chemistry

Initiation (chemistry)

Initiation (chemistry) 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 Initiation (chemistry) rather than just read about it. In short: In chemistry, initiation is a chemical reaction that triggers one or more secondary reactions. Initiation creates a reactive centre on a molecule which produces a chain reaction.

Key takeaways

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

Reference excerpt

In chemistry, initiation is a chemical reaction that triggers one or more secondary reactions. Initiation creates a reactive centre on a molecule which produces a chain reaction. The reactive centre generated by initiation is usually a radical, but can also be cations or anions. Once the reaction is initiated, the species goes through propagation where the reactive species reacts with stable molecules, producing stable species and reactive species. This process can produce very long chains of molecules called polymers, which are the building blocks for many materials. After propagation, the reaction is then terminated. There are different types of initiation, with the two main ways being thermal initiation and photo-initiation (light).

Thermal initiation Thermal initiation involves initiating a reaction in the presence of heat, usually at very high temperatures. Heating a reaction can result in radical initiation of the substrate(s). In the presence of heat, a monomer can self-initiate and react with other monomers or pairs of monomers. This process is called spontaneous polymerization and requires a lot of heat to occur (up to 200 °C). For monomers to initiate and polymerize with the same type of monomer (called Homopolymerization), ~180 °C is needed for the monomers to initiate. Copolymerization, which is when different kinds of monomers are initiated and react with each other, is more stable and can happen at lower temperatures than Homopolymerization. Self-initiation between homo-monomers is a difficult mechanism to observe because species that are initiated aren't always the same kind of monomer. Sometimes impurities found in the reaction flask with the monomers get initiated and polymerize with monomers, instead of the monomer getting initiated.

Photoinitiation (light) Photo-initiation occurs when monomers get initiated by light irradiation. LED light passes through the reaction flask which excites the monomers turning them into reactive species, mainly radicals and ions, which can then polymerize. There are two mechanistic classifications of photo-initiation reactions, being either a photoredox process or intramolecular photochemical process. This type of initiation can happen at much lower temperatures, mainly room temperature, then thermal initiation. This makes photo-initiation much more practical than thermal initiation. Photo-initiation also produces less side reactions than thermal and has less impurities. Though thermal initiation is hard to maintain, photo-initiation provides an easy way to initiate monomers to polymerize. Photo-initiation is even used in application such as making various coatings, adhesives, inks, and microelectronics.

Illustrations

Initiation (chemistry): Simple initiation reaction of dichlorine into two chlorine radicals; initiated by light. — Simple initiation reaction of dichlorine into two chlorine radicals; initiated by light.

Worked examples

Example 1 — a first encounter with Initiation (chemistry)

Start with the simplest possible case. Write down what Initiation (chemistry) 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 Initiation (chemistry) 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 Initiation (chemistry) 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 Initiation (chemistry)

In research: Initiation (chemistry) 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 Initiation (chemistry) 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: Initiation (chemistry) is common in secondary-school and first-year university syllabi. It links to neighbouring topics Reaction mechanisms, so understanding it makes those chapters shorter.
In everyday life: Look for Initiation (chemistry) 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 Initiation (chemistry) in 20 minutes

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

Frequently asked questions

What is Initiation (chemistry) in simple terms?

In chemistry, initiation is a chemical reaction that triggers one or more secondary reactions. Initiation creates a reactive centre on a molecule which produces a chain reaction.

Why does Initiation (chemistry) 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 Initiation (chemistry)?

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 Initiation (chemistry).