Questions tagged [chirality]
Applicable to questions about the ability of a molecule (or class of molecules) to be superimposed on their mirror image(s).
168
questions
0
votes
1answer
37 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
votes
1answer
66 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....
2
votes
0answers
41 views
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 ...
0
votes
0answers
37 views
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
votes
2answers
153 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 ...
2
votes
2answers
102 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 ...
3
votes
1answer
58 views
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 ...
9
votes
3answers
279 views
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 ...
-1
votes
2answers
448 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 ...
0
votes
1answer
23 views
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.
0
votes
2answers
350 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 ...
1
vote
0answers
37 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 ...
4
votes
1answer
105 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
votes
0answers
150 views
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 ...
5
votes
0answers
115 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
votes
1answer
527 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
votes
1answer
68 views
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
votes
3answers
220 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
votes
1answer
292 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. ...
2
votes
1answer
99 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 ...
0
votes
2answers
303 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
votes
2answers
144 views
Identifying Meso compounds [closed]
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 up on how to identify ...
4
votes
1answer
240 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 ...
2
votes
0answers
89 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?
10
votes
5answers
2k views
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
481 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 ...
-1
votes
1answer
113 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 ...
-1
votes
1answer
134 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, ...
1
vote
0answers
254 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?
2
votes
0answers
44 views
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 ...
1
vote
0answers
34 views
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, ...
8
votes
4answers
661 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
votes
1answer
65 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 ...
1
vote
1answer
1k 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
votes
1answer
142 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
votes
1answer
265 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 ...
1
vote
0answers
171 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 ...
1
vote
1answer
350 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 ...
5
votes
1answer
662 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 ...
-1
votes
1answer
260 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
votes
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 ...
1
vote
1answer
354 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)....
0
votes
0answers
175 views
Difference between chiral and stereogenic centre?
I've seen in some books where they state all chiral centres are stereogenic centres, but not the other way around.
Is "chiral centre" related to only to optical isomerism and "stereogenic centre" ...
2
votes
1answer
1k views
Is a carbon chiral it two of its groups are cis - trans isomers? [duplicate]
For example:
In this image, the two groups sticking to a carbon are cis-trans isomers. So does that make the carbon chiral, exhibiting optical properties?
What if the two groups were both having ...
4
votes
0answers
927 views
In-vivo racemization of thalidomide
In 1961, thalidomide was first introduced as an over-the-counter cure for morning sickness. Pregnant women across the country began to take the drug, which worked well, but shortly after, babies began ...
-1
votes
2answers
244 views
Why does the optical rotation prefix differ for glyceraldehyde and glyceric acid when both rotate polarised light in the same direction?
When both glyceraldehyde and glyceric acid rotate the plane-polarised light in the same direction, why is glyceraldehyde assigned as D(+) and glyceric acid assigned as D(-)?
The first image shows the ...
1
vote
1answer
877 views
Why is a racemic mixture formed in the Diels-Alder cycloaddition?
Why is a racemic mixture formed in the Diels-Alder cycloaddition? I note that for both endo and exo products, either enantiomer can be formed. Why is this so?
5
votes
1answer
343 views
Help understanding this passage on optical activity
Other than mirror images, compounds having opposite configurations do not necessarily cause opposite directions of optical rotation any more than do compounds of the same configuration necessarily ...
1
vote
1answer
347 views
How does hybridisation affect an otherwise chiral centre? [closed]
In basic theory, a carbon atom with four nonidentical substituents attached, makes a chiral centre. Thus any molecule is chiral as long as it has a chiral centre (except meso compounds). I thought ...
12
votes
1answer
2k views
Does a chiral centre have to have 3 or 4 different groups attached?
I am seeing conflicting answers on the net
e.g.
A carbon atom is chiral if it has four different items bonded to it at the same position. (Wiki)
compared to
Stereocenter (chiral center): An ...
