chemistry

Melem

Melem 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 Melem rather than just read about it. In short: In chemistry, melem is a compound with formula C6N10H6; specifically, 2,5,8-triamino-heptazine or 2,5,8-triamino-tri-s-triazine, whose molecule can be described as that of heptazine with the three hydrogen atoms replaced by amino groups. It is a white crystalline solid.

Key takeaways

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

Reference excerpt

In chemistry, melem is a compound with formula C6N10H6; specifically, 2,5,8-triamino-heptazine or 2,5,8-triamino-tri-s-triazine, whose molecule can be described as that of heptazine with the three hydrogen atoms replaced by amino groups. It is a white crystalline solid.

Preparation Melem can be prepared by thermal decomposition of various C−N−H compounds, such as melamine C3N3(NH2)3, dicyandiamide H4C2N4, ammonium dicyanamide NH4[N(CN)2], cyanamide H2CN2, at 400 to 450 °C.

Structure and properties

Crystal structure Melem crystallizes in the group P21/c (No. 14), with parameters a = 739.92(1) pm, b = 865.28(3) pm, c = 1338.16(4) pm, β = 99.912(2)°, and Z = 4. The almost-planar molecules are arranged in parallel layers spaced 327 pm apart. The molecule is in the triamino form, rather than one of the possible tautomers.

Thermal decomposition When heated above 560°, melem transforms into a graphite-like C−N material.

Melemium cations Melem accepts up to three protons yielding cations called melemium [(NH2)3(C6N7Hx)]x+. Some salts described in the literature are melemium sulfate, [(NH2)3(C6N7H2)]SO4 • 2H2O, melemium perchlorate, [(NH2)3(C6N7H)]ClO4 • H2O, melemium hydrogensulfate [(NH2)3(C6N7H3)](HSO4)3 and two melemium methylsulfonates [(NH2)3(C6N7H2)](SO3CH3)2 • H2O and [(NH2)3(C6N7H)][(NH2)3(C6N7H2)](SO3CH3)3 • H2O. The protons can be inserted in any of the six outer nitrogen atoms of the heptazine core, yielding many tautomers of apparently similar energies.

See also Triazine H3C3N3, with a single C-N ring Melamine (NH2)3(C3N3), triamino triazine Melaminium [H(NH2)3(C3N3)]+, a cation derived from melamine Melam ((NH2)2(C3N3))2NH, a condensation dimer of melamine Melamium [H((NH2)2(C3N3))2NH]+, a cation derived from melam Melon (NH2)(NH(C6N7H)NH)nH, a condensation oligomer of melem

References

Illustrations

Worked examples

Example 1 — a first encounter with Melem

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

In research: Melem 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 Melem 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: Melem is common in secondary-school and first-year university syllabi. It links to neighbouring topics Amines, Heterocyclic compounds with 3 rings, Nitrogen heterocycles, so understanding it makes those chapters shorter.
In everyday life: Look for Melem 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Melem in 20 minutes

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

Frequently asked questions

What is Melem in simple terms?

Why does Melem 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 Melem?

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 Melem.