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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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 ...
6 votes
1 answer
5k views

Why is benzenediazonium fluoroborate water insoluble and stable at room temperature?

Benzenediazonium fluoroborate is water insoluble and stable at room temperature. Why is this salt, water insoluble? Also I am told that benzenediazonium salts are stable only at low temperature(<5°...
14 votes
2 answers
11k views

Resonance stability: ester vs. thioester

My problem set solution cites: "Although sulfur is less electronegative than oxygen, overlap is a more important consideration. Sulfur is a member of the third period. As a consequence, a ...
2 votes
1 answer
1k 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 votes
0 answers
585 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 ...
-2 votes
1 answer
2k 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 ...
-1 votes
2 answers
770 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 ...
3 votes
1 answer
2k views

According to MO theory, why is the dilithium cation more stable than the dilithium anion?

According to molecular orbital theory, $\ce{Li2}$ fills up two electrons in the $\sigma_\mathrm{g2s}$ molecular orbital; $\ce{Li2+}$ fills up one electron in the $\sigma_\mathrm{g2s}$ MO, and $\ce{...
1 vote
2 answers
878 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 ...
17 votes
3 answers
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Why are acetals stable to bases and nucleophiles?

Why are acetals stable to bases and nucleophiles? Could it be due to electronic effects? Lone pairs on the two oxygen atoms create an unfavorable environment for the approaching nucleophiles and ...
-1 votes
1 answer
958 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 vote
0 answers
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What is the stability order for these octahydrobiphenylene structures?

According to me most stable is Z because it has maximum alpha hydrogen, Between X and Y both have same alpha hydrogen, but X has conjugation. So it is more stable than Y. So Order is Z>X>Y. Is my ...
-2 votes
1 answer
1k 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 ...
4 votes
1 answer
631 views

Influence of neighboring fluorine and hydroxyl on carbocation

Which of the 2-fluorobutan-3-yl and butan-2-ol-3-yl carbocations will be more stable? I know that fluorine has a greater electron-withdrawing inductive effect, but what about the resonance effect of ...
0 votes
1 answer
768 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?
13 votes
1 answer
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Stability of keto-enol vs. conjugation

I am trying to figure out which tautomer of creatinine: is more stable. We see that the enol tautomer is more highly conjugated: the $\pi$ electrons from the alcohol to the double bond to the $\pi$ ...
20 votes
2 answers
11k views

Why is cis-1,2-dichloroethene more stable than trans-1,2-dichloroethene?

Why is cis-1,2-dichloroethene more stable than trans-1,2-dichloroethene? Usually, trans compunds are more stable than cis ones, due to less strain and its non-polarity. But, in this case it's quite ...
0 votes
1 answer
167 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 ...
11 votes
2 answers
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Is the ethyl cation really more stable than benzylic and allylic carbocations?

Source: Concepts of Organic chemistry by O.P. Tandon, page no. 235 My book appears to state that the ethyl cation (a primary carbocation) is more stable than both allyl and benzyl carbocations. I ...
0 votes
1 answer
126 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 ...
10 votes
2 answers
3k views

Why is triplet carbene sp2-hybridised?

Triplet carbene has a carbon with 6 electrons, of which 2 are unpaired. I would expect the carbon to be $\ce{sp}$ or $\ce{sp^3}$ hybridised and the two singly occupied orbitals to be degenerate. ...
2 votes
1 answer
18k views

Alkali metal carbonates, their thermal stability and solubility [duplicate]

From Li to Cs, thermal stability of carbonates increases. From Li to Cs, due to larger ion size, hydration enthalpy decreases. So, solubility should decrease from Li to Cs. But, experimentally, order ...
2 votes
0 answers
896 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 ...
-3 votes
2 answers
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Why is cyclopropane planar?

What would cyclopropane look like if it weren't planar? How and why does non-planar cyclopropane have higher torsional strain than planar cyclopropane? can you please show me visually via image that ...
18 votes
3 answers
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What exactly is "B-strain"?

On factors that influence the stability of carbocations, I came across this peculiar one: Bulky groups attached to the positively charged $C$-atom (of the carbocation), stabilize it by B-strain, ...
0 votes
1 answer
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Thermodynamic stability and Inertness [duplicate]

The following is from my teacher's notes: The reaction (where the reaction mixture is thermodynamically unstable but kinetically inert) tends to go as indicated by a positive total entropy change, ...
5 votes
1 answer
3k views

Energy required to break the "delocalised electron cloud" of benzene

I learned that when benzene undergoes hydrogenation, $\pu{208KJ}$ of energy is given off and thus $\pu{152KJ}$ less energy than what would be given off if Kekule's structure was correct. My confusion ...
4 votes
2 answers
294 views

Are all highly shock sensitive chemicals highly temperature sensitive too?

I found that some highly shock sensitive explosives like lead azide, mercury fulminate have a relatively high auto-ignition temperature. I want to know if it's a general property or not and why so? ...
6 votes
1 answer
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What is the order of stability of the resonance structures of furan?

I want to know which are the most stable furan resonance structures. I know that structure number 1 is the most stable, but which one comes after?
3 votes
3 answers
980 views

Is there a thermodynamic driving force for racemisation?

Why does racemisation occur? My doubts are: Is it due to entropy? If it is due to entropy, how is the reduction of optical activity by racemisation a consequence of increased thermodynamic ...
2 votes
0 answers
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Comparing thermal stabilities of MgCl2 and BaCl2

I read that to compare thermal stabilities of ionic solids: if the solid has a monoatomic anion, we compare thermal stability on the basis of lattice energy which is inversely proportional to size. ...
-1 votes
1 answer
671 views

Resonance structure and stability

Does the existence of resonance structures always translate as stability? I've been taught that resonance structures generally "spread out" charge in order to compensate for deficiency or excess of ...
2 votes
1 answer
2k views

Why doesn't cyclopropyl methyl carbocation stabilises itself by ring expansion? [duplicate]

I have been taught that ring expansion stabilises smaller cyclic compounds to a great extent. So why does cyclopropyl methyl carbocation shows such type of resonance rather than expanding its ring ...
2 votes
2 answers
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Stability of geometrical isomers in cycloalkanes

Among the following, which should be the most stable compound? 1)Cis-cyclohexane-1,2-diol 2)Trans-cyclohexane-1,2-diol 3)Cis-cyclohexane-1,3-diol 4)Trans-cyclohexane-1,3-diol My thought process is-...
4 votes
1 answer
1k views

Stability of alkenes by hyper conjugation

I have learnt that for carbocations, electrons are delocalized from the $\ce{C-H}$ $\sigma$-bond to the empty p-orbital of carbon. Moreover, alkenes are stabilized by the delocalization of electron ...
7 votes
1 answer
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Hyper conjugation in acetic acid?

While comparing the relative stabilities of acetic acid and formic acid why don't we consider the 3 possible hyper conjugative structures which would stabilize the positive charge on carbon thus ...
7 votes
1 answer
9k views

Why can't NH5 form?

In ammonia a nitrogen atom forms 3 covalent bonds with hydrogen atoms and has one lone pair which can be used in a dative covalent bond with another hydrogen atom to form an ammonium ion. Instead of ...
29 votes
1 answer
8k views

Why is cyclooctateraene shaped like a "tub" rather than a "chair"?

I understand that for cyclooctatetraene (COT) to "escape" the horrible prospect of becoming an anti-aromatic molecule, it must adopt a non-planar conformation. The widely touted conformation of COT ...
1 vote
1 answer
284 views

How good is aromaticity at stabilization?

I've been taught that aromaticity is often a very good stabilization factor. Then I came across this question in which another compound was said to have more stability. Upon deprotonation arrange in ...
9 votes
2 answers
189 views

Are such high oxidation states as reported by Vojovodic et al. possible?

I am a student in theoretical chemistry and I am confused about the paper: Trends in adsorption of electrocatalytic water splitting intermediates on cubic $\ce{ABO3}$ oxides (Montoya, J. H.; Doyle, A. ...
2 votes
2 answers
585 views

Why is dipositive dilithium more stable than neutral dilithium? [closed]

According to J.D Lee, compounds with fraction bond number are unstable. I calculated that the bond order of $\ce{Li2^2+}$ is 0.5 while that of $\ce{Li2}$ is 1. Hence, $\ce{Li2^2+}$ must be less stable ...
3 votes
1 answer
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Why are long oxygen chains unstable? [duplicate]

H-O-H (water), H-O-O-H (hydrogen peroxide), H-O-O-O-H, H-O-O-O-O-H, etc. This is analogous to hydrocarbon chains, methane, ethane, propane, butane, etc. Note the Hydroxygen Chains satisfy 2 covalent ...
7 votes
0 answers
702 views

Bredt's rule applied to fused bicyclic systems

Ultimate question: Is Bredt's rule equally valid for fused bicyclic system (no bridgehead alkenes without a ring 8 carbons or more), but for other reasons (historical?) it is only defined as applying ...
-3 votes
2 answers
169 views

How two neutral atoms are together with no force between [duplicate]

How sodium atoms exist together when they all have unstability due to an extra electron present in their outermost shell? I mean how two neutral atoms Na atoms are existing together in form of white ...
16 votes
1 answer
16k views

Why are 7-membered rings less likely to form than 5- and 6- membered rings?

I see 5- and 6-membered ring products as the major products even when 7-membered rings are possible. Why is that 5- and 6-membered rings are more likely to form than 7-membered rings? Is it even true? ...
-3 votes
1 answer
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Why does fluorine form stable oxides while chlorine form unstable oxides? [closed]

The fluorine however it says my text book doesn't combine well with oxygen, nitrogen and itself but when about its oxides they are quite stable as $\ce{O3F2}$ has a melting point of $\pu{363 °C}$ ...
7 votes
2 answers
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Why is the acylium ion stable?

Why is the acylium ion stable? Doesn't the inductive effect of oxygen destabilize it? Compared to an alkyl cation, is an acylium ion more stable or less stable?
0 votes
1 answer
238 views

Effect of halogen atom on Markovnikov's rule

I know that the Markovnikov's rule is because of the stability of carbocations. If a halogen atom (electron-withdrawing group) is directly attached to the carbon atom carrying a positive charge, would ...
7 votes
4 answers
4k views

Why do chromyl bromide and chromyl iodide not exist?

It is known that chromyl chloride exists (popularly known as the product of a test for presence of chloride ion) but chromyl bromide and chromyl iodide are unknown. Why is it so? Why don't they exist?...
0 votes
1 answer
2k views

Stability comparison of benzylic carbocation and benzene

Which is more stable - benzylic carbocation or benzene - and why? Benzylic carbocation may have more resonance structure, but these structures are destroying its aromaticity as well. So, how do we ...

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