Questions tagged [isomers]

Compounds that have identical molecular formula but different chemical structure.

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Structural isomers for dipeptides prepared from a mixture of alanine and glycine

How many structural isomers exist for dipeptides that are prepared from a mixture of alanine and glycine? I am working on my scholarship exam practice and struggling with this question. The answer ...
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1answer
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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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1answer
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What is the total number of isomers, considering both structural and stereoisomers of cyclic ethers with the molecular formula C4H8O?

According to me, it should be 11 and this is how I have worked out as shown in the attached diagram. However, I am not sure whether all these 11 isomers can be considered as those belonging to ...
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Which is more stable: isobutylene or cis-2‐butene?

How do you compare which is more stable without using the heat of hydrogenation or combustion or any other numeric factual value: $\ce{(CH3)2-C=CH2}$ or $\ce{CH3-CH=CH-CH3}$ (cis)?
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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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How do we know if this following molecule is a superimposable mirror image or non-superimposable mirror image ? [See Image attached]

How do we know if this following molecule is Super Imposable mirror image or Non Super Imposable mirror image ? [See Image attached]
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2answers
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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
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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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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 ...
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1answer
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Cis and Trans Isomerism given three different groups around the reference plane

In the following problem I am meant to deduce the molecules that are cis-trans isomers of each other. This question does not make much sense in my head because I thought that cis/trans isomerism was ...
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1answer
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What is the name of “cis/trans” isomerism when all four groups are different?

How would you call a pair of isomers on the picture below? They look a lot like regular cis/trans isomers, except all four groups are different. I can tell they are spacial isomers (stereoisomers) ...
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Interchangeable isomers [closed]

I am a clinical research professional. I have a question regarding clinical chemistry. I would like to know that whether it is possible to get testosterone undecanoate from ursolic acid and vice-versa ...
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The van't Hoff rule for stereoisomers with planes of symmetry

We know that the maximum possible numbers of stereoisomers of a molecule is given by the van't Hoff rule, which says that: $$Total \space stereoisomers = 2^{n}$$ Where $n$ is the number of ...
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What does the dissociative mechanism for cis/trans interconversion of [Mo(CO)4(PPh3)2] look like?

All I can find in the literature is that the cis→trans interconversion proceeds via dissociation of one of the PPh3 ligands resulting in a square-pyramidal Cs intermediate, with the remaining PPh3 in ...
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3answers
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Why are carbons of Inositol chiral centers?

I was asked to draw all possible stereoisomers of inositol (1,2,3,4,5,6-cyclohexanehexol). To obtain the answer I had to assume that all six carbons of the molecule are asymmetric, which (bearing in ...
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2answers
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Melting point of unsymmetrical dimethylhydrazine vs 1,2-dimethylhydrazine

Unsymmetrical dimethylhydrazine ($\ce{H2NN(CH3)2}$) has a melting point of −57 °C, but its isomer, 1,2-dimethylhydrazine ($\ce{(CH3NH)2}$) has a melting point of −9 °C. That looks to me like a ...
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ionisation isomers [closed]

With ionisation isomers, how do you know which ligand (out of $\ce{Br}$ and $\ce{NH3}$ for example) exchanges with the compound outside the bracket?
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isomerism-position versus chain

For nitriles carbon of nitrile group is part of the carbon chain. So what is the isomerism shown by pentanenitrile and 2-methylbutanentrile? Chain isomerism or position isomerism?
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302 views

number of optical isomers of a cyclic molecule

What is the number of optical isomers for this compound? Also, there seems to be no clear-cut boundary between geometrical isomers and optical isomers. Referring to a post in StackExchange, is (RS)- ...
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1answer
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Can anyone tell me what reaction is this?

I came across this reaction, but I have no idea what reaction is this. Can anyone please tell me? What will be the products? My first guess is that a carbene will be formed which will attack on the ...
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1answer
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How many stereoisomers are possible for 1,2-dimethyl-4-(propan-2-ylidene)cyclopentane?

How many stereoisomers (not counting different conformers) does 1,2-dimethyl-4-(propan-2-ylidene)cyclopentane have? I think the answer should be 3. There are two geometrical isomers (cis and ...
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4answers
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Total number of stereoisomers of 2,3,5,6-tetrachlorooctane

I tried the following combinations: RRRR, SSSS, RRRS, SSSR, RRSS, RSRS, SRRS, RSSR, RSRR, SRSS, RRSR, SSRS, SSRR, SRSR. So total stereoisomers which I got is 12 but my teacher says it's 16. I don't ...
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Hydrate isomerism

My book specifically mentions in the solution to a question: $\ce{[CrBrCl2 (H2O) (NH3)2].H2O}$ is not the hydrate isomer of $\ce{[CrCl2 (H2O)2 (NH3)2]Br}$ But the author hasn't provided any ...
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1answer
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Classification in Stereoisomerism [closed]

I was trying to understand stereoisomerism. I am having trouble creating a 'flow chart' of Stereoisomerism. While there are many sources available over the internet and books, I don't find a standard ...
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2answers
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Why does 1,3-dichloropropane not show stereoisomerism?

It is a multiple choice question: Which compound does not show stereoisomerism? A 1,2-dichloroprop-1-ene B 1,2-dichloropropane C 1,3-dichloroprop-1-ene D 1,3-dichloropropane I ...
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Are Anomers Epimers?

epimers are the class of stereoisomers which differ along configuration at any carbon in a carbohydrate(generally), And anomers are the kind of stereo isomers that differ at the carbonylic carbon, ...
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1answer
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Why is there only one ionization isomer of [Cr(NH3)5(NO2)]Cl2?

How many isomers are possible for $\ce{[Cr(NH3)5(NO2)]Cl2}$? Consider all possible types of isomerism and draw each isomer. My texbooks presents only three possible isomers: $\ce{[Cr(NH3)5(NO2)]Cl2}$ ...
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5answers
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If a chiral molecule reacts with an achiral molecule will the product be chiral or achiral?

My book says that a pair of enantiomers will react the same way with an achiral substance. How is this possible? Does this imply that the product is achiral, even though the enantiomers are chiral? ...
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2answers
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Number of spatial arrangements of tetrasubstituted biphenyl

According to my book 2-bromo-2'-(1-chloroethyl)-6'-iodo-6-(prop-1-en-1-yl)-1,1'-biphenyl has eight possible spatial arrangements. How can this be so? I can think of only four – left two groups being ...
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Ortho vs para alkylation of chlorobenzene

I have a question to the solution regarding the product formed in a reaction with chlorobenzene with the use of (i) $\ce{CH3CH2Cl}$ and (ii)$ \ce{AlCl3}$. Since the -Cl substituent is ortho- para-...
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1answer
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why do the complex [Cu(NH3)5NO2]SO4 show ionisation isomerism?

In ionisation isomerism, secondary valencies can be replaced by primary valencies on the condition that net charge going outside the coordination sphere must be equal to net charge coming inside it . ...
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1answer
466 views

How are there only 8 structural isomers of C5H11Br?

Everywhere I see mentioned, that there are only 8 structural isomers of $\ce{C5H11Br}$. That is, the simple $\ce{C5}$ straight chain, $\ce{C4}$ with substituted methyl and $\ce{C3}$ with two ...
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Why do highly branched alkanes have higher octane numbers than their corresponding linear isomer?

The octane number of fuels are based on a set of primary reference fuels, which are mixtures of iso-octane and n-heptane. Now iso-octane being branched alkane has very less tendency to react and given ...
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Why are some strucutres isomers while others are not? [closed]

Why are some structures considered isomers but others are not? Take C3H9N for instance, according to https://www.chegg.com/homework-help/questions-and-answers/four-constitutional-isomers-molecular-...
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1answer
783 views

Explain optical activity in Biphenyl compounds

How is optical activity explained in biphenyl compounds using atropisomerism. NOTE: I was taught that if vertical symmetry exists then optical activity is not shown by any substituted biphenyl ...
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What are the metamers of penta-1,2-diene?

First of all, are there any metamers for dienes? If there are any, how can I find them?
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Are ortho, meta and para used in IUPAC nomenclature?

I was presented with the following question in an online test: To avoid any confusion, here are the arranged options: A. 2-Chlorotoluene B. 1-Chloro-2-methylbenzene C. B and D D. O-...
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1answer
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Systematic Approach to Finding Number of Isomers [duplicate]

I have this compound I want to know how many isomers (including stereoisomers) may have this constitution. Is there a systematic approach towards solving such types of problems related to the total ...
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1answer
133 views

No.of isomeric ethers of formula C3H6O

I managed to get 3 ethers:- 1.4-member ring ether(Oxetane) 2.Vinyl ether 3. Epoxy ether This question was asked in my school exam and the teacher had given its answer as 4..Could anyone please tell ...
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1answer
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Number of total stereoisomers of a piperazine derivative

How do I find out the total number of stereoisomers of 3,6-dimethylpiperazine-2,5-dione? As far as I can see, the compound has two chiral carbons. Would the nitrogens make a difference? They seem ...
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0answers
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Does dihydroimidazole show geometrical isomerism?

Does dihydroimidazole (above) exhibit geometrical isomerism? Does the fact that the lone pair is involved in conjugation with a double bond affect anything? As far as I know, it does not exhibit ...
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2answers
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Number of stereoisomers of tetramethylspirononane

The above compound – 2,3,7,8-tetramethylspiro[4.4]nonane – clearly exhibits both optical and geometrical isomerism. The question is, how many stereoisomers does it have in all? As the number of ...
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Reactivity of different isomers of N2F2

$\ce{ N2F2}$ exists in two forms cis and trans. Today my chemistry teacher tells me that among the two only cis form takes part in reactions and that it is more reactive. But I have read elsewhere ...
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Is 3,4-diethyl-3-hexene cis or trans? [closed]

I'd really appreciate it if someone could explain this one, please! According to my answers sheet it is not cis nor trans. But it looks like it is cis? Why, according to my answers sheet, is this ...
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1answer
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What is it meant by two different groups in stereoisomerism?

I understand there are some properties in an organic compound that allow stereoisomerism. double bond can't rotate two double bonded carbon atoms each have two different atoms or groups attached I'm ...
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Structural isomers given a molar mass [closed]

How many structural isomers are possible for compound containing $\ce{C}$, $\ce{H}$ and $\ce{O}$ atoms only with their molar masses $100$ as well as the isomers are simultaneously ketones 3 ...
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Why are conformational isomers considered as isomers?

I was taught that geometric (cis-trans) isomers are considered isomers because there is a high energy barrier to breaking the double bond for rotation (to convert into the other isomer). Given that ...
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1answer
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Why dichlorobenzene doesn't show geometrical(cis/trans) isomerism? [duplicate]

As it has restricted rotation due to the presence of a double bond, it should show geometrical isomerism. Then, why doesn't it show cis/trans isomerism?
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1answer
233 views

Why is mer-AlQ3 more stable than fac-Alq3?

Several research papers and books say that the meridional isomer of tris-(8-hydroxyquinoline) aluminium is thermodynamically more stable than the facial isomer. What is the reason behind this ...
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Coordination isomerism variation

The school book and Wikipedia state that coordination isomers are: In a coordination isomer the total ratio of ligand to metal remains the same, but the ligands attached to a specific metal ion ...