All Questions
Tagged with molecular-orbitals or molecular-orbital-theory
792 questions
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Jahn-Teller effect in a square planar configuration
In the original paper of Jahn et Teller (https://royalsocietypublishing.org/doi/pdf/10.1098/rspa.1937.0142, section I-Two Examples) are described two examples: a linear molecule and one with square ...
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What is the difference between a 3c-4e bond vs 2 covalent bonds?
A 3c-4e bond is a bond in which 4 electrons are shared between 3 centers, but 2 covalent bonds between 3 atoms is also the sharing of 4 electrons between 3 centers (according to MOT)? Where is the ...
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Molecular orbitals in complex aromatic systems
I am a new computational chemistry student currently running calculations to generate orbitals. However, I am finding it challenging to identify the types of orbitals I have.
I would appreciate any ...
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MO energy of p-orbitals with different substituents
Why is the HOMO of reaction 3 raised in energy, compared to the others, if the carbocation has partial sp2 character due to resonance? Wouldn't the donation into the p-orbital be stabilizing thus ...
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How do I derive the second-order mixing coefficient from Perturbational Molecular Orbital (PMO) Theory?
Hi I need help deriving a result from the PMO theory. I'm currently reading the second edition of the book Orbital Interactions in Chemistry by Thomas A. Albright, Jeremy K. Burdett & Myung-Hwan ...
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The localized Molecular orbitals of water?
Could someone provide me with the localized molecular orbitals of water from localization methods like fouster boys method on molecular orbitals. I have tried but havent found this anywhere on google ...
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Confusion about S-P Mixing in Molecular Orbital Theory
I am currently a chemistry undergraduate student and have yet to attain a deep understanding of Quantum Mechanics and the underlying principles of orbitals. I am only aware that orbitals are regions ...
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I don't understand the difference between Valence Bond Theory and Molecular Orbital Theory
What does it mean that VBT is localized and MOT is delocalized?
"Unlike valence bond theory, which uses hybrid orbitals that are assigned to one specific atom, MO theory uses the combination of ...
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Wavefunction of multinuclear system
While considering a multinuclear system, I ignore the movement of nucleus and only consider the electrons to be movable. All electrons are identical. The wavefunction of the system must will depend on ...
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The MO diagram of chlorine dioxide?
I have tried to draw a MO diagram of chlorine dioxide using carbon dioxide but I am severly struggling - I have only managed to do pi molecular orbitals but I am struggling on sigma molecular orbitals ...
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Why does H2S have different bond angles to H2O but same MO diagram [duplicate]
I have read that Hydrogen sulfide has lower bond angles than water. It is the same with series of pnictogen hydrides - ammonia has higher bond angles than phosphine. It says that there is no ...
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The MO diagram of sulfur hexafluoride?
Although I have seen it explained, I haven't seen a MO diagram of SF6 on this website showing LCAO - only written explanations and vague diagrams. I was wondering if anyone could share the MO diagram. ...
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Do we always use the Hamiltonian operator in solving for the wavefunction of a chemical system? If so, why not some other operator?
As I understand it, in order to obtain the wavefunction for a system we solve the eigenvalue equation for the Hamiltonian:
$$\hat{H}\psi=E\psi$$
The wavefunction obtained contains all the information ...
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Excited states: S0, S1, S2 interpretation
Good morning, everyone. I have a question about molecular excitation. I'm studying photochemistry, and I came across the terms excited states S₀, S₁, and S₂. Initially, I thought that S₁ represented ...
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Why is tetrazole acidic?
Why is tetrazole acidic? It is already aromatic, so why would the negative charge of its conjugate base be more stable and how? Does it really delocalize in the pi orbitals?
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How do you write the electron configuration using gerade and ungerade notations?
My textbook shows the higher energy bonding and antibonding orbitals, and starts naming them from $1\sigma_\mathrm u.$
I don't think this is correct and it's really confusing me. What can I write if a ...
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Why does LCAO determined based on ground state molecular structure also apply under thermal vibration?
Why does the linear combination of atomic orbitals (LCAO), which is determined based on the symmetry of a molecular in its ground state atomic structure, remains valid considering that the molecule is ...
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Why do we use the labels t2g and eg for complexes in other point groups
The octahedral point group contains the irreducible representations T2g and Eg, which correspond to the triply degenerate and doubly degenerate irreps which are symmetric with respect to a centre of ...
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Unrestricted Hartree Fock Procedure and Implementation
I am currently working on a homemade Hartree Fock program which works well for RHF calculations, but is currently failing for UHF; I was wondering if my general procedure for solving the Pople-Nesbet ...
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What is the Coulson-Fischer method of Quantum Chemistry
Recently, after understanding how the Valence Bond theory and Molecular Orbital Theory are similar through the "Modern Valence Bond Theory", I stumbled upon the Coulson-Fischer method. This ...
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What is the difference between Modern Valence Bond Theory and Valence Bond Theory
I found out that modernized VBT calculates its wavefunction by basically taking average of ground, non-ground covalent state and ionic states. So hydrogen main contributor is ground covalent state. ...
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How exactly mutually shared electrons revolves around nucleuses? [duplicate]
In the first year, this question stroked my brain again. I have asked this question to my chemistry teacher on how exactly shared electrons move when it forms a covalent bond. He said, it is maybe ...
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How do the Valence Bond Theory and Molecular Orbital Theory describe the same wavefunction
How do valence bond theory and molecular orbital theory describe the same wavefunction despite one having localized electrons in a bond overlap and one having wave superimposition forming delocalized ...
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How accurate is the Molecular Orbital Theory
When you take it to its core, when forming a covalent bond, which is more accurate, the MO theory with idea of electron behaving as waves and superimposition, and idea of forming Molecular orbitals ...
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Accuracy of localization in the Molecular Orbital Theory
When I was looking about how the Molecular Orbital Theory complements the Valence Bond Theory, It talked about how they specialize at certain properties like how VB well explains chemical reactivty of ...
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Hybridisation/bonding of XRn oxides
PH3 has a bond angle of around 93o, suggesting the s orbital has a minor role in the bonding, with the p orbitals in p-s σ bonding contributing to the orthogonality of the bonds according to Drago’s ...
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Why is the C-Cl bond length in 4-chlorobenzaldehyde shorter than in chlorobenzene?
I understand that the -COH group in 4-chlorobenzaldehyde withdraws electron density from the benzene ring via the mesomeric (resonance) effect. This should, theoretically, reduce the electron density ...
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Visualizing bonding and antibonding orbitals
When two Helium atoms come together, they produce a helium dimer molecule with 2 MO - A filled sigma star antibonding orbital and A filled Sigma bonding orbital. I have seen how bonding orbital is ...
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p-d combination of orbitals
In JD Lee Concise Inorganic Chemistry, Page 83, p-d combination of orbitals it is written,
" A p orbital on one atom may overlap with d orbital on another atom. Since the orbitals do not point ...
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H_2 Hamiltonian matrix off diagonal elements between RHF state and open shell
I am currently trying to calculate the Hamiltonian matrix of the H$_2$ molecule. To describe that I use the second quantized molecular Hamiltonian:
$\hat{H} = \sum_\sigma\sum_{pq} h_{pq} a_{p\sigma}^\...
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Does MO theory show delocalized electrons
Does the MO theory deem the pi MO delocalized in systems with delocalized electrons like nitrate, benzene and ozone
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Non-radiative decay rates computation
What is the most straightforward computational method to estimate the non-radiative decay rates in organic molecules? I have done TD-DFT calculations and really struggling to compute the rates.
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Pi MO Diagram of Guanidinium Cation
My organic chemistry professor has asked us to draw the pi MO diagram of the guanidinium cation.
I only got as far as the lowest and highest energy orbitals (with zero and three nodal planes ...
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Colours of Halogens
It is known that the halogens have the following colours:
$\ce{F_2}$: Pale Yellow
$\ce{Cl_2}$: Greenish Yellow
$\ce{Br_2}$: Reddish Brown
$\ce{I_2}$: Violet
If we talk about predicting the colours ...
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Is LCAO only valid for equilibrium state?
If I understand correctly, LCAO states that the molecular orbitals in Born-Oppenheimer can be written as a linear combination of Atomic Orbitals for single nuclei. The coefficients in the sum can be ...
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Why are the two $\pi$ green circled orbitals of dioxygen and difluoride degenerate?
The following images have two $\pi$ orbitals circled in green that are on the same energy level. Why is that? Why aren't there three $\pi$ orbitals corresponding to $p_x,p_y,p_z$? I'm pretty sure it ...
user151171
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Why zero-overlap approximation is used for explaning the relation between the ΔE(AO) and the effectiveness of resulted MO?
In Atkins' physical chemistry 10e, page 424, eq 10D.8c, zero overlap approximation is used to obtain an expression for the energies for the molecular orbitals. I could not understand why zero overlap ...
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How to interpret molecular orbital (HOMO - LUMO) plots in Chem3D 22.0?
Recently, I have been trying to understand the origin of the difference in reactivity of alkynyl-boron(ate) complexes so I tried to generate a molecular orbital plot on Chem3D (Version 22.0.22 64bit) ...
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How to make the energy level diagram of dichlorodiammineplatinum(II)?
The oxidation state of platinum in $\ce{[PtCl2(NH3)2]}$ complex is $+2,$ so its configuration will be $\ce{5d^8 6s^0 6p^0}$ and the shape will be square planar.
But this complex has two strong field ...
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Reconciling bonding and antibonding MOs with how reactions proceed
Take the reaction between MeI and some nucleophile (Nu:) to give Me-Nu. Does the approach of the Nu, provide the energy input necessary to promote the Me-I electrons to the antibonding MO? Do the Me-I ...
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What do the pi antibonding orbitals of 1,5-hexadiene look like?
Hi so right now I'm learning about the Cope and Claisen rearrangements, and often something is shown where the antibonding pi orbitals of the two alkenes have to overlap in a certain way, like in the ...
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Do σ→π* and/or π→σ* transitions occur in ultraviolet spectroscopy?
I was taught that the only transition that occur in UV-vis spectroscopy are:
σ→σ*
π→π*
n→π*
n→σ*
Wikipedia seems to support this claim but I have trouble understanding why this must be the case. ...
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How to explain oxidizing power from Molecular Orbital Theory
I am trying to explain the oxidizing property of $\ce{Fe^3+}$ in $\ce{H2O}$ and $\ce{CN^-}$ which is $\ce{[Fe(H2O)6]^3+}$ and $\ce{[Fe(CN)6]^3-}$.
The electrochemical reactions along with their ...
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Can you tell if a HOMO to LUMO transition is allowed just by picturing the MOs?
Someone told me that they said the HOMO to LUMO transition is allowed in benzene and naphthalene just by looking at the MOs and without using the irreps for each orbital and the character tables?
How ...
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Is the energy difference between the 2s and 2p orbital smaller than the difference between 3s and 3p?
on this website (https://physics.nist.gov/PhysRefData/ASD/levels_form.html), you can look up atomic spectra. For example, if you query "Na I", you will see that the Level (cm^-1) for the ...
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Why are Mo(NR2)3 complexes isolobal with the nitrogen atom in N2
In a Molybdenum complex of the form Mo(NR2)3, the Mo is in the oxidation state of +3, leaving it with 3 d electrons. When combined with an additional 2*3 electrons from the ligands, this leaves it ...
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Bonding and antibinding orbital energy difference
Reading Claydens organic chemistry, in chapter 5 it states that Br-Br makes a good electrophile while the C-C in ethane doesnt because the energy difference between bromines bonding and anti bonding ...
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Why hyperconjugation is called as σ to π* donation for alkenes and alkynes?
Why hyperconjugation is called as σ to π* donation for alkenes and alkynes if for C2 lowest unoccupied molecular orbital is σ2p not π*2p?
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Jahn-Teller Distortion: How to compare magnitudes (in Cu2+ complexes)?
Octahedral complex of copper(II) undergo structural distortion (Jahn-Teller). Which one of the given copper(II) complexes will who the maximum structural distortion? (en - ethylenediamine)
(A) $[Cu(...
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How can H2 emit light with only 2 molecular orbitals?
I know that light is emitted when an electron is excited to a higher energy state and then decays back to its ground state, emitting a photon whose energy corresponds to the difference in energy of ...
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