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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19 views

Radical Chain Reaction, termination steps

In the termination step of radical chain reaction, we often neglect the recombination of hydrogen atom radicals and it will not be included in the mechanism. Let say the reaction is between $\ce{H2}$ ...
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Is “double dot” (“··”) notation used for a double radical?

I wondered if this was a typo in the notes given to me. I haven’t come across notation like this before: Branching — steps in which number of radicals increases (can lead to explosion) $$\ce{H^. + O2 ...
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Flavonoid Xanthine Oxydase Inhibitors vs Hydroxychloroquine

Regarding COVID-19 and hydroxychloroquine (HCQ), HCQ is known to increase pH in lysosomes by 1-2 orders of magnitude, and also results in lethal intracellular heme overload in parasites responsible ...
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Hybridisation of free radicals and carbonium ions

What hybridisation do the following carbonium ions and free radicals exist in: $\ce{CH#C+}$ $\ce{CH2=CH+}$ $\ce{CH#C^\circ}$ $\ce{CH₂=CH^\circ}$ According to me all are $\mathrm {sp}$ hybridised. ...
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Stabillity of ethyl, iso propyl and vinyl free radicals

Well this might seem like a dumb question but I was just wondering if any other factor would apply here as well? By simply looking at the number of hyperconjugative structures, I could easily tell ...
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TEMPO Radical Analogue

After investigating what makes the persistent radical TEMPO stable, I was wondering if another compound which is more feasible for my needs would be comparable to it. Would oxidizing 2,2’-dimethyl-...
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33 views

Photodissociated iodine laser and population inversion

Iodine molecules ($\ce{I2}$) can absorb in the visible region and dissociate into $\ce{2 I^.}$ radicals. One of the I atoms is in ground electronic state $\mathrm{^2P_{3/2}}$ and the other I atom is ...
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242 views

Why doesn't fluorine harm the ozone layer the way chlorine and bromine do? [closed]

I don't understand the chemistry here: fluorine is a halogen too. I read that fluorine in the atmosphere readily forms HF, which is (somewhat) stable and doesn't catalytically break down ozone. But, ...
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132 views

What is the geometry of a tri-substituted methyl free radical?

My teacher explained that free radicals could have a geometry that is planar or pyramidal(tending to tetrahedral) based on whether or not it is substituted by lone-pair containing atoms. For example, $...
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Why is gasoline consisting of heavily branched alkanes better fuel than gasoline consisting of more linear alkanes? [duplicate]

As far as I know, the reason isooctane is better than octane in gasoline engines is because the octane is more prone to ignition by pressure. This makes it ignite when it is not supposed to, which ...
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What are some convenient examples of so-called dissolved organic matter (DOM) for lab work?

Background, I have come across a chemical reaction system, occurring in nature, that apparently involves the presence of dissolved organic matter (in a catalytic role). My research returns, for ...
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Measured g-factor of a free-radical changing as a function of something. But I cant work out what?

I'm looking at EPR of a paramagnetic organic molecule in solution that has a very stable free-radical signature with gfactor ~2.0035. All good. Except when watching one particular experiment I saw ...
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Reaction of 1,3-dibromobutane with zinc dust upon heating

I've studied that when 1,3-dibromopropane (or in general any halogen, not just bromine) is heated with Zn dust, the electrons produced cause the halogens to break away homolytically and two free ...
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After neutralizing a free radical, why don't anti-oxidants become free radicals themselves?

This is my understanding: A free radical is a molecule with a single unpaired electron. This molecule is highly reactive because it wants to steal an electron from another molecule (oxidation). Anti-...
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Major product from allylic halogenation of alkenes

Allylic halogenation of butene happens in the following way: The RDS of this radical chain mechanism is allylic hydrogen abstraction ($\ce{H_a}$) from the allylic position to give a 1° allylic ...
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Geometry of a free radical at the bridgehead carbon

With reference to J. Am. Chem. Soc. 1968, 90 (19), 5266–5267, they state: The most favorable geometry of aliphatic free radicals remains an unsolved problem, since existing data are consistent with a ...
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Chemical reaction of radicals with different multiplicity

I am studying the chemical reaction of radicals by computational chemistry software. I just want to know what is the rules for multiplicity. I have two radicals for which, the ground state of one is a ...
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125 views

Electrophilic addition on cyclopropane using sunlight

I encountered a weird question in an exam. The statement says that instead of radical substitution, cyclopropane undergoes electrophilic addition reaction in sunlight. I know that all saturated ...
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42 views

Stability of radicals

I recently came across a question about the stability of radicals and this option was given as correct. $\ce {F2C^.H}>\ce {C^.H3} $ And the solution was given that $\ce{FC^.H2}$ and $\ce{F2CH^.}$...
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208 views

sp2 hybridisation of alkyl radicals causing formation of racemic mixture

What I know about $\ce{^{.}CR3}$ radical is that it has both $\ce{sp^2}$ and $\ce{sp^3}$ character but the $\ce{sp^2}$ character dominates and so the radical is $\ce{sp^2}$ in nature. So, suppose we ...
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Mulliken Spin Density

I would like to know if a Mulliken population analysis to calculate spin densities is in general a valid choice. I see that it is made use of, for example here1. So up to-date researches apparently ...
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106 views

Preparation of Grignard reagent. Free radical rearrangement

Mechanism of formation of Grignard Reagent $$\ce{R-X + ^.Mg^. ->[\text{r.d.s.}] R^. + ^.Mg+X-} $$ $$\ce{R^. + ^.Mg+X- -> R-Mg+X-} $$ As the mechanism of preparation of Grignard reagent suggests,...
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Name for H2O- radical? (H2O+ radical is Oxoniumyl)

Radical are atoms with unpaired electrons, and they have short lifetimes because the unpaired electrons are highly chemically reactive. The $\ce{H2O^{.+}}$ radical is named oxoniumyl. Is there a name ...
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Do reactions carried out in light always follow free radical mechanisms? [closed]

If light is used in a reaction, is it necessarily a free radical reaction? Or are there some other reactions as well which involve light but don't follow a free radical mechanism?
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Quinones - Radical Scavengers

In the textbook of "A Guidebook to Mechanism in Organic Chemistry" by Peter Sykes, it is mentioned that peroxides are radical sources and quinones are radical absorbers or scavengers, but it ...
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Oxidation to allylic alcohols without stoichiometric metal reagents

Common methods of oxidation of alkenes to allylic alcohols in one step usually use stoichiometric metal oxidants, e.g., sodium dichromate. Without using this type of reagent, are the other methods ...
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Reaction Mechanisms: Free Radical Halogenation

In Free Radical halogenation using chlorine and sunlight, why does the chlorine-free radical get attached to the allylic carbon? Will it be correct to say that it follows the anti-Markovnikov rule? ...
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Feasibility question: Is the following presented chemistry leading to very dilute H2O2 with fast created radicals, effective H2O2? [closed]

I start by noting that, theoretically starting by the action of oxygen on acidic FeCl2, one can form in situ hydrogen peroxide and other reactive oxygen species, albeit in very small amounts. The ...
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292 views

Radicals vs atoms having unpaired electrons [closed]

In organic chemistry course, I read that a radical is an atom, molecule or ion which have unpaired valence electrons. So does there any difference between chlorine atom or cholrine radical? Also ...
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307 views

In free radical substitution of propane with halogens, how do you know which carbon ends up with an unpaired electron after fission of C-H bond? [duplicate]

In free radical substitution of propane with a halogen (eg- chlorine), how do you know which carbon out of the three ends up with an unpaired electron after fission of C-H bond? This image shows ...
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Could the Superoxide Radical Anion Be Responsible for the Removal of Chlorine Dioxide Used to Treat Natural Waters?

Some background facts: $\ce{ClO_2}$ is a gas that is highly soluble in water (some 8 g/L at 20 °C). However, per Wikipedia , to quote: It does not hydrolyze when it enters water, and is usually ...
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Why does the heat of formation of organic radicals and positive ions decrease with their size and degree of branching at the radical or ionic site?

I am currently studying the textbook Mass Spectrometry, third edition, by Jürgen H. Gross. Chapter 2.4.3 Bond Dissociation Energies and Heats of Formation says the following: The heat of formation ...
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240 views

Deriving rate law from a reaction mechanism for a chain reaction using steady-state approximation

I am trying to derive the overall rate equation for the photocatalysed halogenation (chlorination) of an alkane that proceed via this 4 step chain reaction: $\ce{Cl2->2Cl^. \quad(1) initiation}$ $\...
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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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268 views

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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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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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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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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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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136 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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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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220 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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477 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 ...