chemistry

Quinacridone

Quinacridone 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 Quinacridone rather than just read about it. In short: Quinacridone is an organic compound used as a pigment. Numerous derivatives constitute the quinacridone pigment family, which finds extensive use in industrial colorant applications such as robust outdoor paints, inkjet printer ink, tattoo inks, artists' watercolor paints, and color laser printer toner.

Key takeaways

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

Reference excerpt

Quinacridone is an organic compound used as a pigment. Numerous derivatives constitute the quinacridone pigment family, which finds extensive use in industrial colorant applications such as robust outdoor paints, inkjet printer ink, tattoo inks, artists' watercolor paints, and color laser printer toner. As pigments, the quinacridones are insoluble. The development of this family of pigments supplanted the alizarin dyes.

Synthesis The name indicates that the compounds are a fusion of acridone and quinoline, although they are not made that way. Classically the parent is prepared from the 2,5-dianilide of terephthalic acid (C6H2(NHPh)2(CO2H)2). Condensation of succinosuccinate esters with aniline followed by cyclization affords dihydroquinacridone, which are readily dehydrogenated. The latter is oxidized to quinacridone. Derivatives of quinacridone can be readily obtained by employing substituted anilines. Linear cis-Quinacridones can be prepared from isophthalic acid.

Derivatives

Quinacridone-based pigments are used to make high performance paints. Quinacridones were first sold as pigments by Du Pont in 1958. Quinacridones are considered "high performance" pigments because they have exceptional color and weather fastness. Major uses for quinacridones include automobile and industrial coatings. Nanocrystalline dispersions of quinacridone pigments functionalized with solubilizing surfactants are the most common magenta printing ink. Typically deep red to violet in color, the hue of quinacridone is affected not only by the R-groups on the molecule but by the crystal form of the solid. For example, the γ crystal modification of unsubstituted quinacridone provides a strong red shade that has excellent color fastness and resistance to solvation. Another important modification is the β phase which provides a maroon shade that is also more weather resistant and light-fast. Both crystal modifications are more thermodynamically stable than the α crystal phase. The γ crystal modification is characterized by a criss-cross lattice where each quinacridone molecule hydrogen-bonds to four neighbors via single H-bonds. The β phase, meanwhile, consists of linear chains of molecules with double H-bonds between each quinacridone molecule and two neighbors. Basic modifications to the chemical structure of quinacridones include the addition of CH3 and Cl substituents. Some magenta shades of quinacridone are labeled under the proprietary name "Thio Violet" and "Acra Violet".

Semiconductor properties Quinacridone derivatives exhibit intense fluorescence in the dispersed state, and high carrier mobility. These properties complement good photo-, thermal, and electrochemical stability. These properties are desired for optoelectronic applications including organic light-emitting diodes (OLEDs), organic solar cells (OSCs), and organic field-effect transistors (OFETs). Due to interplay of intermolecular H-bonding and pi-pi stacking, quinacridone can form a self-assembling, supramolecular organic semiconductor.

References

Additional reading Chenguang, Wang; Zuolun, Zhang; Yue, Wang (2016). "Quinacridone-based π-conjugated electronic materials". J. Mater. Chem. C. 4 (42): 9918–36. doi:10.1039/C6TC03621J. Głowacki, Eric Daniel; Irimia-Vladu, Mihai; Kaltenbrunner, Martin; Gsiorowski, Jacek; White, Matthew S.; Monkowius, Uwe; Romanazzi, Giuseppe; Suranna, Gian Paolo; Mastrorilli, Piero; Sekitani, Tsuyoshi; Bauer, Siegfried; Someya, Takao; Torsi, Luisa; Sarıçiftçi, Niyazi Serdar (2013). "Hydrogen-Bonded Semiconducting Pigments for Air-Stable Field-Effect Transistors". Advanced Materials. 25 (11): 1563–9. Bibcode:2013AdM....25.1563G. doi:10.1002/adma.201204039. PMID 23239229. S2CID 205247943.

Illustrations

Worked examples

Example 1 — a first encounter with Quinacridone

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

In research: Quinacridone 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 Quinacridone 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: Quinacridone is common in secondary-school and first-year university syllabi. It links to neighbouring topics Acridines, Diketones, Heterocyclic compounds with 5 rings, so understanding it makes those chapters shorter.
In everyday life: Look for Quinacridone 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 Quinacridone in 20 minutes

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

Frequently asked questions

What is Quinacridone in simple terms?

Why does Quinacridone 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 Quinacridone?

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 Quinacridone.