Questions tagged [stereochemistry]
Applicable to questions about the spatial arrangement of atoms in a molecule and how they affect its physical or chemical properties.
638
questions
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Diastereomers or not
Why is the first one not a pair of diastereomers while the second is?
The only reason I could think of was in the first $\ce{Me}$ is the same as $\ce{CH3}$ that is same groups even though differently ...
-2
votes
0answers
64 views
Is nitrogen a stereocenter in amides? [closed]
Consider $\ce{CH_3CONH-CH3}$. Is the amide nitrogen a stereocentre? I know 2 factors that can affect the chirality: amine inversion and resonance. I don't know if they apply here.
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votes
1answer
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How to obtain optically pure mixture from racemic mixture
I recently studied stereo chemistry in school.All i know is that compound are optically active if they have no plane of symmetry and about the nomenclature we follow nomenclature.......
My questions
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6
votes
1answer
153 views
In the absence of a physical model, how can I use free software to visualize stereochemistry?
In a different question, the task was to turn a wedge-and-dash representation into a Fischer projection. This involved rotation of a fairly complex molecule - either as a physical model or a mental ...
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votes
0answers
29 views
Is nitrogen with 3 different substituents and lone pair a chiral center? Does it make the whole compound chiral too? [duplicate]
Is nitrogen considered a chiral centre or stereocenter when it has three different substituents attached to it along with a lone pair.
By definition LG Wade says
An asymmetric carbon atom is the ...
2
votes
1answer
93 views
Mechanism of three-membered lactone hydrolysis in base
I was reading up on the participation of neighboring functional groups and in the reaction below, I was wondering why hydroxide attacks the C–O bond instead of the carbonyl group of the lactone. ...
2
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0answers
33 views
Solvent shell collapse
In "advanced organic chemistry part A" book page:306&307 , the author uses the term 'solvent shell collapse' when talking about the reason for retention of conformation in tertiary ...
1
vote
1answer
58 views
ᴅ-amphetamine, ʟ-amphetamine
The following structural formula (source: Wikimedia) is labelled ᴅ-amphetamine:
A Fischer projection of this molecule would contain, I think, the following line:
$$\ce{H2N-C-H},$$
and I would have ...
10
votes
1answer
331 views
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 ...
0
votes
1answer
126 views
sp2 hybridisation of alkyl radicals causing formation of racemic mixture
What I know about $\ce{^{.}CR3}$ radical is that it has both $\ce{sp^2}$ and $\ce{sp^3}$ character but the $\ce{sp^2}$ character dominates and so the radical is $\ce{sp^2}$ in nature.
So, suppose we ...
10
votes
1answer
409 views
How is plane polarized light rotated by chiral compounds? [duplicate]
There are plenty of questions related to this topic on this site but no proper answer.
Can anyone please explain to me how plane polarized light is rotated by chiral compounds, and why it cannot be ...
0
votes
0answers
48 views
Which has a higher enol content between 4-Pyridone and Cyclohexa-2,5-dien-1-one?
I am new to organic chemistry but here is what I feel. 4-Pyridone will have a lower enol content as in its keto form it has higher resonance stabilisation due to the involvement of lone pairs on ...
4
votes
2answers
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Conversion of molecular structure into Fischer projection for compounds having more than two chiral carbons
Question
What is the Fischer projection of the given compound's enantiomer?
Answer
My attempt
I tried to solve this by first converting it into the Fischer projection of the given compound and then ...
1
vote
1answer
53 views
Assigning R/S configurations to Fischer projections of 3‐chloro‐2‐hydroxybutanoic acid
A question requires you to assign the R/S configuration for 3‐chloro‐2‐hydroxybutanoic acid:
In the answer, while assigning the configuration to carbon #1, apparently the group below is given the ...
1
vote
2answers
114 views
Is chirality absolute or relative?
While going through some questions on chirality and optical isomerism, I came across this compound:
Note that I have marked 3 carbons as $C_1,C_2,C_3$
Its obvious that $C_1,C_3$ are chiral carbons.
$...
4
votes
1answer
203 views
C₂ axis of symmetry in 1,3-dichloroallene
Is there an $C_2$ axis of symmetry in $\ce{Cl-CH=C=CH-Cl}$?
A $C_2$ axis of symmetry means that I should be able to rotate the molecule about an axis by $180^\circ$. But I would need a composition ...
2
votes
2answers
129 views
Why is biphenyl not planar? [closed]
I've seen in a lot of books that biphenyl is not planar. I don't know why that is because both the carbon are $\mathrm{sp^2}$ hybridized so it should be planar. Can someone explain it to me?
3
votes
1answer
113 views
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 ...
14
votes
3answers
632 views
Can geometrical isomers be enantiomers?
I have just been pondering upon the question above. I have found this example and I am sure they are enantiomers, but do they also count as geometrical isomers?
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votes
1answer
81 views
I need help with Cahn-Ingold-Prelog (boat conformation)
I need to decide if the chiral carbon (with the attached hydrogen) is in R-configuration or S-configuration. To be able to do that, I need to know which of the atoms are pointing backward, forward and ...
0
votes
0answers
49 views
E-Z system without a double bond
Can we apply E-Z nomenclature to geometrical isomers without a double bond. For example, can we use it for cis and trans isomers of 1,2-dimethylcyclohexane?
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votes
1answer
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Are the C1 and C3 carbons of cis 1-bromo-3-chloro-cyclobutane chiral?
I have tried to approach this from 2 directions:
The ‘official’ method my textbook gives, which gives the correct answer - They are achiral
It consists of going ‘priority-wise’ from the two carbons ...
3
votes
1answer
33 views
Total number of isomers formed on monobromination of 2-methylbutane
What is the total number of isomers formed on monobromination of 2-methylbutane (including configurational and stereoisomers)?
I tried working it out. However, I found only five:
According to the ...
0
votes
1answer
80 views
Optical activity of 3‐chlorobutan‐2‐ol
In the picture that I have uploaded, I have read that the given compound is chiral.
But on drawing the sawhorse structures (for better visualisation), I feel like the compound is symmetric about a ...
3
votes
1answer
70 views
Total number of stereoisomers of truxillic acid
Total number of stereoisomers of the compound will be:
This was a question asked in our mock test. I've tried by considering pseudo-chirality on the carbon atoms. But I don't know where to start.
I ...
3
votes
1answer
92 views
Which ethanol derivatives display the gauche effect?
How many of the following ethanol derivatives of the form $\ce{GCH2CH2OH}$ have a more stable gauche conformer compared to their anti conformer?
$G = \ce{F}, \ce{Cl}, \ce{OH}, \ce{NH2}, \ce{OMe},...
2
votes
1answer
175 views
What is the difference in dehydration of cis- and trans-1,2-cyclohexanedicarboxylic acid in anhydride formation?
Is there some required stereochemistry for anhydride formation? Do both of them form the same product, or does one not even undergo dehydration?
I looked up cyclohexane-1,2-dicarboxylic anhydride's ...
2
votes
0answers
43 views
Strains in conformations of cyclohexane
I know some the basic kind of strains that can exist in molecules namely Torsional strain (Vanderwaals' strain), steric strain and angle strain.
Is it possible to associate a particular type of ...
3
votes
0answers
20 views
Chemical shift difference methyl groups in 4-hydroxy-2,5-dimethyl-3-hexanone
Can someone explain why the NMR Spectrum of 4-hydroxy-2,5-dimethyl-3-hexanone shows a chemical shift difference for the methyl groups at the end? Why aren't the other carbons have a difference?
Below ...
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votes
1answer
84 views
MA3B3 isomers - is this same as meridional one? [closed]
I'm new to studying stereo chemistry. (Now I'm studying coordination complexes.)
In my class material and other some datas(from google), it says that there is two, fac and mer.
I want to know is ...
1
vote
2answers
87 views
How to check which compound will show optical isomerism?
So my teacher told that those compounds which have one or more chiral carbon present in them it will definitely show optical isomerism because it has an optically active stereoisomer, but there are ...
6
votes
0answers
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Is it possible to estimate the abundance of conformers from J values?
I have a system of two disubstituted cyclohexanes and I want to estimate the abundance/ratio of the two based on the J values and if possible, roughly estimate the difference in free energy.
To get ...
1
vote
0answers
78 views
Find stereo isomers of camphor
The compound given is camphor:
We have to find the total number of stereoisomers for this compound. Now I can see two chiral carbons so I thought the number would be $4$ but it turns out that there ...
0
votes
0answers
42 views
Converting Fischer formulas to Newman projections
How are line diagrams of molecules converted to their Newman projections? All I got from looking it up is that one may convert a Fischer formula to an eclipsed conformation directly, and that this may ...
-1
votes
2answers
65 views
Find the number of geometrical and optical isomers of 1,2,3,6-tetramethyl cyclohex-1,4-diene
The compound given to me is 1,2,3,6-tetramethyl cyclohex-1,4-diene.
The geometrical isomers for the following compounds are:
The isomer on the right can also be an optical isomer with its enantiomer....
12
votes
4answers
1k views
How is exact racemization possible? [closed]
A racemate consists of 50 % $d$ and 50 % $l$ forms of an optically active compound. But how can someone ensure exact 50% quantity comparing molecule by molecule? There will always be some difference ...
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votes
1answer
42 views
R-S configuration or Cahn-Ingold-Prelog configuration [closed]
How to assign R and S configurations in alkenes and more complicated structures ?
I know that the groups attached to the sp3 hybridized carbon is first prioritized by atomic number then we see the ...
3
votes
2answers
117 views
Number of optically active isomers of [Co(NH3)2Cl2(NO)(OH)]?
My Attempt:
Since Compound is of the form M[a2b2cd]
I got three optically active isomers of the form M[(ab)(ab)(cd)] , M[(ab)(ac)(bd)] , M[(ab)(bc)(ad)]
and since NO is a bidentate ligand, total ...
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votes
1answer
25 views
If a molecule with 3 chiral centers that are all R, is it the same as the S version? [closed]
Consider a molecule with 3 chiral centers all marked R. Is this molecule the same as the S version?
1
vote
0answers
43 views
Does orientation matters to this extent in reactions?
In the above question I know that the three reactions involved are $\mathrm{S_N2}$ reactions and therefore there shall thrice inversion of the substitute.
So, I got the solution for the MCQ as:
...
5
votes
1answer
185 views
Why is 3,6-dimethylpiperazine-2,5-dione optically active in spite of having a centre of symmetry?
I learnt in my chemistry class that if a molecule has an element of symmetry (either a plane of symmetry or a centre of symmetry), it will not be chiral and hence will not show optical activity.
My ...
0
votes
0answers
47 views
Are centre of symmetry(COS) and alternate axis of symmetry(AAOS) dependent on each other?
COS=Centre of symmetery
AAOS=Alternate axis of symmetry
Lets suppose a molecule has a COS. Does it need to have AAOS?
What about the converse? If a molecule has AAOS does it necessarily have a COS?
...
0
votes
1answer
91 views
A question about geometry of benzenetetrol
In the 3d conformation of 1,2,4,5 - benzenetetrol, how could i determine the direction to which hydrogen atoms of hydroxyl groups would point? and if there were tertiary butyl groups in positions 3 &...
2
votes
0answers
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Differences in efficacy of oxime reactivators in organophosphate poisoning
Compounds containing an oxime functional group, such as 2-PAM and obidoxime, are used in the treatment of poisoning with organophosphorus compounds. These oximes reactivate the enzyme ...
0
votes
1answer
90 views
Will the following complex show optical isomerism
So there is this question which asks whether the following complex
$\ce{[Co(NH3)4Br2]+}$
will show optical isomerism or not.
According to my knowledge it will show optical isomerism in cis ...
1
vote
1answer
907 views
Number of possible isomers (including optical/geometric ones) with C4H8O molecular formula [closed]
I found 32 isomers but I think I made a miscount.
Chain alcohols: 6, chain ethers: 5, and chain carbonyl compounds
(ketones/aldehydes): 3
Three-member ring alcohols: 7, three-member ethers: 6 (...
2
votes
0answers
90 views
Shortcuts for finding geometrical isomers
Our teacher provides us extra questions for pratice, so one of the questions was :-
Find number of products if following are reacted with excess $\ce{NH2OH}$ (hydroxyl amine):
Cyclohex -
(i) 1,4-...
1
vote
0answers
41 views
What is the priority order of the four groups?
I'm trying to figure out whether this is in R/S configuration....I thought it would be R since the groups seem to be decreasing in priority in the clockwise direction (since F has the largest atomic ...
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votes
1answer
45 views
Comparing different stereochemistry terms [closed]
What is the difference between:
Meso compound and an optically inactive compound
Chiral compound and an optically active compound
For all examples i have seen, chiral compounds were optically active ...
0
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0answers
34 views
Why doesn't anomeric effect predominate over steric effects in glucopyranose?
$\beta$-D-(+)-glucopyranose is more stable than $\alpha$-D-(+)-glucopyranose. Why is this?
I know that in $\beta$-D-glucopyranose all the hydroxyl groups are in the equatorial position and thus it ...
