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22 votes
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Structure of Br3O8

The electron didn't go anywhere. It's in an unhybridized p orbital on the central bromine, and yes, $\ce{Br3O8}$ is a free radical. That is why it decomposes above -80ºC.$^{[1]}$ $^{[1]}$ Cotton, F. ...
ringo's user avatar
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22 votes

Why doesn't TEMPO react with itself?

I believe the first part of your question is asking why the oxygen with the unpaired electron doesn't find a second one to form a peroxide. The answer is actually quite simple. It is by design. Next ...
Zhe's user avatar
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17 votes
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Carbon tetraradical

In its ground state, naked carbon is triplet $^3P$, with two metastable singlet states $^1D$ and $^1S$ ($^1D$ being the one that participates in most reactions) while the tetraradical is the least ...
EJC's user avatar
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13 votes

What is the hybridisation of trifluoromethyl free radical?

Hyperconjugation between the orbital that contains the lone pair and the $\ce{C-F}$ antibonding orbital contributes to the pyramidalization of $\ce{CF3^·}$ radical: In the planar geometry the ...
EJC's user avatar
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13 votes
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Mechanism of radical cyclisation to form hydroazulene core

This reaction is taken from Tetrahedron Lett. 1995, 36 (17), 3015. (DOI: 10.1016/0040-4039(95)00502-4) The heat (provided by refluxing) is required to initiate the reaction by the decomposition ...
orthocresol's user avatar
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11 votes

Comparing the stabilities of allylic, benzylic, and tertiary radicals

Imagine your favorite activities are playing Video games (Most Favourite), and other ones are reading chemistry, spending time in a chemical lab. (these two are activities are those activities in ...
Aditya Shrivastava's user avatar
11 votes

Can an organic molecule have a triplet ground state?

As Martin has mentioned, carbenes are a good starting point if you are looking for organic compounds with a triplet ground state. In these carbenes, the HOMO is not twofold degenerate, as your ...
orthocresol's user avatar
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11 votes

What is "dot" sign in •NO?

Usually the dot is put there to emphasize that the nitric oxide is a free radical that includes an unpaired electron. This is especially notable by comparison with $\ce{NO^+}$, which does not have ...
Oscar Lanzi's user avatar
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10 votes
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Why can toluene be chlorinated at either the benzylic position or the ring depending on the conditions?

The halogenation of toluene is possible by two mechanisms. In German, they are referred to by the shorthands KKK and SSS, where KKK stands for Katalysator, Kälte, Kern (catalyst, cold and core) while ...
Jan's user avatar
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9 votes

Can an organic molecule have a triplet ground state?

There are various examples of molecules in triplet ground state. The smallest (organic) is possibly methylene, $\ce{:\!CH2}$. Carbenes in general may adopt triplet state as their ground states. ...
Martin - マーチン's user avatar
9 votes
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Why doesn't the N-Br bond dissociate quickly in NBS?

Actually, the sequence of reactions leading to a low but constant concentration of $\ce{Br^.}$ radicals is very simple: $$\begin{align}\ce{R2N-Br &<<=> R2N^. + Br^.}\tag{1}\\[0.4em] \ce{...
Jan's user avatar
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9 votes

Why doesn't TEMPO react with itself?

Steric hindrance is the way to make them stable. I have never worked with TEMPO, but I have seen this one in our lab: Here the steric hindrance is very evident. This is also a nice stable solid.
Raoul Kessels's user avatar
8 votes

Comparing the stabilities of allylic, benzylic, and tertiary radicals

Using the same concept as to distinguish whether the t-butyl carbocation is more stable than the benzyl carbocation, I calculated the isodesmic reactions of the form in $\eqref{isodesmic}$ at the DF-...
Martin - マーチン's user avatar
8 votes
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The major product of radical halogenation: Why is it a halogen attached to a primary carbon and not a tertiary carbon in the given example?

The experimental relative rates of chlorination to primary, secondary, and tertiary positions are $1$, $3.8$, and $5$, respectively. In the given compound $\ce{(CH3)3CH}$, there are $9$ identical ...
Infinite's user avatar
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7 votes

What makes a radical 'free'?

TLDR; It depends who you are talking to (organic chemist, ESR spectroscopist, or physical chemist/chemical physicist), and when. The way I read the quote below the fold, there have been three major ...
hBy2Py's user avatar
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7 votes
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Major product of radical fluorination vs bromination

There is nearly no thermodynamic aspect to this reaction. The activation energy for any alkane hydrogen abstraction by a fluorine radical is essentially 0$^{[1]}$. This means that there is an equally ...
ringo's user avatar
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7 votes
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Can we synthesize alcohols by the photolysis of hydrogen peroxide?

I do not believe so. The mechanism of decomposition of $\ce{H2O2}$ is: $\ce{H2O2(g) -> 2HO.(g)}$ $\ce{H2O2(g) + .OH(g) -> H2O(g) + HOO.(g)}$ $\ce{HOO.(g) + .OH(g) -> H2O(g) + O2(g)}$ $\...
AS_1000's user avatar
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7 votes
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sp2 hybridisation of alkyl radicals causing formation of racemic mixture

In the first step, due to the selectivity of bromine in a free radical reaction, the tertiary carbon which has a $\ce{-CH3}$ group attached to it forms the radical. Now, since the radical is a $\ce{^{....
Safdar Faisal's user avatar
7 votes
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How would this reaction occur through free radical substitution?

Zn reacted with the allylic bromide to create an allyl zinc species. This is known as the zinc-mediated Barbier- Grignard reaction wikipedia. The allyl zinc species then reacts nucleophilically with ...
Waylander's user avatar
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6 votes

What determines the high degree of selectivity in free radical brominations?

First, let’s take a look at the radical chain reaction that leads to the substitution in question: $$\begin{align}\ce{Br^. + H-R &-> HBr + R^.}\tag{1}\\[0.4em] \ce{R^. + Br-Br &-> R-Br +...
Jan's user avatar
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6 votes

Why are radical intermediates are more stable on tertiary carbons?

Before thinking about why tertiary radicals are 'stable', you need to have some kind of understanding about the structure of radicals. Carbon centered radicals adopt similar geometries to ...
NotEvans.'s user avatar
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6 votes

Free radical vs radical cation

A radical cation is simply a free radical with a positive charge. Similarly a radical anion is a free radical with a negative charge. In other words, radical cations and radical anions are subsets of ...
hBy2Py's user avatar
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6 votes
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Can a free radical be created by chemical reaction of non-radical species?

A free radical cannot be created in a simple, one-step process from non-radical reactants other than by bond dissociation (which you explicitly excluded). A fundamental principle of quantum chemistry ...
Jan's user avatar
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6 votes

Can a free radical be created by chemical reaction of non-radical species?

As for #3, photoinduced electron transfer (PET) reactions do what you want. Imagine that 2,4,6-triphenylpyrylium tetrafluoroborate ($\ce{P+BF4-}$) is irradiated at $\lambda = 350~\mathrm{nm}$ in the ...
Klaus-Dieter Warzecha's user avatar
6 votes
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Why can UV light initiate a reaction between hydrogen and chlorine gas?

Before going into the mechanism of this reaction, I suggest you look up free radical mechanism, as this reaction takes place through that. $\ce{Cl-Cl}$ bond in $\ce{Cl2}$ is weak enough to be broken ...
CupC_56's user avatar
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6 votes
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Why does chlorine replace a hydrogen in propene instead of adding to the double bond?

It's not that the chlorine radical doesn't attack the $\pi$-bond, it just doesn't do it as fast. Alkyl radicals are much less stable than allyl radicals, so hydrogen abstraction will occur much faster ...
ringo's user avatar
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6 votes

How to find if the unpaired electron is placed in hybrid orbital or pure orbital in odd electron species?

When discussing hybrid orbitals, they are justified by the experimentally observed or calculated/simulated molecular geometry. For instance, the $\ce{^.C(CH3)3}$ radical was found to be planar by ab ...
MasterYoda's user avatar
6 votes
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What is the difference between a radical and a neutral alone atom?

A chlorine radical and a chlorine atom are effectively the same thing. This does not mean that "radical" and "atom" are interchangeable as jargons. They are used in fairly particular contexts, namely ...
Vinícius Godim's user avatar
6 votes
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Rank the following radicals in order of decreasing stability

Here, 1 and 3 are aromatic since they follow Huckels rule(Or am I wrong here? Yes you're wrong over here, for applying the Huckel's rule the compound must be a closed circuit of delocalized ...
Avyansh Katiyar's user avatar
6 votes

Radicals vs atoms having unpaired electrons

Yes, a chlorine atom is very much the same as chlorine radical. With sodium, the two things are technically similar too, but you'll hardly ever encounter a mention of "sodium radical". Why is that? ...
Ivan Neretin's user avatar
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