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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Question about resonance structures [duplicate]

I stumbled upon an exercise asking to draw the resonance structure of $\ce{SO4^{2-}}$. We can choose between the resonance structures by calculating the formal charges and by checking which one gives ...
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Which is the most acidic hydrogen in vitamin C

I thought it would be the lower first $\ce{-OH}$ because it's close to the double bond with oxygen, so I thought there would be more electron withdrawal from the oxygen atom due to its ...
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1answer
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Will the carboxylate groups of the citrate anion undergo hydrogen bonding?

The citrate anion of trisodium citrate has three carboxylate groups. I am concerned with whether or not there will be hydrogen bonding in water, with hydroxyl groups of other ions or alcohols. It has ...
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Rules to identify the most stable resonance structures

While studying resonance from this Chemistry LibreTexts article, I found the rules to follow in order to decide which structure is the most stable. Among them: The structure with the least number of ...
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Comparing Basicity of Aniline Derivatives

Why is 4-hydroxyaniline more basic than 2-hydroxyaniline? Hydroxyl is an electron donating group, and their resonance structures suggest that they both isolate a negative formal charge on the carbon ...
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1answer
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Where do the lone pairs go in the “true” resonance structure?

Consider the "true" resonance structure of $\ce{CO3^2-}$: The bottom diagram leaves out the 2 lone pairs, so 4 electrons disappeared in the bottom image as compared to the top one. Are these ...
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Why does HNO2 not have resonance?

A question on the 1996 AP Chemistry Free Response asks: The $\ce{N-O}$ bonds in the $\ce{NO2-}$ ion are equal in length, whereas they are unequal in $\ce{HNO2}$. Explain. Since the nitrogen ...
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Is steric inhibition of resonance or steric inhibition of protonation dominant in o-toluidine?

I wish to know which effect out of steric inhibition of resonance (SIR) or steric inhibition of protonation (SIP) is dominant over the other when comparing basicities of o-toluidine and aniline: ...
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Stability of canonical forms

Which of the following ions is more stable? Use resonance to explain your answer. When we have to compare stability of resonance structures we generally check for the following features in the ...
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Lewis dot structures of CO2

I know the general Lewis dot structure of carbon dioxide is the one where there are two double bonds connecting oxygens to carbon. However the question is, does $\ce{CO2}$ have resonance structures? ...
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Confusing stability order of free radical structures

I have question regarding the solution that has been given. Question: In the given compound the order of case with which hydrogen atom can be abstracted from carbons I to VI is The solution that ...
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Resonance in benzenylium cation [duplicate]

Why is this type of resonance not possible? My book says that the positive charge is localised, and resonance is not possible. But I have drawn the resonance structures (though you can note that the ...
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Resonance in Organic Compound

Is the pi bond of a $\ce{sp}$ hybridised carbon in conjugation with another π-bond capable of resonance? Examples: $\ce{={C}=C-C=}$ $\ce{#{C}-C=}$ Is resonance possible?
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The pyridine/benzene stability 'paradox'?

So, apparently pyridine is more stable than benzene. My lecture notes are saying that pyridine will undergo electrophilic aromatic substitution much more slowly than benzene will, which got me ...
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What is the reason for the exceptional stability of tricyclopropyl-cyclopropenyl carbocation?

The stability order of the following is: A. III > II > I > IV B. II > III > I > IV C. I > III > IV > II D. I > III > II > IV Answer: I came across a question where we had to ...
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1answer
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Theoretical comparison of dipole moments of N,N-dimethyl-4-nitroaniline and N,N,2,3,5,6-hexamethyl-4-nitroaniline

These two compounds are given in my workbook, and I am supposed to compare their net dipole: The solution given in the workbook is that: Molecule A (N,N-dimethyl-4-nitroaniline) has a "net shifting ...
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1answer
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Resonance of carbonyl

Carbonyl has two resonance structures, where the $\pi$-bond between C and O breaks and the electrons "move" to the oxygen atom. This gives an empty p-orbital in carbon and a p-orbital in oxygen with ...
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Major contributor for resonance [duplicate]

I was doing some practice problems, and apparently 6 is the main contributor, due to having all full octets, but I'm not seeing how the oxygen with the + formal charge has a full octet in this case. I ...
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Comparison of Resonance Energies of some Carbocations

We were given the following carbocations and asked to compare their resonance energies. $\ce{L-CH2+}$, where $\ce{L}$ is: $\ce{NH2}$ $\ce{OCH3}$ $\ce{Ph}$ $\ce{F}$ $\ce{Cl}$ $\ce{NO2}$ and the ...
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1answer
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How to explain (non-/anti-) aromaticity in fulvene with the help of resonance structures?

Can someone please explain why the resonance structures of fulvene 1 is non-aromatic and 2 is anti-aromatic? Why is fulvene non-aromatic, even though it has $4\pi$-electrons and no $\mathrm{sp^3}$ ...
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1answer
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Why can't oxalate ion donate two pairs of electrons from the two double-bonded oxygen atoms

So, I read that an oxalate ion is a bidentate ligand but since I saw that it has 4 oxygen atoms I was confused as to why it isn't a tetradentate ligand instead. I searched it on Google and found this:...
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On the directing nature of these groups in electrophilic aromatic substitution

These three groups are listed in our workbook. I don't know the answer and our teacher isn't sure either: (each has a free valency through which it is attached to a benzene ring): ...
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How does the cyclopropyl group influence conjugation and aromaticity?

While answering the question Why isn't cyclobutane planar?, I recollected that cyclopropane and its derivatives behave like double-bond compounds, e.g. a cyclopropyl group can potentially be ...
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Meisenheimer complex in Preparation of 2-Naphthol from 2-Naphthalenesulfonic acid

I'm trying to figure out the addition-elimination mechanism for the preparation of 2-naphthol from 2-naphthalenesulfonic acid. I know that the $\ce{SO3^2-}$ group is functioning as the leaving group, ...
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Nitration of (E)-4-Phenyl-3-buten-2-one

What would happen if (E)-4-Phenyl-3-buten-2-one, shown above is nitrated, and is this compound more or less reactive than benzene? My Attempt: By drawing the resonance structures of the above ...
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Why do dithiins have 8 π-electrons?

It is mentioned on Wikipedia that dithiins have 8 π-electrons. Why is this so? I was thinking it would suffice for just one of the lone pairs on one of the sulfur atoms to participate in resonance ...
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Is II a resonating structure of I? [closed]

Is the structure II a resonating structure of I? If yes, then how? Isn't the lone pair on N non conjugated so as not to participate in resonance? I II
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Can resonance take place in between biphenyls? [closed]

I thought since both phenyl rings are not coplanar, the resonance between them is not possible. But my book says the following: Resonance effect is partially nullified Partially nullified means ...
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2answers
762 views

How are these two organic resonance structures different?

I've been working through some questions online (self study, not homework) predicting the various forms for molecules. One of the questions involved the following molecule (see image below). It had ...
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Is the middle ring of this organic compound aromatic?

Is the middle ring with 5 atoms of (4⁠Z)-4-[(4-methoxyphenyl)methylidene]-5-methyl-2-phenyl-2,4-dihydro-3⁠H-pyrazol-3-one aromatic? The carbonyl group could become a negatively charged oxygen, the ...
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Which of these carbocations are more stable?

The line of text that follows this figure in my work-book reads: Cation (A) is more stable than cation (B), since the former is resonance stabilized but the latter isn't (due to steric effects). ...
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1answer
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Why is carbonic acid a weaker acid than acetic acid?

Is it because the $\ce{OH}$ group next to $\ce{COOH}$ in carbonic acid donates electron density to the $\ce{COO-}$ by resonance, making it a stronger base, compared to a weaker electron donating ...
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Can the effect of resonance on acidity be generalised?

A basic trend for acid: if the conjugate base is more stable, then the acid has a lower $\ce{pKa}$. Therefore, it would quite intuitive to think that resonance in the conjugate base will make the acid ...
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1answer
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Forming the resonance structures for the nitrite anion

Yesterday I learned about resonance structures and came across this problem. The resonance structures are formed when there is a delocalized π electron cloud. I understand that for benzene, there are ...
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851 views

Steric inhibition of resonance vs. hydrogen bonding

I have to compare the acidic strength of these compounds: Now, in A and B hydrogen bonding will be present which will help stabilize the negative charge of the conjugate base. However, the hydroxyl ...
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1answer
529 views

Which rings of this heterocyclic compound are aromatic?

I am wondering which of the inner two rings of this compound are aromatic? I know the rules for aromaticity. But this case is difficult for me. Regarding the smaller ring, I guess the sulfur ...
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Why is aniline less basic than methylamine?

The reason given for the question is that in aniline the lone pair on N atom is delocalized throughout the benzene ring, making it less available for donation. But the conjugate acid of aniline ...
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3answers
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Is 1,2-dihydronaphthalene “partially aromatic”? [duplicate]

I've learned that if any one ring of a structure like the below is aromatic, the whole compound is aromatic. But one of my friends suggested that such compounds cannot be aromatic and gave the ...
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Carbene mesomeric structure of vinyl carbocation?

Why isn't a mesomeric structure with carbon having only two single bonds and a lone pair used for depiction of vinyl carbocation?
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Is the cyclopropenyl anion aromatic? [duplicate]

Shouldn't cyclopropenyl anion be aromatic as it will keep its lone pair in an unhybridized orbital? My teacher says that the lone pair will be a part of a hybrid orbital and the compound will be anti-...
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Why aren't free radicals considered resonance forms?

In C, the answer states that electrons must come in pairs. And so C does not show resonance forms. But here I read that if there is an unpaired electron, it is a free radical. Why can't free radicals ...
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Which resonance structure to use for writing curved arrow mechanisms?

If a structure with delocalized electrons participates in a reaction, which resonating structure do you use to write down the mechanism? Is using either equivalent? Is it preferred to use the ...
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Anitaromatic compounds: Why do they have lower stability? [duplicate]

What is the cause for some compounds like cyclobutadiene to be antiaromatic? I know they don't satisfy Huckle's rule but I don't understand why that leads to the decrease in stability of the ...
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2answers
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The most stable resonance structure [duplicate]

I came across this question: Which is the most stable resonating structure of p-nitrosobenzene among the following? I have been taught about the priorities for resonance structure ...
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1answer
390 views

Does triphenylphosphine show resonance?

The lone pair of phosphorus and the double bonds in benzene looks to be in conjugation. Do the molecule show resonance? If so, how?
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Cyanamide mesomeric contributors

Which form of the cyanamide ion is more stable? As per the resonance rules, I find both of them equally stable as number of bonds is the same, more electronegative atom has negative charge and so on. ...
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Do conjugated double bonds take priority over a +1 formal charge?

Do conjugated double bonds take priority over a +1 formal charge? The first one is what I solved for (ignore the hexagon that has no double bonds attached to it), and the one below it is the answer ...
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Which carbocation is more stable?

Which one of Tropylium cation (cycloheptatrienyl carbocation) and Cyclopropylmethyl carbocation is more stable? Several references present opposing views on this topic, hence the confusion. Reasons ...
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How many valid resonance forms can be constructed for aniline?

Based on the above picture, it seems that there are four. However, I have two questions: Aren't the top right and bottom left forms simply mirror images of each other, and thus considered the same? ...
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Why does oxygen atom allow positive charge on its surface when its electron pair is in resonance with benzene ring?

Oxygen atom is a highly electronegative element. Why does oxygen atom allow positive charge on its surface when its electron pair is in resonance with benzene ring? The reason can be that its octet ...