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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9
votes
1answer
28k views

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 ...
20
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5answers
14k 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{...
12
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1answer
653 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 ...
14
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1answer
700 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 ...
22
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3answers
3k 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 ...
2
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1answer
1k 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 ...
5
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1answer
4k 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 degrees, while it is actually 120 degrees.
5
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1answer
4k views

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(\...
4
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2answers
766 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 ...
28
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3answers
563 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 ...
19
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3answers
2k 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 ...
14
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3answers
8k 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?
7
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1answer
239 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.
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1answer
4k views

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 ...
0
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2answers
1k 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"?
8
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2answers
10k 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 ...
5
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3answers
7k 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 ...
4
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1answer
3k 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?
2
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1answer
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)....
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0answers
1k views

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 ...
0
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1answer
2k 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 ...