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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Conversion of a compound to a racemic mixture of enantiomers

I am studying for the GRE Chemistry and came across this question. I was not sure how to proceed with it. The answer is A but I do not know why. It has been a little bit since Organic chemistry, but I ...
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How Mabcd type co-ordinate compound exhibiting geometrical isomerism without having 2 identical identical ligand [closed]

According to my understanding ,2 co-ordinate compounds are considered as -cis or -trans form based on the spartial arrangement of 2 identical ligands but in the co-ordinate compound of Mabcd (square ...
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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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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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Chirality and number of sterioisomers

I have recently read that the number of sterioisomers in a compound having n chiral centres is $2^n$. (That is, if no meso form is present) The below question asks for the number of sterioisomers in ...
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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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How much can the photoisomerization wavelength of a molecule be redshifted by the addition of conjugation?

Adding electron withdrawing groups or conjugation will redshift the wavelength requiered to photoisomerize a molecule. However, how much can this really be used push the frequency down? What is the ...
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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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Is 2-bromobutane chiral?

My textbook says 2-bromobutane is chiral, but it look like it will form superimposition mirror image
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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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Posible Pair of Enantiomers

What is the number of possible enantiomers in monochlorination of 2-methybutane? My approach When $\ce{Cl2}$ is added to any alkane it prefers $3^\circ > 2^\circ > 1^\circ$. When it is being ...
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What are the CIP rules for cyclic substituents?

Here's what I read on Wikipedia (section "Cycles"): To handle a molecule containing one or more cycles, one must first expand it into a tree (called a hierarchical digraph by the authors) by ...
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In the Haworth projections of D and L glucose, is the stereochemistry at every carbon except the anomeric carbon just inverted?

I'm having a bit of trouble grasping sugar stereochemistry. Using glucose as an example, if you cyclize D and L glucose, is the stereochemistry at every carbon just inverted from the other form? ...
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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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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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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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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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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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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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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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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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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 ...
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3answers
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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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Ramachandran plot Phi(ϕ) Psi(ψ) dihedral angle Convention for Zero, Positive and Negative value- old and new

Update: possible duplicate: What is the precise definition of Ramachandran angles?. Question modified. G.N. Ramachandran et al, in their own work (PMC) (DOI), did not used phi(ϕ) and psi(ψ) as we use ...
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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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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 ...
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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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1answer
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Free rotation of sigma bonds; diastereomer formation; thermodynamic and kinetic products

For the reaction of 1,3-butadiene with DBr (D = heavy hydrogen), I found that several possible products could be formed. Kinetic products A pair of enantiomers is formed. One of the pi bonds ...
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1answer
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What is the reason for enantiomerically pure ketone reaction under acidic conditions giving a 1:1 mixture of diastereoisomers?

(b) Treatment of the enantiomerically pure ketone C under acidic conditions leads to a 1:1 mixture of diastereomers My thinking is that perhaps the explanation has something to do with the carbonyl ...
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2answers
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R & S Stereochemistry of an unsaturated ring system

Using the R- & S- nomenclature assign a configurational symbol to decalin 4-methyl (above the plane), 4-hydroxy (below the plane), 7-isopropyl (above the plane), 1,9 diene. (Numbering the carbons ...
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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. ...
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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 ...
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1answer
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How many stereoisomers of 1-methylidene-2-(4,4,6-trimethylhepta-2,5-dien-1-yl)-1,2-dihydronaphthalene are there?

What is the total number of stereoisomer of this compound? 2 4 8 16 As there is only 1 chiral carbon, and 2 out of 4 C=C double bonds that contribute to geometric isomerism (cis/trans), I think ...
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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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1answer
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Number of Stereoisomers of C(CHClCH3)4

I am having trouble understanding why the structure $$\ce{C(CHClMe)4}$$ has only five stereo isomers. According to my textbook, the stereo isomers correspond to the following series of absolute ...
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1answer
227 views

Number of stereoisomers of 3-ethylpent-1-ene-1,4-diol

I am trying to figure out how many stereoisomers this compound has. I know that there are two chiral carbon atoms, which allow $2\times2 = 4$ possible isomers. There is also a double bond which, as ...
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R/S configuration of bridging carbon in bicyclic system

I am trying to figure out the R and S configuration of bridging carbons in bicyclic systems. In the image, there are two bicyclic systems and depending on the position of the Br substituent, the R or ...
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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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Determining priority for a cyclic compound [duplicate]

I have problem in determining the CIP priorities in (S)-ketamine. What is the order of priorities for esketamine? Does the carbon bonded to the ring with chlorine have higher priority compared to the ...
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1answer
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Assigning E–Z configuration for alkenes with cyclic substituent groups [duplicate]

I was taught that according to CIP rules, we must check the priority order for the substituents. But how can we do the same for molecules with cyclic groups as substituents? How do we compare the ...
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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.
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How can a compound having a plane of symmetry be Chiral?

The compound( Given in the image below) is treated with $\ce{excess H2 in Pt}$. Here, (a) - The given compound. (b) - What the answer should be according to me. (c) - What the actual answer is: Q1 - ...
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How do we know the natural abundance of isotopes on Earth?

Without knowing the Average Atomic Mass or the percent abundance, how do we know that Protium is the most prevalent hydrogen isotope? What methods did scientists use to come to this conclusion? How ...
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When is rotation around double bonds to form cis-trans isomers allowed?

Textbook Question: The rhodopsin molecules in the retina contain a derivative of vitamin A called cis-retinal (Figure 6). On exposure to light, cis-retinal becomes an isomer called trans-retinal. ...
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stereochem of epoxide opening

Here I have an epoxide opening reaction, but I was wondering that when a nucleophile attacks, How would the stereochemistry work? I have 2 products I predicted and I'm not sure which one would be ...
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How do electrostatic effects effect facial selectivity in addition to cyclic oxo-carbeniums?

I was reviewing Dave Evans' notes for stereochemistry of C=X electrophile additions, and found this slide detailing differences in additions to cyclic oxo-carbenium electrophiles, but I don't ...
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How is chirality center defined for an atom with 5 substituents?

I understand that carbon atoms normally only have up to 4 substituents and the R and S chirality centers are defined for 4 substituents. Is there a similar convention of 'chirality' for an atom with 5 ...
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What are the limitations of the D, L system and the (+), (-) system for naming organic compounds

In organic chemistry, both the D, L system and the (+), (-) system are widely used, in conjunction with the modern (R, S) system. The D, L system names an organic molecule based on the direction that ...

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