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.
622
questions
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Comparing O−O bond length in hydrogen peroxide and dioxide(2−) ion
Problem
How can we qualitatively compare the bond lengths between $\ce{H2O2}$ and $\ce{O2^2-}?$
Answer
Attempt
I tried using molecular orbital theory, but since both have peroxide $\ce{O2^2-},$ the ...
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2answers
55 views
Why electrons do not distribute evenly among the atoms in a molecule?
I was wondering why the state where electrons are evenly (or the closest to being evenly) distributed among the atoms in a molecule is not the lowest energy state? For example, in a water molecule it ...
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0answers
34 views
Rigorous but terse introduction to molecular orbital theory
Is there a terse but rigorous introduction to MOT? I'm looking for the 'Berge's Real Analysis' of MOT, if that analogy resonates with anyone. If not, I'm looking for a book that I can use as a ...
4
votes
1answer
99 views
Why is oxygen more stable than oxygen dication?
According to molecular orbital theory (MOT), $\ce{O2^2+}$ has a greater bond order than $\ce{O2}$ and two less antibonding electrons. So why is molecular oxygen $\ce{O2}$ more stable than the ...
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0answers
28 views
Angle made by orbital with y-axis
What is the hybridization and angle (in degrees) with respect to the y-axis for the following hybrid orbital $ψ=\frac{1}{√3}c×(s-\frac{1}{√3}×p_x+\frac{√3}{√2}×p_y)$
The answer given is 30 degrees but ...
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0answers
42 views
question about electron donor-accpetor polymer
I'm reading a paper about electron-donor-acceptor polymer.
Explaining donor unit, the paper says,
'Donor unit refers to an electron-rich unit. Thiophene and benzene are the two most basic donor units, ...
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0answers
10 views
How can I determine whether sp-mixing occurs for heteronuclear diatomics?
I'm trying to draw out the molecular orbital diagram of nitrogen monoxide (NO) but I do not know whether sp-mixing occurs. This is important in order to determine the arrangement of molecular orbitals....
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0answers
21 views
MO diagram of N2O4 [closed]
How do you draw MO diagrams of larger more complex molecules? I understand how to do for simple diatomic molecules like O2, N2, CO, and ions, but what about polyatomic molecules such as CO2, NO2, N2O4?...
4
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0answers
57 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 ...
5
votes
2answers
107 views
Explanation of the orbital energies resulting from Jahn-Teller distortion of octahedral complex using MO theory
I am confused about the energies of the orbitals after Jahn-Teller distortion of an octahedral complex. Take elongation for example.
To my understanding, since the ligands on the $z$ axis move away, ...
5
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0answers
33 views
+50
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 ...
1
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1answer
39 views
Regarding the probability density of finding an electron in between a bond
I'd found the image attached on a website explaining the molecular orbital theory.
My question is, shouldn't the graph have a maximum at the middle of the two hydrogen atoms? since my intuition tells ...
0
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0answers
28 views
are the exact and kohn-sham electron densities totally symmetric?
For any molecule with open or closed shells considering the electronic state to be the ground state:
Is the exact electron density totally symmetric?
is the Kohn-Sham electron density totally ...
2
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1answer
63 views
How can I know which molecule is more stable when bond order it's equal?
So, I was wondering, I have these molecules $\ce{O^+2}$, $\ce{O^-2}$, $\ce{O2}$ and $\ce{C^+2}$.
When I try to find their bond order and their magnetic nature I get this:
$\ce{O^+2} = \frac{1}{2} \...
3
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0answers
40 views
Can cycloaddition reactions be antarafacial?
Cycloaddition reactions of the form [4+2] and [2+2] are always suprafacial, as the geometry is too constrained to allow for antarafacial interaction between the FMO's. However, for cycloaddition of ...
5
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0answers
78 views
How do bonds rotate in pericyclic reactions?
In Pericyclic reactions, it is shown that the terminal bonds rotate (conrotation or disrotation) to allow for allignment of the FMO's, thereby forming the sigma bond
However, a detail that most of my ...
2
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2answers
79 views
Half sigma bonds
$\ce{N2+}$ has $2$ $\pi$-bonds and a half sigma bond.
First of all, how can a "half" sigma bond exist? Usually when we encounter non integral bond orders, it is mostly because of resonance ...
1
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1answer
56 views
Origin of Virtual Molecular Orbitals in Hartree-Fock equations
Let's look at scheme
Do I understand correctly, the origin of Virtual Orbitals is a solution of (for, exampre, restricted) HF equation eigenfuncions?
4
votes
1answer
63 views
Does cyclooctatetraene also have a diradical anti-aromatic electronic state?
I read that the molecular orbital diagram of cyclobutadiene predicts that it should have a diradical nature as it has two unpaired electrons in two degenerate non bonding orbitals (one in each).
Why ...
6
votes
1answer
166 views
Why are hydrogen bonds in an antiparallel beta sheet stronger than those in parallel beta sheets?
Beta sheets are illustrated as such in most diagrams, where:
In an antiparallel β-sheet, the polypeptide strands are arranged such that a $\ce{C=O}$ and an $\ce{NH}$ from adjacent strands face each ...
6
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1answer
135 views
Can we observe the shapes of MOs? [duplicate]
Condensed question formulation:
Is there an experimental method to directly visualise the 3D form of a MO wave function, or at least the electron density associated with it?
Full statement:
...
0
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1answer
63 views
Energy levels of combined orbitals
I saw the MO diagram for a NH3 molecule but couldn't understand why the combined atomic orbitals were in the positions they were, and if these positions were fixed.
Why is the sigma anti bonding ...
0
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0answers
51 views
Help determining normalisation constant in SALC of methane
We have been told that a symmetry adapted combination of four hydrogen orbitals is used to create localised hydrogen orbitals for methane. These orthonormal combinations are denoted ψa1, ψt’2, ψt’’2 ...
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0answers
19 views
Question on symmetry-adapted, possibly antibonding combinations of core orbitals
In this question, it is said that the core electrons do mix and form delocalised, symmetry-adapted orbitals.
The boron trifluoride molecule is often said to have no anti-bonding orbitals filled, with ...
4
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0answers
66 views
How to read character table?
I am having some problems reading character table. I will describe what I understand and thought to be right.
Consider the $\pi$ MOs formed from overlap of p-orbitals in benzene.
These two degenerate $...
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0answers
49 views
Molecular Orbital Theory and s-p mixing
I understand the bulk of MO theory , the formation of the bonding and anti bonding MOs etc. However, the topic about s-p mixing is quite puzzling to me. As a general rule of the thumb, I was taught ...
0
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1answer
53 views
Bonding in d10 metals such as Zn
I recently learned about the MO bonding model in metals, where many metal atoms form lots of orbitals close in energy that form bands. However, I can't understand the bonding in d10 metals. It seems ...
0
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1answer
53 views
Forcing atoms closer together [closed]
Is there a method in chemistry to alter the energy of atomic bonds by forcing atoms closer together in a smaller volume?
Similar to how pressure squeezes atoms closer together.
5
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0answers
50 views
Molecular orbital diagram for carbene-metal and carbodiphosphorane-metal interaction
I am interested in understanding how carbenes and carbodiphosphoranes interact differently with a transition metals. I would like to use qualitative molecular orbital theory arguments (with an ...
3
votes
2answers
64 views
MO diagram when three orbitals of the same symmetry is allowed to mix
How exactly should we combine three orbitals when we have three orbitals that are of correct symmetry to interact?
Take $\ce{H2O}$ for example. $\mathrm{2s},$ $\mathrm{2p}_z$ and the $A_1$ group $(\ce{...
2
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2answers
76 views
Insight into covalent bonds from electrostatic perspective
I try to understand, from the electromagnetic side only, how the molecule could be more stable than each atom, and concluded that it could not. Where is my mistake?
Here is an illustration :
By using ...
2
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0answers
48 views
Symmetry Operation on Product of Functions
In regards to direct product representations, I'm trying to find a proof for:
$R(X_iY_j)=R(X_i)R(Y_j)$
Where $R$ is a symmetry operation of a group and $X_i$ and $Y_j$ are members of different basis ...
1
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0answers
116 views
Comparison between Molecular Orbital Theory and Valence Bond Theory
I have been reading about introductory Molecular Orbital Theory lately. Till now, I have used Valence Bond Theory to evaluate bonding. I have a few questions about it:-
In VBT, we used the idea that ...
4
votes
1answer
66 views
Can we relate approximate Hartree-Fock orbitals to true solutions in the basis-set limit?
Assume that we've "solved" the RHF Hartree-Fock equations in some finite basis, that is, we have arrived at a self-consistent set of coefficients $c_{\mu{}i}$ such that each spatial ...
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1answer
34 views
Do higher orbitals have more energy or less energy? [duplicate]
I've recently learned that as an orbital gets larger, its energy gets closer to 0. Before this, I learned that when an electron moves down an orbital it releases the energy difference between those ...
1
vote
1answer
90 views
Why do PES graphs list 4s after 3d? [duplicate]
Coming straight off of some electron configuration worksheets, our teacher started to teach us how to read photoelectron spectroscopy (PES) graphs and I'm having a bit of trouble with the two.
During ...
1
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1answer
623 views
Why is the first ionization enthalpy of molecular O2 less than atomic O?
A cousin of mine asked for my help to answer one of his homework questions. It stated-
Explain why- The first ionization energy of molecular oxygen $\ce{O2}$ ($\pu{1175 kJ mol-1}$), is lesser than ...
5
votes
1answer
701 views
Is there s-character in the HOMO of dinitrogen?
State true or false:
The highest occupied molecular orbital in nitrogen molecule has no s-character.
The answer given is that this false. Why is it so?
The highest occupied molecular orbital in $\ce{...
0
votes
1answer
60 views
Jahn Teller Effect on Metal Complexes
I've been learning how the Jahn Teller Distortion effects the orbitals in Metal complexes and how the splitting of eg and t2g orbitals happens.
But the book mentions that the effect is strong for ...
2
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0answers
123 views
Why is it rational that salt-bridges (in proteins) are described as a combination of H-bond and ionic bond?
This is a fundamental question that came to me as I was trying to draw the electrostatic attraction between Aspartate (D) and lysine (K). I have always considered the charge on nitrogen, in the lysine ...
2
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0answers
24 views
Is there any way we can arrive at a general principle of magnetic character based on the bond order (ie; fractional or integral)?
So, after going through two assignments on Chemical Bonding and the Molecular Orbital theory, I saw that in most of the problems where we were asked about the magnetic character of a molecule (...
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0answers
127 views
Hybridization state of oxygen in carbonyl sulfide (COS) [duplicate]
I've been scratching my head on this one for awhile here. In a carbonyl sulfide (COS) molecule, what is the hybridization state of oxygen?
Carbonyl sulfide is composed of a single carbon atom double ...
1
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1answer
109 views
Book Recommendation for Molecular Orbital Theory [duplicate]
I posting my question here since I have seen similar questions but I haven't found the specific answer I am searching for. I am seeking textbook recommendations on Molecular Orbital Theory with ...
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0answers
47 views
How is Pi antibonding orbital more polar than Pi bonding orbital?
While reading about the solvent effect on electronic transition in ESR spectroscopy, I found it written somewhere that the pi anti-bonding orbitals are more polar compared to pi bonding orbitals.
Can ...
1
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1answer
34 views
Chemical reaction of radicals with different multiplicity
I am studying the chemical reaction of radicals by computational chemistry software.
I just want to know what is the rules for multiplicity.
I have two radicals for which, the ground state of one is a ...
2
votes
1answer
138 views
Intuitive Explanation for why more negative charge on ligand does not imply more splitting effect?
I have studied coordination chemistry as part of my school curriculum and we covered Crystal Field Theory as our final theory, and the book says that Ligand Field Theory and Molecular Orbital Theory ...
9
votes
2answers
234 views
How is Bent's rule consistent with LCAO MO theory?
Bent's Rule states that $s$ orbitals on a central atom participate contribute more to molecular orbitals directed towards more electropositive ligands. (For a longer explanation, see this question and ...
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0answers
118 views
Molecular orbital diagram of 2-butene
I encountered a practice question in a textbook according to which the hyperconjugative stability of 2-butene is due to σ-π electron delocalization but somehow I believe it should be σ-π* electron ...
0
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2answers
63 views
Average energy concept
Problem
When the number of electrons in bonding molecular orbitals is equal to number of electrons in anti-bonding molecular orbitals bond cannot be formed between two atoms because
A) Bonding effect ...
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1answer
127 views
molecular orbital theory explaining molecular orbitals [closed]
i am a high school student,,and i am confused in molecular orbital theory,,,my confusion is that how bonding and non bonding orbitals are formed at the same time my teacher taught me that the two wave ...
