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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92 views

Stability of dialkyl substituted alkenes

The stability order of alkyl substituted alkenes with respect to heat of hydrogenation was given as $$\ce{R_2C=CH2} > \ce{RHC=CHR}~(\textit{trans}) > \ce{RHC=CHR}~(\textit{cis}).$$ While I ...
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1answer
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Is there any method to find the energy of a molecule? [closed]

We say that a compound is more stable, when it has less energy. And, a compound with more energy wants to form a compound with less energy. But how can we exactly calculate the energy of a molecule? ...
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2answers
55 views

Thermal Decomposition of Sulfur Hexafluoride

What is the thermal decomposition temperature for $\ce{SF6}?$ I've heard it decomposes into $\ce{F2}$ and $\ce{SF4}$ only to decompose further into $\ce{S2}$ and $\ce{F2},$ but I haven't found much on ...
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Is it possible to create an acid anhydride that's stable in water and if so what conditions must its structure satisfy?

I ask this question because if acid anhydrides are always unstable in water then my interest, as a student of pharmacology, would be greatly diminished. Acid anhydrides are, in my books, at least, the ...
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2answers
47 views

Stability of F- Cl- Br- I-? In aqueous state [closed]

If we talk about hydrolysis F- will be more heavily hydrolysed so it should be more stable in aqueous state. But I know that HI is a stronger acid than HF. So the stability of conjugate acid ie I- ...
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1answer
30 views

Why are bonded ions more stable than separate ions? [closed]

I was reading on the Born-Haber cycle when I encountered a problem. The textbook seemed to suggest that since energy must be supplied to separate an ionic compound into it's composite ions, then the ...
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1answer
97 views

What does it actually mean by stability of an atom

There are several rules related to stability of an atom, like octet rule, half filled or fully filled d orbital etc. But none of them (at my best knowledge) does not explain why an atom is stable when ...
3
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3answers
189 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 stabilisethe ...
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2answers
2k views

Why exactly is a fluoride anion a stronger base than iodine anion?

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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2answers
723 views

I am confused about the stability of carbanion III and IV in the image

I am confused about the stability of carbanion III and IV in the image, I think III is more unstable because of electron donating effect (+R) of $\ce{-OCH3}$ group but my book says III is more stable ...
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1answer
65 views

Newman projections: how to tell which groups are bulkiest to determine what is the most stable conformation?

The scenario Let's say we have a molecule where in the Newman projection the front carbon has a hydrogen, methyl and an ethyl, and in the back carbon there's a hydrogen, something like a S, Cl or Br (...
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1answer
197 views

Stability of CI4 and PbI4

I have read in my textbook that $\ce{CI4}$ is more stable than $\ce{PbI4}$ due to inert pair effect. But shouldn't we also consider the effect of steric repulsions? In $\ce{CI4}$, four large iodine ...
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1answer
512 views

Reactivity and transport safety of substituted methyl benzoates

This was a practice question from an MCAT book whose answer I didn't really understand: The normal reactivity of methyl benzoate is affected by the presence of certain substituents. Which of the ...
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2answers
56 views

Ortho effect in cyclohexane

Compare the acidities and basicities of the compounds in the first and second row respectively. In aromatic compounds the methyl group would cause an "ortho" effect. Here we don't have an aromatic ...
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0answers
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Get fractional coordinates from special Wyckoff positions (IUCr)

I'm trying to get the fractional coordinates for Mo and S, for MoS$_2$-2H, where 2H means the phase. MoS$_2$-2H is a bilayer, in which each layer is separated from each other by Van der Waals forces. ...
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1answer
45 views

Energy lost due to stability [closed]

We used to say that when an atom is stable it is in its minimum energy state.Every shell has its fixed energy. So from where does the energy come which is lost by an atom to achieve stability. Do ...
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2answers
12k views

Why Cu+ is unstable in aqueous medium?

This was one of the question that was given in the school exam. But what I am expecting is that $\ce{Cu+}$ attains a $d^{10}$ configuration by losing one electron from s-subshell. Since it has fully ...
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0answers
28 views

Stability of Peroxynitric Acid in cold temperature

I have a question about the stability of Peroxynitric Acid i.e. $\ce{HO2NO2}$ at cold temperature. I know that it becomes stable when temperature decreases, but what is the specific reason for it? I ...
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0answers
48 views

Cis-Trans Isomers Heat of Combustion

Consider the 4 cis-trans isomers for the above compound. In what way would the cis-trans isomers affect their heat of combustion. I think that if the substituents are on alternating sides of the ...
2
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2answers
82 views

Why is hofmann product prefered here?

In the following reaction, Hofmann elimination is preferred. This reaction takes place by E1 mechanism. I thought the Zaitsev product would be major due to 1 extra hyperconjugating structure. In the ...
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5answers
10k views

Is the t-butyl carbocation more stable than the benzyl carbocation?

Various authors have different views regarding stability order of the benzyl and t-butyl carbocations. $$\ce{PhCH2+ ; (CH3)3C+}$$ In my opinion, resonance effect dominates, so the benzylic ...
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0answers
26 views

What explains the stability of aromatic compounds? [duplicate]

We are taught in High school that aromatic compounds are highly stable. Why is that true? Also, Why are Antiaromatic compounds highly unstable? Aromatic compounds have 4n+2 (n is a whole number) ...
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2answers
7k views

Are geminal disubstituted alkenes more stable than their cis/trans isomers?

I know for a fact that cis alkenes are less stable than trans alkenes due to steric repulsions. But what bugs me is the fact that why systems such as 2-methylprop-1-ene, where I believe steric ...
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1answer
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Polarity and stability

Why is cis-1,2-cyclohexadiol less polar than trans-1,2-cyclohexadiol? I know it has something to do with stability and chair conformations, but I'm not sure how it relates to polarity. I know cis-1,...
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66 views

Stability order of p-quinone, o-quinone and diphenoquinone

Question Determine stability order: Answer Thoughts I found this question quite tricky and confusing. According to my concepts and logic 3 should be non-aromatic, while 1 and 2 are antiaromatic. ...
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2answers
69 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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1answer
903 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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1answer
327 views

Why is iron pentacarbonyl known, but iron(III) hexacarbonyl is not?

Why is the neutral complex $\ce{[Fe(CO)5]}$ known, but the cationic carbonyl complex $\ce{[Fe(CO)6]^3+}$ is not known?
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1answer
48 views

Para effects on substituents in aromatic compounds

I wanted to know how to compare the following compounds on basis of acidic strength. I have to find the acidic strength of following compounds with $\mathrm{X}=\ce{CH3, \ OCH3,}$ and $\ce{NO2}$. For ...
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0answers
52 views

Are all ions stable? [closed]

My science teacher says that all ions are stable, which seems wrong to me. For example $\ce{He^{-1}}$ is an unstable ion of helium, and although it might not exist in the real world, it is still ...
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1answer
121 views

Are all stable Xenes (graphene-like 2D honeycomb sheets) buckled?

background: Per this abstract Silicene, germanene and stanene are part of a monoelemental class of two-dimensional (2D) crystals termed 2D-Xenes (X = Si, Ge, Sn and so on) which, together with ...
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0answers
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Why isn't protium nucleus considered most stable nucleus?

My chemistry teacher told me that $\ce{^{56}Fe}$ is the most stable nucleus because of the highest binding energy per nucleon. But if we consider a protium nucleus, it has only 1 proton so there is no ...
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1answer
496 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
515 views

Which is more stable chemically: DNA or peptide

Assuming enzyme-free environment, and the DNA and peptide are lyophillized, and then stored in vials under the same conditions (temperature and humidity). On average, which would be more chemically ...
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1answer
51 views

Why do stable compounds have a lower heat of combustion?

My brain somehow doesn't accept that more stable compounds require have less enthalpy. Isn't it like, if a compound is stable, it requires more energy to break the bonds because the compound doesn't ...
2
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1answer
3k views

Stability of Allenes and Alkynes,

In Allenes, the $\ce{C=C=C}$ structure makes sure that the $p$-orbital of central carbon overlaps with 2 other carbons and the $p$-orbital of central carbon spreads out over the 3 carbons. In ...
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3answers
64 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
123 views

The Evasive Ether: Existence of diethynyl ether?

I tried to find online whether the compound diethynyl ether, $\ce{HC#COC#CH}$, exists in a stable state at STP, mainly out of curiosity, but also because it would be interesting to study the ...
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1answer
65 views

Why is the chlorine ion more stable than the chlorine atom? [closed]

In heterolytic cleavage, for instance, $\ce{NaCl}$ breaks in two fragments $\ce{Na+}$ and $\ce{Cl-}$. If chlorine is fully filled because it takes one electron from sodium, then why does chlorine make ...
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1answer
159 views

How to figure out the most stable conformation of the diastereomer?

I guess my main question is looking only at the newman projection how does one determine the stereochemistry? In the molecule to the right, I get for the first carbon, (et, H, Me,) R ( I flipped it ...
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1answer
35 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 ...
3
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1answer
57 views

Quantitative measurement of ring strain

While looking for data about ring strain in cycloalkanes, I came across two types of data: Ring strain per methylene group (let's denote this quantity by X): The difference between heat of combustion ...
4
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1answer
199 views

Heats of combustion of cycloalkane homologues

Heat of combustion increases as the number of carbons increases, but on comparing ethyl cyclopentane, ethyl cyclohexane, andethyl cycloheptane, shouldn't you consider ring stability too? In that ...
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1answer
332 views

What is the trend of thermal stability of group 1 oxides?

The thermal stability of most compounds of Group 1 elememts (hydroxides, carbonates, nitrates) increases down the group due to decrement in charge density of the cation. Now, according to one of my ...
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3answers
1k views

Why don’t all objects melt and liquefy when heated sufficiently?

Certain objects such as metals, glass, plastic, sugar etc. melt when heated to a certain temperature but other materials such as a piece of wood, paper, a piece of rock etc. do not. Why is that?
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1answer
53 views

For group 13 elements M³⁺, why is the formation of MCl₄⁻ more favorable than for group 12 elements M²⁺?

I'm not a chemist and I'm trying to understand a chemistry point from a talk I went to recently. Any help would be much appreciated. The speaker was talking about $+3$ (Group 13) elements in the ...
4
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1answer
3k views

Why are noble gases stable? [duplicate]

Generally, noble gases are very unreactive. Why? I understand that it has to do with electron shielding prospective electrons that could join the atom or leave and the energies associated with both ...
25
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3answers
11k views

Why are noble gases stable

I was recently asked the question "Why are noble gases stable? with the expectation of providing an answer beyond the general explanation of "they have full valence layers" and I couldn't think of one....
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3answers
806 views

Acetone-resistant clear plastic

Is there a plastic that's clear, acetone resistant, and ideally sold in sheet stock that's ~1/8" or 1/4" thick? Both acrylic and polycarbonate are out, they turn cloudy on contact with acetone. I ...
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0answers
58 views

Effect of intramolecular hydrogen bonding on the stability of a molecule

What will be the effects of intramolecular hydrogen bonding on the stability of a molecule? Will it increase or decrease the overall stability of a molecule? Or will it not have any impact on the ...

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