Questions tagged [chirality]

Applicable to questions about the ability of a molecule (or class of molecules) to be superimposed on their mirror image(s).

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What exactly is a 'chiral centre' in a carbon compound?

The typical progression (in books, YouTube videos) of explanation of chiral carbons in a compound is as follows: Chiral compounds are non-superimposable by their mirror-image; It is easily seen that ...
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In a pair of diastereomers, which of the following is true?

While going through my book, I came across this question and got really confused. Here's what the problem was: In a pair of diastereomers, Both can be laevo-rotatory or both can be dextro-rotatory ...
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Is 2-bromo-3-methylbutane chiral? [closed]

Is 2-bromo-3-methylbutane chiral?
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Does the chlorination of 4-methylcyclopentene generate two enantiomers or two diastereomers?

Does the chlorination of 4-methylcyclopentene generate two enantiomers or two diastereomers? I think it makes two enantiomers (or one pair of enantiomer) since the starting compound is achiral, but ...
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Is 1,1,2,2-tetramethylcyclohexane not meso? (And visualizing cis-1,2-dimethylcyclohexane)

Considering the fact that cis-1,2-dimethylcyclohexane is not meso, does that mean that 1,1,2,2-tetramethylcyclohexane is also not meso? I'm also having trouble understanding how the chair ...
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Is 2 ethyl 3 methyl oxirane optically active?

According to me this molecule does not have any any plane of symmetry nor centre of symmetry, but in my textbook it is given that this is optically inactive.
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1answer
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Why is ephedrine optically active? [closed]

Acyclic amine in which three groups are different with a lone pair of electron is optically inactive and nitrogen is achiral because of the rapid pyramidal inversion. Does similar inversion happen in ...
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346 views

How is the central carbon in 3‐bromopentane‐2,4‐diol chiral?

My teacher told us the middle carbon in 3‐bromopentane‐2,4‐diol is chiral: $$\ce{CH3-CH(OH)-\overset{\star}{C}H(Br)-CH(OH)-CH3}$$ Since there are two identical groups around it, I would guess it ...
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What are the criteria for a molecule to be chiral?

What are the criteria for a molecule to be chiral? (We frequently get questions of this type, so this is an attempt to construct a suitable general answer for duping.)
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Chirality and Optical activity

Do all chiral objects rotate the plane of polarization of EM waves? For example my hand is chiral, will it rotate the plane of polarization of EM waves of suitable wavelength?
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Is (1R,3aR,4S,6aS)‐1,4‐dibromo‐octahydropentalene chiral or achiral?

Is this molecule on the left chiral or achiral? I believe it is achiral because its mirror image (on the right) is essentially the same molecule. But I was told that it is chiral because it doesn't ...
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Are all 'dextrorotatory' sugars in biology actually 'd' or '+' in chirality?

When papers or articles say that all proteinogenic amino acids are 'levorotatory' or 'L', they often make a point of saying that only half of them are truly, optically levorotatory. All of them (...
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Why is 1-Ethyl-1-methylcyclohexane achiral? [closed]

I was wondering why the 1-Ethyl-1-methylcyclohexane molecule is achiral. Thank you in advance.
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Can aldol reaction using Evan's auxiliary yield diastereoselective products for ketone substrates?

Evan's diastereoselective aldol reaction commonly uses aldehyde as a substrate and I have never come across an example that uses ketone yet.
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How come the C1 is above the ring in fructose-6-phosphate and C1 is below the ring in fructose-1,6-bisphosphate?

Does the phosphofructokinase-1 flip the position of the covalent bonds? If I've understood correctly, C2 is a chiral atom, so it would make a difference if C1 goes from above the C2 to below the C2.
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In which of the these structures C-3 carbon is not a chiral centre?

In which of the these structures C-3 carbon is not a chiral centre? I think that the answer to the above question should be both (b) and (c) as C-3 is attached to same groups and also they have a ...
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1answer
309 views

Example of an achiral molecule without a plane of symmetry or inversion center?

Some websites, such as this textbook, mention how generally a plane of symmetry or inversion center in a molecule is enough to consider it achiral. Nonetheless, this source clarifies but if these ...
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Why does [Ni(gly)2] show optical isomerism despite having no chiral carbon?

For optical isomerism chiral carbon should be present i.e. carbon with four different groups but this compound doesn't have one then why does it show optical isomerism?
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Is plane of symmetry a necessary and sufficient condition for optical inactivity in coordination compounds? [closed]

In organic chemistry, we have to check for all three types of symmetry in a compound to check its chirality, ie, plane, alternate axis and centre of symmetry. But in coordination compounds, do we need ...
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Do we need to check for all kinds of symmetry in a compound to declare it achiral?

I know that a compound is achiral if it contains any one of the following kind of symmetry. 1.Plane of symmetry 2.Centre of symmetry 3.Normal axis of symmetry 4.Alternate axis of symmetry It is ...
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Type of chirality in polycyclic compounds

Ignoring whether or not this molecule could exist, is there a name for this type of chirality? This molecule's mirror image cannot be superimposed on itself but there are no chiral centres. Even ...
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Why can't an “upside down” chiral molecule neutralize the polarized light effect? [duplicate]

Steve Mould did a nice video a few months back called "Why Sugar Always Twists Light To The Right" (link is timestamped at the critical part). However his explanation was not complete. He ...
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Why has this molecule a S-chirality? [closed]

Can someone explain to me, why this molecule has an (S)-chirality? I don't get it. I tried to apply the rules, but I get only an (R)-chirality. Is there something special with cyclo-alkanes?
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Number of chiral centers in penicillin V

I have often seen that in many drugs chirality plays a role. So I was trying to analyze the structure of Penicillin V. What is number of chiral centers in the structure of penicillin V? Is the ...
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Which chiral carbon do L and D in L- or D-glucose refer to? [duplicate]

I see and D- and L- glucose are mirror images of each other. and I understand D and L are for chirality. But it is not clear which carbon do D and L refer to. Could anybody let me know? Thanks. What ...
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Do different alkyl groups affect chirality?

I am a bit confused on the definition of a chiral center; A carbon atom is chiral if it has four different items bonded to it at the same time. source However I am not sure whether different alkyl ...
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Are there reactions where the stirring direction would make a difference?

I'm not a chemist. I don't really do anything with chemistry, so I know little of the subject. I know a bit about chiral molecules. For example, I know that homochirality can affect light polarity. I'...
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Can a chiral molecule be optically inactive?

Does there exist a chiral compound with zero optical activity? It seems possible that for some (chiral) arrangement of atoms, the optical activity of one section of the molecule could be exactly ...
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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 ...
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1answer
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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 ...
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Identification of the organic compound

An organic compound A $(\ce{C10H14O})$ exhibits following characteristics. A) It reacts with metallic sodium to give a colorless odorless gas. B) It is oxidized by $\ce{KMnO4}$ to benzoic acid. C) It ...
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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. $...
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Chiral carbons in glucose

In the open chain structure of glucose, one can identify 4 chiral carbon atoms but some sources consider the ring structure and then say that glucose has 5 chiral carbon atoms. If asked to state the ...
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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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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 ...
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1answer
211 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 ...
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1answer
273 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 ...
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695 views

SN2 reactions and inversion of configuration in compounds with more than one chiral centre

Suppose I have a compound with 2 chiral centres which are at (S,S). Now, suppose I have an iodine atom attached to the back carbon, and I wish to carry out an $\mathrm{S_N2}$ type substitution in a ...
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2answers
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Nitrogen inversion barriers of trimethylamine and N,N-diisopropylmethylamine [closed]

Which would have a smaller nitrogen inversion barrier: $\ce{NMe3}$ or $\ce{N(i-Pr)2Me}?$ I think that $\ce{NMe3}$ should have a smaller inversion barrier as it is less bulky, but data shows otherwise....
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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 ...
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In the reaction mentioned what percentage of reaction proceeds via SN1 mechanism?

2-iodo butane (having radioactive iodine) reacts with KI (having non radioactive iodine). Rate of loss of optical activity was 1.96 times the rate of loss of radioactivity. What percentage of reaction ...
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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....
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1answer
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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 ...
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How can randomly oriented molecules in a liquid solution create a certain polarization pattern (d or l)? [duplicate]

How can a large number of moving, randomly-oriented chiral molecules in a watery solution twist light only to the left or only to the right? Wouldn't a levorotary molecule become dextrorotary if I ...
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Enantiomers and Flipping chiral centres [closed]

Hello, Normally, it seems like enantiomers have inverted R/S configuration at every chiral centre. However, in the pair below which are clearly enantiomers (note the methyl and benzyl groups are ...
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Do isotopic groups cause optical activity?

I understood the simplified reason for optical activity of a compound based on the difference in the angular velocities of counter-rotating circularly polarized light. The difference is due to the ...
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1answer
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Are there optically active molecules in which all atoms lie in the same plane?

I've learnt that when a molecule is non-superposable on its mirror image, it exists as a pair of enantiomers and is optically active. Absence of plane of symmetry is given to be one of the properties ...
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Is there an anisotropy factor (g factor) for TDDFT Abs and CD calculations?

Experimentally, anisotropy factor is calculated by dividing the CD spectra by the absorbance spectra multiplying by a factor of 32980 (in order to get a nondimensional quantity) Theoretical ...
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1answer
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The number of optical isomers of 3,4-dichlorobutan-2-ol

The number of optical isomers possible for the given organic molecule is? $\ce{CH_3-C^*H(OH)-CHCl-CH_2Cl}$ (the configuration is fixed at $\ce{C^*}$) The given answer is 2. The carbon marked with an ...
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Why is the name 'propylene oxide' preferred for epoxypropane?

This is the molecule I know as epoxypropane: In my neck of the woods (example), this molecule is used as one of the standard examples of small chiral molecules. The name 'epoxypropane' makes a heck ...

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