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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How is resonance energy measured?
Is it the difference of energies of formation of the resonance hybrid and the average of the energy of formation of all the contributing structures? How would we even calculate the energy of a ...
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Resonance hybrid and octet
I am a student of grade 11. I am learning about resonance phenomena. I am a beginner with this and I am a bit confused about this. I wished to know whether atoms in resonance hybrid (not resonating ...
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Comparison of carbocation stability in bicyclo compounds
Question
Which is the most stable carbocation ?
Answer
My attempt
I answered as 1 as the first one had +M of -O- and hyperconjugation effect as the positive charge is at para position. Why is the ...
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Clar's rule of polycyclic aromatic hydrocarbons
Clar's rule states that the Kekulé resonance structure with the largest number of disjoint aromatic π-sextets, i.e., benzene-like moieties, is the most important for characterization of properties of ...
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Rate of dehydration of alcohols having keto group
The following question was asked in IITJEE-Screening 2000,
Which of the following will be most readily dehydrated in acidic conditions?
I thought that the answer would simply be (c), as its ...
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Why doesn't but-2-yne show acidic character?
I found this in several sources and also found this while solving a few questions that but-2-yne does not show acidic character (or atleast not a significant amount of acidity) compared to terminal ...
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Does Genistein remain in resonance stabilised form in physiological pH or acidic pH? [closed]
As a follow up, does the Carbonyl group at 4 position group get deprotonated or Hydroxyl group at 5 position get deprotonated? How does the resonance structure look? I have been looking through ...
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The most acidic hydrogen among ethane, ethene, ethyne and allene
Among
$$\ce{CH3-CH3}\qquad\ce{CH2=CH2}\qquad\ce{HC≡CH}\qquad\ce{CH2=C=CH2}$$
I need to find out the one having highest acidic hydrogen.
As per my observations, there are two equivalent resonating ...
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Ortho-para directing and meta directing groups: Activating or deactivating the aromatic ring?
Determine the reactivity of the above compounds (activating or deactivating; ortho-para or meta directing). Explain your answers. You may use resonance structures in your explanation. Which molecule ...
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Mesomeric effect in crotonaldehyde [closed]
I tried making structures using lone pair of oxygen but I am unable to achieve a structure which doesn't violate the octet rule.
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Does Cl- Have more -I effect or +M effect ( Resonance effect)?
In this question my answer was (A) because I thought $\ce{NH2}$ group would give more electrons than $\ce{Cl-}$. But the correct answer is (D) and my teacher's reason is that chlorine has more ...
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Stability of α-chlorocarbocations
I'm trying to compare the relative stability of two carbocations:
$$\ce{CH3-\overset{+}{C}H-Cl}\quad\text{vs}\quad\ce{CH3-\overset{+}{C}H2}$$
Does the $\ce{Cl}$ exert a +M effect to stabilise the ...
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Resonance of lone pair of nitrogen in 4‐nitroaniline and piperidin‐2‐one
While working out some questions on comparing the basic nature of various compounds, I came across the following two compounds:
In case of A I could see several resonating structures, and also the −M ...
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What is "ionic-covalent "resonance?
Advanced Inorganic Chemistry: A Comprehensive Text on Pg. 228, Chapter 8 titled 'Boron' talks about three factors which appear to be responsible for the shortness of $\ce{B-X}$ bonds(where $\ce{X}$ is ...
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Electrophilic addition to benzene [closed]
A question deals with electrophilic addition to the following compound;
Apparently, the benzylic carbon gets a positive charge during electromerism, invoking resonance stabilization.
Benzene is an ...
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Fastest way to determine if molecule has resonance structures [closed]
I came across this old exam problem:
For which of the following choices, is every molecule a resonance hybrid with resonance structures?
A. $\ce{SO2},$ $\ce{NH3},$ benzene
B. $\ce{SO3^2-},$ $\ce{NH3},...
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Resonance hybrid of nitrosobenzene
In nitrosobenzene, there are two ways that the $\ce{-N=O}$ group can show mesomeric effect.
It can show positive mesomeric effect by becoming $\ce{=N+=O}$
It can show negative mesomeric ...
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Carboxylic acid bond lengths in 3-carboxycyclobutane-1-carboxylate
Select correct order of bond length of the above bond P, Q, R & S:
(A) P > R > S > Q
(B) Q > R = S > P
(C) S > Q > R > P
(D) None of these
I think the answer should be (D) ...
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Isotopes and electronegativity
Is there any difference between electronegativities of isotopes of the same element. For example consider the above compound. Will all the resonance structures be equivalent?
Also if I place the ...
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Methyl group and acidic nature [duplicate]
After reading various answers here on StackExchange (like Why is the methyl group electron-donating via the inductive effect? and Strongest negative inductive effect group between trimethylammonium, ...
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Resonance of diazomethane [closed]
I understand the diazomethane resonance forms that have two double bonds between $\ce{C=N}$ and $\ce{N=N}$ in the structure and also the form that has one single between $\ce{C-N}$ and triple between ...
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Why is formic acid stronger than acetic acid [duplicate]
Even when acetate ion is stabilized due to resonance why is it a weaker acid than formic acid. It is true that acetic acid has +I effect due to methyl group present on it but resonance is a stronger ...
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Which resonance structure would be favorably contributed to the actual structure?
Total number of pairs of resonating structure in which second is more favorable than first:
I know (d) and (e) have second structure more stable.
(f) has both same.
According me to, (a) and (c) ...
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Resonance energy in benzene
Quoting from my textbook:
Although stabilized by resonance compared with other carbocations, its resonance energy is much less than that of the starting benzene ring.
Here is more context :
Isn'...
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Why does meta directing group also pull electrons from ortho and para positions?
I have been taught that electron withdrawing groups are meta directing. If it cannot modulate electron density over ortho and para positions during resonance, why does it help in nucleophilic ...
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Comparison of basicity of Aniline, p-Anisidine, and o-Anisidine [duplicate]
I have a question where I am required to compare the basicity of Aniline, o-Anisidine, and p-Anisidine.
Now here's what I do know:-
In ortho substituted aniline, an ortho effect acts which reduces ...
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Acidity of naphthol vs hydroxynaphthoquinone [closed]
I have the following two compounds whose acidity I need to compare. I tried drawing out the resonating structures but I seem to not be able to draw final conclusion.
I know that the conjugate base of ...
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Why does Chem3D minimize nitrogen dioxide (radical) so badly? [closed]
I build from text O-N+O (the SMILES of this is O=[N+][O-]), I delete the hydrogen atom added automatically on N, then I start MM2 Minimization. Both the bond length ...
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No resonance in Anti Aromatic compounds
My teacher commented on Anti aromatic compounds as being less stable compounds as it doesn't undergo resonance inspite of having π-bonds/electron pairs in conjugation. I didn't understand why so. Can ...
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Effect of phenyl and vinyl substituents on Acidity of carboxylic
Recently I came across this statement in my textbook:
Direct attachment of groups such as phenyl or vinyl to the carboxylic
acid, increases the acidity of corresponding carboxylic acid contrary
...
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3
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Odd looking carbocation stability order [duplicate]
I am studying introductory organic chemistry, suddenly this one started looking odd,
The carbocation stability for three compounds as given by my book is shown below,
Let me call those as ...
user91694
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Why is o-nitroaniline not more basic than aniline? [closed]
We know from SIR effect (Steric Inhibition of Resonance) that in o-nitroaniline, the nitrogen's p-orbitals will change their plane, causing the conjugation/resonance of its lone pairs to stop. So, the ...
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Why dosen't NO₂ form according to the octet rule?
Supposedly every atom that is in the second period of the periodic table has to obey the octet rule; this means that they have to be surrounded by 8 electrons (or so I was taught). Studying resonance ...
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Acidity order of organic compouds
Here is the question:
We have to find the order of their acidity.
Here is my thought process:
We check the acidity order by finding which conjugate base is more stable. Thus we remove $\ce{H+}$ from ...
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Mesomeric Effect and its Strength
While solving a question in organic chemistry, I needed to compare the strength of mesomeric effects of various groups.
I looked it up on Wikipedia, and it goes like this :
+M EFFECT ORDER :
–O− > –...
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Why aren't all bonds in cyclobutadiene not equal? [duplicate]
Cyclobutadiene is like benzene in that it has alternating single and double bonds in a ring. However, it's bonds are not the same length, the double bonds being shorter than single bonds. The molecule ...
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How to determine the relative contribution of resonance structures when different rules give contradictory outcomes? [duplicate]
In order to determine the relative contributions of resonance structures, my textbook gives the following rules (in order):
The more covalent bonds a structure has, the higher it scores.
Structures ...
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How far does the delocalisation (resonance) effects for substituents extend for a conjugated system?
Let's say we have a conjugated system like this one:
Now, the delocalisation of the benzene electrons with the nitrate system means that the ortho, and para positions on the immediate benzene ring ...
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IUPAC name of Dewar benzene [closed]
Dewar benzene according to Wikipedia has the IUPAC name bicyclo[2.2.0]hexa-2,5-diene.
Is it correct to give this name because resonance takes place and if we fix a certain numbering, as resonance ...
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What is the significance of the downward arrows in energy level diagrams in organic chemistry?
The following text is from Solomons, Fryhle and Snyder Organic Chemistry Third Edition, chapter 1 "The Basics: Bonding and Molecular Structure", page 13, topic 1.5 "Resonance Theory&...
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Which one is the strongest base among the following compounds?
I am confused between option (2) and (4). Both lone pairs of nitrogen are localized, so next, I looked at the hybridization of $\ce{N}$ in each compound. As in (2), the $\ce{N}$ is $\mathrm{sp^2}$ ...
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Can this sp2 lone pair resonate?
In methyl isocyanate, $\ce{CH3CNO}$, shown below,
it seems that the nitrogen lone pair can resonate with the carbon oxygen double bond, generating a resonance structure something like acetonitrile ...
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Stabilization by resonance
My textbook (NCERT Chemistry. Part I. Textbook for Class XI [1, p. 106]) states that
Resonance stabilizes the molecule as the energy of the resonance hybrid is less than the energy of any single ...
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Difference in transition lifetimes for near-resonant v/s non-resonant Raman effect
I have read that a virtual state is created when Raman scattering occurs. Since this state is forbidden, the molecule upon absorbing a photon (not enough to take it to the next electronically excited ...
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Which one is the most stable canonical structure?And why? [closed]
According to my book the answer is given that structure III is the most stable because all the atoms have complete octets.
But I think it should be II because of,
(a) Structure III has positive ...
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Structure of dihydrogen peroxy-phosphate ion
In structure of Dihydrogen peroxy-phosphate ion $\ce{H2PO5-}$, shouldn't negative charge be on oxygen linked directly to phosphorus, rather than on oxygen linked through peroxy linkage with another ...
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Why are only two bond structures considered for ozone and not three? [duplicate]
We were taught in chemistry that:
Formal charges can be determined by drawing the Lewis dot structure, then subtracting the nonbonding electrons and half of the bonding electrons from the number of ...
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Resonance structures of 4‐aminobut‐3‐en‐2‐ylium
Problem
How many resonance structures can be drawn for the following molecule?
(a) 1
(b) 4
(c) 3
(d) 2
Answer
Question
I think that the molecule can be drawn in three ways, which contradicts the ...
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How can we calculate the "degree" of conjugation?
So a conjugated system is a system of connected p orbitals or alternating single and multiple bonds.
I know that conventionally, we count the number of adjacent parallel p orbitals or alternating ...
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Why hyperconjugation can't stabilize carbanion?
If Resonance can stabilize both carbo cation and anion then why can't hyperconjugation stabilize carbanion ? Since both Resonance and Hyperconjugation are pretty much the same, i.e both involve ...
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