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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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4
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1answer
98 views

Does presence of alkyl groups on alpha carbon increase yield of alkane in Kolbe's Decarboxylation?

We know that, during the synthesis of alkanes by Kolbe's Decarboxylation reaction, the reaction proceeds via a free radical $\ce{R.}$ at the anode. So, an alkyl group, say methyl, when substituted at ...
12
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1answer
678 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 ...
0
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1answer
464 views

Why do electron donating groups stabilize free radicals?

Why do electron donating groups stabilize free radicals? I have read this fact in various websites and it is not mentioned why. Isn't a free radical like a highly reactive individual molecule? Why ...
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3answers
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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?
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0answers
45 views

Bromine radical reaction with an alkene - What factors determine whether radical addition occurs as oppose to radical abstraction?

From what I can tell, radical addition occurs when using HBr + Organic peroxides as reagents, and radical abstraction occurs when using trace amounts of bromine radicals (generated by NBS, trace HBr ...
5
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2answers
1k views

Reactions in water radiolysis - producing hydroxyl radicals

There’s an excellent question on Stack Exchange regarding the radiolysis of water here but I have one simple outstanding question that perhaps someone might now; in radiobiology, a common DNA damaging ...
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 ...
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 ...
4
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1answer
1k views

Rank the following radicals in order of decreasing stability

Question Rank the following radicals in order of decreasing stability Aromaticity makes a cyclic compund more stable. Here, 1 and 3 are aromatic since they follow Huckels rule(Or am I wrong ...
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0answers
258 views

How many different alkyl chlorides result from C4H10 and chlorine?

Let's say there's a reaction $\ce{C4H10 + Cl2}$ taking place under UV light. How many different alkyl chlorides do we obtain? I'm not sure if the resulting molecule would be monochlorinated or ...
4
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1answer
2k views

Free radical vs radical cation

What is the difference between a free radical and a radical cation? Are they different thing or do they mean same?
4
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1answer
404 views

Why is antimony oxide used as a flame retardant?

What is the mechanism of action of antimony oxide as a flame retardant? Is this to do with radical absorption?
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1answer
3k views

Why can UV light initiate a reaction between hydrogen and chlorine gas?

Can someone explain me how does UV light help combine chloride gas and hydrogen to produce hydrochloric acid? $$\ce{Cl2(g) + H2(g) -> 2HCl(g)}$$
6
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1answer
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What is the hybridisation of CF3 free radical?

Having 3 sigma bonds in a similar manner to CH3 free radical it should also have hybridisation sp2. However, if we look at its shape, it is pyramidal and not planar unlike CH3 free radical(which is ...
2
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2answers
5k views

What is the hybridisation of the carbons in the allyl radical?

The example I am talking about is $\ce{CH2CHCH2^.}$. To find the steric number and hence the hybridization, we use steric number = No. of lone pairs + number of sigma bonds. In this example, the ...
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0answers
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How long can solid DPPH powder last for in terms of shelf-life before its free-radical status is quenched by the atmosphere?

I am writing in my research on the free-radical scavenging activity of various flavylium compounds. I may need to have DPPH shipped as a result of a lack of supply; I am just wondering what sort of ...
2
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1answer
815 views

What is the difference between a radical and a neutral alone atom?

I've done a bit of googling but can't find a clear answer to this question. Is there any difference to e.g. an alone neutral chlorine atom and a chlorine radical?
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1answer
112 views

Radical halogenation regioselectivity [closed]

What is the drawn product drawn here the major product? I thought the radical (intermediate) is more stabilized at a primary carbon than at a tertiary one.
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154 views

Why is cyclopropylmethyl radical opening so fast?

Ring opening of the cyclopropylmethyl radical is reliable and fast, and so has been used as a radical trap and a radical clock. Could someone please explain what exactly makes this reaction so fast, ...
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2answers
172 views

Carbon tetraradical

I was just reading through Reactions: The private life of atoms by Peter Atkins and I noticed that in Chapter 3, the chapter on the combustion reaction, the author writes: As we watch we see $\ce {...
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1answer
101 views

Electronic strucure of cyclopropene radical cation

Suppose I have a cyclopropene molecule with a + charge on the singly bonded carbon.I think the singly bonded carbon is $\mathrm{sp^2}$ hybridised, isn't it? To obtain this species from cyclopropene, ...
2
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0answers
272 views

Differences in specific free radical reactions enthalpies

Iodination of alkanes using iodine $(\ce{I2})$ is usually an unfavorable reaction. Tetraiodomethane $(\ce{CI4})$ can be used as the iodine source for iodination, in the presence of a free-radical ...
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Can equivalent mass be more than the molecular mass? Can it be applied to radical reactions?

Consider a reaction involving radicals: $$\ce{CH3^. + Cl^. -> CH3Cl}$$ Is the definition of equivalent mass applicable here? If yes, how? Are there reactions where equivalent mass of a reagent ...
5
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2answers
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What is the mechanism for thermal decarboxylation of a generic carboxylic acid (not special cases like beta-ketocarboxylic acid or malonic acids)?

I am looking for the mechanism for thermal decarboxylation for any RCOOH, and I am guessing that its possible for the thermal energy to cleave the R-C bond homolytically leaving a R• and •COOH. Then I ...
13
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1answer
184 views

Ring opening of aziridinylmethyl and oxiranylmethyl radicals

When a radical is alpha to a three-membered ring, it is common for the ring to open via β-scission (to relieve ring strain): When the ring contains a heteroatom there are a couple of different ...
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2answers
1k views

What is the difference between radical initiator and radical inhibitor?

I am confused between these two concepts. My book gives $\ce{O2}$ as an example of a radical inhibitor and peroxide as an example of an initiator. But I don’t know why this is so? Both have $\ce{O-O}$ ...
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3answers
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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 ...
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412 views

Different behavior of bromine radical with alkenes

Let's assume we have propene and it's undergoing two different reactions: a Kharasch reaction and allylic substitution reaction. In both reaction bromine radicals are formed, and the attacking ...
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2answers
3k views

Stability of cyclic radicals

How do we arrange the following in increasing order of stability? The answer given is: $5<3<1<2<4$ (numbering according to their order in the image). My Approach: I can figure that in ...
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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2answers
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How does neutralization of free radicals by $\beta$-carotene work?

In my understanding, by bonding to the free radical species, say by one of the double bonds, a new free radical on the $\beta$-carotene develops.
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289 views

Regarding allylic free radicals and anti-Markovnikov product

I was searching a question "What is the primary product when cyclohexene reacts with bromine in the presence of UV light?" and in a website they said: 3-Bromocyclohexene will be the product ...
4
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1answer
450 views

Why doesn't the N-Br bond dissociate quickly in NBS?

NBS is used to provide a constant, small amount of $\ce{Br2}$ which then dissociates to give $\ce{Br^.}$ free radical. Why doesn't the $\ce{N-Br}$ bond simply dissociate to give $\ce{Br}$? This ...
8
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1answer
3k views

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

Odd electron species contain an unpaired electron which can either be placed in hybrid orbital or in pure orbital. Example: In the case of $\ce{.CF3}$ radical, the unpaired electron is placed in $\...
14
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1answer
719 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 ...
8
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2answers
772 views

Can an organic molecule have a triplet ground state?

Can the ground state of an organic molecule be a triplet. This would imply something like a "HOMO" formed by 2 degenerate levels and less than 4 electrons to fill them. If yes, what are the conditions?...
5
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1answer
527 views

Why does chlorine replace a hydrogen in propene instead of adding to the double bond?

I read about the following reaction in my book: $$\ce{CH3-CH=CH2->[Cl2][\pu{773 K}] (Cl)CH2-CH=CH2}$$ It surprises me that the $\ce{Cl}$ doesn't attack the $\pi$ bond, rather it attacks the $\...
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0answers
232 views

Is OH + CO → CO2 + H an elementary reaction?

Is $$\rm OH + CO \longrightarrow CO_2 + H$$ an elementary reaction? How could I tell? I could break the reaction into $$\rm OH\ (+ M) \longrightarrow O + H\ (+ M)$$ $$\rm CO + O \longrightarrow ...
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0answers
402 views

Why aren't free radicals considered resonance forms?

In C, the answer states that electrons must come in pairs. And so C does not show resonance forms. But here I read that if there is an unpaired electron, it is a free radical. Why can't free radicals ...
1
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1answer
465 views

Free Radical Reaction of Methane and Chlorine

The problem statement: Lets say you have $1 L$ of $2 M$ methane and the same amount of chlorine. Lets also say that both are liquids since those are most likely to react. Now the only way they can ...
-1
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1answer
440 views

Explain mechanism for first step in synthesis of acetone and phenol

"The following reaction is the first step in the industrial synthesis of acetone and phenol. AIBN initiates radical reactions by breaking down upon heating to form two isobutyronitrile radicals and ...
6
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3answers
122 views

Determining the product which is not possible in the reaction

This is an objective type question I encountered in a objective test. NBS (N-bromosuccinimide) is used for the allylic substitution of $\ce{Br}$ in a reaction. In this reaction, since the allylic ...
3
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1answer
361 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 ...
-1
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1answer
47 views

Are nitrogen oxides always radicals?

Some reactions between nitrogen oxides and ozone can be the following: $$NO\cdot(g) + O_3(g) \rightarrow NO_2\cdot(g)+O_2(g)$$ $$NO_2\cdot(g) + O\cdot(g) \rightarrow NO\cdot(g)+O_2(g)$$ Where the $...
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1answer
31k 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 ...
-1
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1answer
804 views

Side chain chlorination of substituted toluene

I know that we can convert toluene to benzaldehyde using side chain chlorination in presence of light, followed by hydrolysis. Is it possible to use the same method to convert a substituted toluene? ...
4
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1answer
402 views

Major product of radical fluorination vs bromination

I understand what structure is formed by using $\ce{Br2}$ to brominate this alkane, and I know that $\ce{F2}$ will be less selective in its abstraction of hydrogen. However, how can I know where $\ce{...
7
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1answer
192 views

Why does the light catalyzed radical addition of tetrachloromethane to an alkene produce only a single regioisomer?

This reaction always occurs in the following, regiospecific way: $$\ce{CCl4 + R-CH=CH2 ->[$h\nu$] R-CHCl-CH2-CCl3}$$ The same should apparently also happen when there is a carbon that has two ...
-3
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1answer
5k views

Is hydroperoxyl radical(HO2) toxic to the human body, or even flammable?

I understand that radicals are damaging to cells, due to their high chemical reactivity. Though I do not know whether they are flammable in any level.
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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"?