Questions tagged [resonance]

Resonance refers to the representation of the electronic structure of a molecular entity in terms of contributing structures. The tag should be applied to any question that concern resonance structures or resonance energy. This tag should not be applied to questions about aromatic compounds (use the [aromatic-compounds] tag instead)

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What is the hybridisation of the carbons in the allyl radical?

The example I am talking about is $\ce{CH2CHCH2^.}$. To find the steric number and hence the hybridization, we use steric number = No. of lone pairs + number of sigma bonds. In this example, the ...
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1answer
129 views

Arrow pushing: why does the O become positive when its lone pair becomes a double bond?

In the following image: The oxygen's top pair of electrons forms a double bond. But in a covalent bonds, aren't the electrons shared? So won't the oxygen still have these $2$ electrons (that it ...
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1answer
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Structure of nitric oxide

These are the two resonating strctures of NO given in my textbook. In the first resonating structure, oxygen is shown to have 9 electrons. How can that be possible since oxygen does not have the third ...
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427 views

Are there any acid-base indicators whose protonated and deprotonated forms have the same number of resonance structures?

This question asks about the color change of 7-hydroxyphenoxazone, the active compound in litmus paper, and the relation of that color change to the conjugated system in the molecule. In Klaus ...
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1answer
4k views

Does the carboxylate group show a positive or a negative inductive effect?

In the benzoate ion, does the carboxylate group show a $-I$ or a $+I$ effect? I learnt that the carboxylate group is a $-I$ group, but according to a website the carboxylate group in benzoate shows a ...
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Do Fermi resonances show in Inelastic Neutron Scattering spectra?

The Raman and FTIR spectra of a urea based mixture shows a strong Fermi resonance in the N-H stretching region, which difficults its interpretation. In an inelastic neutron scattering spectra of the ...
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1answer
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What are the resonance structures of methyl azide?

I am supposed to construct the major resonance structures of methyl azide, $\ce{CH3N3}$. I know that in compounds such as the carbonate anion $\ce{CO3^2-}$, resonance can be depicted by ...
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1answer
835 views

All resonance structures of the hydrogen molecule

This answer written by Jan says that "a professor of mine claimed to have drawn some 18 (or was it 80?) different resonance Lewis structures." Please reproduce those resonance structures of the ...
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1answer
234 views

how do electromeric / inductive effect theories compare with resonance

Back in high school, long time and many seas away, I learned about electrons moving within organic molecules based on electromeric and inductive effect. Googling them today, I found that they are ...
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1answer
573 views

Which hydrogen of 3-methylcyclohex-2-en-1-one is the least acidic?

Which hydrogen of 3-methylcyclohex-2-en-1-one is the least acidic? According to me it should be 2, as on its removal there won't be any resonance stabilization as would happen in the other ...
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3answers
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Why is +M effect of OH greater than OR?

In some books it is written that +M (mesomeric effect) effect of OH is less than that of OR . The reason they give is inductive effect of R (group) which sounds senseful . But at some places it is ...
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How are the hybrid orbitals of sulfur hexafluoride shaped?

On the fluorine end the fluoride atoms are simply completing a $3p$ orbital. On the sulfur end one could posit a hybrid of one $3s$ orbital, two $3p$ orbitals and a three inner $2p$ orbitals. However,...
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Can atoms delocalize in molecules?

Electrons can delocalize over multiple equally probable bonding structures. Can atoms delocalize over multiple equally probably bonding structures in certain cases? It seems to me that any such ...
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Paracetamol: does oxygen participate in the delocalization of p-orbitals

I'm analyzing the molecular structure of paracetamol and one of the things I have to do is to make a commentary about the delocalization of p-orbitals in this compound. Well I know that in the cyclic ...
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1answer
8k views

How many resonating structures of Carbon Monoxide are there?

Anywhere I look, I get 3 resonating structures for CO molecule, like in this answer. However, according to the rules stated for drawing resonating structures in this site, I wonder why there can't be ...
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1answer
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If I can't draw resonance structures for a pi system, does that mean it doesn't exist?

Whilst trying to answer this question I came across an interesting situation regarding the relationship between resonance structures and molecular orbitals. There are two places that you can ...
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What is resonance, and are resonance structures real?

My teacher told me about resonance and explained it as different structures which are flipping back and forth and that we only observe a sort of average structure. How does this work? Why do the ...
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3answers
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Why is meta-nitrophenol less acidic than para-nitrophenol? [closed]

My professor said while explaining the acidic nature of phenol that meta-nitrophenol is less acidic than para-nitrophenol, and gave the reason that resonance doesn't play on meta, but I didn't get it.
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Does benzene structure stand for a single resonance form or the whole molecule?

It is known that benzene has two main resonance forms Often we still draw benzene molecule as one of them My question is, actually when we draw the lower figure, do we refer to the whole benzene ...
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1answer
820 views

Acidic strength of organic acids. Substituted PhCOOH acids

Could someone please explain the order of acidity of ortho, para and meta substituted benzoic acids with the substituent as methyl group? Methyl group operates +I and +R effect, I believe.
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1answer
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N-O bonds in Nitric acid

The wikipedia article on nitric acid mentions the following structure of $\ce{HNO3}$ in which the two $\ce{N-O}$ bonds (other than that of $\ce{N-OH}$) are of different length i.e., $119.9\,\pu{pm}$ ...
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2answers
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Why can one double bond exist in some resonance structures but two can't?

I am doing some biology and have not done chemistry in ages. I have two concepts I am struggling with. When drawing Lewis structures, am I right in assuming that the central atom will always require ...
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1answer
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What is the meaning of “charge separation” in resonance?

I've read that the resonance structures in which there is lesser 'charge separation' contribute more to the resonance hybrid than the ones with greater charge separation. But I am unable to ...
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1answer
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Why are anti aromatic compounds unstable?

Just like aromatic compounds, anti aromatic compounds have several resonance structures and some of them are also conjugated ( 1,3-cyclobutene). Why is it that just having 4n electrons makes them ...
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Resonance in phenoxide anion [duplicate]

Why is resonance possible in phenoxide anion as when the electron pair of oxygen is involved in conjugation we have 4 pairs of electrons in resonance which should imply that the ring has become anti ...
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1answer
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Relative stability of carboxylic acid derivatives

This picture depicts the relative stability associated with resonance structure. My questions are: 1.1. Teacher says anhydride is less stable because of two reasons above. but it seems there's no ...
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1answer
253 views

Stabilization of ipso and para position in Birch reduction by EWG of aromatic ring

I'm trying to grasp the Birch reduction. In the lecture about it, it's said that the EWG group stabilizes ipso and para position through resonance. I tried to understand that by drawing resonances ...
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1answer
88 views

Canonical structures of (1E)-prop-1-en-1-yl acetate

I have to find all of the possible canonical structures of this molecule And here's what I did Are they correct and if yes, did I miss any possibility?
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1answer
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Why only the unstable resonating structure proceeds in the reaction?

For example, in the given image, I have starred the step where the relatively unstable resonating structure proceeds forward in the reaction. Why?
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1answer
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Stability Comparison between the Tropylium and Tricyclopropylcarbinyl Carbocation

Why is the Tropylium carbocation less stable than the tricyclopropylcarbinyl carbocation? The tricyclopropylcarbinyl carbocation undergoes a sigma-tropic rearrangement whereas tropylium is highly ...
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2answers
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Which will be the most acidic hydrogen in the following organic compounds?

Which will be the most acidic hydrogen in both cases? Please explain. According to me, in the first compound 2 should be most acidic as in both 1 and 2, resonance occurs but 2’s carbon is closer to ...
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1answer
6k views

Why is HClO4 the strongest oxyacid?

Why is $\ce{HClO4}$ the strongest oxyacid? My effort: The structure of $\ce{HClO4}$ should be tetrahedral. So when there is a negative charge on oxygen, it should not be in resonance with other ...
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0answers
725 views

Thermodynamic control or kinetic control?

In my notes, it is written that the case 1 product will be major one. The explanation given is as follows:- However, since the pi clouds of alkenes are perpendicular to each other, the resonance ...
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What is an algorithm for drawing resonance structures?

Question What is an instance of a procedure for writing resonance structures for any given compound's name or structural formula? I would prefer any of these formats to represent the algorithm: ...
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1answer
670 views

Why can't antiaromatic compounds just escape planarity and become non-aromatic to avoid destabilization?

Why can't just all anti-aromatic systems lose planarity (and hence conjugation) and be non-aromatic like cyclooctatetraene ? ...
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1answer
399 views

Aromaticity of 1,1'-bi(cycloprop-2-en-1-ylidene) and 1,4-dioxine

Are these Anti aromatic/aromatic or non aromatic? 1. Here, if we were to consider the resonating structure(s) with charge separation One ring is aromatic and other is anti aromatic, and secondly ...
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2answers
2k views

Halogen and inductive effect

background : As proved by rate of EAS, mesomeric or simply conjugated resonance is weaker for halogens than inductive and make them electron taking, with fluorine almost doing nothing due to ...
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1answer
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Number of resonating structures (hypothetical)

To my knowledge, resonance happens where more than one lewis stucture can represent the compound with no shift in sigma bonds so, suppose in a simple conjugated system even like 1-3 pentadiene , two ...
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3answers
2k views

Why does fluorine stabilise a carbocation? [duplicate]

I have read that halogens have a stonger -I (inductive effect) than +M (mesomeric effect),then why do they stabilise a carbocation instead of destabilising it? I asked this doubt to my teacher and he ...
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2answers
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Understanding the mechanism of Blanc chloromethylation

I have seen this question: Mechanism for chloromethylation of benzene. The answer there uses a picture from wikipedia which confuses me. It gives $$\ce{H2C=O <=>C[HCl] H2C+-OH <-> H2C=O+H}...
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Can we break the covalent bonds of water molecules using resonance frequencies?

Can we break the covalent bonds of water molecules $\ce{H2O}$ using resonance frequencies? What is the wavelegth of the water's molecule? Can we create a vibration like this and use it to separate ...
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3answers
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Difference between Resonance Effect and Mesomeric Effect

While studying electron displacement effects in organic chemistry, I read that the Resonance Effect and Mesomeric Effect are the same. Every source I checked used the heading or opening "The Resonance ...
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1answer
3k views

Which of the following has higher enol content?

Which of the following has higher enol content? The enol form of (A) and (B) is: Both the enols have hydrogen bonding. If the oxygen were to accept the pi electrns from carbon forming a carbocation ...
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Why is diene more reactive than alkene?

The chemical reduction of 1,3-butadiene with sodium in alcohol gives mainly the 1,4-addition product that is but-2-ene. Under these condition the isolated double bond are not reduced. This suggest ...
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1answer
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Why do alcohols not undergo resonance?

Take for example $\ce{CH3OH}$. The lone pair on the oxygen atom may be donated to form a double bond and giving $\ce{CH3-}$ and $\ce{O+}$ ? Is it because we cant have + charge on $\ce{O}$ atom?
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1answer
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Determining the order of basicity of acetate, phenoxide, hydroperoxide, and hydroxide ions [duplicate]

Arrange the following ions in order of basicity: (1) $\ce{CH3COO-}$ (acetate) (2) $\ce{PhO-}$ (phenoxide) (3) $\ce{HOO-}$ (hydroperoxide) (4) $\ce{HO-}$ (hydroxide) The first thing I see is ...
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1answer
792 views

Resonance in ozone and benzene [duplicate]

In inorganic chemistry, I learnt that stability of some atoms like ozone cannot be explained by one structure alone and hence the hybrid of possible structures is taken and assumed to be the structure ...
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2answers
27k views

Number of resonance structures of nitrobenzene

I was studying about the resonance and here's my doubt: How many resonating structures are there in nitrobenzene? Is it 5 (as drawn) or is it 4 because first and the last structures are same or is it ...
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2answers
8k views

Why does the phosphate ion have resonance structures?

My first-year chemistry teacher depicted $ \mathrm{PO_{4}^{3-}}$ as exhibiting the resonance structure inset below this question. However, I can't figure out what diagramming rules (which is what ...
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1answer
222 views

Stability of carbocations

We know that if a structure has all equivalent resonance structures, then it will be highly stabilised. So then why benzylic carbocation is more stable than other cyclic allylic carbocations, though ...

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