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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Monochlorination of (R)-2-chlorohexane: Number of possible chiral dichloro products

How many possible chiral dichloro products can be formed when (R)-2-chlorohexane reacted with one equivelent of $\ce{Cl2}$ in the presence of UV radiation (monochlorination only)? $$\ce{C6H11Cl + Cl2 -...
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PVP-iodine and octenidine can stain skin purple, does the reaction create iodine radicals?

In this paper it is mentioned that ... octenidine can release iodine radicals from the PVP complex, resulting in a tissue irritation as well as strong brown to violet discolouration in the border ...
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Calculate frequency dose from different light intensities

The quantum yield for homolytic O-O cleavage of (CH$_3$)$_3$COOC(CH$_3$)$_3$ at $266$ nm is $0.21$. In one experiment, a pulsed laser of this wavelength was used to induce the formation of t-butoxyl ...
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Two wavelength photo-initiators?

Not a chemist so I hope you'll forgive any amateur mistakes. I found an overview of 3D printing resin photo-initiators here: https://pubs.acs.org/doi/10.1021/acsapm.8b00165#tbl1 All these activate ...
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The major product of radical halogenation: Why is it a halogen attached to a primary carbon and not a tertiary carbon in the given example?

There's this problem that I saw in my Organic Chemistry book: The reaction between $\ce{(CH3)3CH}$ and $\ce{Cl2}$ forms two products: $\ce{(CH3)2CHCH2Cl}$ (63%) and $\ce{(CH3)3CCl}$ (37%). Why is the ...
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Why are radicals considered electron deficient?

I have often read that radicals are electron-deficient and are therefore stabilized by things like electron-donating groups (EDGs) and hyperconjugation. However, today I learned that electron-...
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How are antioxidants different from other compounds that contain hydroxyl group?

From my book: An antioxidant is a substance that prevents oxidation by reacting with an oxidizing agent If that's the case, why do we distinguish between antioxidants? Are all compounds containing ...
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Reaction rate of 2 H2 + O2 → 2 H2O

I am interested in the kinetics of the reactions: $$ \begin{align} \ce{2 H2 + O2 &-> H2O}\tag{R1}\\ \ce{2 CO + O2 &-> 2 CO2}\tag{R2}\\ \end{align} $$ I looked at the NIST website hoping ...
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How does Hyperconjugation stabilize a Carbon Free Radical? [closed]

I tried drawing the resonance structures but just cannot see how donating two electrons to a carbon that only needs one electron make it more stable? I stumbled upon this question asked years ago ...
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Kharasch Peroxide effect with heating

From what i have learnt, kharasch Peroxide effect is only applicable for HBr. The reason for this is for the other halogens, HCl and HI the propagation steps in the radical mechanism are endothermic. ...
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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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Can uv light cause heterolytic cleavage?

All sources I've read stated that UV-light can only cause homolytic cleavage (homolytic fission), producing radicals while not mentioning whether it was possible for it to cause heterolytic cleavage ...
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How to name radical

The name of biradical —CO—CH2–O—CH2–CO— is Oxybis (1-oxo-2,1-ethanediyl). Why is it wrong to write 1,2-ethanediyl instead of 2,1? Thanks in advance!
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Why do radical inhibitors inhibit a reaction by creating a "more stable" radical, but for monohalogenation, we WANT to form the most stable radical?

According to my notes, radical inhibitors tend to turn a more reactive radical into a less reactive radical by making it more stable. For instance, the hydroquinone reacts with a radical species, ...
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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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Why is carbon tetrachloride more stable than methane?

When a mixture of methane and chlorine is exposed to ultraviolet light – typically sunlight – a substitution reaction occurs and the organic product is chloromethane. However, the reaction doesn't ...
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Reaction Mechanism for a radical ring opening

I have a radical reaction which I got from an organic chemistry lecture and was drawing the possible mechanism for it. Fig 2. shows my thought process. The I is removed making a radical and ISnBu$_3$. ...
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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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2 votes
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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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g-tensor and hyperfine tensor for nitroxide spin label with 15N

Does anyone know where I can find numerical data for the $g$ tensor and hyperfine tensor for a nitroxide spin label where the nitrogen-14 atom has been replaced by a nitrogen-15 atom? I'm really ...
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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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How would this reaction occur through free radical substitution?

So, I was trying to solve this through free radical substitution: (Side note, the (ac) means (aq)) The best product I managed to do/think was the following: However, according to what I've seen, it'...
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2 votes
1 answer
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Bromochlorofluoromethane as a reagent in Riemer-Tiemann reaction

The reagent usually used in Riemer-Tiemann reaction is $\ce{CHCl_3 }$ however one of the variations I read used $\ce{CHFClBr}$ as a reagent. Now $\ce{CHCl_3}$ produces the $\ce{:CCl_2}$ radical using ...
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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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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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8 votes
1 answer
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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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2 votes
1 answer
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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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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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3 votes
1 answer
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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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2 votes
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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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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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2 votes
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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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7 votes
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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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4 votes
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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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6 votes
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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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1 vote
1 answer
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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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3 votes
1 answer
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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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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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1 vote
1 answer
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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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6 votes
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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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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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1 answer
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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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3 votes
2 answers
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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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