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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.

3
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0answers
22 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 ...
0
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0answers
11 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.
2
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1answer
35 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 ...
12
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5answers
599 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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0answers
16 views

Is this the most stable chair conformer? [closed]

Is this the more stable chair conformer or the opposite one where the two axial groups will become equatorial?
-1
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1answer
42 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 $(\ce{CH2=C=CH2})$ (...
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0answers
23 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 ...
-1
votes
0answers
25 views

Will a helium atom feel more stable having the electron configuration of another noble gas with more electrons?

Will a helium atom feel more stable having the electron configuration of another noble gas with more electrons? For instance, is an atom composed of 2 protons, 2 neutrons, and 2 electrons less stable ...
3
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0answers
36 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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0answers
50 views

Which group will show mesomeric effect?

If both $\ce{-CH2+}$ and $\ce{-NO2}$ groups are attached to benzene ring then which group would be more effective in showing $\ce{-M}$ effect?
2
votes
1answer
274 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 ...
-1
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0answers
34 views

How is hexanamide more acidic than aniline?

To compare the acidic strength, we compare how stable the conjugate base is right? So both of the conjugate bases have a negative charge on nitrogen. And both show resonance stabilization. What I ...
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0answers
73 views

Which effect is more dominating between hyperconjugation/no bond resonance and normal resonance?

In between hyperconjugation and resonance , is resonance effect always the dominating effect ? In the above example , the 1st structure has 9 alpha hydrogens and thus 10 hyperconjugative structures....
2
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0answers
55 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
1answer
59 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
2answers
43 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 ...
0
votes
2answers
88 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
votes
3answers
95 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 ...
-1
votes
1answer
58 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 "...
0
votes
1answer
81 views

Carbanion Stability [closed]

I was wondering that wether a Cross-Conjugated or a Extended-Conjugated carbanion is stable I have sort of memerise that a Cross-Conjugated one is more stable For example, Which of the Carbanion is ...
-2
votes
1answer
87 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 ...
1
vote
1answer
79 views

Stability of formyl chloride

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
votes
1answer
56 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
votes
1answer
57 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
votes
0answers
50 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 ...
0
votes
1answer
87 views

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, ...
1
vote
1answer
154 views

Which has more enol content?

According to me, resonance in {a} is more effective than {b}. And for monocyclic ketones, enol has very less content. I say {1} has lesser enol than {2}. Which is right?
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votes
3answers
153 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
1answer
348 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{...
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votes
1answer
71 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 ...
3
votes
0answers
142 views

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. ...
3
votes
1answer
46 views

Instability due to neutrons

Why does an excess of neutrons leads to instability? For example, both $\ce{^{3}H}$ and $\ce{^{4}H}$ are unstable, with respective half-lives of $3.89\cdot 10^8$ and $1.39\cdot 10^{-22}$ seconds. ...
0
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0answers
99 views

Why is ninhydrin stable as a geminal diol? [duplicate]

The following image depicts the structure of ninhydrin - $\ce{C9H6O4}$ Ninhydrin, as you see has two hydroxyl group attached to same carbon. In general, geminal diol (or gem-diol, for short) are ...
2
votes
1answer
146 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 ...
0
votes
1answer
47 views

Ring Expamsion And Final Structure

[IF you don't like to read the question just look at the 3 pictures the first one have carbocation which have to be stablised by ring expansions the other 2 are my predicted structure so please ...
2
votes
2answers
449 views

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-...
6
votes
1answer
475 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 ...
13
votes
1answer
178 views

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 $\pi$ ...
5
votes
1answer
247 views

What is the most stable structure amongst the keto-enol tautomers of pentane-2,4-dione?

I was assigned the following question and I cannot decide which is the correct answer. Which is the most stable structure? (a) pentane-2,4-dione (b) 4-hydroxypent-4-en-2-one (c) (Z)-4-...
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votes
2answers
146 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
2answers
196 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 ...
2
votes
1answer
164 views

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 ...
6
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0answers
158 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 ...
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0answers
10 views

where to find data on thermal decomposition of polysaccharide in aqeuous solution

This is a follow up of my previous question: "effect of over-pressure on lowering viscosity of polysaccharide solution" I would like to know where to find data on thermal decomposition of ...
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0answers
405 views

Compare stability of transition metal cations in aqueous solution

I have to compare the stability of the following transition metal cations: $\ce{Co^3+, Fe^3+, Cr^3+, Sc^3+}$ in aqueous solution. (Source: Joint Entrance Exam (JEE) 2013 Mains India) The first thing ...
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0answers
17 views

Rate of hydrogenation for alkenes [duplicate]

Which of the two alkene will react fastest with $\ce{H2}$ under catalytic condition? I know that rate is inversely proportional to the stability of alkene but here which will be more stable. ...
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votes
2answers
67 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 ...
7
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2answers
226 views

Can a six member ring expand to achieve octet completion to stabilize a carbocation?

(Probably unnecessary background: I came up with this carbocation while predicting the major product of $\ce{NaNO2/HCl}$ with 1-(methylamine)cyclohexan-1-ol) Will the following carbocation ...
0
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1answer
88 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 ...
0
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0answers
107 views

Reaction of pentadiene with HBr

$\ce{H2C=CH-CH=CH-CH3}$ reacts with $\ce{HBr}$ at low temperature. What would be the product? At low temperature, product would be kinetic and less stable, while the carbocation intermediate would ...