chemistry

Methylidyne radical

Methylidyne radical is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Methylidyne radical rather than just read about it. In short: Methylidyne, or (unsubstituted) carbyne, is an organic compound whose molecule consists of a single hydrogen atom bonded to a carbon atom. It is the parent compound of the carbynes, which can be seen as obtained from it by substitution of other functional groups for the hydrogen.

Key takeaways

Methylidyne radical belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Methylidyne radical to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Methylidyne radical from memory before moving on to harder problems.

Reference excerpt

Methylidyne, or (unsubstituted) carbyne, is an organic compound whose molecule consists of a single hydrogen atom bonded to a carbon atom. It is the parent compound of the carbynes, which can be seen as obtained from it by substitution of other functional groups for the hydrogen. The carbon atom is left with either one or three unpaired electrons (unsatisfied valence bonds), depending on the molecule's excitation state; making it a radical. Accordingly, the chemical formula can be CH• or CH3• (also written as ⫶CH); each dot representing an unpaired electron. The corresponding systematic names are methylidyne or hydridocarbon(•), and methanetriyl or hydridocarbon(3•). However, the formula is often written simply as CH. Methylidyne is a highly reactive gas that is quickly destroyed in ordinary conditions on Earth but is abundant in the interstellar medium (and was one of the first molecules to be detected there).

Nomenclature The trivial name carbyne is the preferred IUPAC name. Following the substitutive nomenclature, the molecule is viewed as methane with three hydrogen atoms removed, yielding the systematic name "methylidyne". Following the additive nomenclature, the molecule is viewed as a hydrogen atom bonded to a carbon atom, yielding the name "hydridocarbon". By default, these names pay no regard to the excitation state of the molecule. When that attribute is considered, the states with one unpaired electron are named "methylylidene" or "hydridocarbon(•)", whereas the excited states with three unpaired electrons are named "methanetriyl" or "hydridocarbon(3•)".

Bonding

As an odd-electron species, CH is a radical. The ground state is a doublet (X2Π). The first two excited states are a quartet (with three unpaired electrons) (a4Σ−) and a doublet (A2Δ). The quartet lies at 71 kJ/mol above the ground state. Reactions of the doublet radical with non-radical species involves insertion or addition:

[CH]•(X2Π) + H2O → H• + CH2O (major) or [CH2(OH)]• whereas reactions of the quartet radical generally involves only abstraction:

[CH]3•(a4Σ−) + H2O → [CH2] + [HO]• Methylidyne can bind to metal atoms as tridentate ligand in coordination complexes. An example is methylidynetricobaltnonacarbonyl HCCo3(CO)9.

Occurrence and reactivity

Fischer–Tropsch intermediate Methylidyne-like species are implied intermediates in the Fischer–Tropsch process, the hydrogenation of CO to produce hydrocarbons. Methylidyne entities are assumed to bond to the catalyst's surface. A hypothetical sequence is:

MnCO + ⁠1/2⁠ H2 → MnCOH MnCOH + H2 → MnCH + H2O MnCH + ⁠1/2⁠ H2 → MnCH2 The MnCH intermediate has a tridentate methylidine ligand. The methylene ligand (H2C) is then poised couple to CO or to another methylene, thereby growing the C–C chain.

Amphotericity The methylylidyne group can exhibit both Lewis acidic and Lewis basic character. Such behavior is only of theoretical interest since it is not possible to produce methylidyne.

In interstellar space In October 2016, astronomers reported that the methylidyne radical ⫶CH, the carbon-hydrogen positive ion :CH+, and the carbon ion ⫶C+ are the result of ultraviolet light from stars, rather than in other ways, such as the result of turbulent events related to supernovas and young stars, as thought earlier.

Preparation Methylidyne can be prepared from bromoform.

See also Methylene group Methylene bridge Methine group (methylylidene group, =CH-) Methylidyne group (≡CH)

References

Illustrations

Worked examples

Example 1 — a first encounter with Methylidyne radical

Start with the simplest possible case. Write down what Methylidyne radical claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Methylidyne radical before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Methylidyne radical ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Methylidyne radical

In research: Methylidyne radical appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Methylidyne radical in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Methylidyne radical is common in secondary-school and first-year university syllabi. It links to neighbouring topics Free radicals, Organometallic chemistry, so understanding it makes those chapters shorter.
In everyday life: Look for Methylidyne radical outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Methylidyne radical in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Methylidyne radical means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Methylidyne radical out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Methylidyne radical in simple terms?

Why does Methylidyne radical matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Methylidyne radical?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Methylidyne radical.