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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1answer
45 views

How is a molecule defined front/back view? [closed]

In the YouTube video How Your Nose Uses Quantum Physics to Smell exactly at 7:30 mark they explain two identical molecules: one is left handed and the other is right handed: But, isn't it just ...
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Are monosubstituted cyclopropanes achiral or chiral?

A classmate an I were discussing the chirality of this molecule which is a monosubsituted cyclopropane. I argue this is an achiral molecule because that carbon which is bonded to bromine cannot be a ...
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Which of the following isomers of 2,3‐dihydroxy‐4‐methoxy‐4‐oxobutanoic acid are identical?

Which of the following are identical? A and B are identical A and B are diastereomers A and C are enantiomers A and B are enantiomers What I know is that when we rotate a ...
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511 views

Which biphenyl is optically active?

Which biphenyl is optically active? I know that it can never be 1. I don't think it will be 4 either as I read that it should be ortho-substituted biphenyl. So, when I look at 2 and 3, I can't ...
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What is the absolute configuration of carbon 5 in 5-bromo-2-methylhex-2-ene

I am trying to work out the absolute configuration around carbon atom 5 in 5-bromo-2-methylhex-2-ene. Could someone please let me know if my working is correct? Does the wedged bond from C4 to C5 ...
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Why does Pubchem show cis-1,3-cyclohexanediol with the hydroxyls in the equatorial position?

I am a beginning organic chemistry student and trying to reason about something based on information in my book, but seeing that Pubchem gives a different structure than I'd expect. In considering a ...
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1answer
48 views

Conformers of a meso-compound [duplicate]

In a particular question in one of my reference book, I was asked if the given compound (meso-butane-2,3-diol) was a meso compound or not. In it’s solution part, to show that the compound was ...
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Optical activity of cis coordination compounds

I came across a statement saying, "Consider a Octahedral coordination compound of type [MA2X2]. Then, if the compound is in a cis form, it shows optical activity as there is no plane of ...
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1answer
117 views

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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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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1answer
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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
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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
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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
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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,...
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1answer
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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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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
113 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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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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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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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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993 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 ...
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2answers
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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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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. ...
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260 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
156 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 ...
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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 ...
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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 ...
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1answer
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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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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
138 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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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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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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1answer
178 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....
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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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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 ...
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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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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 ...
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1answer
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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 ...
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1answer
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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 ...
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1answer
203 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?
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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
184 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 ...
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1answer
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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 ...