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.

Filter by
Sorted by
Tagged with
3
votes
0answers
20 views

Why is 4-t-butyl aci-nitro cyclohexane stable whereas aci-nitro cyclohexane is not?

During my PhD, about fifty years ago, I had reason to use 4-t-butyl aci-nitro cyclohexane and found it to be remarkably stable. Usually aci- nitro compounds revert to nitro compounds very quickly ...
2
votes
1answer
31 views

Molecular antibonding orbitals energy

When we heat hydrogen the energy of the molecular orbital of H2(1s) is increased .What happens to the energy of the antibonding molecular energy of hydrogen(1s*)?
1
vote
1answer
29 views

Projection Operator Method on Cl4+

I am not quite sure how to start on 1b.We are given 2 diagrams but I am not sure how to use the second one in the question, or if we have to. I got the point group for Cl4+ to be (D2h) however, but ...
4
votes
0answers
72 views

Does the hybridization of sp3d2 type exist?

Is the hybridization of $\ce{XeOF4}$ $\mathrm{sp^2}$ rather than $\mathrm{sp^3d^2}$, because the latter type of hybridization does not exist? Every answer in the Quora thread "How can we find the ...
3
votes
1answer
82 views

Why is the carbon monoxide triple bond stronger than the nitrogen-nitrogen triple bond?

The $CO$ triple bond has a bond enthalpy of 1072 kJ/mol while the $N_2$ triple bond has a bond enthalpy of 945 kJ/mol, at least according to my source. The molecules are isoelectronic, so I couldn't ...
1
vote
0answers
33 views

Why is the top SN2 reaction faster? (Molecular Orbital Theory)

I'm having trouble understanding why the top SN2 reaction proceeds faster. I know that benzylic and allylic halides react faster in SN2 reactions than non-conjugated halides. I think it's because the ...
1
vote
1answer
44 views

How can ionic bonding in lanthanides occur without valence orbitals available for overlap?

I've recently been taught that the 4f orbitals in lanthanides are "core-like", supposedly meaning they have radius smaller than the 4d orbitals, therefore they are not available on the outside of the ...
1
vote
0answers
55 views

What exactly are frontier orbitals? [closed]

I read about frontier orbitals, namely HOMO, LUMO. But what's exactly HOMO/LUMO? I know HOMO stands for highest occupied molecular orbital and LUMO stands for lowest unoccupied molecular orbital. But ...
3
votes
1answer
131 views

What can we learn from the energies of molecular orbitals?

Molecular orbital theory is successful in calculating the structure of molecules (minimizing the total energy with respect to atomic positions). The solutions of an MO calculation are useful in ...
1
vote
0answers
21 views

CO2 dynamics-vector correlations [closed]

I would like to ask if anyone has any information (schematic diagram)of vector correlations for CO2 molecule. (Is it bending in the excited state with μ in plane? How CO fragment can be ejected after ...
5
votes
1answer
97 views

For molecular orbitals, how is an energy of zero set or defined?

When labeling the energies of molecular orbitals, often some anti-bonding MOs are shown with a positive energy. For example, MolCalc has the following energies for methane (the anti-bonding MO #8 at +...
1
vote
0answers
50 views

Why does ψ^2 ( square of orbital wave function ψ) give the probability of an electron in a given region? [duplicate]

Today I was introduced to the Orbital Wave Function for electrons. $\Psi$ is a mathematical function for coordinate of electrons and has no physical meaning. But $\Psi^2$ gives probability of an ...
2
votes
1answer
290 views

Electron pairing in atoms

A question asks: This question refers to isolated gaseous atoms. In which atom are all electrons paired? Ba, Br, S or Si? I thought it was Ba as its electron configuration is [Xe] 6s2. However, ...
3
votes
0answers
42 views

Why does the binding of DMSO to metal via the S atom (k-S) strengthens the S=O bond?

So, DMSO (dimethyl sulfoxide) can form metal complexes in both $\mathrm{\kappa O}$ and $\mathrm{\kappa S}$ mode i.e. binding with the oxygen or the sulfur respectively. The general explanation given ...
0
votes
0answers
12 views

MO analysis of a radical reaction of chlorine radical with methyl radical

Im trying to create an MO energy diagram for the reaction of a chlorine radical with a methyl radical by creating the 5 group orbitals for methyl radical(with pyramidal geometry) and then creating ...
1
vote
0answers
46 views

Does the number of bonding MOs always equal the number of antibonding MOs

In (I think all) of the molecular orbital (MO) diagrams I have seen, I have observed that the number of antibonding molecular orbitals is the same as the number of bonding molecular orbitals. Here ...
0
votes
1answer
82 views

Why is the HOMO-LUMO gap in N2 and CO of different sizes? [closed]

Why is the HOMO-LUMO gap in $\ce{N2}$ and $\ce{CO}$ different even though they have the same number of valence electrons?
0
votes
0answers
35 views

How many π-electrons are there in 2-methylene-2H-pyran?

I thought that the structure will be aromatic and stabilised because one of the lone pairs being delocalised with the help of conjugated double bond system but still only 3 π-bonds will be present at ...
2
votes
1answer
200 views

Geometry of Ni(acac)2

The complex $\ce{Ni(acac)2}$ is paramagnetic as expected , i.e it has two unpaired electrons giving rise to a magnetic moment of $ \sqrt{8}$ BM but doesn't have the tetrahedral geometry consistent ...
1
vote
1answer
19 views

Mathematical equivalence of ionic-bond resonance structures and d-orbital participation in hypervalent molecules

It is now routine in the scientific community that "main-group hypervalent molecules, under certain conditions, tend to be better represented by resonance structures involving ionic bonds, rather than ...
3
votes
1answer
74 views

How to perform Mulliken population analysis by hand with GAMESS output?

I did a simple calculation on hydrogen fluoride with GAMESS and I wanted to reproduce the Mulliken population analysis for atomic orbitals. A molecular orbital is a linear combination of atomic ...
1
vote
0answers
23 views

pi-type bonding interaction along the bond

I was given the diagram of $\ce{BF3}$'s LUMO and asked to assess its bonding character as shown below: Below is the model answer for the annotated version. I managed to correctly answer the HOMO MO ...
0
votes
0answers
167 views

Molecular orbital diagram of hydroxide ion?

I would like to understand how to create a molecular orbital diagram for the hydroxide ion from scratch. This includes understanding the shape of the molecular orbital. Here is an attempt I have come ...
0
votes
0answers
19 views

Books for organic chemistry [duplicate]

What is the best book to start organic chemistry once I know the basic knowledge of reaction mechanisms like substitutions (nucleophilic, electrophilic and some basic other mechanisms that are given ...
3
votes
1answer
47 views

Symmetry of an FO

I want to ask a question about the symmetry of an FO for $\ce{[CuL2]^-}$ where L is a $1e^-$ donor sigma bonding ligand (e.g. Me). For the ligand orbitals, I produced the following orbitals shown ...
0
votes
2answers
82 views

Questions in MO theory

Τhe electrons in the antibonding MO are the unpaired electrons of the molecule? E.g. $\ce{O2}$, by writing down the diagram for the MO we notice that there are only 2 electrons in the top antibonding ...
4
votes
1answer
60 views

How to understand the (non-)degeneracy of states of singlet Σ and Δ terms for a ππ configuration of two nonequivalent electrons?

As instructed in Levine's Quantum Chemistry 7th edition, Chapter 13.8, page 377, for a $\pi \pi$ configuration of two nonequivalent electrons, four functions $\pi_{+1}(1) \pi_{-1}^{\prime}(2)$, $\pi_{+...
0
votes
0answers
22 views

Energy Levels of Molecular Orbitals formed by combination of Atomic Orbitals

In general when we talk about chemical bonding, we say that it is "nature's way to stabilize the systems" and the energy of the molecule formed by atoms will be lower than that of the individual atoms;...
2
votes
1answer
82 views

Effective Bohr Radius in Transition Metal Complexes?

I am playing around with a toy model of a transition metal complex where the HOMO are $d$-electron states of predominantly transition metal character. Let's say this is a $d^1$ (or $d^9$) system and ...
1
vote
0answers
9 views

Energy diagram of copper iodide complex

We did an experiment where copper iodide 4-methylpyridine and copper iodide imidazole was formed and now we are asked what orbital the electron is excited from and to. After much research we still ...
9
votes
1answer
121 views

Hybrid orbitals, photoionization and time dependence

Wikipedia, in the article on Orbital Hybridisation, states the following: One misconception concerning orbital hybridisation is that it incorrectly predicts the ultraviolet photoelectron spectra of ...
-1
votes
1answer
42 views

Question about d-orbitals [closed]

I saw somewhere that, "in PF5, the 3d orbitals of phosphorus end up in the anti-bonding molecular orbitals, and thus contribute less to the final molecule" and that "the hypervalency of some ...
4
votes
1answer
308 views

Question about the role of d-orbitals in polarisation

I know that, although many elementary books say that d-orbitals are involved in the bonding of hypervalent main group compounds period 3 or higher such as the sulfate ion but in reality they are only ...
3
votes
0answers
43 views

Overlap matrix for finite sized square lattice of hydrogen atoms

So I'm trying to use the LCAO method to calculate molecular orbitals on a square lattice of hydrogen atoms. To this end, I need to compute the Hamiltonian matrix. With the nearest neighbor interaction ...
0
votes
1answer
61 views

Why must there be degeneracy in the orbitals to have a Jahn-Teller effect? [closed]

Why is it the case that for Jahn-Teller effects to occur in transition metals there must be degeneracy in either the $\mathrm{t_{2g}}$ or $\mathrm{e_g}$ orbitals?
0
votes
0answers
29 views

Sigma bond by combining two p orbitals

If I combine two p orbitals in such a way that they form σ bonds, which linear combination will represent bonding and antibonding? My work on this problem: $$ \begin{align} &\text{Bonding:} &...
3
votes
0answers
24 views

Energy level of molecular orbitals in heteronuclear diatomic compounds

I have been studying the molecular orbital theorem. I read that the energy levels for the $\ce{p}$ orbitals in the first series of $\ce{p}$ block molecules are something to the tune of $$\pi_x=\pi_y&...
7
votes
1answer
171 views

Energies of Virtual Molecular Orbitals (LUMO)

I just had a question about molecular orbitals. I was just wondering if the energies of the LUMO (virtual orbitals) derived from CCSD(T)/cc-pTVZ calculations could be trusted. I remember reading some ...
2
votes
1answer
71 views

Is there a hypervalent molecule which has no contribution of d-orbitals at all?

I thought that d-orbitals were used to "extend the octet rule" in these molecules until I looked it up on Google and saw that they actually contributed only a little to the molecule. A little, but not ...
2
votes
1answer
90 views

Relative Energies between LGOs and 2s orbital of oxygen in H2O MO Diagram

In this MO diagram, we find that the LGOs of the two premixed H1s orbitals are significantly higher in energy than oxygen's 2s orbital. Although oxygen's $Z_{eff}$ is considerably higher, is it really ...
4
votes
1answer
96 views

On mathematics behind molecular orbital energies

When explaining the mathematics behind calculating molecular orbital energy , namely HOMO and LUMO energies, using quantum chemistry, Chainer Chemistry documentation states that From mathematical ...
7
votes
0answers
239 views

Mathematical relation between bond angle and fraction of s or p character

In Concise Inorganic Chemistry by J.D.Lee (Adapted by Sudarsan Guha, Fourth Edition), on page 75, under the topic "Effect of Electronegativity - When the surrounding atom is same with different ...
1
vote
0answers
31 views

Stabilizing donor-acceptor interaction between orthogonal orbitals in the SN2 transition state?

For the $\mathrm{S_N2}$ reaction between chloroacetone and iodide, my professor has drawn a donor-acceptor interaction between the iodine lone pair attacking the Cl-substituted carbon and the π ...
5
votes
0answers
147 views

diborane fragment orbitals energy of dihydrogen

I want to ask a question about the fragment orbitals of the $\ce{B2H6}$ system, specifically when I combine the $\ce{B2H4}$ with the $\ce{H2}$ fragments. I am halfway through my inorganic chemistry ...
2
votes
0answers
35 views

Varying sizes in LUMO of acrolein

I want to ask a question about the varying sizes in the LUMO of acrolein during a 1,2- or 1,4-addition. Today in our introductory lesson to Organic Synthesis with 1,2- and 1,4-addition we were ...
2
votes
0answers
22 views

How to deal with non-symmorphic space groups for orbital/vibrational analysis?

I am learning about how to apply group theory analysis of MO diagrams and vibrational in the solid state context (not isolated molecules). I think the strategy for calculating representations and ...
-2
votes
1answer
151 views

Sulfur can violate the octet rule because it has an “empty D orbital” is there any other information the periodic table isnt telling us?

In sulfur or any atom with an expanded octet on the 3rd row, where does the idea that they have an empty D orbital come from ?
1
vote
0answers
45 views

Calculating the Molecular Orbitals of a Molecular State [closed]

I am performing ab initio calculations on a heteronuclear diatomic compound using the MRCI method on the MOLPRO quantum chemistry package. I obtained the molecular states of the compound but I was ...
1
vote
0answers
213 views

What is the purpose of phase matching when drawing a MO diagram?

During the lecture, we were learning how to draw the MO diagram for $\mathrm{BF_3}$. I understand that only orbitals with the same symmetry labels can interact and form molecular orbitals. My ...
2
votes
0answers
27 views

Properties that probe electron kinetic energy

This post is inspired by a question regarding the meaning of off-diagonal elements of the KE matrix (in some AO basis). One answer suggests that a diagonalized KE matrix might not be very useful. I ...

1
2 3 4 5
12