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Template reaction

Template reaction 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 Template reaction rather than just read about it. In short: In chemistry, a template reaction is any of a class of ligand-based reactions that occur between two or more adjacent coordination sites on a metal center. In the absence of the metal ion, the same organic reactants produce different products.

Template reaction — main illustration
Template reaction — illustration

Key takeaways

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

Reference excerpt

In chemistry, a template reaction is any of a class of ligand-based reactions that occur between two or more adjacent coordination sites on a metal center. In the absence of the metal ion, the same organic reactants produce different products. The term is mainly used in coordination chemistry. The template effects emphasizes the pre-organization provided by the coordination sphere, although the coordination modifies the electronic properties (acidity, electrophilicity, etc.) of ligands. An early example is the dialkylation of a nickel dithiolate:

The corresponding alkylation in the absence of a metal ion would yield polymers. Crown ethers arise from dialkylations that are templated by alkali metals. Other template reactions include the Mannich and Schiff base condensations. The condensation of formaldehyde, ammonia, and tris(ethylenediamine)cobalt(III) to give a clathrochelate complex is one example.

The phosphorus analogue of an aza crown can be prepared by a template reaction. Where it is not possible to isolate the phosphine itself.

Limitations Many template reactions are only stoichiometric, and the decomplexation of the "templating ion" can be difficult. The alkali metal-templated syntheses of crown ether syntheses are notable exceptions. Metal Phthalocyanines are generated by metal-templated condensations of phthalonitriles, but the liberation of metal-free phthalocyanine is difficult. Some so-called template reactions proceed similarly in the absence of the templating ion. One example being the condensation of acetone and ethylenediamine, which yields isomeric 14-membered tetraaza rings. Similarly, porphyrins, which feature 16-membered central rings, form in the absence of metal templates.

Concept in catalysis In a general sense, transition metal-based catalysis can be viewed as template reactions: Reactants coordinate to adjacent sites on the metal ion and, owing to their adjacency, the two reactants interconnect (insert or couple) either directly or via the action of another reagent. In the area of homogeneous catalysis, the cyclo-oligomerization of acetylene to cyclooctatetraene at a nickel(II) centre reflects the templating effect of the nickel, where it is supposed that four acetylene molecules occupy four sites around the metal and react simultaneously to give the product. This simplistic mechanistic hypotheses was influential in the development of these catalytic reactions. For example, if a competing ligand such as triphenylphosphine were added to occupy one coordination site, then only three molecules of acetylene could bind, and these come together to form benzene (see Reppe chemistry).

References

Illustrations

Template reaction illustration
Template reaction: 18-Crown-6 can be synthesized by the Williamson ether synthesis using potassium ion as the template cation.
18-Crown-6 can be synthesized by the Williamson ether synthesis using potassium ion as the template cation.
Template reaction: Structure of nickel-aquo nitrate complex of the ligand derived from the templated trimerization of 2-aminobenzaldehyde.[5]
Structure of nickel-aquo nitrate complex of the ligand derived from the templated trimerization of 2-aminobenzaldehyde.[5]
Template reaction: Scheme 4. Phosphacrown
Scheme 4. Phosphacrown
Template reaction: 14-membered N4 macrocyclic ligands, called Curtis macrocycles, arise from the condensation of acetone and a nickel complex of ethylenediamine.
14-membered N4 macrocyclic ligands, called Curtis macrocycles, arise from the condensation of acetone and a nickel complex of ethylenediamine.

Worked examples

Example 1 — a first encounter with Template reaction

Start with the simplest possible case. Write down what Template reaction 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 Template reaction 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 Template reaction 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 Template reaction

In research
Template reaction 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 Template reaction 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
Template reaction is common in secondary-school and first-year university syllabi. It links to neighbouring topics Polymer chemistry, so understanding it makes those chapters shorter.
In everyday life
Look for Template reaction 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 Template reaction in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Template reaction means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Template reaction out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Template reaction in simple terms?

In chemistry, a template reaction is any of a class of ligand-based reactions that occur between two or more adjacent coordination sites on a metal center. In the absence of the metal ion, the same organic reactants produce different products.

Why does Template reaction 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 Template reaction?

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 Template reaction.

Tags

  • Polymer chemistry

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