Questions tagged [symmetry]
The description of the symmetry present in molecules. Molecular symmetry is useful for explaining or predicting of a molecule's chemical properties.
254
questions
-2
votes
0
answers
40
views
Are all helicenes optically active? Aren't they having a plane of symmetry? [closed]
Are all helicenes optically active?
Aren't they having a plane of symmetry or centre of symmetry?
Please give a detailed explanation
- 7
2
votes
1
answer
73
views
Identifying Type of Symmetry Operations
From the given set of symmetry operations for a space group, say, P-3m1 or Cmma, how can one identify the type of all symmetry operations. For example, how to distinguish the axis of rotation symmetry ...
- 123
0
votes
0
answers
45
views
Why is α-truxillic acid not meso compound? [duplicate]
I know that for a compound to be meso it should be optically inactive and should have multiple chiral centres but in case of α-truxillic acid, it is optically inactive due to centre of symmetry being ...
- 33
0
votes
0
answers
59
views
How do we determine the local symmetry of anatase TiO2?
In this physical review B paper, the authors mentioned that the local symmetry of anatase TiO2 is D2d point group. Also, in this applied physics letters paper, the authors mentioned that the symmetry ...
- 273
0
votes
0
answers
20
views
Tips for determining molecular point groups
Does anybody have tips on how to easyily determine the point group of a molecule? I am having a hard time even with the simple molecules. For example:
Determine the symmetry of the conformation of ...
- 79
-1
votes
1
answer
48
views
Optical rotation and chirality
I had the same question as in Molecular chirality and optical rotation
In the answer, it says that there can't be such a mirror position where the effect of one molecule be cancelled by other. But I'm ...
- 3
0
votes
0
answers
101
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) $[Cu(...
1
vote
1
answer
88
views
Electronic configuration and symmetry labels of 3d$^7$ ions
In 3d$^7$ ions, e.g. Co$^{2+}$, the ground state is $^4$F, and it contains different levels due to the crystal field, such as $^4T_{1g}$, $^4T_{2g}$ and $^4A_{2g}$. Can anyone tell me what exactly ...
- 11
2
votes
0
answers
82
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, ...
- 109
-2
votes
1
answer
199
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 ...
- 59
1
vote
1
answer
98
views
H-NMR Analysis of C15H24O
I was able to figure out that the structure of this compound was a benzene ring with 2 equivalent trimethyl groups to give the 18H singlet. Another non-equivalent methyl group to give the 3H singlet. ...
- 11
2
votes
1
answer
109
views
How do you determine point groups of more complex molecules when there are 2 or more central atoms?
I am trying to determine the point group of Fe2(CO)8 and am having difficulty with the bond angles and geometry. How would one go about this in a logical sense?
- 107
0
votes
0
answers
46
views
Bromate ion point group?
Would the bromate ion have C3v point group due to the trigonal pyramidal geometry? I see a C3 rotational axis and a vertical plane of symmetry. Am I missing anything in terms of the double bonds or ...
- 107
3
votes
0
answers
27
views
What prevents an octahedral complex from always assuming the quadratic planar limiting case, due to the Jahn–Teller distortion?
When a given high-spin complex is Jahn–Teller distorted, this does not change the relative position of the total energy of the complex (assuming $\mathrm{d^{10}}$ configuration).
Indeed, the ...
- 83
2
votes
2
answers
520
views
What does the 2 in t2g stand for?
I have read so far that it is about whether the d-Orbital is symmetric to a C2 element perpendicular to its main rotational axis. If all the given orbitals in a group are symmetric to that element, ...
- 83
7
votes
2
answers
850
views
Why is prismane explosive but cubane is not?
So I was reading about polyhedral hydrocarbons, because I dig the topic, and I read (admittedly on wikipedia entries... But they cited papers, I swear!) that prismane is explosive due to the massive ...
- 731
-2
votes
2
answers
128
views
How does the anti isomer below have a plane of symmetry? The R group and the H end up in opposite sides if you divide in half [closed]
If we add substituents R to this structure, we can have two diastereoisomers with the two R groups on the same side (syn) of the flat ring or on opposite (anti) sides. Although the plane of the paper ...
3
votes
0
answers
74
views
Energy of d(x²-y²) and d(xy) orbitals the same with respect to trigonal symmetry?
In the orbital splitting diagrams of trigonal planar and trigonal bipyramidal complexes the d$_{x² - y²}$ and d$_{xy}$ orbitals have the same energy. I have always assumed that this is because they ...
- 286
2
votes
0
answers
133
views
Deduce the shapes of stretching modes of a tetrahedral molecule
This question is in relation to the [FeCl4]- molecule, which is tetrahedral. I previously deduced, using symmetry analysis, that the vectors corresponding to the bonds of the molecule will be A1+T2, ...
8
votes
2
answers
356
views
What's the relation between two symmetry groups, if one has all the symmetry of the other and some more?
Question:
Consider two molecular symmetry groups, for example $C_s$ and $C_{2v}$.
$C_s$ has one inversion plane, and two irreductible representations: the symmetric $A'$, and the antisymmetric $A''$.
...
- 239
2
votes
1
answer
134
views
Why are certain lattices compatible with only certain point groups and not all point groups?
I will limit this discussion to 2 dimensions for ease of intuition. My understanding of the 17 crystallographic plane groups is that these 17 groups represent all the possible symmetry groups of any ...
- 241
1
vote
0
answers
49
views
How do I assign functions for cartesian coordinates and rotations to irreducible representations of a character table?
I do not really understand the intuition behind the functions assigned to irreducible representations.
For example, in H₂O, the A₂ representation is given by
...
- 128
2
votes
1
answer
208
views
Is there a difference between $A_{1g}$ modes and $A_{g}$ modes?
I know that both are totally symmetric and that the '$1$', according to the Mulliken table, refers to symmetry around the $C_2$ axis but I was reading some papers and found that modes were sometimes ...
- 65
3
votes
1
answer
50
views
Are A1g modes reduced at 180 degrees polarisation in Raman spectra?
I have read that A1g modes are identifiable in Raman spectra by looking at cross-polarised Raman spectra and seeing peaks that strongly reduce in intensity. So essentially, the intensity of A1g modes ...
- 65
7
votes
2
answers
101
views
Point group of harmonic oscillator
The book Molecular Quantum Mechanics by Atkins and Friedman [1] says the point group of a harmonic oscillator is $C_\mathrm{s},$ composed by the identity operator $E$ and a reflection $\sigma_\mathrm{...
- 461
2
votes
0
answers
77
views
Factor Group Analysis of Na2SO4 - Site Group Symmetry
I'm still trying to understand how to construct a factor group analysis for a given molecular point group and the resulting solid state group symmetry. For this I searched for some examples and found ...
- 4,322
3
votes
1
answer
305
views
Relation between symmetry of a reciprocal vector and lattice planes perpendicular to it
What is the relation the symmetry of a high-symmetry point in the first Brillouin zone and lattice planes perpendicular to it? Are the two symmetries equivalent?
I have this question because I want to ...
- 273
1
vote
1
answer
81
views
What does it mean that a state belongin to a given irrep transforms like $Rx$, $Ry$ or $Rz$
The present question is related to this other question I did few days ago.
Given a point group and the list of the irreps (see for example here) the meaning of an irrep which transforms like $x$ or $x^...
- 267
0
votes
0
answers
128
views
When does the angle between the planes in tetrahedral molecule with central atom deviate from 90°?
Consider an atom X bonded to four other atoms A, B, C, D in a tetrahedral fashion with sp³ hybridisation. If A, B, C, D are the same, every bond angle is 109.47°, and the angle between the planes ...
- 340
7
votes
1
answer
411
views
How do I show that a transition is electric dipole allowed with group theory/symmetry?
This is actually a follow up of this question
The follow-up is not because of the electric instead of magnetic dipole (this is trivial).
It is because I'm interested in extra info.
Suppose I have a ...
- 267
2
votes
1
answer
405
views
What is m.2m point group?
I'm using Bilbao Crystallographic Server to find 3D crystallographic point groups of the K points of anatase TiO2.
Since the space group of anatse TiO2 is $I4_1/amd$, on this page, I found the point ...
- 273
3
votes
2
answers
388
views
Determination of energies in MO diagrams
How do we determine the relative placements of molecular orbitals in their diagrams? I understand that we can use point groups to find symmetry-allowed interactions between orbitals that we write on ...
1
vote
1
answer
1k
views
is this compound meso? trans-1,4 dimethylcyclohexane [duplicate]
I had a question on a quiz that asked if the compound below was meso or not. I thought that it would be meso because there is a plane of symmetry going through the two methyls, but the answer was that ...
- 49
3
votes
1
answer
1k
views
How do we find the SALCs?
I am trying to understand exactly what IRREPs are and, in order to know more about it, I started reading the chem.libretext course on molecular symmetry which up to this point seemed fairly ...
- 131
5
votes
1
answer
518
views
What does it mean by non-bonding p pi orbital?
In a paper by Peng et. al.,[1] I read about the valence band maximum of $\ce{TiO2}$ consists of non-bonding O pπ orbitals
... the valence band maximum (VBM) consists of non-bonding O pπ states
What ...
- 273
6
votes
2
answers
2k
views
Why are there only 14 types of Bravais lattices and not 28 when there are 7 types of unit cells and each can have four variations?
As the title suggests, I can't understand why certain kinds of variations (like Face-centred or Body-centred) are restricted to certain types of unit cells. An orthorhombic unit cell has Primitive, ...
- 317
0
votes
1
answer
272
views
Of 2-bromobutan-2-ol and trans-1,2-dimethylcyclobutane which is chiral as well as dissymmetric?
In an examination I was asked to determine the molecules which are chiral as well as dissymmetric. There were four options, and among them, two were achiral, as they had an improper axis of symmetry. ...
- 371
7
votes
1
answer
154
views
Why does twistronic 'magic angle' graphene have only 180-degree symmetry?
From Graphene superconductors may be less exotic than physicists hoped[1]:
Excitement rose earlier this year with the discovery of
superconductivity in a similar
system[2]:
three layers of graphene ...
- 1,795
3
votes
0
answers
137
views
Why does an improper rotation axis preclude chirality?
Can anybody prove that any molecule with an axis of improper rotation is nonchiral? I still do not understand why this is so, any proper mathematical proof or visualisation of a generalised molecule ...
- 39
0
votes
1
answer
582
views
d orbital irreducible representations in metal in ML4 model [closed]
In ML4 (Metal—4 ligands)model which has a square planar shape and D4h point group, what is the irreducible representation for the 5 kinds of d orbitals in the central metal?
10
votes
0
answers
141
views
Using symmetry and group theory arguments to explain iron(II) in a tetrahedral crystal field
I am trying to figure out how to explain $1s \rightarrow 3d$ spectroscopic transitions for $\ce{Fe^{2+}}$ in $T_\mathrm{d}$ symmetry. These transitions make up the pre-edge region in K edge X-ray ...
- 101
1
vote
0
answers
92
views
High symmetry points and x-coordinates
Is it possible to work out the x-coordinates related to high symmetry points?
The software I'm using doesn't provide me with that, so I was wondering if there is a way to manually figure it out, as I ...
- 11
0
votes
0
answers
444
views
How many stereoisomers are present in octahedral complexes of type MA3B2C?
Does $\ce{MA3B2C}$ type have optical isomerism or just geometric isomerism? I was told that it has three isomers, two cis and one trans. Are the two cis isomers optically active?
1
vote
0
answers
583
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 ...
- 21
1
vote
0
answers
18
views
Why does hydrogenation of this compound not result in a diastereomeric mixture? [duplicate]
In a question, this compound was given and it was asked:
"Hydrogenation of the above compound in the presence of poisoned Palladium catalyst gives?"
When I was answering it, I thought that ...
- 119
5
votes
2
answers
1k
views
Why is the base-centered orthorhombic crystal lattice a unique crystal system?
I'm having difficulty understanding why the base-centered orthorhombic crystal system is a unique crystal system. When I draw two base-centered orthorhombic unit cells next to each other there appears ...
2
votes
3
answers
432
views
Planes of symmetry of a molecule
Are we limited to use only xy, yz and zx planes to check for planes of symmetry of a molecule? Because I see a plane of symmetry in the following molecule through the two shown H atoms or OH groups. ...
- 31
1
vote
0
answers
48
views
electronic transition for polyenic molecules
I am having troubles with polyenes states symmetry.
I found an exercise on the pentadien, where they ask us to analyze the symmetry of the singlet excited states corresponding to:
State S1: π+ →π+
...
- 31
12
votes
2
answers
4k
views
How are there two C3 rotation axes in ammonia?
If we look at the character table for the $C_\mathrm{3v}$ point group (which $\ce{NH3}$ is an example of), we see that these are the symmetry elements ${E, 2 C_3, 3 \sigma_v}$ present in the molecule. ...
- 682
3
votes
1
answer
178
views
Solution of the Roothaan Equations of H2 by Symmetry Arguments
FWIW my background is in physics and maths, but I am just starting a chemistry PhD (the last time I took a chemistry class was high school). I have only some background in representation theory, and ...
- 141