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Questions tagged [stability]

Applied to a chemical species, the term expresses a thermodynamic property in reference to a standard, stating that one state is lower in energy than another. The tag should be applied to questions seeking answers with respect to the stability (or instability) of a certain chemical species, molecular entity and/or electronic structure. It must not be applied to questions about the reactivity of particular chemical species.

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40 views

What is the stability order of the carbocation and carboanion?

So I came up with examples as below: 1 2 Now I am confused about the +I and -I effect in these structures since to my knowledge it can only be applied when there is a substituent (I might be wrong)...
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37 views

Classic/killer/easy application for the deuterium kinetic isotope effect?

I'm a physicist. While visiting someone's o-chem class I learned about the existence of the deuterium kinetic isotope effect. This seems like an extremely sweet example of zero-point energy, and I ...
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42 views

Stability of alkenes

The following question was asked on myPAT website: I started with the solution by counting the hyper-conjugative structures available to each alkene. Based on this concept only, order is: I > ...
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0answers
27 views

What is the order of stability of the cyclobutyl and cyclopropyl carbocations?

I know about the exceptional stability of Cyclopropylmethyl carbocation. In some books it is given that cyclopropyl and cyclobutyl carbocations are highly unstable due to their high strain. That ...
2
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0answers
46 views

Why do alkyl substituents stabilize alkenes?

My textbook states that because $sp^2-sp^3$ bonds are stronger than $sp^3-sp^3$ bonds, alkenes are more stable than alkanes. The rule given is that bonds with more $s$ character are stronger. However,...
2
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1answer
567 views

Reaction of aqueous sodium carbonate with aluminum foil

Aqueous sodium hydroxide is known to react with aluminum foil in an exothermic, hydrogen-gas releasing reaction like $$\ce{2NaOH(aq) + 2Al(s) + 2H2O(\ell) → 2NaAlO2(aq) + 3H2(g)}$$ However, on ...
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1answer
41 views

Cupric and cuprous copper [duplicate]

Copper has two chlorides: $\ce{CuCl2}$ and $\ce{CuCl}.$ Copper reacts directly with chlorine to form a copper(II) chloride. Why doesn't it form copper(I) chloride? Is it because $\ce{CuCl2}$ is more ...
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2answers
123 views

Why exactly is a fluoride anion a stronger base than iodine anion? [closed]

First off, I've learnt that stronger acids produce weaker conjugate bases (through Brønsted–Lowry acid–base theory). Then I looked at the $\mathrm{p}K_\mathrm{a}$ values of $\ce{HF}$, $\ce{HCl}$, $\...
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0answers
100 views

How does cross-conjugation destabilizes a molecule?

Wikipedia article on ortho effect suggests that o-toulic acid is more acidic than benzoic acid. This fact is rationalized by suggesting that steric effect causes COOH group to "twist" out of the plane ...
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0answers
54 views

Maximum lifetime of plastic on earth

[EDITED] If humans disappeared today, and aliens visited in the future, for how long would plastic or other "obviously" non-natural polymers be detectable on the planet, using known or plausible ...
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0answers
35 views

Does 2,2-dimethylpropan-1-ol give a positive Lucas test?

I learnt that the Lucas test involves the formation of a carbocation and it gives a positive test based on the stability of the carbocation formed, and hence primary alcohols do not show turbidity (...
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1answer
36 views

Things to consider to determine stability of a compound to another? [duplicate]

Some Compounds with higher bond dissociation energy seem to be more reactive towards certain compounds then ones with lower bond dissociation energy , so what are the things you need to factor in to ...
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3answers
230 views

Shouldn't it take more energy to break CO2 compared to CO? [closed]

I read in a book that bond dissociation energy of carbon monoxide $(\ce{CO})$ is $\pu{749 kJ/mol}$ and carbon dioxide $(\ce{CO2})$ is $\pu{532 kJ/mol}.$ Shouldn't it take twice as much energy to break ...
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1answer
64 views

How to find the strongest base using stability arguments

Answers: The most acidic is D and the most basic is A. So first off I compared A with B: I'm kinda confused on this. I looked at the base NH one and saw that when it was protonated it lost its ...
3
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0answers
29 views

On the stability of methyl mercury

Question: Given that $\ce{Zn, Hg}$ are in the same group, how to explain that $\ce{Hg(CH3)}$ is stable but $\ce{Zn(CH3)}$ is unstable and $\ce{Hg(CH3)Cl}$ is stable? $\ce{Hg(CH3)}$ seems to have an ...
3
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1answer
61 views

Molecular Orbital Hybridization vs Delocalization for positive charge stabilization

While studying Molecular Orbital Theory, I ran into a comparison of basicity between pyridine and piperidine. The latter was concluded to be more basic because of the sp3 hybridization of the ...
3
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0answers
90 views

Which is more stable: isobutylene or cis-2‐butene?

How do you compare which is more stable without using the heat of hydrogenation or combustion or any other numeric factual value: $\ce{(CH3)2-C=CH2}$ or $\ce{CH3-CH=CH-CH3}$ (cis)?
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122 views

Why are palladium and platinum carbonyls unstable at room temperature?

By palladium and platinum carbonyls, I mean the mononuclear, homoleptic, charge-neutral, binary carbonyl complexes of the form $\ce{M(CO)_n}$ and not any heteroleptic complexes like $\ce{Pd(CO)(PPh3)3}...
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1answer
56 views

Relevance of strain energy, total energy and stability of molecule?

Would anybody please highlight the difference between total strain energy of a molecule, total energy of a molecule and what we can infer about the stability of the molecule using the total strain ...
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3answers
61 views

Reason Behind Decrease In Potential Energy [closed]

Atoms combine to gain stability. They gain stability when they lose energy. In my book, it's given that the potential energy of the system is reduced during chemical combination. But I am eager to ...
2
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0answers
38 views

Stability of the alkenyl and phenyl cations

One reason often cited for why alkenyl and phenyl halides do not undergo nucleophilic substitution by the $\ce {S_N1}$ mechanism is that the formation of the alkenyl and phenyl cations involve a ...
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0answers
65 views

Stability of Cycloalkyl Carbocations

What is the order of stability of the cycloalkyl carbocations? I think the stability should increase as we move from cyclopropyl carbocation to cyclohexyl carbocation, since the angle strain is ...
2
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2answers
323 views

Which of the following carbanion is most stable?

The carbanion which is most stable is The answer is 1. But why won't the answer be 2 because it shows resonance, whereas 1 only shows I effect and resonance effect is more dominant?
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0answers
38 views

Which of these chlorides is more reactive? [duplicate]

We do learn that for $\mathrm{S_N1}$ reaction the rates are tertiary > secondary > primary > methyl. The reasons mentioned are usually inductive and hyper-conjugative effect. But which of the ...
0
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1answer
421 views

Half/fully filled orbital stability

Beryllium the configuration is [He] 2s2 i.e fully filled but still quite reactive Also in neon [He]2p4 , neither half filled nor fully filled, still quite stable compound (As it forms compound with ...
55
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3answers
12k views

Why doesn't H₄O²⁺ exist?

I know this question has been asked previously but I cannot find a satisfactory explanation as to why is it so difficult for $\ce{H4O^2+}$ to exist. There are explanations that it is so because of $+2$...
2
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0answers
21 views

More stable carbocation, tertiary or benzylic? [duplicate]

This is a very confusing question that which is more stable, benzylic or tertiary butyl carbocation? Some sources say benzylic due to resonance some say tertiary due to +i effect and 9 ...
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0answers
44 views

Determination of the most acidic hydrogen in an organic compound

Identify the most acidic hydrogen in the compound below: Can someone please explain why is $\ce{H^\mathrm{a}}$ in the compound below more acidic than $\ce{H^\mathrm{b}}$? This is what is ...
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0answers
32 views

Stability and Resonance [duplicate]

The linked answers do attempt to clarify on 'stability' but I wanted an answer with specific connection to resonance. For example, the ethanoate ion can exist in many forms but, as we know from data,...
5
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1answer
168 views

Which of the two structures is more stable?

Which of the two structures is more stable? As far as I know, alkenes with a greater number of hyperconjugating structures are more stable. Hyperconjugation has a greater stabilizing effect ...
3
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0answers
57 views

Chugaev and Selenoxide Elimination giving different products

In class we are going over intramolecular elimination. In this question I will provide two similar reactants that provide a different mixture of products. The chugaev elimination gives a 50/50 ...
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0answers
25 views

What are the total amount of resonance structures for these two cations and which is the most stable cation?

Please see the following two cations. I have proposed the following resonance structures. Please let me know if I have missed something. Thank you.
3
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1answer
82 views

Does hyperconjugation into sigma-star explain methylamine's increased basicity relative to ammonia?

The inductive effect with the polarisation of the C-N bond obviously plays a role in stabilising the positive charge of the conjugate acid. But given the similar electronegativities for C and H, CH3 ...
15
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5answers
1k views

Define, (actually define) the “stability” and “energy” of a compound

When we say a conformer or compound is of "higher energy" than another, are we quantifying energy in terms of the bond strength? Or are we going off of how much energy it takes to break the bond? I ...
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2answers
328 views

Stability of alkadienes

Which of the following is the most stable? (i) Conjugated alkadiene $(\ce{CH2=CH-CH=CH2})$ (ii) Isolated alkadiene $(\ce{CH2=CH-CH2-CH=CH2})$ (iii) Cumulated alkadiene $(\ce{CH2=C=CH2})$ (...
0
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0answers
31 views

Why benzene has more heat of hydrogenation than cyclohexene? [duplicate]

According to me, benzene is more stable than cyclohexene due to its aromatic nature. Therefore the heat of hydrogenation of cyclohexene should be more than benzene (because I read that heat of ...
3
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0answers
84 views

Stability of carbocation

While comparing the stability, as the $\ce{CH3}$ group is electron donating, the first structure should be more stable due to this reason. But apparently the second one is more stable. Is there ...
2
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1answer
483 views

Why is Acetic acid (pKa = 4.76) stronger than carbonic acid (pKa = 6.36)? [duplicate]

In order to try and understand this, I evaluated it via stability of conjugate bases. The acetate vs carbonate ion. The only difference is what's attached to the carboxyl group, the $\ce{-CH3}$ and ...
2
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0answers
162 views

Stability of methoxy-methyl and tropylium carbocations

Which is expected to be more stable: methoxy-methyl carbocation $(\ce{CH3-O-CH2+})$ or tropylium $(\ce{C7H7+})$ cation? I think because oxygen would donate its lone pair so there will be complete ...
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1answer
418 views

Stability order of carbocations [duplicate]

These are some of the most stable carbocations, but what is the relative stability order between them. According to me it should be: C>D>B>A........ I came to this conclusion because both C and D ...
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2answers
81 views

Perpendicular orbitals in aryl and vinyl carbocations? [duplicate]

This point (iv) has been given under reasons for extremely low reactivity of aryl and vinyl halides. I cannot understand it. First of all, isn't the positive carbon atom in phenyl as well as vinyl ...
1
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2answers
127 views

Why does delocalization lead to stability? [duplicate]

If the electrons are relatively more stable when they are delocalized than when they are localized between two atoms, then why do we have bonds formed in the first place? Forming of bonds between two ...
2
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3answers
202 views

How does hyperconjugation lead to stability?

I know that hyperconjugation leads to delocalization of electrons between filled and unfilled orbitals and thus greater stability (that's what most textbooks said). However, I think that it reduces ...
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1answer
168 views

Why is a carbon to iodine pi-bond less stable than a carbon to fluorine pi-bond?

This question comes from a second semester undergraduate organic chemistry course. Please refer to the image below with regard to the question. My understanding of the trend in section 4a is that "...
1
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1answer
414 views

Carbanion Stability [closed]

I was wondering that whether a Cross-Conjugated or a Extended-Conjugated carbanion is stable I have sort of memorise that a Cross-Conjugated one is more stable For example, Which of the Carbanion is ...
-2
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1answer
461 views

Which Carbocation is most stable among the three? [closed]

According to me the answer should be (C) as that Carbocation will be stablized by resonance with Chlorine. I have read that resonance is the biggest deciding factor about the stability of a ...
0
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1answer
362 views

Stability of formyl chloride [duplicate]

Why is formyl chloride unstable? I know it is just a combination of CO and HCl. But why it is unstable whereas other acyl chlorides are stable, like acetyl chloride?
0
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1answer
72 views

Stability of tertiary carbocation [duplicate]

Our teacher told us that a carbocation connected to 3 cyclopropane rings is among the most stable carbocations. But I am unable to understand how, as resonance (the most important factor governing ...
0
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1answer
70 views

Stability of alkene

Sorry for this silly doubt but why is CR2=CH2 alkene more stable than CHR=CHR alkene? Both have same number of alpha hydrogens. I thought that the latter is more stable as in its trans isomer, the R ...
2
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0answers
219 views

Could Be2- exist?

I understand that Be2 cannot exist, since it has as many electrons in the antibonding as in the bonding orbitals. But it seems to me that since the next electron would go into the πu orbital, which ...