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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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28
votes
3answers
11k views

What is the reason for the exceptional stability of the cyclopropylmethyl carbocation?

Can someone explain this to me by drawing resonance structures for the cyclopropylmethyl carbocation please? Also one more question, is the tricyclopropylmethyl carbocation more stable than tropylium ...
20
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2answers
4k views

What is the favoured geometry of chlorine trifluoride?

Why is the first structure on the left more stable than the second one on the right? In the first one the angle between the two pair of nonbonding electrons is about 120° which is a lot less than ...
17
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1answer
12k views

Why is 2-methylpropene less in energy than its alkene counterparts?

Other isomers include 1-butene, cis 2-butene, and trans 2-butene. Why would 2-methylpropene be less in energy if there is more steric hindrance?
23
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3answers
10k 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....
20
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5answers
7k 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 ...
11
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2answers
10k 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 ...
8
votes
1answer
319 views

Why don't we see these lanthanide species?

For most lanthanide metals$^{[1]}$, the stable oxidation state is III. The general electronic structure$^{[2]}$ is $$\ce{[Xe] 4f^{0}^{-14} 5s^2 5p^6 5d^{0}^{-1} 6s^2}.$$ Elements that have the d-...
26
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1answer
12k views

Relative stability of cis and trans cycloalkenes

Why is the stability of (Z)-cyclodecene 2 greater than that of (E)-cyclodecene 1? I'd think that since 1 contains a trans double bond instead of a cis double bond, it should experience less steric ...
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 $+2$...
37
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5answers
110k views

Difference between thermodynamic and kinetic stability

What is the difference between thermodynamic and kinetic stability? I'd like a basic explanation, but not too simple. For example, methane does not burn until lit -- why?
21
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1answer
11k views

Stability Comparison between the Tropylium and Tricyclopropylcarbinyl Carbocation

Why is the Tropylium carbocation less stable than the tricyclopropylcarbinyl carbocation? The tricyclopropylcarbinyl carbocation undergoes a sigma-tropic rearrangement whereas tropylium is highly ...
21
votes
2answers
491 views

Why are lithides not known?

In the last few decades, many alkalides - anions of alkali metals - have been synthesised. The most famous is undoubtedly that of sodium: $\ce{[Na(\text{2.2.2-cryptand})]+Na-}$, but the alkalides $\ce{...
13
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2answers
14k views

The effect of hyperconjugation on the stability of alkenes with MO theory

Hyperconjugation stabilizes carbocations and that makes sense because electrons are given to the empty p orbital. But how does it stabilize alkenes? Can molecular orbital theory be used to explain it?...
13
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1answer
2k views

Stability of cyclobutyl methyl carbocation

I know that cyclopropyl methyl carbocation is exceptionally stable compared to say, benzyl carbocation. But I want to know how stable is cyclobutyl methyl carbocation compared to say, tertiary/...
11
votes
1answer
6k 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? ...
24
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4answers
5k views

Which molecule is more acidic: CHF3 or CHBr3?

I know that fluorine is more electronegative than bromine. However, because of the size of bromine, it is more stable with a negative charge. In the case of $\ce{HF}$ vs. $\ce{HBr}$, to me, $\ce{HBr}$ ...
20
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5answers
15k views

Comparing the stabilities of allylic, benzylic, and tertiary radicals

Which is the most stable free radical among the given species? (1) $\ce{CH2=CH-CH2^.}$ (allyl radical) (2) $\ce{C6H5-CH2^.}$ (benzyl radical) (3) $\ce{(H3C)3C^.}$ (t-butyl radical) (4) $\ce{...
14
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2answers
3k views

Why are aromatic compounds so stable?

I've never actually been told deeper reasons for this. In organic chemistry classes (1 and 2) we're usually told that aromatic compounds are very stable whereas anti-aromatic ones are not, and also, ...
14
votes
1answer
575 views

Why can't antiaromatic compounds just escape planarity and become non-aromatic to avoid destabilization?

Why can't just all anti-aromatic systems lose planarity (and hence conjugation) and be non-aromatic like cyclooctatetraene ? ...
4
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1answer
12k views

Why are double bonds at more substituted carbon more stable?

That $\ce{C=C}$ bonds are more stable at more substituted carbon atoms is a common argument used throughout Clayden et al., but is never actually explained (at least not in the first 21 chapters). ...
8
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1answer
1k views

Why is N₂ stable but HCN and C₂H₂ unstable?

Compounds with triple bonds generally seem to be unstable. $\ce{HCN}$ and $\ce{C2H2}$ are high-energy, relatively short-lived molecules that will readily polymerise or react with other organic ...
3
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0answers
265 views

Predominance of III oxidation state for lanthanides [closed]

For most lanthanide metals, the stable oxidation state is III [*]. The general electronic structure is $$\ce{[Xe] 4f^{0}^{-14} 5s^2 5p^6 5d^{0}^{-1} 6s^2}\ \ [**].$$ Elements that have the d-electron ...
3
votes
1answer
7k views

Why is a C–D bond stronger than a C–H bond?

I have heard that the carbon–deuterium bond is stronger than the carbon–hydrogen bond. What are the possible reasons for it? Is this also the reason that C–H bonds participate more in hyperconjugation ...
14
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2answers
7k views

Why is sulfur hexafluoride more stable than selenium or tellurium hexafluoride?

I was just reading about p Block elements from two different books. Both books say that $\ce{SF6}$ is extremely stable in 16th group due to steric reasons but my question is why is it more stable than ...
15
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5answers
16k views

Is oxygen with a positive charge more stable? (comparison of canonical structures)

Which of the contributing structures of the resonance below is more stable? I'm watching a video lecture by a professor of my college where he puts this question to the class. The class ...
8
votes
4answers
3k views

Why does stannous chloride occur despite the octet rule?

Shouldn't reaching an octet be any atom's "goal"? However, I've recently learned about cases that are either expanding octets, or have lesser than "enough" electrons for an octet abiding. e.g.: S in ...
18
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1answer
6k views

Stability of carbocations: CF3+ vs CH3+

Is $\ce{CF_3+}$ more stable than $\ce{CH_3+}$? In $\ce{CF_3+}$, there is $\ce{C-F}$ back bonding that increases stability of the carbocations. But -I effect of $\ce{F}$ dominates +R effect and this ...
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 ...
6
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2answers
3k views

How can two electrons lie together in an orbital?

Two electron of opposite spin can lie in a single orbital.. But what about the electron-electron repulsion. Okay! I got that the nuclear charge rather the large Z-effective overcome this repulsion by ...
8
votes
1answer
661 views

Why are bromine oxyanions uncommon?

Sodium hypochlorite is used in bleach, calcium hypochlorite is used in public swimming pools, ammonium perchlorate is used in solid rocket fuel. Sodium periodate is used in the cleaving of syn-...
7
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1answer
3k views

Is the phenyl cation or ethynylium more stable?

I recently gave an exam and I received an interesting question to which I believe the answer is wrong. Given two compounds, a benzene molecule with carbocation at one of its constituting carbon atoms ...
8
votes
1answer
612 views

What is the reason for the exceptional stability of tricyclopropyl-cyclopropenyl carbocation?

The stability order of the following is: A. III > II > I > IV B. II > III > I > IV C. I > III > IV > II D. I > III > II > IV Answer: I came across a question where we had to ...
6
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1answer
2k 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 ...
4
votes
2answers
14k views

What is the explanation of the changes in stability going down a group for carbonates, bicarbonates, fluorides, and chlorides?

For carbonates and bicarbonates, I know that stability increases down the group, and for chlorides and fluorides, stability decreases down the group. Why does this happen? Can someone explain this in ...
8
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1answer
3k views

Ring expansion in cyclic compounds

My attempt In the first case: $\ce{H+}$ adds to the $\ce{OH}$ group, giving us a carbocation. The carbocation thus formed is exceptionally stable due to back bonding. I wonder why would it go under ...
5
votes
1answer
832 views

Why is tin-112 stable, but indium-112 radioactive?

According to Wikipedia, tin-112 is a stable nuclide, but indium-112 is radioactive (half-life only 14 minutes). What is the explanation for this?
5
votes
2answers
1k views

Delocalised electrons and stability of benzene

In most high school chemistry books, it is said that the delocalised electrons in benzene makes it particularly stable. However, how does it contribute to stability? Is there any simple way of ...
4
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2answers
1k views

Carbocation rearrangement involving three membered rings

Question: Taking into account of various carbocations and, as well as the rules governing mechanisms of carbocation rearrangements, which reaction is most likely to occur during the given reaction? ...
6
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1answer
2k 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°...
5
votes
3answers
970 views

Which tautomer of hexane-2,4-dione is more stable?

Which tautomer will be more stable? Both 1 and 2 show intramolecular hydrogen bonding and form 6 membered cyclic ring, thus increasing the stability. I think I need to compare the effect of the two ...
5
votes
2answers
724 views

Does the compound KFO₃ exist?

As the compound potassium chlorate exists, is there something as $\ce{KFO3}$? All the other halogenates are mentioned somewhere on the web but what about this? If no, then why?
4
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1answer
498 views

Is there an A value for the carbaldehyde and vinyl groups?

A methylene ($\ce{=CH_2}$) group ist sterically less hindered than a methyl ($\ce{CH_3}$) group. I'm wondering if the carbonyl ($\ce{C=O}$) group is sterically more or less larger than a methylene ($\...
4
votes
1answer
109 views

Why don't decomposition reactions form pure elements as products?

For example, if I had a reaction like this: $$ \ce{NaHCO3 -> Na2CO3 + H2O + CO2} $$ Why does it not break down all the way down to its elements? What makes it form such "intermediate" products, ...
3
votes
1answer
796 views

Is Tollen's test safe?

Tollen's test is an important test to distinguish between aldehyde and ketone. $$\ce{2 [Ag(NH3)2]+ + RCHO + H2O → 2 Ag(s) + 4 NH3 + RCO2H + 2 H+}$$ But is this reaction safe? Is there any threat in ...
22
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2answers
6k 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 ...
26
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2answers
2k views

Which of the following is the more stable carbocation?

Which of the following is the more stable carbocation? I thought the 1st carbocation would be the more stable one as the pi-electron density of phenyl group can overlap with the vacant orbital on ...
11
votes
3answers
15k views

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 ...
7
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2answers
17k views

Which is more stable ? - A carbanion on benzene ring or a carbanion on a vinylic carbon on an aliphatic chain?

I came across a question which asks to work out the stability order for the following species. Can the lone pair on benzene carbanion participate in resonance? - If yes how and how is it more stable ...
20
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2answers
4k views

For a given element do heavier isotopes form stronger bonds than lighter isotopes?

I know that $\ce{C-D}$ and $\ce{C-T}$ bonds are stronger than $\ce{C-H}$ bonds, but is this generally true for isotopes of all elements? (By isotopes I mean stable ones with large half lives.)
18
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1answer
1k views

What dictates the lifetime of a solvated electron in a given solvent?

Solvated electrons have a long lifetime in ammonia solutions, but their counterparts in water (called hydrated electrons) have a much smaller lifetime, of the order of microseconds in very pure water. ...