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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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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227 views

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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468 views

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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45 views

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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273 views

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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243 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 ...
4
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1answer
92 views

Terminology for "proton stripping"?

This is going to probably be an easy question for an organic chemist, but I am looking for the proper terminology to describe the following reaction mechanism. In particular, what is a more precise ...
3
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1answer
73 views

Ozone depletion with the OH radical

$\ce{OH*}$ radicals are known to deplete the ozone layer. Fill out the gaps below to complete the propagation stage: \begin{align} \ce{? + O3 &-> ? + O2}\\ \ce{? + O3 &-> ? + O2} \...
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26 views

Preferred radical attack on a polyester

My question concerns the relative stability of a radical next to an ester oxygen compared to a radical next to an ester carbonyl carbon. The stabilizing effect of the electron pairs of ether oxygen ...
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23 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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222 views

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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372 views

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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451 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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165 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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100 views

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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759 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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54 views

Can someone explain the differences in decomposition rates for when two molecules which have 2 different substituents?

Just having trouble on why these two have such different decomposition rates, I would like to think its because NO2 is electron withdrawing but I cannot see why this would change the rate...some ...
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151 views

Could any constituent of normal human urine produce a false positive in a Kastle-Meyer test for presence of blood?

From my understanding, one forensic test for the presence of traces of blood at a crime scene is (or was) the Kastle-Meyer test. Doing some research, I understand that in the test, hemoglobin reacts ...
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22 views

What is the reaction steps taken when producing auroral forcing?

As described in here: https://www.nasa.gov/feature/goddard/2018/sounding-rocket-mission-will-trace-auroral-winds A mixture of Trimethylaluminium, Barium and Strontium reacts and ionize in the upper ...
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45 views

Plotting second order reaction with different reactants

In a laser flash photolysis experiment, $\ce{C6H5NH2}$ $(C_0 = \pu{60 \mu M})$ is oxidize to its corresponding radical cations. There are three possible reaction pathways for the formation of the ...
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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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1answer
144 views

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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44 views

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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169 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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36 views

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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870 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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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 ...
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505 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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How to analysis the amount of reactive oxygen atom in specific molecules

From a Phd dissertation here, I read about the material follows: "Odd oxygen is a measure of oxidative capacity of the atmosphere. It contains species with an oxygen atom avaliable to serve as ...
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37 views

Photobromination of cyclohexene

During bromination of cyclohexene in the presence of hv via free radical mechanism, there are two allylic carbons. Why does the major product have only one Br an not a Br on either side of double bond....
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44 views

How to graph a second order reaction with two different reactants

In a laser flash photolysis experiment, $\ce{C6H5NH2}$ $(C_0 = \pu{60 \mu M})$ is oxidized to the corresponding radical cation. The disappearance of radical cation is monitored spectrophotometrically ...
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1answer
171 views

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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34 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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112 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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193 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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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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228 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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608 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 ...
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86 views

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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331 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 ...
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638 views

Properties of a free radical scavenger

Antioxidants are free radical scavengers and are able to reduce free radicals to make them stable. What I am interested in is why some molecules make for superb free radical scavengers and why others ...
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630 views

Free-Radical chlorination: Find all unique mono-chlorinated products

I'm having trouble with this problem. I suspect that there is a typo, as the methylcyclohexene described in the wording does not match the methylcyclopentene shown in the image(someone please confirm ...
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Mechanism for Hydrogen Peroxide decomposition?

Someone asked this question earlier and made no attempt at understanding it on their own so the question was flagged. However, it prompted me to attempt to figure it out. This is what I have come up ...
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Why we can use ΔH to determine reaction rate in free radical bromination reaction steps?

I am trying to understand why we can use ΔH to determine reaction rate in this a free radical halogenation reaction. Given: (CH3)2CH2 + Br• → (CH3)2CH• + HBr = 397 - 368 = +29 kJ/mol = ΔH (CH3)2CH• + ...
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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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126 views

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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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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45 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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171 views

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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33 views

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 ...