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.
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How to pass a Plane of symmetry?
While passing a plane of symmetry through any compound inorganic or organic should it contain a minimum number of atoms or can it be passed without containing any atoms ?
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ligand pi system irreducible representation for trigonal bipyramidal transition metal complex
I am considering a D$_{3h}$ trigonal bipyramidal transition metal complex MX$_5$. I have found that the irreducible representation for the ligand s and $\sigma$ systems is 2A$_1'$+A$_2''$+E$'$. I ...
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Determining overtones bands of degenerate modes
I have a question of a more mathematical nature on the mathSE (Symmetric Direct Product Distributive?) that received a good answer, but I think an answer more oriented to chemists would be a useful ...
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How are these molecules chiral and achiral?
I always thought that a molecule couldn't be chiral if it had a plane of symmetry. Doesn't the chiral molecule here have symmetry diagonally across the OHs?
The achiral one doesn't look symmetrical ...
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Why are there no dihedral mirror planes in the D3h point group?
Consider the molecule $\ce{BH3}$, which belongs to the $D_\mathrm{3h}$ point group. Why are the three mirror planes in this point group labelled as $\sigma_\mathrm v$ instead of $\sigma_\mathrm d$? ...
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For two compounds that are symmetrical, why does the more compact one have a higher melting point?
In this post, I refer to two molecules B (Di-tert-butyl ether) and C (Dibutyl ether).
Wikipedia: Di-tert-butyl ether (B)
b.p. 107.2 C
m.p. - 61 C
...
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D3d point group matrices
I am trying to construct all the matrices for the point group D3d operations. I find that the matrices of E, i, S6, inverse of S6, C3, and inverse of C3 are easy, but I do not know how to construct ...
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Can a molecule be neither gerade nor ungerade?
Or can any molecular orbit always be written a linear combination of gerade and ungerade basis states?
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Rotovibrational selection rules for symmetric tops
The selection rules for symmetric top molecules are
$\Delta J = 0, \pm1$ and $\Delta K = 0$ for $K \neq 0$ (parallel transition)
$\Delta J = \pm1$ and $\Delta K = 0$ for $K = 0$ (parallel ...
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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.
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What system of nomenclature can I use to indicate the positions of specific kinds of atoms of a surface reconstruction?
I was reading a journal based on SiC reconstructions, and they seem to mention that every dangling bond in the $(1\times 1)$ unreconstructed Si face or the $(0001)$ direction bonds up with a Si adatom ...
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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 ...
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Is there a possible distortion of XeF6 from Oh point group to reduced symmetry?
Below the molecular orbital diagram for $\ce{XeF6}$ (from What is the molecular structure of xenon hexafluoride?)
I am trying to figure out if a distortion from $O_h$ can take place and to which (...
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How do I show that a transition is magnetic dipole allowed with group theory/symmetry?
I am taking an introductory course in symmetry and bonding and have so far learnt about SALCs and various point groups etc... one of my problems asks me to show a $\mathrm{^{2}T_{2g}\rightarrow\ ^{2}...
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What constraints are imposed on a wavefunction by the symmetry of the system?
As a follow-up to my answer here, I'd like to ask what exactly does it mean for a wavefunction to "respect the symmetry" of the system.
The original context is: immediately after ionisation of $\ce{...
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How is group theory (and matrices) used in symmetry operations? [closed]
I am a high school IB student. For my 2-year math course, there is an internal assessment called "exploration" which should be max. 12 pages long. The goal of this assignment is for students to ...
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Are there any non-Jahn-Teller type distortions?
My question is essentially, if ANY gradual type of deviation from a higher possible symmetric arrangement of the nuclei in a molecule is covered by the Jahn-Teller model.
More specifically I have in ...
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Enantiotopic hydrogens in cyclopropanone
Are the hydrogens that on the same carbon and those that are cis enantiotopic? And are they isogamous or anisogamous?
And will they anisochronous in a chiral environment NMR?
Isochronous - hydrogens ...
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In a molecular dynamics context, is the methyl rotation in propene a symmetric or asymmetric internal rotor?
In a prior question, I asked about the (a)symmetry of the potential energy surface of the methyl rotation of propene. In that context, the kinetic energy of the nuclear motions is of course assumed ...
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Does the methyl rotation in propene have a symmetric or asymmetric potential energy surface?
Depending on how one imagines the methyl rotation of propene to occur, it seems like it could exhibit either a symmetric or an asymmetric potential energy surface. If the $\ce{H2C=CH\! -}$ portion ...
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What is the point group of hexachloridotitanate(III)?
I found the answer to this question to be $D_\mathrm{3h}$ but I am not convinced. Can someone explain me with a diagram if possible and explain why it doesn't belong to the octahedral point group $O_\...
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Theoretical basis behind orbital correlation diagram for pericyclic reactions
When discussing pericyclic reactions, the Woodward-Hoffman rules allow one to predict whether a reaction will be thermally/photochemically allowed. This has been discussed in many questions on chem.SE,...
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What is the mathematical basis behind the Jahn-Teller effect?
Both first-order and second-order Jahn-Teller distortions play a very important role in chemistry.
It is often said that the Jahn-Teller effect is based on symmetry arguments, and hence nothing can ...
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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 $\sigma_v'$, $\...
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Nomenclature: equivalent atoms by single locant
Sometimes the IUPAC name is too verbose despite the structure's high symmetry. If we could use only the first locant of the ("topologically symmetrically") equivalent set of locants, and designate all ...
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What is the criteria for determining structure of a molecule?
Does the shape of the molecule depends on symmetry?
Why is the shape of dinitrogen trioxide ($\ce{N2O3}$):
(oxidation number of nitrogen atoms: +4, +2)
Instead of my proposal, which is much more ...
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Does Ni(H2O)6 have Oh symmetry or Th?
I optimized a geometry of $\ce{Ni(H2O)6}$ using quantum chemistry and got a molecule which is symmetrical for the $\ce{Ni-O}$ distances as shown
here:
In the literature it says that this complex has ...
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High Degrees of Symmetry in Molecules
I recently encountered a question on a test:
Substances whose molecules have a high degree of symmetry will have:
A. a low specific heat
B. a high melting point
C. a high heat of ...
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Relation between molecule symmetry and crystal symmetry
How much is crystal symmetry dependent on molecule symmetry?
Can one make any kind of inferences on the symmetry of the molecule looking at the symmetry of its crystal or the other way around?
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Biphenyl symmetry group dependence on torsional angle [closed]
What is the symmetry group of the biphenyl when the torsional angle between the phenyls is 20 degrees? What about when it is 90 degrees?
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What is the symmetry of the cuboctahedron (FCC metal)?
The background to this is that I've recently given a tutorial wherein we had to go through the determination of point groups for atoms in various lattices (BCC, FCC/CCP and HCP). BCC and HCP, I have ...
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Enantiomer or not?
My professor said that this compound is an enantiomer but I think it has a plane of symmetry and has no chiral carbons. Am I missing something ?
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Spectroscopy pyrazine molecule
Considering pyridazine and pyrazine molecules, I am asked to say if I can distinguish one from the other in a sample.
I supposed that is possible because pyrazine belongs to D2h and so it has the ...
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Potential wells and symmetry in absorption spectroscopy
In a course I am following, we are analyzing the potential wells in molecular absorption spectroscopy.
For molecules with more than one normal mode, we can study the potential wells involved in ...
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Symmetry and SALC: choosing coordinate basis
When we construct symmetry adapted linear combinations of orbitals (aka SOs) to build an MO diagram, we choose the z axis as the axis of highest symmetry and all other axis to make symmetry operations ...
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Determination of +/- reflections in sigma molecular term symbols
This page, which depicts the molecular term symbols for the $\ce{O2}$ and $\ce{O2-}$ (Edit: Mistaken on $\ce{O2-}$) molecules, perhaps best summarizes the full scope of my questions. In general, I don'...
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Equivalent Wyckoff position in different groups
I am not a chemist, I am a physicist, so please bare with me if what I am asking is rather obvious.
If I have two symmetry groups ($P4/mmm$ and $P\!-\!1$), is there a way to find their respective ...
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Is trans-1,2-dimethylcyclobutane chiral?
If we look at its mirror image about a mirror which is perpendicular to plane of the molecule, the two $\ce{-CH3}$ groups which are pointing upwards and downwards (implied by the wedge and the dash) ...
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Derivation of the Orgel diagram for octahedral d2 complexes
The Orgel diagram for a typical octahedral $\mathrm{d^2}$ complex is shown below:
(source: Kettle, Physical Inorganic Chemistry, p 146)
I understand that the right-hand half of the graph shows how ...
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Deriving the irreps of the d-orbitals under C3 and S6 operations in octahedral symmetry
Contextual background: I am trying to reproduce the symmetries in the graph on this page (MO diagram for $\ce{ML6}$ complex). I have reproduced the metal s and p orbital representations as well as the ...
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Identifying the C3, C4, S4, and S6 symmetry operations in the Oh point group
The Oh character table has ten symmetry classes. I am trying to identify them, but my stumbling block is in identifying the order of each class.
I will use this diagram as a reference, from Sydney ...
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How do I find the ground state term symbol for transition metal complexes?
I have a problem where I'm trying to match metal complexes with the proper ground state term symbol. I've tried doing a Google search and looking for a process, but haven't had any luck. I decided ...
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What is the rotational symmetry number used to calculate the rotational entropy from an ORCA frequency calculation?
The quantum chemistry software ORCA gives the following warning on frequency calculations:
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Are the $+\leftrightarrow+$ and $-\leftrightarrow-$ methanol rotational transitions dipole-allowed?
I am quite confused about the origin and justification of the rotational selection rules of methanol, and I would appreciate any help or references. As far as I understand, there are three irreducible ...
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Does trans-decalin really have a plane of symmetry?
My teacher told me that trans-decalin (see below) is achiral due to the presence of both, a centre of symmetry and a plane of symmetry. But I could not spot the plane of symmetry untill now. Can ...
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How do I determine the number and order of ligand orbitals?
I am trying to create interaction diagrams for transition metal species by reducing the representations for both $\sigma$ and $\pi$ ligand orbital sets and mixing them with the metal orbitals. The ...
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Are Meso compounds isomers? [duplicate]
According to my chemistry manual meso forms are "a particular case of of stereoisomers" implying that they are isomers, anyway right after this sentence the manual states that if you rotate the 2 ...
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Rule of mutual exclusion: is the converse true?
There is a "famous" rule in spectroscopy,1 that goes this way:
If a compound is centrosymmetric, then its normal vibrational modes cannot be simultaneously IR and Raman active.
and this is simple ...
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How to tell if a vibrational mode in benzene is IR and/or Raman active?
Consider the vibrational mode that corresponds to the boat-like bending of a benzene ring. Is it (i) Infrared active? (ii) Raman active?
This question was asked in an assignment in my college. ...
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Why do square pyramidal molecules have only two vertical mirror planes?
I would have expected molecules like IF5 to have 4, with two planes along the bond axes, and two planes bisecting the bonds. This is similar to how square planar molecules have four vertical mirror ...
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