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 name of the glyoxal radical after removing two hydrogen atoms?

What is the name of the radical that results from removing two hydrogen atoms from glyoxal ($\ce{CHO-CHO}$)? It has a roughly this structure: $$\ce{O=C^.-C^.=O}$$ It is an important intermediate in ...
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why is peroxide a weak bond (compared to Cl-Cl bond) [duplicate]

In my the book it is written that we can use peroxides as radical initiators since their bonds are weaker than $\ce{Cl-Cl}$ or $\ce{Br-Br}$ bonds. I googled and some pages said $\ce{O-O}$ bonds are ...
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Why does not aqua regia burn filter paper?

We were doing basic radical analysis in lab and we were asked to add aqua regia on the filtered PPT collected on the filter paper and collect the formed solution , my question is if aqua regia can ...
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UV-Vis absorbtion spectra of a radical cation/anion. Is it different compared to its even counterpart?

I am studying gas-phase Uv-Vis spectra of radical molecules. If one electron is removed/captured from the neutral even electron molecule, what can I expect from the absorption spectra? Will new peaks ...
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What is the largest one step radical cyclization ever achieved?

When I was an undergrad, roughly around 2005, I took a grad level class that covered various topics in advanced organic synthesis. I don't remember much clearly from the class, but one thing that I ...
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2answers
137 views

Atmospheric methane to carbon [closed]

I read an article by popsci that talked about huge fans forcing methane over a catalyst. Now that got me wondering, can't we produce hydroxyl radicals with powerfull uv lasers blasting the sky, ...
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1answer
62 views

Radical monobromination of cycloalkane

I'm trying to figure out the isomeric products of the radical monobromination of bicyclo[2.2.1] heptane. I'm not sure at which site the bromination would happen and what makes one site better than the ...
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4answers
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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?
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Is it possible to arrest the post-actinic effects of photodegradation in ABS polymers?

Polymers like acrylonitrile butadiene styrene (ABS) are adversely effected by UV exposure, both visually (by yellowing) and with regard to other material properties [1]. What's worse is that the ...
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Why are “diene” structures in the C-ring of anthocyanins singled out for their singlet-oxygen quenching ability?

Anthocyanins are a class of water-soluble vacuolar pigments. They are sensitive to pH, and can undergo a series of structural changes according to a pH-dependent equilibrium as illustrated in Figure 1....
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Mechanism for the addition of chlorine to benzene to form hexachlorocyclohexane

I am familiar with electrophilic substitutions of benzene, with chlorine using a halogen carrier catalyst such as $\ce{AlCl3}$, to produce chlorobenzene, and I am aware of the mechanism. But, ...
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What, if any, are the differences between radical scavenging and radical quenching?

Hindered amine light stabilizers (HALS), introduced in the 1970s, function mainly as free radical scavengers, although they also may act as quenchers or peroxide decomposers. (Polypropylene: The ...
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1answer
56 views

Which is more stable in gas phase, free radicals or ions?

Answering some kinetics questions I came across this statement: Free radicals are more stable in the gas phase than ions. Is this correct or not? Why? Is there a different trend in liquid or ...
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what is the material used to detect the presence of free radicals in the reaction?

To detect the presence of free radicals in the reaction usually, acrylonitrile used but this material is not available in my university. Is there another material used to detect the presence of free ...
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Can a Hydrogen Radical form in a chemical reaction?

Original question: During kolbe electrolysis of Formic acid, H2 is released at which electrode? What I thought: H2 will form at cathode due to reduction of water. But will the Formic acid decompose ...
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132 views

How does conversion of a free radical to a carbonyl compound take place? Unsure about mechanism

Came across a question that talked about fragmentation of peroxyesters, about the peroxide linkage of course. After the fragmentation of the peroxyester was done, it gave out three products (2 being ...
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1answer
151 views

Why is a 7-endo radical cyclisation favoured over a 6-exo in this synthesis?

Normally, according to Baldwin's rules, 3-exo to 7-exo cyclisations are preferred over endo cyclisations. But in the following example, a 7-endo-trig reaction is favoured over a 6-exo-trig and I am ...
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1answer
614 views

Which will be the major monochlorination product? [closed]

Which of these compounds represents the major monochlorination isomer formed in the following reaction? According to selectivity theory, the answer should be (c). However, the given answer is (...
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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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2answers
386 views

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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2answers
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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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1answer
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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
336 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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2answers
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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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182 views

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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1answer
453 views

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
164 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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100 views

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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104 views

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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462 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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456 views

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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1answer
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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
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 ...
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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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1answer
403 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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1answer
812 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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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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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
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, ...
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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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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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331 views

Confusing stability order of free radical structures

I have question regarding the solution that has been given. Question: In the given compound the order of case with which hydrogen atom can be abstracted from carbons I to VI is The solution that ...
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1answer
2k views

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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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 ...