Phenylsodium

Key takeaways

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

Reference excerpt

Phenylsodium C6H5Na is an organosodium compound. Solid phenylsodium was first isolated by Nef in 1903. Although the behavior of phenylsodium and phenyl magnesium bromide are similar, the organosodium compound is very rarely used.

Synthesis The existence of phenylsodium was originally proposed by August Kekulé after observing the formation of sodium benzoate in the reaction of bromobenzene with sodium under carbon dioxide.

Transmetalation In the original synthesis, diphenylmercury and sodium was shown to yield a suspension of phenylsodium:

(C6H5)2Hg + 3 Na → 2 C6H5Na + NaHg The Shorigen reaction is also used in the generation of phenylsodium, where an alkyl sodium compound is treated with benzene:

RNa + C6H6 → RH + C6H5Na The method can also result in the addition of a second sodium. This dimetallation occurs in the meta and para positions. The use of certain alkyl sodium compounds such as n-amyl sodium is known to greatly increase this dimetallation effect.

Metal-halogen exchange A common route to phenylsodium utilizes powdered sodium with bromobenzene:

C6H5Br + 2 Na → C6H5Na + NaBr The yield of this method is lowered by the formation of diphenyl due to phenylsodium reacting with aryl halide starting material

Lithium exchange A more modern synthesis involves the reaction of phenyllithium and NaOtBu:

C6H5Li + tBuO−Na+ → C6H5Na + tBuO−Li+

Properties and structure

The first syntheses of phenylsodium which employed the organomercury route seemed to yield a light brown powder. It was discovered by Wilhelm Schlenk that this product was contaminated by sodium amalgam. Centrifugation allowed for the isolation of pure phenylsodium which appears as a yellowish-white amorphous powder which readily bursts into flames. Like phenyllithium, adducts of the compound with PMDTA have been crystallized. While phenyllithium forms a monomeric adduct with PMDTA, phenylsodium exists as a dimer, reflecting the larger radius of sodium. Complexes of phenylsodium and magnesium alkoxides, especially magnesium 2-ethoxyethoxide Mg(OCH2CH2OEt)2, are soluble in benzene. The complex is formed by the reaction:

NaPh + Mg(OCH2CH2OEt)2 → Na2MgPh2(OCH2CH2OEt)2 Although the phenylsodium is complexed, it maintains its phenylation and metalation ability. Additionally, the complex is highly stable in benzene retaining its reactivity after a month of storage. Phenyllithium can also be used to modify the properties of phenylsodium. Ordinarily, phenylsodium reacts violently with diethyl ether, but Georg Wittig showed that by synthesizing PhNa with PhLi in ether, the complex (C6H5Li)(C6H5Na)n was formed. The phenylsodium component of the complex reacts before the phenyllithium, making it an effective compound to stabilize the highly reactive sodium compound. This complex could be isolated as solid crystals which were soluble in ether and remained stable in solution at room temperature for several days. Phenyllithium is able to stabilize phenylsodium in a ratio as high as 1:24 Li:Na, although this produces an insoluble mass which could be still used for reactions.

Reactions Reactions involving phenylsodium were employed as early as the mid 19th century, although before 1903. Typically phenylsodium is prepared in situ analogous to methods used for Grignard reagents. The work of Acree provides a number of examples of reactions involving the compound.

Cross-coupling The reaction with ethyl bromide produces ethylbenzene:

NaPh + BrEt → PhEt + NaBr An analogous reaction also occurs in the preparation of phenylsodium to produce diphenyl:

NaPh + PhBr → Ph-Ph + NaBr Reaction of benzyl chloride and phenylsodium results in diphenylmethane and (E)-stilbene. Diphenylmethane is the expected product from the substitution of chloride. The formation of stilbene is implicates radical intermediates like those proposed in the Wurtz-Fittig reaction mechanism. The reaction of phenylsodium with benzoyl chloride yields, after hydrolysis, triphenylcarbinol. Benzophenone is proposed as an intermediate.

2NaPh + PhCOCl → Ph3CONa + NaCl

Metallation Metallation reactions with phenylsodium proceed in the following general form:

PhNa + RH → C6H6 + RNa The metallation is confirmed/detected by treatment of the metallated compound with carbon dioxide, affording the corresponding sodium carboxylate which can be acidified to yield the carboxylic acid:

RNa + CO2 → RCO2Na Metallation follows a generally predictable order of reactivity. Benzene can be metallated by alkylsodium compounds resulting in phenylsodium. The phenylsodium is then able to metallate other aromatic compounds. The most commonly used reagent for metallation by phenylsodium is toluene, producing benzylsodium. Toluene can be metallated by synthesizing phenylsodium in toluene instead of benzene:

C6H5Cl + 2Na + C6H5CH3 → C6H6 + NaCl + C6H5CH2Na The benzylsodium can then be used in a nucleophilic addition. The effectiveness of the metallation can be determined by carbonating and isolating the phenylacetic acid product.

Illustrations

Worked examples

Example 1 — a first encounter with Phenylsodium

Start with the simplest possible case. Write down what Phenylsodium 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 Phenylsodium 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 Phenylsodium 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 Phenylsodium

In research: Phenylsodium 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 Phenylsodium 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: Phenylsodium is common in secondary-school and first-year university syllabi. It links to neighbouring topics Organosodium compounds, Phenyl compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Phenylsodium 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.

How to study Phenylsodium in 20 minutes

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

Frequently asked questions

What is Phenylsodium in simple terms?

Phenylsodium C6H5Na is an organosodium compound. Solid phenylsodium was first isolated by Nef in 1903.

Why does Phenylsodium 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 Phenylsodium?

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 Phenylsodium.