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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Ratio of Resonance Hybrid? [closed]

In 1932 A.A Levine and A.G Cole studied the ozonolysis of o-xylene and isolated three products : glyoxal, 2,3-butanedione, and pyruvaldehyde. In what ratio glyoxal : 2,3-butanedione : pyruvaldehyde ...
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Which resonance hybrid structure of NO2- is correct? [closed]

I saw on youtube that you could write the Lewis structure of $\ce{NO2-}$ as given in the second image where we can add the red dots on either side since both of them have an equal formal charge $(-1/2)...
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Comparing stability of radicals

I was asked to compare the stabilities of the following radicals: Allyl radical, Methylcyclohexyl radical, 3-bromo-butyl radical, methyl radical and 2-methylphenyl radical This is the order I came up ...
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Major product from allylic halogenation of alkenes

Allylic halogenation of butene happens in the following way: The RDS of this radical chain mechanism is allylic hydrogen abstraction ($\ce{H_a}$) from the allylic position to give a 1° allylic ...
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metal ion complex with carbon dioxide [closed]

Using ORCA and Avogadro, I stimulated the possible MO orbitals of carbon dioxide complex with lithium ion (Lithium chloride) and cesium ion (cesium chloride) each at a time. i expected that Due to ...
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29 views

Resonance and basicity

A base donates a lone pair or accepts an $\ce{H+}$. Thus if a copound has resonance where the lone pair is involved, there is less tendency to donate a lone pair and basicity decreases. But if a base ...
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59 views

Resonance Structures of 9H-Fluorene [closed]

How many resonance structures does a 9H-Fluorene carbocation have with a positive charge on the top of the cyclopentane ring (a secondary carbocation)? I came up with four different structures.
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Application of Markovnikov's rule with EWG's and Resonance

I want to ask a question concerning Markovnikov's rule. Consider the following question: We can tell that there will be two types of stabilisation upon formation of the carbocation: Resonance via ...
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Contribution of resonating forms to molecular electron density distribution [closed]

When multiple resonating structures exist for a molecule, it does not actually exist in either state, but in a hybrid of both.I have been lead to believe that in conjugated systems, several adjacent p ...
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1answer
59 views

Estimation of dipole moments in aromatic compounds

If it asks to compare dipole moment in aromatic compounds then do we see inductive or resonance effects or do we see a mix of both? E.g. we have to compare dipole moment in pyrrole and furan then in ...
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Resonance forms of diazomethane [duplicate]

Most references show resonance structures of diazomethane as a dipolar molecule with positive charge on first nitrogen atom and negative charge at carbon or second nitrogen atom. why isn't there a ...
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Why is Cl2-P-O-Cl an unfavourable structure for POCl3?

Why is the structure $\ce{(Cl)2P - O - Cl}$ unfavourable compared to the two structures in the picture? The latter in the picture and the one I stated both have zero formal charge, so I don't really ...
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Cross-conjugation and aromaticity in pyrene

I have read about non-huckel double bonds and clar's rule, but what made me confuse is that huckel's perception gives me the feeling that central bonds in polycyclic aromatic hydrocarbons (ex: pyrene) ...
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1answer
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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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1answer
93 views

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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60 views

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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Acidity of cyclopentadiene [duplicate]

Why is cyclopentadiene more acidic than dibenzocyclopentadiene although in the latter, the negative charge will be more distributed and consumed in resonance stabilization.?
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2answers
138 views

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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1answer
42 views

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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1answer
62 views

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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1answer
270 views

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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1answer
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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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2answers
155 views

Does Cl- Have more -I effect or +M effect ( Resonance effect)?

In this question my answer was (A) because i though $\ce{NH2}$ 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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1answer
139 views

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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1answer
34 views

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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1answer
40 views

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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1answer
79 views

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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228 views

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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1answer
180 views

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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1answer
82 views

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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2answers
72 views

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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Reactivity Order of Nucleophilic addition

My teacher asked me this question. "Compare the reactivities of acetaldehyde and trimethylacetaldehyde towards nucleophilic addition". I explained how trimethylacetaldehyde was sterically hindered and ...
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0answers
99 views

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 ...
4
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1answer
84 views

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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1answer
46 views

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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1answer
143 views

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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1answer
396 views

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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3answers
85 views

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 ...
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1answer
118 views

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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1answer
57 views

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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1answer
37 views

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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2answers
419 views

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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