Applicable to questions about the ability of a molecule (or class of molecules) to be superimposed on their mirror image(s).
2
votes
1answer
38 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
80 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 ...
-1
votes
0answers
32 views
Trouble visualising plane of symmetry
I am struggling to find out whether a compound has a plane of symmetry or not? Do you all visualise the structure or draw it? Please give me suggestions as it is really confusing how the plane has to ...
5
votes
0answers
71 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
404 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
51 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 ...
4
votes
3answers
129 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
78 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
54 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
132 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 ...
1
vote
2answers
85 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 ...
0
votes
0answers
36 views
R/S descriptors in long carbon chain
I'm trying to figure out how to assign R/S descriptors using a Fischer model without transforming it into a spacial one.
What I learned so far is the method to assign it for 'terminal' (I'm gonna use ...
2
votes
1answer
81 views
Chirality on Carbon of PVC molecule
PVC polymer is formed by a monomer CH2=CHCl.
Below picture is a section of PVC molecule. My question is:
Is there any chiral carbon centre in this polymer molecule.If yes, then how?
I have a source ...
2
votes
0answers
76 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?
9
votes
5answers
1k 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
467 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
72 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
56 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
124 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
30 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 ...
0
votes
0answers
29 views
Effect of interaction between lactic acid and glucose monohydrate on optical rotation
Would anyone know why I get double the expected optical rotation (OR) result for a solution containing D(+)-glucose and L(+)-lactic acid in comparison to a solution of D(+)-glucose on its own?
When I ...
1
vote
0answers
28 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
477 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
50 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
584 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
111 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
159 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
132 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
270 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
606 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
198 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
1k 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 ...
0
votes
1answer
152 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
130 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" ...
1
vote
1answer
576 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
571 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
148 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
580 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
204 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
232 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
1k 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 ...
0
votes
1answer
522 views
How exactly do we superimpose molecules while checking optical activity?
I am struggling with these type of questions where in some cases we rotate a molecule's mirror image by 180 degrees to check superimposability.
Like when checking any tetrahedral chiral compound, ...
1
vote
2answers
117 views
Why a particular enantiomer of a diastereomer shows affinity towards another? [closed]
A particular enantiomer can show affinity towards another enantiomer of another diasteromer eg. body receptors with chiral drugs, chiral stationary phase of chromatography etc.
But what's the reason ...
2
votes
1answer
222 views
Will the dextrorotatory and laevorotatory enantiomers always have a set of stereocenters with opposite absolute configuration?
I was faced with a question where the skeletal structure of of D(+)-glucose was given and I was asked to give the right structure of L(-)glucose. I noticed that the correct answer was the one where ...
1
vote
1answer
615 views
Is (2R,3S)-2,3-dichloropentane optically inactive?
Two confusing thing about (2R,3S)-2,3-dichloropentane:
The 2 stereocenters have opposite absolute configuration.
But there is no plane of symmetry.
So, is (2R,3S)-2,3-dichloropentane optically ...
0
votes
2answers
986 views
Monochlorination of 2-chloropentane and possible enantiomer products
I found a question to determine the number of possible chiral products of monochlorination of 2-chloropentane.So, first the products are (with possible number of enantiomers in the parentheses:
2,2-...
5
votes
1answer
271 views
Why left and right circularly polarized light have different index of refraction in chiral media?
This is a followup question of (Dependence of the angle of rotation on the wavelength of plane polarized light).
Ron's answer tells about the difference between left and right circularly polarized ...
4
votes
2answers
1k views
Dependence of the angle of rotation on the wavelength of plane polarized light
Wavelength difference is a big deal, I know. It can solely change the whole interaction between the chiral molecule & the light. But I am not sure what's the mechanism by which light of different ...
1
vote
2answers
1k views
How to assign priority groups of tartaric acid?
How do we assign priority groups of tartaric acid? Counting outwards from any of the chiral carbons we get the same atom.
0
votes
1answer
161 views
Why pyranosides do not mutarotate?
For mutarotation, at least one hemiacetal group must be present in the
sugar. Therefore, non-reducing sugars do not show mutarotation.
Why?
Consider the following reaction:
$$\ce{\beta-D{-glucose}...
