Questions tagged [molecular-orbital-theory]
Use of molecular orbital (MO) theory allows for an understanding of the observed properties (shape, reactivity) of molecules. The tag should be applied to all questions related to MO theory, from questions about the qualitative use of the theory to questions about the underlying quantum mechanics and applications in computational chemistry.
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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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NMR for diamagnetic uranium molecule's isotopic enrichment
Inspired by Dr. Raizen's MAGIS isotope enrichment scheme, I looked for another way.
While uranium elementally has unpaired electrons making its nuclear magnetic moment much weaker than electron ...
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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 ...
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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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I need a good 3d drawing of ferropericlase [closed]
I'm not a scientist, I'm an artist and I need a good 3d drawing of ferropericlase, where can I find that?
Thank you!
Niki
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Why do bonds interact with other bonds and exhibit overlapping effect?
In carbocations, alkenes and carbon free radicals during hyperconjugation, overlapping of molecular orbitals take place. So how and why does this happen?
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HOMO and LUMO energy levels diagrams
Good time of day. I want to draw the same beautiful pictures in my work as I will attach below taking from some articles. Are there any programms or scripts which can do this? I would be glad if ...
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Why does the two OH bonds in H2O have different bond disassociation enthalpies? How does the bond cleavage happen here?
I came across this question, and in the text it was written as 'change in the chemical environment'. I wasn't satisfied with this explanation, so I am looking for a more detailed answer on this matter ...
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VBT and MOT at the same time!
In the SNAr reaction, it is said that the electron withdrawing groups should be at the ortho or para position for the effective electron delocalization to take place, and we draw Kekule's structure to ...
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How do two orbitals need the same symmetry to bond? Do they need the same mulliken label?
I heard that in order for two atomic orbitals to form a bonding molecular orbital, they need:
Similar energy
Similar symmetry
and Possibility of overlap with the same sign
but, for example in methane, ...
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Mulliken Labels: How do I tell apart E, doubly degenerate, symmetry apart from T, triply degenerate, symmetry for a molecular orbital?
With A and B, it's pretty simple. If you rotate the molecule about its principle axis to where the orbitals line up, and the signs change, it's Mulliken label has a B. otherwise, it's A.
I heard E ...
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In a few species such as dicarbon (shown below) why are the pi bonding orbitals of lower energy than the sigma bonding orbitals?
Normally the pi bonding orbitals are of higher energy because pi orbitals experience less direct overlap than sigma orbitals however in a few species this is not the case and I could not find any ...
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Why can s and p orbitals of one atom form hybrid orbitals but the overlaping of s & p orbitals of two different atoms don't form a molecular orbital?
So my question is in the title : Why can s and p orbitals of one atom form hybrid orbitals but the overlapping of one s orbital and one p orbital (perpendicular to the bond axis) of two different ...
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Why we apply Pauli Exclusion Principle to Molecular Orbital Theory?
Can we say that an electron with a specific set of quantum numbers of a fluorine atom is exactly the same as that of another electron with the same set of quantum numbers of another fluorine atom.
If ...
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Why is cyclohexane more polarizable than benzene?
Looking at figure 4.2 here, we can see experimentaly that cyclohexane is more polarizable than benzene.
Why is this the case?
Intuitively, I would think that because the orbitals in benzene are more ...
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Bond order of carbon monoxide and nitrosyl cation
The following question was asked in JEE Mains exam in 2022, a competitive exam for engineering in India.
The difference between bond order of CO and NO$^+$ is $\frac{x}{2}$ where $x$ = ____. (Round ...
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Which is better ligand, PH3 or PF3?
It confuses me that many researches pointed out different results about phosphine ligands properties (σ-donor and π-acceptor). Since both phosphine $\ce{PH3}$ and phosphorus trifluoride $\ce{PF3}$ ...
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What kind of hybridisation is there around the central carbon atoms?
I am currently working on an assignment and I am confused about what kind of hybridisation exists for the first condensed structure CH3CN. Does the CH3 have sp2 hybridisation? I suspect its that ...
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Why is there a point of orbits along with quantization in case of energy gaps?
As per my textbook and online sources. The definition of Energy bands I have found is this:
A) Energy levels:
( In a simplified view of an electronic structure of a single atom or isolated molecule.
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If a crystal has multiple oxidation states of the same transition metal element, is there only one possible configuration?
Here is the crystal structure of soluble Prussian Blue $\ce{KFe[Fe(CN)6]}$. The Fe(II) and F(III) are spaced alternatively like NaCl with cyanides in between. You can see that the places of Fe(II) and ...
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