chemistry

Oxalyl chloride

Oxalyl chloride 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 Oxalyl chloride rather than just read about it. In short: Oxalyl chloride is an organic chemical compound with the formula Cl−C(=O)−C(=O)−Cl. This colorless, sharp-smelling liquid, the diacyl chloride of oxalic acid, is a useful reagent in organic synthesis.

Key takeaways

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

Reference excerpt

Oxalyl chloride is an organic chemical compound with the formula Cl−C(=O)−C(=O)−Cl. This colorless, sharp-smelling liquid, the diacyl chloride of oxalic acid, is a useful reagent in organic synthesis.

Preparation Oxalyl chloride was first prepared in 1892 by the French chemist Adrien Fauconnier, who treated diethyl oxalate with phosphorus pentachloride. It can also be prepared by treating oxalic acid with phosphorus pentachloride. Oxalyl chloride is produced commercially from ethylene carbonate. Photochlorination gives the perchloroethylene carbonate C2Cl4O2CO and hydrogen chloride HCl, which is subsequently degraded to oxalyl chloride and phosgene COCl2:

C2H4O2CO + 4 Cl2 → C2Cl4O2CO + 4 HCl C2Cl4O2CO → C2O2Cl2 + COCl2

Reactions As originally determined by Staudinger, oxalyl chloride reacts with water giving off gaseous products only: hydrogen chloride (HCl), carbon dioxide (CO2), and carbon monoxide (CO).

(COCl)2 + H2O → 2 HCl + CO2 + CO Other acyl chlorides hydrolyze with formation of hydrogen chloride and the original carboxylic acid.

Applications in organic synthesis

Oxidation of alcohols Addition of a primary or secondary alcohol to a solution of oxalyl chloride in DMSO, followed by quenching with an organic base such as triethylamine converts alcohols to the corresponding aldehydes and ketones via the process known as the Swern oxidation.

Synthesis of acyl chlorides Oxalyl chloride is mainly used together with a N,N-dimethylformamide catalyst in organic synthesis for the preparation of acyl chlorides from the corresponding carboxylic acids. Like thionyl chloride, the reagent degrades into volatile side products in this application, which simplifies workup. One of the minor byproducts from the N,N-dimethylformamide catalyzed reaction, dimethylcarbamoyl chloride, is a potent carcinogen, stemming from the N,N-dimethylformamide decomposition. Relative to thionyl chloride, oxalyl chloride tends to be a milder, more selective reagent. It is also more expensive than thionyl chloride so it tends to be used on a smaller scale.

This reaction involves conversion of N,N-dimethylformamide to the imidoyl chloride derivative (chloromethylene(dimethyl)ammonium ion (CH3)2N+=CHCl), akin to the first stage in the Vilsmeier–Haack reaction. The imidoyl chloride is the active chlorinating agent.

Addition of carboxylic acid groups to arenes Oxalyl chloride reacts with aromatic compounds in the presence of aluminium chloride to give the corresponding acyl chloride in a process known as a Friedel-Crafts acylation. The resulting acyl chloride can be hydrolysed to form the corresponding carboxylic acid.

Preparation of oxalate diesters Like other acyl chlorides, oxalyl chloride reacts with alcohols to give esters:

2 R−CH2−OH + Cl−C(=O)−C(=O)Cl → R−CH2−O−C(=O)−C(=O)−O−CH2−R + 2 HCl Typically, such reactions are conducted in the presence of a base such as pyridine. The diester derived from phenol, phenyl oxalate ester, is Cyalume, the active ingredient in glow sticks. A similar reaction occurs with amines to give substituted oxalamides:

2 R−NH2 + ClC(=O)−C(=O)Cl → R−NH−C(=O)−C(=O)−NH−R + 2 HCl

Other Oxalyl chloride was reportedly used in the first synthesis of dioxane tetraketone (C4O6), an oxide of carbon.

Precautions In March 2000, a Malaysia Airlines Airbus A330-300 was damaged beyond repair after a cargo of prohibited oxalyl chloride (falsely declared as hydroxyquinoline) leaked into the cargo bay. It is toxic by inhalation, although it is over an order of magnitude less acutely toxic than the related compound phosgene.

Illustrations

Worked examples

Example 1 — a first encounter with Oxalyl chloride

Start with the simplest possible case. Write down what Oxalyl chloride 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 Oxalyl chloride 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 Oxalyl chloride 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 Oxalyl chloride

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

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

Frequently asked questions

What is Oxalyl chloride in simple terms?

Why does Oxalyl chloride 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 Oxalyl chloride?

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 Oxalyl chloride.