Talk:Methyl radical

Chemistry confused

Today's two edits by Plasmic Physics are somewhat confused as to chemical terminology.

1. The word compound generally refers to a substance that can be isolated in reasonably pure form. Methyl is too unstable to qualify, and should be called either a radical or a molecule.
2. The word metastable means long-lived but not absolutely stable. A single isolated molecule of methyl radical is stable indefinitely and not metastable. A collection of methyl radicals is extremely reactive and will recombine to ethane, or react with something else if possible. Neither qualifies as metastable.
3. Strong acid is totally inapplicable. Methyl radical undergoes typical free-radical reactions, which correspond neither to Bronsted acidity nor to Lewis acidity.
4. Corrosive is not a very suitable word because the concentration of methyl radical will generally not become high enough to corrode anything. It is of course very reactive.
5. The history of laboratory studies of methyl radical started long before 2000. The discovery of methyl in the interstellar medium is interesting, although a source is needed, but the paragraph should be relabelled, perhaps to Methyl in interstellar space. Dirac66 (talk) 01:02, 17 June 2013 (UTC)

Not entirely correct. A compound is chemical which consists of an union of two or more elements, that can only be severed by what is classed as chemical reactions. Isolation does not play a role whatsoever. A substance can both be a compound and a radical, e.g. nitrogen dioxide.

Metastable refers to an ability to persist in an energy state which is higher than the ground state for a definite period, as opposed to indefinite. Formic acid is metastable, as it converts to carbon dioxide and hydrogen gas over time (or is it formaldehyde). This is paraphrased, though the word metastable is directly quoted. Even though methyl autoreacts, it can persist as a rarified gas.

A Lewis acid is an electrophile, and methyl is a very strong electrophile. It will gladly attack anything with a spare electron, and even some that don't. Corrosively does not depend on the concentration, corrosion can be a slow or fast process. Granted, a low concentration of methyl is going to take a long time to corrode anything, but quickly changes with higher concentrations. Sulfuric acid is any less corrosive when it's diluted, it just takes a long time to do the same amount of damage, if the total amount in solution remains constant; and of course neglecting its dehydration capability as a function of concentration.

As for the section heading, consider the section as a stub section. I just coincidently chose to start with its interstellar discovery, feel free to add about other historical factoids. Plasmic Physics (talk) 01:26, 17 June 2013 (UTC)

Re Lewis acid: you may be thinking of the cation CH3+ which has an empty valence-shell orbital and is an electrophile or Lewis acid. But this article is about the neutral radical CH3 with one more electron, so that there is no empty orbital to accept an electron pair.

Re last section: I agree that the interstellar discovery could potentially form part of a history section. If someone wants to write a more complete history section, then it could be called History. Dirac66 (talk) 02:19, 17 June 2013 (UTC)

No, I'm thinking of the neutral radical species, the methyl radical is one electron short of a full octet, while it cannot accept an electron pair, not counting the generation of methanide, it can accept a lone electron. It neutralizes with ammonia to produce methylamine and hydrogen gas.

I would write more under History, were it not for an impending advanced calculus examination, which I am preparing for. Plasmic Physics (talk) 02:34, 17 June 2013 (UTC)

The hethyl radical is NOT a Lewis acid, a Lewis acid is an electron PAIR acceptor and the methyl radical can only accept one electron. As Dirac66 has noted, the methyl cation is a Lewis acid but the methyl radical is not. EdChem (talk) 13:53, 18 June 2013 (UTC)

I have a reference that says otherwise. Plasmic Physics (talk) 21:09, 18 June 2013 (UTC)

Kuech, T.F. (1 September 1984). "Mechanism of carbon incorporation in MOCVD GaAs". Journal of Crystal Growth. 68 (1): 148–156. doi:10.1016/0022-0248(84)90410-X. Retrieved 18 June 2013. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)

Plasmic Physics (talk) 21:27, 18 June 2013 (UTC)

The paper does contains the sentence "The methyl radical is classified as a Lewis acid or proton donor", but the context is the deprotonation/dehydrogenation of chemisorbed methyl radicals to give chemisorbed CH₂. So yes, it's a Lewis acid if you deprotonate it - but this makes it about as much as a Lewis acid as methane is. Project Osprey (talk) 23:19, 18 June 2013 (UTC)

(edit conflict) Now there is confusion. They must mean that it is both Lewis acid and a Brønsted–Lowry acid, the former deals with electrons, whereas the latter deals with proton transfer. I did use the term apologetically under the Amphotericity section to indicate that it depends on the reaction on whether methyl is acidic or alkaline, since it is oxidized by water, which is the standard comparison, it is a basic gas. Ok, regardless of what type of acid/base methyl is, it is at least an acid/base. Plasmic Physics (talk) 23:50, 18 June 2013 (UTC)

(e.c.) Thanks for providing the reference. That is an original research paper which itself references the claim to a 1977 book by John D. Roberts (which would, incidentally, be a much better reference) but which has not been republished since. A search on Google books fails to find any recent (last 15 or so years) organic chemistry text that supports a claim of the methyl radical as a Lewis Acid. If this were true there should be a good reference for it. Further, the paper you cite refers to methyl as a Lewis acid or proton donor, yet if methyl lost a hydrogen radical the resulting methylene species would be a Lewis acid. Your paper is speaking of mechanisms on a GaAs surface at elevated temperatures, these are not circumstances that represent the 'typical' chemistry of the methyl radical. The paper is also discussing Ga(CH₃)₃, which is a Lewis Acid. I recognise that you have a verifiable reference but the claim is inconsistent with the IUPAC definition of Lewis Acid and requires more solid referencing, preferably at least one that addresses the contradiction. EdChem (talk) 23:35, 18 June 2013 (UTC)

Considering that, at least it is acidic or basic (depending on the reaction), what do you recommend? Remove the 'Lewis' terms. Plasmic Physics (talk) 07:20, 19 June 2013 (UTC)

My first choice would be to remove all mention of acid, base, and amphoteric behaviour, since methyl does not conform to the accepted definitions of an acid (Lewis or Bronsted) or base. The GaAs paper does not conform to the usual terminology.

My second choice would be to note that a few authors (referencing the GaAs paper) classify CH₃ as a Lewis acid, but then to specify that this does not conform to the usual definition of a Lewis acid because the acceptor orbital is not empty and can only accept one electron. Dirac66 (talk) 15:49, 19 June 2013 (UTC)

Plasmic, it is great that you are enthusiastic about chemistry but at times your entrhusiasm is ahead of your knowledge. This is one of those times. Dirac66's suggestions are good. EdChem (talk) 00:57, 20 June 2013 (UTC)

All references to acid/base has been replaced with oxidant/reductant. Amphotericity has been replaced with redox behaviour. Plasmic Physics (talk) 01:11, 20 June 2013 (UTC)

Radical-radical combination reactions (like methyl + methyl → ethane) are not necessarily redox reactions. EdChem (talk) 01:32, 20 June 2013 (UTC)

True, but I did not imply that to be the case absolutely. It can be discussed separately under chemical reactions, you feel the need. Plasmic Physics (talk) 02:27, 20 June 2013 (UTC)