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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40 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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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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How could burying a copper and zinc plate underground connected by a surface wire (earth-based Galvanic cell) promote crop growth?

Background: To quote a source: In the 1840s, W. Ross of New York reportedly obtained a severalfold increase in the yield of a field of potatoes when he buried a copper plate (5 ft x 14 ft) in the ...
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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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39 views

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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What are the possible products in allylic bromination of 3-methylcyclopentene?

Bromination of an alkene by N-bromosuccinimide (NBS) in the presence of light or peroxide is a radical reaction and produces an allylic bromide. For the following bromination of 3-methylcyclopentene, ...
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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 Markonikov 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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What is the hybridisation of trifluoromethyl free radical?

Having three σ bonds in a similar manner to $\ce{CH3^·}$ free radical, $\ce{CF3^·}$ should also have $\mathrm{sp^2}$ hybridisation. However, if we look at its shape, it is pyramidal and not planar ...
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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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187 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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1answer
176 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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95 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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What is the major product on chlorination of 2-methylbutane?

I came across a question asking for the major product on chlorination of 2-methylbutane. The answer in the back of the book says it will be 2-chloro-3-methylbutane. However, I thought the major ...
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2answers
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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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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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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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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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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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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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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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856 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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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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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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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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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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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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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
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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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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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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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1k 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 (b).
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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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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
571 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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236 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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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 ...