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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3
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1answer
218 views

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 ...
4
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1answer
787 views

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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1answer
222 views

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 ...
2
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1answer
1k views

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 ...
3
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1answer
3k views

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 $\mathrm{sp^3}$ ...
3
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1answer
645 views

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:...
4
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0answers
230 views

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): ...
21
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1answer
681 views

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 ...
3
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0answers
157 views

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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57 views

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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2answers
286 views

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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2answers
101 views

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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1answer
1k views

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 ...
3
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2answers
695 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 ...
9
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1answer
188 views

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 ...
8
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2answers
893 views

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). ...
9
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1answer
5k views

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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0answers
193 views

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 ...
2
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1answer
518 views

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 ...
6
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1answer
831 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 ...
7
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1answer
505 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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2answers
3k views

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
458 views

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 ...
6
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4answers
1k views

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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0answers
91 views

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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0answers
395 views

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 ...
4
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1answer
515 views

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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0answers
38 views

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 ...
3
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2answers
4k views

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
364 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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0answers
25 views

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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3answers
123 views

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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0answers
259 views

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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1answer
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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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0answers
108 views

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 ...
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1answer
5k views

Why do these resonance structures explain meta-directing feature of Nitrobenzene but not other resosance structures?

Consider the following resonance structures of Nitro-benzene: It is written in the book that because the positive charge is always at $-o$ or $-p$ positions, Nitro group in benzene has meta directing ...
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2answers
2k views

Why is benzoic acid more acidic than p-chlorobenzoic acid?

We know that in case of halogens, inductive effect is more dominant than resonance effect. So, the Cl on the para position will withdraw electrons by a -I effect and should make p-chlorobenzoic acid ...
2
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1answer
2k views

Correct stability order of resonance structures

Question no 9 as far as I know none of the rules of relative order of stability apply to this( completion of octate,charge seperation etc.) So they all must be equally stable but the answer is (D)
3
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1answer
2k views

Are resonating structures real or not? [duplicate]

We say that hybrid structure is real. It has distinct properties as compared to its Resonating Structure. Is it because that all the experiments we carry out are on a sample, lots of molecules are ...
2
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2answers
810 views

Stability and resonance structures

In school they ask us to count the number of resonance structures in different organic compounds to determine it's stability. The one with more resonance structures is more stable. Is this notion ...
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3answers
1k views

Why isn't this resonance possible in an imidazole ring?

My question is why isn't the resonance structure drawn in pencil on the right a valid one? My review book states that after initial protonation on the indicated nitrogen no resonance is possible.
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1answer
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Why is the compound 3,4-dihydroxy-3-cyclobutene-1,2-dione more acidic than acetic acid?

Why is the compound 3,4-dihydroxy-3-cyclobutene-1,2-dione more acidic than acetic acid? I don't get how its resonance stabilization is far greater than that of acetic acid despite the fact that the ...
0
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2answers
799 views

Understanding how electrons are counted for lone pairs vs. bonds especially when understanding resonance?

This is taken from the book Organic Chemistry as a Second Language from page 35. In the following image: It is seen that when the electrons from the double bond are pushed into the lone pair ...
3
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1answer
340 views

Is cyclopropyl methyl carbanion also exceptionally stable?

I know that cyclopropyl methyl carbocation is exceptionally stable and in fact more stable than benzyl carbocation but I was wondering if it was the same case with cyclopropyl methyl carbanion. Is it ...
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0answers
1k views

Naphthalene v/s Anthracene reactivity

Both have similar resonance energy per ring, even Naphthalene has a little higher Resonance energy (127.5 KJ per mol per ring v/s 127 KJ per mol per ring ) Can we prove , why there is a small ...
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1answer
3k views

How do I identify resonating structures for an Organic compound [closed]

Basically, my concepts regarding Resonance are not totally clear. I just need some help, on how to find the no. of resonating structures, given a molecule, and how do I draw those structures. Some ...
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0answers
90 views

Valid resonance contributors for 2-methylthiazole [duplicate]

There's a problem from an old exam that I was trying to do. The original structure is given on the left and they want all the possible resonance forms that have closed-shell atoms (octet for S) and ...
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3answers
1k views

Hybridisation of terminal nitrogen in diazomethane

I have a few questions about the terminal nitrogen (highlighted in red) in diazomethane, $\ce{CH2N2}$. Is that nitrogen $\mathrm{sp}$ or $\mathrm{sp^2}$ hybridised? What type of orbitals do the lone ...
4
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1answer
3k views

What is “dancing resonance”?

While searching the Internet for information about the tricyclopropylmethyl carbocation, I found a site (askiitians.com) where it said that its stability was due to "dancing (superfast) resonance". ...
0
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1answer
6k views

Is Phenyl Carbocation very unstable? [closed]

Phenyl carbonation is said to be unstable because the + charge on it cannot be stabilized by Resonance or any other electronic effects, so my question is that if the resonance occurs in the direction ...