chemistry

Vinyl alcohol

Vinyl alcohol 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 Vinyl alcohol rather than just read about it. In short: Vinyl alcohol, also called ethenol (IUPAC name; not ethanol) or ethylenol, is the simplest enol. With the formula CH2CHOH, it is a labile compound that converts to acetaldehyde immediately upon isolation near room temperature.

Key takeaways

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

Reference excerpt

Vinyl alcohol, also called ethenol (IUPAC name; not ethanol) or ethylenol, is the simplest enol. With the formula CH2CHOH, it is a labile compound that converts to acetaldehyde immediately upon isolation near room temperature. It is not a practical precursor to any compound.

Synthesis Vinyl alcohol can be formed by the pyrolytic elimination of water from ethylene glycol at a temperature of 900 °C and low pressure. Such processes are of no practical importance.

Tautomerization of vinyl alcohol to acetaldehyde Under normal conditions, vinyl alcohol converts (tautomerizes) to acetaldehyde:

At room temperature, acetaldehyde (H3CC(O)H) is more stable than vinyl alcohol (H2C=CHOH) by 42.7 kJ/mol. Vinyl alcohol gas isomerizes to the aldehyde with a half-life of 30 min at room temperature.

H2C=CHOH → H3CC(O)H

The uncatalyzed keto–enol tautomerism by a 1,3-hydrogen migration is forbidden by the Woodward–Hoffmann rules and therefore has a high activation barrier and is not a significant pathway at or near room temperature. However, even trace amounts of acids or bases (including water) can catalyze the reaction. Even with rigorous precautions to minimize adventitious moisture or proton sources, vinyl alcohol can only be stored for minutes to hours before it isomerizes to acetaldehyde. (Carbonic acid is another example of a substance that is stable when rigorously pure, but decomposes rapidly due to catalysis by trace moisture.) The tautomerization can also be catalyzed via photochemical process. These findings suggest that the keto–enol tautomerization is a viable route under atmospheric and stratospheric conditions, relevant to a role for vinyl alcohol in the production of organic acids in the atmosphere. Vinyl alcohol can be stabilized by controlling the water concentration in the system and utilizing the kinetic favorability of the deuterium-produced kinetic isotope effect (kH+/kD+ = 4.75, kH2O/kD2O = 12). Deuterium stabilization can be accomplished through hydrolysis of a ketene precursor in the presence of a slight stoichiometric excess of heavy water (D2O). Studies show that the tautomerization process is significantly inhibited at ambient temperatures (kt ≈ 10−6 M/s), and the half-life of the enol form can easily be increased to t1/2 = 42 minutes for first-order hydrolysis kinetics.

Relationship to poly(vinyl alcohol) Because of the instability of vinyl alcohol, the thermoplastic polyvinyl alcohol (PVA or PVOH) is made indirectly by polymerization of vinyl acetate followed by hydrolysis of the ester bonds (Ac = acetyl; HOAc = acetic acid):

n CH2=CHOAc → (CH2−CHOAc)n (CH2−CHOAc)n + n H2O → (CH2−CHOH)n + n HOAc

As a ligand Several metal complexes are known that contain vinyl alcohol as a ligand. One example is Pt(acac)(η2-C2H3OH)Cl.

Occurrence in interstellar medium Vinyl alcohol was detected in the molecular cloud Sagittarius B in 2001, the last of the three stable isomers of C2H4O (after acetaldehyde and ethylene oxide) to be detected in space. Its stability in the (dilute) interstellar medium shows that its tautomerization does not happen unimolecularly, a fact attributed to the size of the activation energy barrier to the rearrangement being insurmountable at temperatures present in interstellar space. The vinyl alcohol to acetaldehyde rearrangement is the only keto-enol tautomerisation to have been detected in deep space, induced by the provision of secondary electrons from galactic cosmic rays.

References

Illustrations

Worked examples

Example 1 — a first encounter with Vinyl alcohol

Start with the simplest possible case. Write down what Vinyl alcohol 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 Vinyl alcohol 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 Vinyl alcohol 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 Vinyl alcohol

In research: Vinyl alcohol 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 Vinyl alcohol 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: Vinyl alcohol is common in secondary-school and first-year university syllabi. It links to neighbouring topics Enols, Organic compounds with 2 carbon atoms, Vinyl compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Vinyl alcohol 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 Vinyl alcohol in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Vinyl alcohol 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 Vinyl alcohol out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Vinyl alcohol in simple terms?

Why does Vinyl alcohol 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 Vinyl alcohol?

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 Vinyl alcohol.