The description of the symmetry present in molecules. Molecular symmetry is useful for explaining or predicting of a molecule's chemical properties.
Questions tagged [symmetry]
249 questions
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Are all cubic point groups encountered?
My symmetry lecture notes state that there are seven high-symmetry 3D point groups, which have more than one rotation axis of order greater than 2: $T$, $T_d$, $T_h$, $O$, $O_h$, $I$, $I_h$. I sometimes see them called the “cubic point groups”.
My…
F'x
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XeF4 - why are there only 2 dihedral mirror planes?
I started studying molecular symmetry and I became somehow confused about dihedral mirror planes. I found a definition, which says, that it is a vertical mirror plane, which bisects two $C_2$ axes.
But when I look at $\ce{XeF4}$ molecule, I see,…
Eenoku
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Does symmetry lower the energy of molecules?
Why does nature "prefer" symmetry? Why is symmetry energy-lowering? I keep hearing statements along the lines of this tossed around by chemists. Here are some…
Dissenter
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How does B2Cl4 have two perpendicular c2' axes?
I have been looking at the symmetry of $\ce{B2Cl4}$ and was cannot understand how it has two perpendicular $C_2'$ axes?
I understand it has a $C_2(z)$, $S_4(z)$ and two dihedral planes bisecting each of the $\ce{Cl-B-Cl}$ bonds. However my book…
RedPen
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Where is the mirror plane in 1-bromo-1-chloroethene?
I'm studying point groups in inorganic chemistry and having a difficult time understanding some of these concepts.
In my book, Inorganic Chemistry: Fifth Edition by Miessler, Fischer, & Tarr, I am presented with a table showing that $\ce{CHFClBr}$…
Melanie Shebel
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A and B irreducible representations?
In character tables, I know that A and B are one-dimensional irreducible representations, but what is the difference them?
And why do some character tables list them as A1/A2, B1/B2 and others have Au/Ag, Bu/Bg?
Patrick Robertson
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Racemic compound widely available
Can racemic compounds be found at the local drug store non-prescription? Where might one be found most readily/cheaply? Only one chiral center is needed. More may actually be unhelpful. The purpose here is to practice separating enantiomers.
Dale
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Primes in symmetry elements/operators
When classifying the molecules in symmetry point groups some non-principal rotation axes $C_2$ and some reflection planes $\sigma_v$ and $\sigma_d$ are primed or double primed, like $\sigma_v'$, $\sigma_v''$, $C_2'$ or $C_2''$. What determines which…
Jonatan Öström
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Symmetry C3V For MeCl
Methyl chloride belongs to the $C_{3\mathrm{v}}$ point group. This is because it has a $C_3$ axis down the $\ce{Cl-C}$ bond.
However what I do not understand is how it has three vertical mirror planes? It has three planes down each of the…
RedPen
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Procedure to assign the irreducible representation of a derivative operator
How can we assign an irreducible representation to a derivative operator like
$\displaystyle\frac{\mathrm d}{\mathrm dx}$ or the whole gradient operator $\nabla$ in a given point group?
Since the Hamilton operator can be assigned to the totally…
Hans Wurst
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Can the plane of symmetry for a compound be the plane of the paper?
1,4-Dichloro-2,5-dimethylbenzene is symmetric about the plane of paper.
I have never seen a plane of symmetry positioned like this. Would it be correct to call it a plane of symmetry?
Avyansh Katiyar
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Manually changing symmetry
I have two crystal structures, one in R3m and one in Cm symmetry. Both structures also differ in stoichiometric ratios, $ABC_4$ and $A_2B_2C_8$, respectively. Both structures look nigh on identical, with the exception of double the amount of atoms…
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no positive $+$ or $-$ or negative label for $\pi$ orbitals
I want to ask a question about the symmetry for $\pi$ orbitals.
We were learning today about the deduction of an MO diagram for a typical $\ce{M-M}$ system with $\ce{D_{\infty h}}$ and I was confused on the labelling of the $\pi$ orbitals.
When…
vik1245
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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
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 is no longer a plane of symmetry, neither isomer…
