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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Number of electrons involved in resonance

To be brief let me an example consider phenol and phenoxide ion here in case of phenol the resonance occurs because of lone pair of electrons is O atom here the number of atoms donated by lone pair ...
Just a student's user avatar
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Resonance stabilization : lowering of kinetic energy or electron repulsion?

Resonance stabilization, or delocalization stabilization, occurs when the overall energy of the molecule is lowered compared the localized "resonance structures". In solid state physics, or ...
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Resonance Structures for mCPBA

Is this a valid resonance structure? I.e. can oxygen donate to positive carbon (i.e. are all oxygens sp2 hybridized)? If not, then why?
NAH Poio's user avatar
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Why does boron have higher affinity for fluorine than oxygen?

$\ce{F-}$ can displace $\ce{OH}$ in $\ce{B(OH)3}$ and form $\ce{BF3}$. $\ce{BF3}$ is stable due to resonance, but donation of oxygen should be stronger, as -I power of fluorine dominates its lone pair ...
EagerToLearn's user avatar
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If a compound has a strong and weak minus I group, will the stronger group always have a δ- charge?

In a compound like acrolein (prop-2-enal or $\ce{CH2=CH-CHO}$, will the oxygen in the $\ce{-CHO}$ group always have a $\delta$- charge? Acrolein does have three resonance structures as shown below, ...
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What are the resonating structures of toluene?

I initially made the resonating structures by first converting toluene into a toluene carbocation. But the resonating structures of a neutral molecule should be neutral. So what are the correct ...
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Aromaticity of chlorobenzene [duplicate]

Hückel's rule predicts that; a planar ring molecule will have aromatic properties if it has 4n+2 π electrons in conjugation. If 4n π electrons are in cyclic conjugation, then it is anti-aromatic. So, ...
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Kekule's description of benzene

“I was sitting writing at my textbook, but the work did not progress; my thoughts were elsewhere. I turned my chair to the fire, and dozed. Again the atoms were gamboling before my eyes. This time the ...
Harikrishnan M's user avatar
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Which is more stable, a secondary allylic carbanion or a primary allylic carbanion?

I came across this picture in a polymer chemistry course, specifically on anionic polymerization of conjugated dienes (butadiene). I dont understand why the secondary carbanion is more stable. Based ...
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VBT and MOT at the same time!

In the SNAr reaction, it is said that the electron withdrawing groups should be at the ortho or para position for the effective electron delocalization to take place, and we draw Kekule's structure to ...
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Why doesn't the reaction between molecule "B" and diethyl oxalate yield a diester?

Problem Answer Question Why isn't this structure the answer for the second reaction? From my understanding, the resonant structure (B) with the full negative charge on the oxygen is the most stable ...
nmrislife's user avatar
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Is size or electronegativity more important in acidity?

For the molecule below, is the hydrogen with the oxygen more acidic or is it the one with sulfur? Since both parts have the same number of resonance structures, I'm guessing it just boils down to ...
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Why does a hydroxyl group decrease the acidity of an Aromatic ring?

We are currently learning about resonance and induction, but I am confused why the addition of the hydroxyl group increases the pKa. As oxygen is more electronegative, should it not increase the ...
Daniel Philip's user avatar
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If charge is quantised, how can It delocalize?

As I was trying to understand resonance, I got to know that it was imaginary phenomenon and it is just a tool to explain mechanisms and structures that are unexplained by Lewis dot structures or ...
Dheeraj Gujrathi's user avatar
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How are Fermi resonances between normal modes possible?

As I understand, Fermi resonances occur when two (nearly) resonant vibrational states—most commonly a fundamental and overtone or combination mode—that are of the same symmetry interact, which, in the ...
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Why is it okay for the central carbon to lose a bond when forming a resonance structure for acetone?

As the title reads, I'm confused as to why it's okay for the central carbon in acetone to have a +1 formal charge when we push the electrons from one of the bonds with oxygen to form a lone pair and ...
Joe Valpuli's user avatar
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Which methoxy- and nitro-substituted azulene has the lower ground state energy?

My contention is that the first azulene structure, with the nitro group on the aromatic cyclopentene ring has a lower ground state energy, as the negative charge can not only resonate into the nitro ...
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Can two resonance structures of a molecule have different cas numbers?

From this Wikipedia article : Specifically, when a molecular structure is said to be represented by a resonance hybrid, it does not mean that electrons of the molecule are "resonating" or ...
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Resonance energy of organic compounds [closed]

I was solving a problem in organic chemistry, where I had to find the resonance energy of a compound with some information which was given in the question itself. Basically, what I had to do was, to ...
Anirudh Sharan's user avatar
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Why does Lewis dot structure of CO not have formal charges close to 0?

If we draw the Lewis dot structure of CO like this: The formal charge on each atom must be 0 But in the actual structure, formal charge on carbon is $-1$ and formal charge on oxygen is $1$. But I ...
I am a Human's user avatar
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+M or -I for chlorine? Major product in free radical chlorination and bromination of 2-chloropropane?

Is the +M or -I effect more dominant in when an alkyl (mono)halide is subject to free radical chlorination/bromination? For example what will be the major product in case of free radical (mono)...
Valoruz's user avatar
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Why does the conjugate base of peracetic acid not have any resonance structures?

Peroxyacetic acid, $\ce{CH3C(O)OOH}$ has its anion form when a proton is detached, like $\ce{CH3C(O)OO-}$. I think it can have two resonance forms like I drew (even though they have several charge ...
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Non Aromaticty due to Cross Conjugated Systems

I was going through this site looking for some answer on aromatic character, definition and other ways of judging an aromatic compound, when is tumbled upon this question: Are p‐xylylene and fulvene ...
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Why is the dipole moment of Anisole less than that of Phenol? [closed]

According to Wikidata, anisole has a dipole moment of 1.38D and according to this page on Researchgate, phenol has a dipole moment of 1.70D. Resonance in anisole: Resonance in phenol: According to my ...
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Planarity of rings [closed]

Can a 7 or less than 7 membered homocyclic ring with unsaturated C atoms and fully conjugated system, lose planarity? The smallest homocyclic non-planar ring that I know is cyclooctatetraene which is ...
Shubhayu Basak's user avatar
4 votes
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Acidic strength of nitrophenols

I've seen the pKa values of Nitrophenol as follows:- pKa of o-nitrophenol= 7.23 pKa of p-nitrohenol= 7.14 so p-nitrophenol is more acidic than p-nitrophenol But both phenoxide ions are stabilized ...
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Acidic strength order among hydroxytetralones [closed]

I can understand in 1 the conjugate base has more stability for better resonance but in 2 and 3 the effect of resonance cannot be considered. How can we compare the inductive effect in such case?
Shubhayu Basak's user avatar
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How does borane target a specific double bond on an indene?

According to the text I am using (Organic Chem, Seyan Ege, 3rd ed, problem 12.57) the halide in the electrophile borane (BH3) binds at site G. But I need to make sure I understand why. First, I ...
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Lewis structure and resonance for arginine ion

I'm working through a problem set in MIT's open courseware 'Principles of Chemical Science' course here. In question 5, it asks: The skeletal structures of two amino acids, leucine and arginine, are ...
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Does propene have resonance structures? [closed]

Propene is an alkene with a double bond between 2 carbon atoms. $\ce{C3H6}$ may have 2 resonance structures due to 2 possible placings of the double bond. E.g. it can be C=C-C or C-C=C (ignoring ...
Yitian Chen's user avatar
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Resonance structures of benzene [closed]

Does benzene have more than two resonance structures? I draw a third resonance structure keeping 1 bond fixed and rotating other two bonds I get opposite charges on two para position. Is this ...
Sunny Vishwakarma's user avatar
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1 answer
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In which orbital is the positive charge of central nitrogen present in diazomethane? [closed]

Where is the positive charge of central nitrogen located? It cannot be in the pure p orbital because in that case there will only s-orbital left for hybridization which is not possible. If it's ...
Ashish 038 Kharb's user avatar
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1 answer
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Lewis structure of XeF2 that comes closer to reality?

Meanwhile, the hypervalency of Xe in XeF2 is explained by the 3c4e bond, where the p orbitals of the 3 atoms overlap to form a delocalized system of 3 MO's in which 4 electrons (two from the Xe p ...
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Why is parafluorophenol is more acidic than phenol?

I have learnt that the +Mesomeric effect (+M effect) of fluorine at para position dominates its -Inductomeric (-I effect) nature. If we see that the acidic strength (with the help of stability of ...
Bhavishya Singhal's user avatar
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Are all resonance forms of pyracyclene equivalent?

This is pyracyclene: If I’m correct, pyracyclene has four resonance forms (double carbon bonds shown in red): Now my problem is estimating the dominance of each form. Are they equal or is there one ...
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Compare acidic strength of two different hydrogen in a Compound (2-hydroxycyclohex-1-encarboxylicacid)

I want to compare acidic strength between hydrogen-(a) and hydrogen-(b), I am getting answer as (a) but my classmate and my teacher said that (b) will have more acidic strength. I think (a) should ...
Bhavishya Singhal's user avatar
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2 answers
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When can lone pairs participate in aromaticity? [closed]

Basically, I'm confused on when lone pairs can participate in aromaticity, by the Huckel definition. Why can lone pairs on a carboanion be aromatic? I thought carboanions are sp3 hybridized, and the ...
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Is resonance possible with consecutive double bonds?

Resonance is delocalisation of pi electrons among parallel unhybridized p orbitals, so if we consider a molecules with 4 carbon chain with all bonds between carbon being doubly bonded then not all ...
Test Test's user avatar
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What is resonance in actuality? (How does electron sharing, bond formation, and overlapping of orbitals take place in resonance hybrids?) [duplicate]

In this post I got an answer to the question "what is resonance". What I understand overall is that "resonance is not something really happening physically, it is just an idea to make ...
Shinchan Nohara's user avatar
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1 answer
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Unequal bond lengths of resonating bonds in dinitrogen trioxide

Here is an image showing the resonance structures of $\ce{N2O3}$ molecule, As the bonds numbered (2) and (3) are in resonance, they will have same bond lengths but each with bond order less than two. ...
Infinite's user avatar
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Is NH2 electron donating or electron withdrawing? [closed]

Can anyone explain why NH2 shows -I in inductive effect and +R in resonance effect? I mean NH2 is ready to take electrons in inductive effect (with its electronegativity) but in the resonance effect, ...
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If two atoms join, do they lose their original spectral lines? [closed]

Each element and even isotope of element has its own set of unique spectral absorption lines. What happens to these lines after two or more atoms join together into molecule? Are all of the lines that ...
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How to establish trend of carboxylic acid acidity in the presence of certain substituents?

I encountered a question in my textbook which asked the following: At first, i thought that i can approach it in the same way i sort the effect of EDG and EWG on the acidity of phenols, that is, ...
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Phenol's resonance structure doesn't match NMR

I've asked a question before and quickly realised that the resonance/mesometric effects played a large role in determining the C-13 NMR spectrum of phenol, shown below. This is the resonance ...
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Why are amides weaker acids than water?

Based on a a recent question I asked on ChemSE, the answer to my question was that amides are weaker acids than water with a typical pKa value of ~20. Although, this answers my question, it got me ...
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3 votes
1 answer
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How do we find hybridization when molecule has resonance?

Consider the following image which shows the resonance structures of $\ce{CO_3^{2-}}$ ion. What is the hybridization of $\ce{O}$? How do we proceed in such cases? In one resonance structure, the top ...
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Resonance structure with allylic lone pair

Draw the appropriate resonance structure for 5-aminolevulinic acid: As there is an allylic lone pair, my first arrow goes from the lone pair to form a π-bond, and the second goes from the π-bond to ...
ninja_fun's user avatar
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Hybridisation of the O atom in the hydroxyl group of ethanoic acid

Currently studying high school organic reaction mechanisms and encountered a question. It goes like this: The C=O bond and the C–O bond of an ethanoate ion is equal at 127 pm, while the C=O bond of ...
warren's user avatar
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How does Hyperconjugation stabilize a Carbon Free Radical? [closed]

I tried drawing the resonance structures but just cannot see how donating two electrons to a carbon that only needs one electron make it more stable? I stumbled upon this question asked years ago ...
Arman Ansary's user avatar
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Does the same name represents all resonance and hybrid structure of a molecule?

The name chlorobenzene represents the following molecule. But the molecule shows resonance and its resonating structures are So does the same name represents all the resonance structures? Does it ...
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