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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why aren't there 5 resonating structures of ch2-c6h5 where ch2 is a free radical

I don't understand why the last one is not considered one of the resonating structure?
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Which is the most stable resonating structure of naphthalene and why?

I read that the symmetric one is more stable than the other two but I didn't understand why. I am in high school so please keep that in mind
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Identifying electron donating or withdrawing groups

I am studying organic chemistry and have been confused on whether some groups are electron donating or withdrawing. Is there any particular rules that I can use to identify whether a group is electron ...
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44 views

When does replacing a double bond with a lone pair result in a valid resonance structure?

Take molecules A and B below. In A, we can move the electrons from the green pi bond into a lone pair on oxygen, then move the blue lone pair of electrons from the other oxygen to form a new π bond, ...
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41 views

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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49 views

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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72 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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37 views

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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35 views

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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71 views

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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32 views

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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107 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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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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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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72 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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368 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
35 views

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
338 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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3answers
215 views

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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216 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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38 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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171 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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83 views

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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84 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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3answers
276 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
433 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
124 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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83 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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149 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 ...
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1answer
90 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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203 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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518 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
101 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
160 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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97 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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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
565 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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242 views

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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1answer
758 views

How to determine the relative contribution of resonance structures when different rules give contradictory outcomes?

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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54 views

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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