Questions tagged [stereochemistry]
Applicable to questions about the spatial arrangement of atoms in a molecule and how they affect its physical or chemical properties.
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How are these two enantiomers?
I was wondering how these two chair conformations are enantiomers, because they do not seem to be mirror images of each other. The molecule on the left undergoes a ring flip to achieve the ...
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Why is C-S-C bond angle in thiirane so small at 48.5 degrees?
Why is the C-S-C bond angle in thiirane (48.5 degrees) so much smaller than C-O-C bond angle in oxirane/epoxide (60 degrees).
Source: https://coek.info/pdf-three-membered-ring-heterocycles-.html
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Isomer only appears in carbon compounds? [closed]
Isomer is a property that appears only in carbon compounds?
Is it the property of an optical isomer that appears only when carbon forms a tetrahedral structure?
Can other atoms come to the center of ...
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Can a Cis alkyl epoxide originate from a halohydrin and does the stereochemistry of halohydrin determine Cis/trans isomerism
Does the stereochemistry of a given halohydrin determine the outcome of the epoxide being either cis or trans. for example if (2S,3R)-3-Chloro-2-butanol is subjected to basic conditions is there a ...
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1answer
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Why total stereoisomers is 1 even if no geometrical isomers and optical-isomers are present [closed]
Let's for example take the complex structure type $\ce{MA_6}$, What will be the Total number of Stereo-isomers (=[Geometrical-isomers]+[optical-isomers]).
My effort was that There will be no G.I and ...
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How do chiral compounds rotate plane-polarised light? [duplicate]
I understand what decides if light is rotated but the exact mechanism through which it happens is still unclear to me.
Could anyone explain the nature of the interaction between a specific chiral ...
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90 views
Total number of Isomers of [Co(NH3)5(NO2)](NO3)2 [closed]
I encountered this question in my country's Chemistry textbook of class 12. No solutions are published, but the answer given at the back states - "There are 10 possible isomers. (Hint: There are ...
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Prochirality and major/minor products
I got the following exercise question on configurations, which the textbook does not have an explanation that matches this question, so could someone please tell me whether my attempt is correct or ...
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For a structure of a compouund optically active, what is the number of stereo isomers if no geometrical isomers are present?
Suppose for example the compounds $\ce{M(AA)3}$ and $\ce{M(AA)3bc}$, with $\ce{M}$, the central metal atom and $\ce{AA}$, a bidentate ligand.
What is the total number of stereo-isomers of both?
I was ...
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Are these two molecules enantiomers or diastereomers?
I had a long discussion with my professor about these two molecules, and we both agreed to do some of our own research and reconvene. These two molecules appear to be non-superimposable mirror images ...
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1answer
55 views
Number of enol forms of acetylacetone
Here is what I tried:
These are the two enolic forms that I could make. So according to me, the total number of distinct enol forms of acetylacetone is $2$. But the answer is 3, what am I missing?
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Converting Newman projection to dash and wedge structure
I want to convert the following Newman projection to a dash and wedge structure but the examples I've seen online are with simple molecules with methyl groups on the side.
I wanted to show the long ...
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2answers
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Why is the chirality center in (1R, 2S)-2-fluorocyclopentane-1-carboxylic acid 1R and not 1S?
I'm confused why the chirality center in (1R, 2S)-2-fluorocyclopentane-1-carboxylic acid, is 1R and not 1S.
I'm personally think that the carboxyl carbon at C1 should have a higher priority than the ...
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88 views
Is syn addition possible with Br2? [closed]
How is this reaction correct? I have studied until now that with $\ce{Br2}$ only anti-addition takes place.
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Sn(II) compound stereoselectivity in aldol reactions
In "advanced organic chemistry: part B" fifth edition, page:130, the authors state that chiral proline-like additives to Sn(II) compounds can further increase stereoselectivity of aldol ...
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(How) can a reaction be both stereoselective and stereospecific?
From what I have learnt, stereospecific and stereoselective reactions are defined as follows -
Stereospecific - The stereochemistry of the reactant dictates the stereochemistry of the product. Thus, ...
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1answer
43 views
Separation of Racemic Mixture
In the racemic mixture below, if it is reacted with Mosher's Acid Chloride, it would form X and Y. Can I ask why my book state that X and Y are not enantiomers and thus can based on differences in ...
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Stereochemical relationship between the given compounds
Are the given compounds enantiomers or diastereomers? Or are they identical? The compound is trans-1,2-dimethylcyclobutane:
My reasoning is that they are identical. They are not mirror images, and on ...
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1answer
178 views
The total number of stereoisomers of 1,2-dibromo-3,4-dichlorocyclobutane
I tried writing all the geometrical isomers for 1,2-dibromo-3,4-dichlorocyclobutane, and then saw if they were optical or not. And I am getting the answer as 10:
However, the given answer is 8. I can'...
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1answer
78 views
Identify E/Z Configuration
[(2E)-4-ethylhept-2-en-3-yl]cyclopropane why it is named E
Where according to cahn ingold prelog rules At left side Methyl is prior
and on the right side the butane should be prior than cyclopropane
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1answer
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Determining R-S configuration with lowest priority groups in plane of paper
I was studying R-S nomenclatures and determining configurations of molecules when I came across a certain problem, which had the 4th priority group on the plan of paper (not on a dash or wedge)
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1answer
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stereoselectivity in aldol reactions
in "Advanced Organic Chemistry, part B" fifth edition book, page:103, the authors compare between aldol reactions where 1-substituted nucleophile is used. They stated that when the 1-...
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Why are glyosidic linkage of glucose and fructose rings often occurring at the 1' and 4' prime positions?
Here are some example combinations from my textbook:
In all of these combined products, the reactive centres seem to be the carbon at first position/ fourth position from the oxygen in priority. Is ...
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1answer
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Of 2-bromobutan-2-ol and trans-1,2-dimethylcyclobutane which is chiral as well as dissymmetric?
In an examination I was asked to determine the molecules which are chiral as well as dissymmetric. There were four options, and among them, two were achiral, as they had an improper axis of symmetry. ...
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Confusion in D/L nomenclature [duplicate]
With regard to carbohydrates, it is known that in a Fischer projection, if the $-OH$ group is on the right side of the lowest priority asymmetrical (chiral) carbon, then we name it as D and if it is ...
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Chirality of conformations of butane
I have read that the conformations of butane are as follows:
I came across a question about number of chiral conformations of butane.
My Attempt :
The total or fully eclipsed is achiral because it ...
3
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1answer
101 views
Confusion in R/S Nomenclature and Chirality [closed]
I have many confusions regarding optical isomerism:
What is the use of the R/S nomenclature? I understand that it is used to distinguish between the different spacial arrangements that are possible ...
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2answers
162 views
How many stereogenic centers exist in the atropine?
I'm pretty sure that both C bonded to N are stereogenic centers. I don't know about the others, any help? Is this correct?
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How do molecules with opposite rotational photoisomerization bonds behave? [closed]
If a molecules bond change upon isomerization with the respective bonds straining the molecules as they orient themselves opposite from each other, would the molecule undergo some kind of ...
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1answer
666 views
Does 1,4-dimethylcyclohexane have a chiral center?
My textbook says that 1,4-dimethylcyclohexane (cis or trans) does not have a chiral centre, since two groups on the tertiary carbon (that are the part of the ring) are identical, and thus the compound ...
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1answer
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Why is [M(AB)2] a geometrical isomer?
Our teacher told us that for coordination number 4 and tetrahedral shape $\ce{[M(AB)2]}$ doesn't have a plane of symmetry, so it shows optical isomerism.
What if we take a plane passing through the ...
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1answer
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How many conformations are possible for ethane?
I am talking on the basis of observations made on the Newman projection of ethane.
According, to the various sources, that I found on many websites, the number of conformational isomers are 2. They ...
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1answer
217 views
Is the SN1 reactions stereospecific or stereoselective? [duplicate]
In the SN1 reaction, the product show retention and inversion. Since one of them is major unless it forms a racemic mixture, does it mean that the SN1 reaction is stereospecific?
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Determining if the product would be cis or trans after an anti elimination on fischer projections
I find these kind of problems really confusing for some reason, but I saw a way on the web and tried doing it that way:
I considered the basic Fischer operations (Vertical: Below the plane of paper, ...
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1answer
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Could Gaussian or Spartan software determine stereoisomers from conformational landscape of a molecule alone?
I read that, on some papers, conformers were generated by stereoconfiguration of the molecules and from there, they evaluated stability of each stereoisomer in terms of free energy differences between ...
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1answer
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How do I label stereogenic centers R or S when there are 3 bonds in the plane and 1 bond coming out?
I need help with question (d). I labeled the O the first priority, then the C that's bonded to an O the 2nd, and the C above that is attached to 3 other C's the 3rd priority. So, I ended up getting S, ...
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Labelling of molecular motor isomeric forms as trans and cis
I am reading Koumura et al. (2002), a paper about molecular motors. It contains this figure:
Being an absolute layman when it comes to naming my molecules I'm a little confused as to why the left ...
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How do you know if a compound with only one stereogenic center is trans or cis? [closed]
I understand that both of these compounds are R but I do not understand why A is trans and C is cis.
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1answer
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D and L configuration of monosaccharides
I got this question in the last week's test from Organic Chemistry.
I am a bit confused in assigning D and L configuration.
Help me understand the topic of D and L configuration and help with this ...
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2answers
836 views
Why do Enantiomers have different chemical properties with optically active reagents?
As I understand Enantiomers have similiar physical properties but they do show different chemical properties with optically active reagents. This point is something which I am not able to logically ...
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3answers
385 views
Chiral center or not? Similar substituents, but still two possible structures!
As far as I know, the central carbon shouldn't be a chiral center because it has two identical substituents. And yet, these two compounds should be different from each other.. Is it possible to denote ...
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Does this molecule show cis-trans isomerism? [duplicate]
I want to find if the above molecule shows cis-trans isomerism, per an assignment. I am assuming that such isomerism, if present, will be shown by the substituted chlorines.
It seems clear to me that ...
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0answers
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How does optical activity work? [duplicate]
I have learnt that chiral molecules are able to show optical activity; that is, they are able to rotate plane polarized light by some angle.
But how does it actually happen? Won't the orientation of ...
4
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1answer
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Why is the A-value of methoxy group lower than that of the hydroxyl group?
I am studying conformational analysis of monosubstituted cyclohexane. "A-value" refers to the energy difference between conformers with substitutent in equatorial (more favored) and axial ...
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Stereoisomers of 1,3,4,6-tetramethylcyclohex-1,4-diene
How many stereoisomers are possible for following compound (1,3,4,6-tetramethylcyclohex-1,4-diene)?
My Approach
the 1,4 methyl groups lie in the plane, whereas 3,6 are possible chiral centers. ...
3
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1answer
366 views
Odd/Even swap rule for chiral compounds in stereochemistry
I had this question asked in my exam, where I was supposed to find if this pair is a diastereomer:
Now, I have learnt this rule where: Making odd number of swaps in a molecule means they both are ...
3
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1answer
226 views
R or S configuration?
The respective configutations of a and b are...?
I tried to find the answer for a (for me is: 2S, 3S) but I'm not sure of my results, can someone help me?
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Does PubChem have stereocenter location data?
I have spent the last couple of days learning to navigate, find useful information and use the download service on the PubChem website. One of the pieces of information you can find is a stereocenter ...
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2answers
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Diastereomers - cyclic compounds [closed]
Why in this problem there isn't a diastereomer with the $\ce{-CH3}$ in the back (dash) and the $\ce{-CH2CH3}$ in front (wedge)?
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1answer
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Enantiomers and diastereomers [closed]
I don't understand why on the problem a. B and C are enantiomers, while on the problem b. B is identical to the last molecule.