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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29 views

Number of possible isomers (including optical/geometric ones) with C4H8O molecular formula

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 (...
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How many stereoisomers are there of 2-bromobutane? [closed]

According to my book, 2-bromobutane has two stereoisomers. However, by plugging the value $n = 1$ (since it has one chiral centre) into the equation $2^{n-1}$ I'm getting one stereoisomer. Is my ...
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35 views

Method of finding wether a compound is chiral or not [closed]

$S_n$ : It means if a molecule is rotated by $\frac{360^\circ}{n}$, then taken a reflection through a plane , and if the compound becomes identical to as it was intially, it is said alternating axis ...
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47 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 - (...
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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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28 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 ...
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18 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 ...
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2answers
43 views

Why are there two structures of L-Glucose in the Fischer projection?

We are told that L-Glucose is an enantiomer of D-Glucose, which would mean that they are mirror images of each other. But then we're also told that the L and D forms is determined by the spacial ...
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Carbon dioxide electronic geometry [duplicate]

It is known that allene (propadiene) $\ce{H2C=C=CH2}$ geometry is such that its hydrogen atoms are not in the same plane – do not form rectangle, but “extended tetrahedron” I wonder if structurally ...
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39 views

Confusion with E/Z configuration

Could someone please illustrate how to determine the E/Z configuration of this molecule? What I understand so far is that if the two highest priority substituent on each side are on the same side, ...
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1answer
28 views

Optical activity of cis-trans isomers of a co-ordination compound [closed]

Why do geometrical (cis and trans) isomers of [Pt(NH3)(Br)(Cl)(py)] not show optical activity ? Thanks In Advance...
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49 views

Why glucose and other similar carbohydrates are oxidised fully by HIO4?

$\ce{HIO4_{(aq)}}$ requires the vicinal diols to have syn configuration, as it forms a cyclic periodate ester. But glucose does not have syn configuration at C3, and if you consider cyclic forms of ...
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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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69 views

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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2answers
790 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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32 views

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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66 views

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
73 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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1answer
106 views

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
137 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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44 views

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
192 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
54 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
57 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
114 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,...
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1answer
37 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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41 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
123 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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42 views

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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40 views

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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1answer
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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
175 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. ...
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2answers
287 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
200 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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1answer
667 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 ...
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1answer
336 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 ...
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1answer
69 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
121 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
195 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
120 views

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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74 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 ...
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1answer
208 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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1answer
86 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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51 views