chemistry

Red 2G

Red 2G 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 Red 2G rather than just read about it. In short: Red 2G is a synthetic red azo dye. It is soluble in water and slightly soluble in glycerol.

Key takeaways

Red 2G belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Red 2G to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Red 2G from memory before moving on to harder problems.

Reference excerpt

Red 2G is a synthetic red azo dye. It is soluble in water and slightly soluble in glycerol. It usually comes as a disodium salt of 8-acetamido-1-hydroxy-2-phenylazonaphthalene-3,6 disulfonate.

Preparation Red 2G is produced by azo coupling of Acetyl-H acid and diazonium derivative of Aniline under basic conditions:

Uses

Food dye In the European Union, Red 2G was used as a food dye (E number E128). However, it was only permitted for use in breakfast sausages with a minimum cereal content of 6% and burger meat with a minimum vegetable and/or cereal content of 4%. Following safety concerns raised by the European Food Safety Authority (EFSA) in its opinion of 5 July 2007, the European Commission has prepared a draft Regulation to suspend use of E128 as a food colouring. This proposed course of action was unanimously approved by European Union Member States at a meeting of the Standing Committee of the Food Chain and Animal Health (Section Toxicological Safety of the Food Chain) on 20 July 2007. and Commission Regulation (EC) No 884/2007 on emergency measures suspending the use of E 128 Red 2G as food colour was published in the Official Journal of the European Union on 27 July 2007. Red 2G is also banned in Australia, Canada, Japan, Norway, and Malaysia. It was banned in Israel in August 2007. It is relatively insensitive to the bleaching effect of sulfur dioxide (E220) and sodium metabisulfite (E223). In the intestines, Red 2G can be converted to the toxic compound aniline, so there are concerns Red 2G may ultimately interfere with blood haemoglobin, as well as cause cancer.

Inks It is also used as a dye for coatings, inks, paper, crepe paper, and fine tissue.

Histology Red 2G can be also used for staining in histology, though rarely, e.g. as a component of Masson's trichrome.

Potential health risks In July 2007, the EFSA established that E128 is potentially carcinogenic because it forms aniline in the body when consumed. The pressure group, The Food Commission, said there had been concerns about Red 2G going back decades and it was suspected of being a carcinogen in the 1980s.

References

Illustrations

Worked examples

Example 1 — a first encounter with Red 2G

Start with the simplest possible case. Write down what Red 2G 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 Red 2G 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 Red 2G 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 Red 2G

In research: Red 2G 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 Red 2G 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: Red 2G is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1-Naphthols, Acetamides, Azo dyes, so understanding it makes those chapters shorter.
In everyday life: Look for Red 2G 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 Red 2G in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Red 2G 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 Red 2G out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Red 2G in simple terms?

Red 2G is a synthetic red azo dye. It is soluble in water and slightly soluble in glycerol.

Why does Red 2G 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 Red 2G?

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 Red 2G.