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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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4 votes
2 answers
6k views

Is it possible for three carbon double bonds to form next to each other in a carbon chain?

In a typical carbon double bond $sp^2$ hybidrization is used to explain the resulting bond. When two carbon atoms A and B form a double bond one $sp^2$ orbital from A bonds to another $sp^2$ orbital ...
3 votes
1 answer
61 views

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 ...
4 votes
2 answers
3k views

Why do halogens have odd numbers as oxidation number?

Halogens like $\ce{Cl}$ always exhibit $+7,+5,+3,+1,-1$ as their oxidation numbers. I found the following answer after checking several sources: Halogen atoms have $7$ electrons in their valence ...
-2 votes
0 answers
45 views

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 ...
7 votes
3 answers
3k views

Nature of a1g Molecular Orbital Interactions in Ferrocene

While learning about ferrocene I've come across this molecular orbital diagram. What particularly confused me is the nature of the a'1g orbital. My professor taught that a'1g and e2g are considered ...
0 votes
0 answers
19 views

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 ...
1 vote
0 answers
38 views

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 ...
66 votes
9 answers
42k views

Why do compounds like SF6 and SF4 exist but SH6 and SH4 don't?

Both $\ce{SF6}$ and $\ce{SH6}$ and $\ce{SF4}$ and $\ce{SH4}$ have the same central atom and the same hybridization, but my teacher specifically mentioned that $\ce{SH6}$ and $\ce{SH4}$ don't exist. I'...
9 votes
1 answer
135 views

Computing energy of Gaussian basis set

I'd like to compute the decay rate using $$ \Gamma = 2\pi \ | \langle ab|V|cd \rangle|^2 \delta\ (\epsilon_\mathrm{f}-\epsilon_\mathrm{i}), \tag{1}$$ where $a,$ $b,$ $c,$ $d$ are the MOs, $V$ is the ...
4 votes
0 answers
5k views

Why CO is a stronger and more common ligand than N2?

Both $\ce{N2}$ and CO are considered sigma-donors and pi-acceptors. Their molecular orbital diagrams are also similar, so why does CO generally bind more strongly and is a more common ligand?
2 votes
1 answer
203 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 ...
2 votes
0 answers
42 views

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. ...
11 votes
1 answer
503 views

Frontier orbital analysis of zinc-catalysed carbonyl-ene reaction

Q1. Is the $\sigma_\ce{C-H}$ bond a donor in this reaction? If not, then can we take the alternate combination (HOMO of alkene, LUMO of the $\ce{C-H}$ bond and, HOMO of the carbonyl)? Q2. We can also ...
5 votes
0 answers
446 views

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 ...
2 votes
0 answers
95 views

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 ...
1 vote
1 answer
91 views

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 ...
3 votes
1 answer
69 views

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 ...
0 votes
0 answers
20 views

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 ...
1 vote
2 answers
7k views

Is p-bromophenol more acidic than p-chlorophenol?

p-chlorophenol is more acidic than p-fluorophenol due to presence of vacant d orbitals. But then is p-bromophenol more acidic than p-chlorophenol since it has vacant f orbitals also? But I guess that’...
0 votes
0 answers
33 views

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?
17 votes
2 answers
1k views

What utility does the tau bond model of orbital overlap have?

In his book on molecular orbital theory, Molecular Orbitals and Organic Chemical Reactions, Ian Fleming notes that Pauling formulated an early alternative model to Hückel theory for explaining the ...
11 votes
0 answers
1k views

Orbital and state correlation diagram for ring-closure of pentadienyl to a cyclic allyl

This is an exam question. I am to construct the orbital and state correlation diagram for one of the reaction below (disrotation or conratation). Also, I should explain whether the reaction is ...
4 votes
3 answers
842 views

The intrinsic electron-withdrawing nature of alkyl groups

What you are about to read may be a very mind-boggling paragraph but please do not regard it as nonsense. Please think through it thoroughly. In Chapter 6 of Organic Chemistry (4th ed.) by Maitland ...
0 votes
0 answers
98 views

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(...
0 votes
0 answers
51 views

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 ...
-2 votes
1 answer
67 views

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
1 vote
0 answers
36 views

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?
0 votes
0 answers
66 views

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 ...
-2 votes
1 answer
71 views

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 ...
0 votes
0 answers
61 views

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 ...
8 votes
2 answers
591 views

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 ...
2 votes
0 answers
80 views

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, ...
2 votes
1 answer
148 views

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 ...
0 votes
0 answers
52 views

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 ...
5 votes
2 answers
2k views

Why aren't chlorides of the noble gases as prevalent as their fluorides?

It is my understanding that compound formation has only been observed for the noble gases argon, xenon, and krypton, while no compounds have ever been observed for neon and helium, and that this might ...
-2 votes
1 answer
192 views

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 ...
0 votes
2 answers
218 views

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 ...
2 votes
0 answers
195 views

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 ...
4 votes
1 answer
143 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 ...
4 votes
0 answers
450 views

Does (BeCl2)n have 3-center-4-electron-bonding or not?

The title really explains what the issue is here. I would think that it has multicenter bonding akin to $\ce{(BeH2)_n}$ polymer, because they are pretty much iso-structural (although it shouldn't have ...
1 vote
1 answer
513 views

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 $\ce{PF3}$ ...
0 votes
2 answers
361 views

Molecular orbital mixing in second period elements

Why do the $\pi_u(2p)$ and $\sigma_g(2p)$ diatomic MO mix within the second period elements as it's shown in the image below?
-3 votes
2 answers
234 views

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 ...
-4 votes
1 answer
28 views

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. ...
3 votes
1 answer
92 views

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 ...
38 votes
1 answer
80k views

Why is [PdCl4]2- square planar whereas [NiCl4]2- is tetrahedral?

The molecule $\ce{[PdCl4]^2-}$ is diamagnetic, which indicates a square planar geometry as all eight d electrons are paired in the lower-energy orbitals. However, $\ce{[NiCl4]^2-}$ is also $\mathrm{d^...
-1 votes
1 answer
107 views

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 ...
1 vote
0 answers
578 views

D-orbitals of point group C2v

I'm trying to construct an MO diagram for cisplatin, which has C2v symmetry. However, there is no Mulliken label for the d(x^2-y^2) orbital in the character table. Does this orbital not form molecular ...
4 votes
2 answers
461 views

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 ...
6 votes
0 answers
78 views

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 ...

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