Questions tagged [chirality]
Applicable to questions about the ability of a molecule (or class of molecules) to be superimposed on their mirror image(s).
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R/S chirality question
Consider [(1S,2S,4S)-bicyclo[2.2.1]hept-5-en-2-yl]acetic acid:
(Source: http://www.chemspider.com/Chemical-Structure.22823922.html)
According to the chemspider nomenclature, this has three S ...
3
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2answers
206 views
Link between centrosymmetry, dipole moment and chirality
What is the relationship between the three concepts in the title?
I know all centrosymmetric molecules are achiral, but not all achiral molecules are centrosymmetric. Thus, there are no molecules ...
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2answers
63 views
Is chirality a property of only molecules with exactly 1 chiral centre? [closed]
I have seen chirality being defined in a number of ways in terms of a molecule not being superimposable with its mirror image.
My syllabus has a statement: "know that optical isomerism is a result of ...
8
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2answers
424 views
d-Menthol vs dl-menthol: Does an enantiomer and its racemic mixture have different melting points?
I am checking out Wikipedia and it shows a different melting point (m.p.) for l-menthol $(\pu{42 ^\circ C}$ to $\pu{45 ^\circ C})$ vs dl-menthol $(\pu{36 ^\circ C}$ to $\pu{38 ^\circ C}).$
How is ...
4
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1answer
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QM9 dataset with chirality
I am trying to find chiral centers of molecules in QM9 dataset. Browsing their SMILES representation, I noticed SMILES yield using
datasets.get_qm9(GGNNPreprocessor(), return_smiles=True)
don't ...
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0answers
54 views
Chirality as atom feature
I have been reading some literature on molecular energy prediction using machine learning techniques and I have noticed that one of the input parameters in many of the available models is "chirality". ...
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56 views
Chirality in carbocations
The following compound is a carbocation.
Clearly, the given compound does not have any element of symmetry. The compound is non planar due to the presence of ethyl group. Thus it must be chiral. But ...
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Stereochemistry of C as non-chiral centre
When a C of a molecule is not a chiral centre, the spatial orientation of its substituent group doesn't affect its stereochemical specification, does it?
Ex:
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1answer
63 views
Priority of carbons attached to chiral group, one with double bonded oxygen, one with two oxygens [closed]
I have a chiral carbon. Two of the atoms attached to the carbon are other carbon atoms. One of those carbons has a double bonded oxygen and a methyl group attached. The other has two oxygens and a ...
3
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1answer
154 views
Cahn–Ingold–Prelog Rules, cyclic structures, and breaking ties
(3S,5R)-3-ethyl-5-methylcyclohex-1-ene
Does anyone know how one reaches the conclusion that the 5C is R? I tried using the Cahn–Ingold–Prelog priority rules but kept getting confused.
From chem....
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Chirality with tautomers
This molecule has 6 peaks in its proton NMR. I think this is due to the following tautomerisation:
However, I am unsure as to whether this molecule would be chiral, as it can freely interconvert ...
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Does a non-chiral substrate (2-bromo-2-methylpropane) also form two products via an SN1 mechanism?
If I have an alkyl halide, in which its tertiary carbon is non-chiral (for example 2-bromobutane), which reacts via an SN1 mechanism does it also produce 2 products?
I am asking because I know that ...
4
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2answers
200 views
Chiral carbon in carvone molecules
This is the structure of carvone, with the chiral carbon noted by *.
I don't understand why this is a chiral carbon, to my understanding a chiral carbon is a carbon with 4 different chemical groups ...
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2answers
232 views
How are these two molecules identical?
I can see that these compounds are identical as we have basically just done a 180 degree rotation of the molecules.
But if we go by the concepts of chirality, the carbons 2 and 4 are chiral centers ...
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1answer
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Is the existence of chirality center equivalent to chiral?
To make my question more clear, I want to ask two questions:
Is it possible for molecule to be achiral even though molecule has chirality center?
Is it possible for molecule to be chiral even ...
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3answers
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Why are carbons of Inositol chiral centers?
I was asked to draw all possible stereoisomers of inositol (1,2,3,4,5,6-cyclohexanehexol). To obtain the answer I had to assume that all six carbons of the molecule are asymmetric, which (bearing in ...
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2answers
582 views
Can we rotate a mirror image by any angle to check if it is superimposable? [closed]
A molecule is chiral when it is different from its mirror image, and achiral if it is identical to its mirror image. To check if the mirror image is identical to the original object, we have to check ...
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1answer
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How would I know that a compound and its isomers are enantiomers? [closed]
How would I know that a compound and its isomers are enantiomers? Considering the chiral carbons
Consider the compound is 2-bromo-2-chlorobutanedioic acid.
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2answers
710 views
Can sp2 hybridised carbon show chirality?
I know that any carbon to show chirality has to be bonded to 4 different atoms (groups of atoms). So a double bond is
considered as that the carbon is achiral. I learnt from my lecturer that ...
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0answers
38 views
Constraints on rate coefficients in chiral catalytic system
Consider some reversible chemical reaction in a closed system:
$$\ce{A <=> B + D} \tag{1}$$
where $\ce{A}$ is some input reagent and $\ce{B}$, $\ce{D}$ are some output reagents. Let's denote ...
6
votes
1answer
141 views
Use of axis of symmetry
Does an axis of symmetry determine chiralty?
Is axis of symmetry considered a true symmetry?
From the above two links, I read that a compound having axis /alternating axis of symmetry is NOT ...
3
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0answers
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X-ray structure analysis mirrored coordinates?
How to ensure, that X-ray crystallography structure analysis was done right to provide correct, non-mirrored atomic coordinates?
Example: Following Wikipedia image,
is generated from data taken from ...
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0answers
149 views
What compound has the strongest optical rotation of polarised light?
A question recently asked here whether compounds know to be chiral can have non-measurable optical rotations: Are there chiral compounds that don't rotate plane-polarized light?.
Apparently they ...
6
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1answer
581 views
Are there chiral compounds that don't rotate plane-polarized light?
I know that meso compounds have chiral centers but don't rotate plane-polarized light, and I know that there can be non-traditionally chiral compounds (e.g. ones with large substituents that prohibit ...
3
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1answer
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Assign stereodiscriptor to 4th carbon of 3-ethyl-2,4-dimethly-5-(propan-2-yl)heptane-1,7-diol
Here is the molecule. Clearly the 4th carbon is chiral. I have drawn the diagraph for it, but the exploratory pathways of the left and right chains are the same. So, the problem is that the two chains ...
5
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3answers
262 views
Can two lone pairs in different orbitals make a chiral centre?
Is it possible that if the two lone pairs in a molecule occupy different orbitals, then could this make the molecule chiral? What I mean is, suppose a carbon atom is attached to two different atoms ...
0
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1answer
610 views
How do we determine molecule chirality in these examples?
I understand that in the first example, the molecule is chiral as there is no symmetry. For the second and third example, I see no symmetry in the 3d conformation after twisting the right hand side. ...
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1answer
132 views
Why does a chiral carbon affect some hydrogen's hydrogen environment?
In the screenshot attached taken from Khan Academy's video (https://www.youtube.com/watch?v=p9B4s0N5yk8&list=PL0pJUwkI0YCZRYrgKqHXZ0XCIu11afbJ8&index=3) the thick pink dot refers to a chiral ...
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2answers
375 views
Fischer projections
Can somebody tell me how why they changed/choose the groups for vertical and horizontal lines. As far as I know the vertical lines represent group going away from us and horizontal depicts coming ...
0
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2answers
215 views
Identifying Meso compounds [closed]
(source: iupac.org)
I can't seem to understand why these compounds are meso compounds..... I don't see any plane of symmetry here. I have trouble identifying meso compounds so can you give me heads ...
4
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1answer
318 views
Are there chiral carbons in PVC polymers?
PVC polymers are formed from the monomer CH2=CHCl.
Below picture is a section of PVC molecule.
Is there any chiral carbon centre in this polymer molecule. If yes, then how?
I have a source of CAIE ...
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91 views
Non central chirality in cheminformatics?
What are compact cheminformatics structural representations that allow to deal correctly with axial chirality, such as in binaphthyl compounds or metal complexes?
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5answers
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If a chiral molecule reacts with an achiral molecule will the product be chiral or achiral?
My book says that a pair of enantiomers will react the same way with an achiral substance.
How is this possible? Does this imply that the product is achiral, even though the enantiomers are chiral? ...
6
votes
2answers
496 views
Do you assume undrawn hydrogens are pointing away from you when determining R/S?
When determining R/S of stereoisomers, the group with the smallest atomic number needs to be in the back (dashed line). But if no group attached to a chiral center is drawn in dashed line, do we ...
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1answer
141 views
Twisting stereoisomers with rings to determine R/S [closed]
I know that if the smallest atomic number group is not in the back, we can twist the molecule so that it is in the back and then determine if it is R/S (Left image). But if the chiral center is ...
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1answer
195 views
Stereogenic Center Question
In cholesterol, I don't understand why the two points I circled are stereogenic centers. Isn't the left carbon attached to an OH, H, CH2, and CH2? And isn't the right carbon attached to CH, CH2, CH, ...
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298 views
Why can tertiary amines not show chirality?
Why is a tertiary amine with three different substituents not chiral? Doesn't the lone pair represent a fourth, different substituent?
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0answers
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Prediction of enantiomeric excess through kinetics
Suppose we have a reaction such as the one represented above. Is there a method to estimate enantiomeric excess of the product if the rate constants are known and the product does not isomerize (and ...
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Readings about chiral resolutions at the undergraduate level
Does anyone know of a resource which clearly explains the scientific theory and experimental methods involved in chiral resolutions?
I have access to the American Chemical Society, Tetrahedron, ...
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4answers
809 views
Mismatch of plane of symmetry vs Gold Book's definition for a pseudochiral carbon
Here is pentane-2,3,4-triol:
At first glance, without deciding the configurations at each chiral carbon, we can clearly see that this molecule has a plane of symmetry, perpendicular to the plane of ...
0
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1answer
95 views
What does it mean if I am unable to write RS configuration for a compound?
We had to write all possible optically active monochloro derivatives of 2-methylbutane.
I was unable to write RS configurations for 1 and 3, since they have carbon atoms with more than one same groups ...
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1answer
2k views
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 ...
0
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1answer
165 views
Are bi-cycles chiral molecules?
I was studying how chirality influences the diastereoselectivity of reactions when I saw 1,4-dihydro-1,4-epoxynaphthalene.
I determine chirality by looking for C with 4 different groups. I see 2 C ...
6
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1answer
319 views
How is the cavity of a cyclodextrin chiral?
I am studying the host-guest chemistry of cyclodextrins with achiral aromatic molecules, and I found out that a useful way of studying them is by induced circular dichroism spectroscopy. This ...
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0answers
192 views
Is methyl phenyl sulfoxide optically active? [duplicate]
I am concerned about the stereogenic centres. But in this compound there is no chiral centres present. Sulphur is $\mathrm{sp^2}$-hybridized, so it cannot be chiral anyway. But I can see there is no ...
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1answer
386 views
Is center of symmetry only valid for symmetric substituents?
The given compound is optically active. Initially I had reasoned that the compound has center of symmetry( two xylene groups across each other). Why doesn't it have a center of symmetry?
Source: MS ...
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1answer
712 views
Why can't we rotate a carbon while checking for chirality?
If I were to rotate the front carbon clockwise by $60^\circ$, it would become achiral. But my text book says that it's chiral. Is it that rotating an individual atom about a sigma bond changes its ...
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1answer
280 views
Chiral Centers and Stereochemistry
I was just wondering how many chiral centers this molecule has. This question might be a bit simple but I was especially confused by the bottom left "chiral center" that is bonded to a wedged ch3 and ...
2
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2answers
3k views
How to assign priorities around the asymmetric carbon with its substituents having multiple bonds?
How do I assign priorities to substituents with triple bonds?
If we take a look at the molecule above, the atom directly bonded to the asymmetric center is carbon for all three substituent.
Moving on ...
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1answer
402 views
Is Inositol chiral or achiral?
I thought Inositol was clearly chiral since it has 6 asymmetric C atoms. But friends of me argue that it is achiral and i've found websites say the same (http://bip.cnrs-mrs.fr/bip10/Inositol-EJB.pdf)....
