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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95 views

How is occupation number of lowest unoccupied natural orbital defined?

I have run some calculations to analyse the occupation of natural orbitals. Since it is needed to run in triplet state, I get two orbitals with occupation number 1. Now, which orbital occupation ...
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What are radicals in chemistry?

I read somewhere that radicals are atoms, molecules or ions that have unpaired electrons, but how do ions have unpaired electrons when an ion has all its electrons paired either by loosing or gaining ...
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Are the bonds in the monomers at the end of a polymer filled or unfilled?

In polymers the bonds between monomers are changed, usually from double to single1, to form a long-chain polymer with the now single bond joining another monomer. But in the monomers at the very ends ...
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Benzophenone Ketyl color origin

I was recently preparing the benzophenone ketyl radical by reacting it with sodium in toluene. Although this compound is really well known and it seems somewhat obvious and accepted in literature that ...
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What is the rate-determining step in free radical halogenation?

Recently, we were learning about free radical halogenation in school. A set of notes given to us wrote that the rate-determining step is the propagation step. This seems to go against my understanding ...
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1answer
546 views

Bromination with NBS on cyclic structures

I found this question and the answer as shown in my book. I didn't understand why the bromine particularly entered the position shown in the answer. First of all, if a free radical was generated ...
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What is the Major product in free radical halogenation of Alkanes. (Between 3°,2°,1°) [closed]

In Free Radical Halogenation in presence of sunlight, a no. Of products are possible. Due to higher stability of a 3°(Tertiary) radical, 3° products should be favored. But another factor that comes ...
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How does the human body deal with free radicals it creates itself?

I know that free radicals are created all over your body all the time as a byproduct of its chemical processes, (or maybe I do not and that is false). However I am confused about the distinction ...
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How can I interpret the CH4+ structure?

I am trying to teach myself about Electron Ionization, and am very confused about the formation of the CH4+ Ion. Do the dotted lines between the C and the H, and between the two Hydrogens indicate a ...
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Mechanism of photochemical hydroamination with LDA

I've recently come across a couple examples of intramolecular alkene hydroamination accomplished by treatment with LDA followed by visible light irradiation (tungsten light bulb):[1,2] I'd assume ...
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1answer
258 views

How to know about radical character of a diradical molecule?

I understand that the radical character is quantified by the occupation number of the lowest unoccupied natural orbital obtained from UHF calculations or from CASSCF calculations. My issue is that I ...
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Which natural orbitals are better for CASSCF calculations for organic diradicals?

I am trying to perform CASSCF calculations for a series of diradicals. As input orbitals I have used two types of natural orbitals. One is unrestricted natural orbitals and the other MP2-based natural ...
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Electrophilic nature of bromine free radical

My chemistry teacher told me that Bromine radical is a weak electrophile, and that it is more likely to join the more electron rich part of a molecule. However I could not verify his statement from ...
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It is possible to make radical Chlorination on the α-position of ketones?

I need examples of radical α-Chlorination of ketones. It is possible to make radical chlorination happen in the alpha position?
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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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Reactivity and selectivity in free radical halogenation of alkanes

I read about the free radical halogenation of alkanes with $\ce{X2}$ and I have the following questions: Given that the first step is the homolytic breaking of the $\ce{X-X}$ bond, and the homolytic ...
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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 ...
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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 ...
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1answer
6k 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 ...
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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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494 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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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 ...
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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 ...
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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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172 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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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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1answer
162 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, ...
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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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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 ...
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1answer
581 views

Confusing stability order of free radical structures

I have a question regarding the solution that has been given. Question: In the given compound, what would be the order of ease with which hydrogen atom can be abstracted from carbon atoms I to VI?: ...
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Why is free radical chlorination exothermic whereas bromination is endothermic?

In the energy profile diagrams below, it can be clearly seen that the free radical chlorination of an alkane $$\ce{RH + Cl2 -> RCl + HCl}$$ is exothermic. However, the corresponding bromination $...
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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 ...
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651 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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170 views

Naming of asymmetric organic molecules with two nitroxides

When writing my diploma thesis I had to name my molecules following IUPAC nomenclature rules. There were several molecules like the following one, that contained two TEMPO groups, but were not ...
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543 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 ...
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1answer
250 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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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 $\...
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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?...
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647 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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492 views

Is propanone responsible for photochemical smog?

Many volatile organic compounds (VOC) are responsible for photochemical smog. Propanone is a VOC. It's produced in a great amount for industrial purposes. So, propanone can be a potential contributor ...
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270 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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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 ...
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Mechanism of radical cyclisation to form hydroazulene core

Recent studies on radical-induced cyclisation reactions have led to a simple, one-step method for the preparation of hydroazulenes from appropriately substituted cyclopentanone precursors. Treatment ...
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542 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 ...
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523 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 ...
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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 ...
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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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126 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 ...
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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 ...
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1answer
1k 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? ...