals the LUMO includes a negative combination (+--+) which results in bonding in the middle with 2 nodes. The fully antibonding molecular orbital has three nodes.
	<br clear='all'>		<br clear='all'>

	The bonding – antibonding character of the HOMO ~~wavefunction~~ translates to the double-bond / single-bond character of the geometry in the ground state. Higher electron density in the π MO corresponds to the double bond that allows the nuclei get closer (shorter bond length), lower density in single bond corresponds to the node between the antibonding orbitals.		The bonding – antibonding character of the HOMO wave function translates to the double-bond / single-bond character of the geometry in the ground state. Higher electron density in the π MO corresponds to the double bond that allows the nuclei get closer (shorter bond length), lower density in single bond corresponds to the node between the antibonding orbitals.
	[[Image:Butadiene_bonding.jpg\|thumb\|left\|200px\|Butadience Bonding and Antibonding- HOMO]]		[[Image:Butadiene_bonding.jpg\|thumb\|left\|200px\|Butadience Bonding and Antibonding- HOMO]]
	[[Image:Butadiene_bonding_lumo.jpg\|thumb\|200px\|Butadience Bonding and Antibonding- LUMO]]		[[Image:Butadiene_bonding_lumo.jpg\|thumb\|200px\|Butadience Bonding and Antibonding- LUMO]]