chemistry

Naphthol Red

Naphthol Red 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 Naphthol Red rather than just read about it. In short: Naphthol Red (Pigment red 170 or PR170) is an organic pigment extensively used in automotive coatings and painting. It is produced synthetically by converting p-aminobenzamide into the corresponding diazonium compound followed by coupling with 3-hydroxy-2-naphththoic acid (2-ethoxy)anilide ("Naphtol AS-PH" dye precursor).

Key takeaways

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

Reference excerpt

Naphthol Red (Pigment red 170 or PR170) is an organic pigment extensively used in automotive coatings and painting. It is produced synthetically by converting p-aminobenzamide into the corresponding diazonium compound followed by coupling with 3-hydroxy-2-naphththoic acid (2-ethoxy)anilide ("Naphtol AS-PH" dye precursor).

In the solid state the hydrazo tautomer forms and several crystal structures exist. In the initial α polymorph the molecules are arranged in a herringbone pattern with extensive hydrogen bonding. The φ polymorph is more dense and more stable and produced industrially by thermal treatment in water at 130°C under pressure. In this phase the molecules are planar and arranged in layers. Extensive hydrogen bonding exists within the layer but between layers the only interactions are Van der Waals forces. Dense crystal structures are preferred for pigments used in coatings because in the event of photochemical decomposition the fragments are locked in place and are able to recombine. Research shows that by replacing the ethoxy group in this compound by a methoxy group the crystal structure is less stable and in the final application and the color fades more easily. By careful selection of substituents it is possible to optimize crystal structure and improve optical properties [1].

References ^ Crystal Structures of Pigment Red 170 and Derivatives, as Determined by X-ray Powder Diffraction Martin U. Schmidt, Detlef W. M. Hofmann, Christian Buchsbaum, Hans Joachim Metz, Angewandte Chemie International Edition Volume 45, Issue 8, Pages 1313 - 1317 2006 Abstract

Illustrations

Worked examples

Example 1 — a first encounter with Naphthol Red

Start with the simplest possible case. Write down what Naphthol Red 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 Naphthol Red 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 Naphthol Red 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 Naphthol Red

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

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

Frequently asked questions

What is Naphthol Red in simple terms?

Why does Naphthol Red 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 Naphthol Red?

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 Naphthol Red.