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Questions tagged [radicals]

Radicals are highly reactive species, that have one or more unpaired electrons. Whether a species has unpaired electron(s) can be experimentally determined through electron pair resonance spectroscopy. Radicals are paramagnetic. This tag should be applied to questions that involve free radicals as a species or radicals in reactions and their mechanisms.

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What is the major product on chlorination of 2-methylbutane?

I came across a question asking for the major product on chlorination of 2-methylbutane. The answer in the back of the book says it will be 2-chloro-3-methylbutane. However, I thought the major ...
Dhruba Banerjee's user avatar
26 votes
5 answers
34k 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{...
Dhruba Banerjee's user avatar
14 votes
1 answer
15k views

What is the hybridisation of trifluoromethyl free radical?

Having three σ bonds in a similar manner to $\ce{CH3^·}$ free radical, $\ce{CF3^·}$ should also have $\mathrm{sp^2}$ hybridisation. However, if we look at its shape, it is pyramidal and not planar ...
James Hunt's user avatar
23 votes
3 answers
6k views

What is the geometry of an alkyl radical?

I encountered this question which asks how many possible radicals are formed when $\ce{CH3CH2C(CH3)3}$ is monosubstituted by $\ce{Br2}$. The answer given is 3 while I think it should be 4, reasoning ...
ℵ_ϵ's user avatar
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1 vote
1 answer
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Why does radical chlorination and bromination of propane occur at different positions?

When propane reacts with chlorine, we will mostly (theoretically) get an isomer with a chlorine on the end. ($\ce{CH_3-CH_2-CH_2Cl}$). However, when propane reacts with bromine, we will mostly get an ...
G. Amber's user avatar
12 votes
1 answer
962 views

Exceptions to motif: nucleophile attacks electrophile

I hear this motif - nucleophile attacks electrophile - all the time with regard to organic chemistry. Are there any exceptions? I think this statement is always true in general because it's a ...
Dissenter's user avatar
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9 votes
2 answers
19k views

Why is O2 a biradical?

$\ce{O2}$ has a double bond in its normal form. That is $\ce{O=O}$. There are no unpaired electrons in this case are there since there are 2 lone pairs on each oxygen. However 1 resonance structure ...
Caters's user avatar
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7 votes
1 answer
430 views

Geometries of methyl and silyl radicals

The $\ce{.CH3}$ radical is planar but the $\ce{.SiH3}$ radical is a trigonal pyramid. Why are they different? After all, $\ce{C}$ and $\ce{Si}$ are in the same group.
Peter's user avatar
  • 71
5 votes
1 answer
1k views

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

In my organic chemistry class, we were asked what determines the relatively high degree of selectivity in the reaction of a bromine radical with primary, secondary, and tertiary C–H bonds. I said it ...
user34748's user avatar
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0 votes
1 answer
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Why don't unstable odd electron species dimerize so that they become stable?

Why doesn't unstable odd electron compound $\ce{NO}$ dimerize to $\ce{N2O2}$? Why doesn't this structure of ozonide dimerize? But why then does $\ce{BH3}$ dimerizes to $\ce{B2H6}$, and $\ce{AlCl3}$ to ...
RE60K's user avatar
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17 votes
1 answer
986 views

Can we synthesize alcohols by the photolysis of hydrogen peroxide?

As I was going through my revision of organic chemistry, I came across free radical substitution of alkanes with halogens. In a similar process where we use hydrogen peroxide, instead of chlorine, so ...
Pritt says Reinstate Monica's user avatar
7 votes
1 answer
6k views

Why is the methyl radical planar?

Why is the methyl radical planar? The VSEPR theory would predict an angle between 120° and 109.5°, while it is actually 120°.
EJC's user avatar
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5 votes
1 answer
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Why is it possible to form bromoalkanes but not iodoalkanes from free radical substitution?

For a free radical substitution (FRS) reaction between iodine $\ce{I2}$ with ethane and bromine $\ce{Br2}$ with ethane $\ce{CH3CH3}$: $E_\mathrm d(\ce{H-I})=299\ \mathrm{kJ\ mol^{-1}}$ $E_\mathrm d(\...
y.han's user avatar
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4 votes
1 answer
849 views

If a bond dissociation energy is listed, does it refer to homolytic or heterolytic fission?

I am perfectly sure than heterolytic fission of a bond needs more energy than homolytic ones, since it requires opposite charge separation. When the bond dissociation energy is listed, which one are ...
Pritt says Reinstate Monica's user avatar
3 votes
1 answer
4k views

Why are free radicals so reactive?

Why are free radicals are so reactive? They can break almost any bond, including $\ce{C-H}$ bonds, which are fairly stable. Don’t they have an activation energy or something? Do they not also ...
TLo's user avatar
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1 vote
0 answers
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Mechanism for Hydrogen Peroxide decomposition?

Someone asked this question earlier and made no attempt at understanding it on their own so the question was flagged. However, it prompted me to attempt to figure it out. This is what I have come up ...
KeatonB's user avatar
  • 630
28 votes
3 answers
1k views

What makes a radical 'free'?

The qualifier 'free' seems to be ubiquitously attached to discussion of radicals as highly reactive species with unpaired spins. What, precisely (or imprecisely, as the case may be) does 'free' really ...
Richard Terrett's user avatar
20 votes
3 answers
3k views

Why doesn't TEMPO react with itself?

TEMPO ((2,2,6,6-tetramethylpiperidin-1-yl)oxyl, or (2,2,6,6-tetramethylpiperidin-1-yl)oxidanyl) has the following structure: Given that it's a free radical, why doesn't it react with itself, despite ...
I. Kor's user avatar
  • 453
19 votes
2 answers
19k views

Why don't free radicals undergo rearrangement like carbocation/carbonium ions do?

Why don't free radicals and carbanions undergo rearrangement like carbocation/carbonium ions undergo in a reaction?
Dimenein's user avatar
  • 449
5 votes
3 answers
12k views

Is a carbon-fluorine bond stronger than a carbon-chlorine bond?

In hydrolysis/nucleophilic substitution of haloalkanes, the bond enthalpy indicates the rate of hydrolysis (e.g. the $\ce {C-I}$ bond is weaker than the $\ce {C-Cl}$ bond so in hydrolysis the alkane ...
user58953's user avatar
  • 497
4 votes
1 answer
245 views

Why does the heat of formation of organic radicals and positive ions decrease with their size and degree of branching at the radical or ionic site?

I am currently studying the textbook Mass Spectrometry, third edition, by Jürgen H. Gross. Chapter 2.4.3 Bond Dissociation Energies and Heats of Formation says the following: The heat of formation ...
The Pointer's user avatar
  • 1,083
4 votes
1 answer
4k views

Why are radicals unstable?

Why are unpaired electrons especially reactive? Does pairing electrons decrease the reactivity of the electrons? But then doesn't forcing two electrons into the same orbital cost energy?
Dissenter's user avatar
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3 votes
4 answers
10k views

What is "dot" sign in •NO?

What is "dot" sign in •NO? I know that it is radical nitric oxide, but I don't know if it is necessary to put the "dot". Is there any difference between •NO and NO?
user80142's user avatar
3 votes
1 answer
716 views

Ullmann's Reaction (similar to Wurtz) - aryl chloride with deactivating groups - stability of free radical

Ullmann's Reaction: Mechanism: Question: My textbook says with $\ce{X} = \ce{Cl}$, the reaction gives less yield compared to using $\ce{X} = \ce{I}$ since $\ce{Cu}$ is not as reactive as $\ce{Na}$ (...
Yashas's user avatar
  • 2,106
2 votes
1 answer
1k views

What has stronger antioxidant potential: BHT or BHA?

Butyl Hydroxy Toluene (BHT) has two tert-butyl groups that can stabilize a free radical. Butyl Hydroxy Anisol (BHA) doesn't, though it has the 4-substituted methoxy group (I'm not sure what that does)....
InquilineKea's user avatar
2 votes
1 answer
175 views

Bromochlorofluoromethane as a reagent in Riemer-Tiemann reaction

The reagent usually used in Riemer-Tiemann reaction is $\ce{CHCl_3 }$ however one of the variations I read used $\ce{CHFClBr}$ as a reagent. Now $\ce{CHCl_3}$ produces the $\ce{:CCl_2}$ radical using ...
Ashish's user avatar
  • 1,409
1 vote
1 answer
454 views

Reaction Mechanisms: Free Radical Halogenation

In Free Radical halogenation using chlorine and sunlight, why does the chlorine-free radical get attached to the allylic carbon? Will it be correct to say that it follows the anti-Markovnikov rule? ...
Devaesh's user avatar
  • 36
1 vote
1 answer
5k views

Percentages of radical constitutional isomers [duplicate]

Is it possible to use the radical selectivity factors for chlorination based on primary, secondary, and tertiary substitutions to calculate the expected percentage of each constitutional isomer formed ...
alehul's user avatar
  • 11
1 vote
2 answers
3k views

Why are radical intermediates are more stable on tertiary carbons?

Is this because there's more electron density? More carbons around means the tertiary carbon "has more electrons around it"?
Hamze's user avatar
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