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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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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What is the function of toluene in this reaction?

I'm trying to find the mechanism for this reaction: My (tentative) thought for a possible mechanism is: EDIT: New thought for mechanism: But this leaves some loose ends that I haven't been able to ...
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Radicals in Gaussian [closed]

I want to do a PES scan of a radical structure in Gaussian. However, I'm not completely sure how to prepare an input file. I've figured out that charge and multiplicity are 0 and 2. What I don't know ...
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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 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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889 views

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 ...
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23 views

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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17 views

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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713 views

Which singlet dihalocarbene has the strongest carbon-halogen bond?

There are three singlet carbenes - difluorocarbene, dichlorocarbene and dibromocarbene. Which has the strongest carbon halogen bond? Obviously backbonding is a point to be considered, as carbene is ...
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1answer
2k views

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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138 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
348 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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1answer
69 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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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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Structure of Br3O8

What is the structure of $\ce{Br3O8}$? It has an odd number of electrons; does that make it a free radical? The structure given in my book shows Where did the 7th electron of the central atom go? ...
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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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732 views

Conditions for free radical bromination using NBS and peroxides?

In the free radical bromination of 1-methylcyclohexene using NBS and peroxides a very important consideration to get the appropriate product is: A. The wavelength of light used for initiation B. ...
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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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221 views

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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1answer
172 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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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 ...
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46 views

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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164 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
694 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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338 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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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{...
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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
425 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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202 views

Nitroxyl anion electron structure

Is the $\ce{NO-}$ a radical species? If so, can someone please explain why because $\ce{NO}$ has an odd number of electrons (11), so adding an additional electron would give 12 valence electrons and ...
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2answers
65 views

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
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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463 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
755 views

Regioselectivity in Kharasch addition of bromotrichloromethane

When hex-1-ene is treated with bromotrichloromethane in the presence of a peroxide initiator (e.g. dibenzoyl peroxide), what is the regioselectivity of the addition? I know that the radical addition ...
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Why can toluene be chlorinated at either the benzylic position or the ring depending on the conditions?

My book mentions a reaction for the preparation of benzaldehyde with toluene in which side chain chlorination of toluene gives (dichloromethyl)benzene, which upon hydrolysis gives benzaldehyde: Why ...
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821 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 ...
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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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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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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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1answer
495 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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113 views

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
156 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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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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106 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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415 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 ...