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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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Specific Trend for Bond Orders of Diatomic Molecules?

Are there any exceptions to this trend observed? TL;DR: Does the observed trend in bond orders for different diatomic electronic species, based on molecular orbital theory, have any exceptions? The ...
Yatharth Shrivastava's user avatar
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Magnetic Moments of compounds with opposite moments in their Coordination and Ionization Spheres

What is their behaviour in a magnetic field for a compound A[bc], where A is paramagnetic, and [bc] is diamagnetic? Do they repel, or do they attract? I looked up dissociations through electric and ...
Akilan SS's user avatar
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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 ...
moreQthanA's user avatar
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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 ...
Bozo San's user avatar
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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 ...
Shira's user avatar
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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 ...
Audrix's user avatar
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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 ...
Theiserino's user avatar
3 votes
1 answer
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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(...
magneticMono_Poal247's user avatar
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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 ...
Manny's user avatar
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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
Nicoletta Barolini's user avatar
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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?
user138995's user avatar
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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 ...
UserIn's user avatar
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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 ...
goldi mathews's user avatar
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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 ...
KeShAw's user avatar
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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 ...
AdamT's user avatar
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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 ...
werymash's user avatar
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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 ...
dispatchh's user avatar
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2 answers
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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 ...
KeShAw's user avatar
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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 ...
McKinley's user avatar
1 vote
1 answer
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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 ...
Bongo Man's user avatar
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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 $\ce{PF3}$ ...
Shira's user avatar
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2 answers
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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 ...
WChan's user avatar
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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. ...
Srijan's user avatar
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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 ...
哲煜黄's user avatar
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1 answer
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Table of molecular orbital extents — what does it even mean? [closed]

In molecular orbital theory, the term molecular orbital extents was mentioned, although I can't really picture it. Does molecular orbital extent refer to the spatial distribution of electrons in a ...
user250756's user avatar
2 votes
1 answer
202 views

How do the orbitals in atoms synchronize their phases during the formation of a bond?

Suppose I have two hydrogen atoms, each with one electron in their 1s orbital. Then we can represent the wave functions of these two as say $|\Psi\rangle_1$ and $|\Psi\rangle_2$ for each of the two ...
Hadi Khan's user avatar
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4 votes
2 answers
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Why does color of substances not disappear after some time?

Some compounds are colored due to HOMO-LUMO transition. We see the complimentary color to the frequency which the electron absorbs to get the high molecular orbital. But after some the electron should ...
Garv Chaudha's user avatar
6 votes
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Why SCF-MO methods fail when treating bond-breaking processes?

I'm currently studying the EVB(Empirical Valence Bond) approach. While reading on this article (https://pubs.acs.org/doi/10.1021/ja00224a011), the author mentioned about the usage of SCF-MO formalism ...
Arete's user avatar
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1 answer
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Help with drawing an Molecular Orbital (MO) diagram for organometallic complex

I do not understand how to draw the MO diagram for this question, i appreciate any help you can give on my 3rd yr Chem. Have i understood this correctly? QUESTION: Using an MO bonding picture and ...
Bailee's user avatar
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1 answer
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Do molecular orbitals in metals form bands like in wave interference? [closed]

For bond that's formed between two identical atoms, I naively understand that one molecular orbital is a bonding orbital and the other is an antibonding one, and I believe they have to do with the ...
Samuel Han's user avatar
-4 votes
1 answer
206 views

What is the molecular orbital diagram of hydroxide anion? [closed]

Context I am a teacher, and, during a class, my student asked me to draw the molecular orbital (MO) diagram of the hydroxide anion ($\ce{HO-}$). First, I made the diagram on the left, and then, when ...
ananta's user avatar
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Does I2 form coordinate covalent bond with PI3 in PI3.I2 (PI5)

As PI5 is uncertainly stated as the combination of PI3 and I2. There are suggestions that phosphorus donates its 3s electron pair to molecular orbital of I2 or I2 donates its electron to 3d orbital of ...
Shira's user avatar
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-1 votes
1 answer
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How does MO theory explain the effect of directing groups on aromatic compounds?

From what I could find, this is usually explained using resonance. For example, from Wade's Organic chemistry, 9th edition, p. 823. but I can't figure out how to see this through the MOs of the ...
Juan Coco's user avatar
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1 answer
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If atomic orbitals are orthogonal, how can one mix then in Molecular Orbital Theory?

If two molecular orbitals are orthogonal, their net overlap is 0. Which means that the mixture of them would result in no observable change in any of the orbitals if they occur. However, this ...
Andres Krasnikovas Perucelo's user avatar
2 votes
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Are the density of states of bonding and the corresponding antibonding states complementary?

As for the bonding and the corresponding antibonding molecular orbitals formed between two types of atomic orbitals, are their density of states (DOS) complementary? This means if the DOS of the ...
meTchaikovsky's user avatar
4 votes
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108 views

What is the driving force of Bartoli indole synthesis?

The Bartoli indole synthesis mechanism begins with a series of attacks on the nitroarene regent by the Grignard reagents. But the atom $\ce{O}$ in $\ce{-NO2}$ should be negative, and Grignard reagent ...
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Formal explanation for why ammonia prefers C3v over D3h

The 2 major possible geometries of ammonia are D3h and C3v, but it prefers C3v. My thought process is that this is simply Walsh's rule - the HOMO in C3v is bonding (2A1), whereas the HOMO in C3v is ...
Bartholomew696969's user avatar
2 votes
1 answer
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What can visual observations of pi-bonding MOs explain about LCAO expansion coefficients?

For examples of CO and N2, what can their MOs tell us about their expansion coefficients? I've thought that in N2, its symmetric so the expansion coefficients would be equal from the pi-bonding MO due ...
Audrix's user avatar
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1 vote
2 answers
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Molecular orbital picture in conjugated molecules - double bonds

I am a not a chemistry student but a physics student. Nevertheless, I am quite familiar with molecular orbital theory and similar quantum chemistry concepts. However, I have problems understanding the ...
Lockhart 's user avatar
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1 answer
86 views

According to molecular orbital theory, is the antibonding orbital empy when electrons are found in the bonding orbital?

According to molecular theory when 2 atomic orbitals combine, 2 molecular orbitals will be created. So if the electrons are in the bonding orbital will the antibonding orbital exist and just be empy? ...
CaptainAmerica Whyso's user avatar
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1 answer
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If the 2 electrons of a hydrogen molecule are more likely to be found between the 2 hydrogen atoms, why does this diagram says otherwise?

So I am reading about bonding and antibonding molecular orbitals and i can't understand how does the probability diagram show that the electron density in the sigma 1s molecular orbital is greatest ...
CaptainAmerica Whyso's user avatar
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Energy of a molecule using MOs diagram (case of CH4)

I'm trying to find the ground state energy of CH4 in order to compare it with simulations I made. I came across this diagram of energy (not sure it gives the true energies though, if you could confirm....
QMLSorbonne's user avatar
2 votes
1 answer
250 views

Is there a difference between Hartree-Fock method and LCAO?

I have to dive in some quantum chemistry for a quantum machine learning project and I came across the so-called Hartree-Fock method. In one of the reference I used, they considered electrons as ...
QMLSorbonne's user avatar
4 votes
1 answer
142 views

Role of spin of electron in splitting of orbitals

What will happen if there are electrons with opposite spins present in the orbitals of ligand and metal atom during the splitting of orbitals in crystal field splitting? Magnetic fields of two ...
Chunks  Drunks's user avatar
1 vote
1 answer
554 views

Lewis structure of XeF2 that comes closer to reality?

Meanwhile, the hypervalency of Xe in XeF2 is explained by the 3c4e bond, where the p orbitals of the 3 atoms overlap to form a delocalized system of 3 MO's in which 4 electrons (two from the Xe p ...
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