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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questions
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Book/article recommendation for isomerism in coordination compounds
This topic is really weak for me. I am aware of the basics but I face difficulties in questions regarding number of sterioisomers for a given compound. I usually mess up the optical isomerism part(...
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1answer
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Number of Stereoisomers for Terpin
Terpin (4-(2-hydroxypropan-2-yl)-1-methylcyclohexan-1-ol) has two $\mathrm{sp^3}$ carbons with different substituents on a cycloalkane, so it has two cis-/trans-isomers, and from what I was taught, is ...
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How to apply the $parvo/amplo$ akamptisomeric stereodescriptors to this bicyclic system?
I'm looking for examples of akamptisomerism[1].
I'm try to find simple molecules able to (theoretically) show this kind of isomerism.
I thought about the isomers of (2R)-2-methyl-9-oxabicyclo[3.3.1]...
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How does compound (a) have R-stereochemistry at both chirality centers? [closed]
How does compound (a) have R stereochemistry at both chirality centers? It looks like the stereochemistry at C-2 is S-configuration. Also, what is the priority for the substituents on C-3?
https://...
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Cis/trans with alkene substituents on cycloalkanes
My chemistry book is saying that the double bond indicated by the red arrow can generate cis/trans isomers:
I don't understand how this can be so, as you need to use E/Z priority rules in this case. ...
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Optical isomerism in spite of plane of symmetry ..?
Shown above is an octahedral coordination complex and it's mirror image. The complex has a plane of symmetry (shown in the left diagram, a diagonal plane passing through bottom left and top right ...
2
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1answer
59 views
What is the number of stereoisomers for hex-4-en-2-ol?
For the following compound, find
Total number of stereoisomers
Number of optically active stereoisomers
Total number of fractions on fractional distillation of all stereoisomers
...
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1answer
35 views
Assigning Cahn-Ingold-Prelog priority numbering rules for 2 groups
I was asked to draw the perspective formula of
$$\ce{(3R,4R)CH2=CH-CH(CH3)-CH(CH3)-CH2-CH3}$$
Then I had to assign priority between the two groups:
$$\ce{-CH=CH2}$$
and
$$\ce{-CH(CH3)-CH2-...
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Diastereoselectivity of the Pauson Khand Reaction
I hope someone may help me. I don‘t know how to determine the diastereoselectivity of the product of the Pauson Khand reaction in generally.
In the following I’ve got 3 practice examples,however in ...
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Enantiomeric excess catalysed
Enantiomeric excess is defined as
$$ee = \frac{[R]-[S]}{[R]+[S]}$$
I found this problem in an IChO paper:
"When using the enantiomerically pure (BINOL)Al(OiPr) as a catalyst for reduction of ...
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1answer
45 views
How a plane of symmetry makes compounds lose their optical activity
I understand that if a compound has a plane of symmetry it loses its optical activity, it is very easy to understand this when we have four different substituents on a single carbon atom but when we ...
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2answers
109 views
Is there any mathematical or logical proof that carbon with 4 different groups would be chiral?
In chemistry; chirality is generally defined in 2 ways.
Lord Kelvin's definition: "I call any geometrical figure, or group of points, chiral, and say it has chirality, if its image in a plane mirror,...
1
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1answer
34 views
When to permute two times to find optical configuration [closed]
I'm learning about S and R configuration, and I know that in case where the 4th substituant is not behind we should permute it with the one which is behind. then we find the new configuration and use ...
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38 views
Confused about inversions in $S_N2$ Reaction
I just learned that in $S_N2$ reaction there is an inversion of configuration. I thought that it is a change of $R$ to $S$ and vice-versa. But that is wrong as mentioned in this answer.
While I was ...
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1answer
102 views
Number of stereoisomers of polysubstituted cubane
The molecule given below is a substituted cubane.
a) How many stereoisomers exist for this molecule?
b) How many pairs of enantiomers are possible?
How do I calculate the number of ...
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0answers
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Finding out more stable conformer via molecular orbital interaction
Out of these two, which one is more stable? I'm unable to imagine the orientation of the lone pairs of O and ABMO of C and Cl bond.
Any tips to tackle these kind of problems?
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2answers
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Number of sterioisomers of 2,3,5,6-tetrachloroheptane [closed]
The answer given by Himanshu Pandey in the book Advanced Problems in Organic Chemistry, Chapter Isomerism, Page 76 is 10. But by calculating using the fundamental principle of counting and by viewing ...
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Stereochemistry of C as non-chiral centre
When a C of a molecule is not a chiral centre, the spatial orientation of its substituent group doesn't affect its stereochemical specification, does it?
Ex:
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30 views
Name of the intermediate in between phosphono and phosphonato group
$\ce{R-PO3^2-}$ is called a phoshonato group (https://www.ebi.ac.uk/chebi/searchId.do?chebiId=30931)
$\ce{R-PO3H2}$ is called a phosphono group (https://www.ebi.ac.uk/chebi/searchId.do?chebiId=48108)
...
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1answer
400 views
Which of the Following is Optically Active?
Which of the Following is Optically Active?
I understand that for a compound to be optically active, it needs to be chiral and not have any planes of symmetry. I know 1 is symmetric, but I am ...
3
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2answers
107 views
Number of stereoisomers of trisubstituted cyclopentane
When 4-methylcyclopent-1-ene reacts with bromine, then 1,2-dibromo-4-methylcyclopentane forms. And I am stuck on determining the amount of stereoisomers that can form as a result.
1,2-dibromo-4-...
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2answers
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Why do chiral biological molecules only exist as one enantiomer? Does it have any advantage?
Why is it that chiral biological molecules are enantiomerically pure? The other enantiomer would have the same reactivity, and the only difference is their angle of rotation of plane polarized light. ...
3
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2answers
236 views
Number of optically active compounds among the products of ozonolysis
The number of optically active compound(s) obtained upon complete ozonolysis of
the following optically active compound is
In the question, I broke all the double bonds and added a $\ce{-CHO}$...
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1answer
92 views
How many products does this reaction yield?
How many products can we get from the monochlorination of 2,4-dimethylpentane including stereoisomerism? I have seen someone say that it yields 3 structural isomers one of which has two enantiomers ...
4
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1answer
238 views
Why does only the cis-isomer of potassium dioxalatodiaquochromate(III) form?
A friend of mine performed a standard synthesis reaction of potassium dioxalatodiaquochromate(III) by adding potassium dichromate to ethandioic acid dihydrate and a little water. The synthesis ...
5
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1answer
174 views
Synthesis of an epoxide from 1,2-diol
Why is there no formation of epoxide when the two OH-groups are on different planes? I do understand the epoxidation mechanism. However, I would be grateful if someone cleared the specific ...
3
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1answer
64 views
Can someone explain 3‐(propan‐2‐yl)cyclohex‐1‐ene forming a carbocation?
Can someone explain this one, especially the formation of the secondary carbocation (in the solution)?
Solution:
After the electrophilic attack by $\ce{H+}$ on the π bond, I had expected the ...
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1answer
76 views
How many dipeptides are possible by the reaction of glycine and alanine?
How many dipeptides are possible by the reaction of glycine and alanine?
Glycine has no chiral centre. Alanine has one chiral centre.
The products are alanylglycine and glycinylalanine (I not sure ...
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1answer
95 views
What are the isomers of a complex having a structure of M(AB)2C2?
Our instructor have us answer an isomerism problem of a crystal structure that has a form of $\ce{M(AB)2C2}$. I keep getting 9 isomers, which includes the optically inactive isomer, and my peers and I ...
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2answers
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What is the mechanism of the reaction of ethyl prop-2-ynoate to ethyl (2Z)-2,3-dibromoprop-2-enoate?
It's really weird for the product is 99％ Z-comformation?
Please tell me why?
This reaction can be found in scifinder.
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1answer
50 views
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 ...
3
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1answer
130 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....
5
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1answer
76 views
Why don't ionic compounds show stereoisomerism?
When I was reading about crystalline nature of ionic compounds, I came across the statement that ionic compound doesn't show stereoisomerism. What does that mean and can anybody explain the reason ...
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2answers
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Optical activity of (1r,3R,5S)-3,5-dimethyl-4-methylidenecyclohexan-1-ol
Could anyone explain why compound L is not optically active?
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Reactivity of Grignard reagent
I had the following question at an exam:
What is the fastest reacting compound towards nucleophilic addition with Grignard reagent?
(a) Acyl chloride
(b) Aldehyde
(c) Ester
It is ...
2
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1answer
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FMO analysis of the [3,3] Sigmatropic reaction regarding geometry. Is it accurate?
While studying the reasons behind the stereospecificity of [3,3] Sigmatropic reactions, I ran into an image portraying both possible transition states for the reaction: The Chair TS and Boat TS. The ...
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2answers
981 views
How to convert wedge–dash structure into Fischer projection? [closed]
I am very confused when a compound with more than one chiral centre is given. How to find whether the two compounds are enantiomers or diasteromers?
Please also explain how to convert more than one ...
5
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1answer
175 views
The maximum no. of isomers (including stereoisomers) that are possible on mono-chlorination of the compound: 3,3-dimethylpentane is?
The maximum no. of isomers (including stereoisomers) that are possible on mono-chlorination of the compound: 3,3-dimethylpentane is?
The answer given is 5.
My working: The fourth carbon is chiral ...
2
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1answer
39 views
Stereochemical dichloride treatment [duplicate]
In this question there is no inversion in A to B, but there is one in C to D. I feel like this must be due to the lone pairs on the $\ce{S}$ (in A) being able to open the ring, whereas this isn't ...
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Retention of configuration in Hofmann rearrangement
Why is there a retention of configuration in Hofmann bromamide degradation/Hofmann rearrangement?
I would think that there should be an inversion of configuration due to the migration of alkyl group ...
2
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1answer
141 views
Is the -OCH3 group bulky?
Our teacher told us that $\ce{OCH3}$ is a less bulky group when compared to other bulky groups like $\ce{CH3}$, $\ce{NO2}$ etc. Is this true? If yes, why?
5
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1answer
103 views
Cyclohexane derivative formation of carambolaflavone using a Lewis acid catalyst
The scheme below summarizes the results from a study into the optimum conditions needed for a key step in the synthesis of the proposed structure of carambolaflavone, a natural product that has ...
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Path to take when labeling R/S
I'm trying to find the R/S for the carbon marked with the asterisk. As I branched out to from the asterisk carbon to the red carbons, the methyl group has the 3rd priority (with the hidden hydrogen ...
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1answer
160 views
Planarity of given molecules in all conformations
Which of these have all its atoms in one plane in all the possible conformations (if any):
A) buta-1,3-diene
B) but-1-en-3-yne
C) $\ce{CH2=C=O}$
D) $\ce{CH2=C=CH2}$
While I was ...
3
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1answer
50 views
Would Z and E isomers show different optical activity?
Consider this compound, which is in E configuration and that red asterik denotes the chiral carbon. If I were to somehow cause the E-configuration of the alkene part to Z-configuration keeping the ...
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2answers
283 views
Which of the following compounds is NOT an isomer? [closed]
Which of the following compunds is not an isomer? I cant figure out how the answer is d
5
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1answer
87 views
Can a double bond extend beyond the plane and if so, how would it be drawn?
Can double and triple bonds, etc., extend beyond the plane in a Lewis structure, and if so, how are they represented? I.e., how would 1 and 2 in this image be drawn if they were doubles or triples?
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0answers
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Why do tetrahedral organic molecules show stereo-isomerism, but not tetrahedral transition metal complexes?
Both types of molecules show different arrangements of the molecule in space, so they should qualify for optical isomerism right?
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80 views
method to certify the number of chiral carbons in fischer and haworth projection of glucose
While reading some notes about Glucose and its various projections:
Fischer Projection: 4 chiral centres
Haworth Projection: 5 chiral centres
My doubt is that is there any (specific) method (...
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1answer
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Confused between structural isomers versus stereoisomerism
So this question wanted me to find two cyclical compounds that are 'structural' isomers of the molecular formula given in the question.
The two isomers I came up with are: 1,2-dichlorocyclopropane ...
