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)
464
questions
0
votes
0
answers
14
views
Stabilization Energy of Pi Bonds [closed]
Why do people calculate the stabilization energy of the pi bonds with an equivalent number of isolated double bonds (ex ethylene)? How would we relate relate to the structural diagram of one resonance ...
0
votes
0
answers
47
views
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 ...
- 67
1
vote
1
answer
176
views
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 ...
- 51
3
votes
1
answer
372
views
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 ...
- 323
0
votes
1
answer
71
views
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 ...
3
votes
1
answer
415
views
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 ...
- 177
2
votes
0
answers
32
views
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 ...
- 211
-2
votes
1
answer
78
views
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 ...
2
votes
0
answers
58
views
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 ...
- 29
0
votes
0
answers
57
views
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 ...
- 669
-4
votes
2
answers
78
views
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 ...
-2
votes
1
answer
2k
views
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 ...
- 23
-3
votes
1
answer
92
views
+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)...
- 89
-2
votes
2
answers
233
views
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 ...
- 9
3
votes
1
answer
236
views
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 ...
- 169
-4
votes
2
answers
157
views
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 ...
- 35
-4
votes
1
answer
128
views
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 ...
4
votes
2
answers
517
views
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 ...
- 144
-2
votes
1
answer
72
views
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?
0
votes
0
answers
47
views
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 ...
0
votes
0
answers
525
views
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 ...
- 39
1
vote
1
answer
666
views
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 ...
- 299
-5
votes
1
answer
58
views
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 ...
-2
votes
1
answer
66
views
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 ...
1
vote
1
answer
400
views
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 ...
- 329
0
votes
0
answers
144
views
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 ...
6
votes
0
answers
90
views
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 ...
- 69
1
vote
1
answer
68
views
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 ...
-1
votes
2
answers
310
views
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 ...
- 37
0
votes
0
answers
70
views
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 ...
0
votes
1
answer
121
views
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 ...
4
votes
1
answer
141
views
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. ...
- 1,614
2
votes
1
answer
2k
views
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, ...
- 31
-2
votes
2
answers
101
views
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 ...
- 25
3
votes
0
answers
336
views
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, ...
- 107
1
vote
0
answers
298
views
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 ...
- 1,526
0
votes
0
answers
165
views
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 ...
user121185
3
votes
1
answer
535
views
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 ...
- 222
0
votes
0
answers
465
views
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 ...
0
votes
2
answers
983
views
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 ...
- 67
1
vote
1
answer
967
views
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 ...
- 21
1
vote
1
answer
269
views
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 ...
- 222
2
votes
0
answers
237
views
Does 'aromaticity' apply to individual resonance structures or the hybrid?
When we define the aromaticity of a compound, is it meant to describe the resonance hybrid of the compound, or for individual resonance structures of the compound?
I think the latter is wrong because ...
- 195
0
votes
0
answers
186
views
What is the order of decreasing stability among following molecules?
I am almost certain that (IV) is most stable and (III) is least stable. How to compare between (I) and (II)? Is it something related to angle strain?
I am also confused if you can compare between ...
- 434
2
votes
0
answers
56
views
How can you explain the pKa of the first protolysis of phosphoric acid without using resonance [duplicate]
The pKa1 of phosphoric acid is 2.14.
As far as I am concerned, phosphoric acid does not have any double bounds and, as a main-group element, obliges to the octet-rule. This does create formal charges ...
- 31
1
vote
0
answers
41
views
Do degenerate states have exchange energy?
I have read that exchange energy exists between non-degenerate levels $1s$ and $2s$ or between $1s$ and $2p_x$ in the Helium atom in the first excited level:
$$K_s = \left< 1s(1)2s(2)|H'|1s(2)2s(1) ...
- 395
5
votes
2
answers
425
views
Acidic strength comparison of squaric acid and rhodizonic acid
These two are dibasic acids with the following structures (squaric acid and rhodizonic acid in order).
Empirical evidence proves that squaric acid is more acidic than rhodizonic acid.
It is a ...
- 145
0
votes
0
answers
56
views
Comparing stability of two carbocations [duplicate]
Which of the following ions(A and B respectively) is more stable? How can we explain this on the basis of resonance?
Here's what the solution said:
Structure (A) is a primary carbocation and has no ...
- 1,208
0
votes
0
answers
391
views
Is it correct to say that benzene is more stable than cylcohexatriene due to delocalization?
I'm virtually all chemistry books I own say that benzene is more stable than the theoretical cyclohexatriene, by 150 kJ to be specific, due to the delocalization of pi electron density around the ring....
- 553
1
vote
0
answers
232
views
Acidity of triphenylmethane
The question is : Why does triphenylmethane have such a high pKa value (going up to $33$)
My reasoning suggests that the conjugate base is highly stabilized and hence triphenylmethane should be a ...
- 513