science

Schlenk line

Schlenk line is a science 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 Schlenk line rather than just read about it. In short: The Schlenk line (also vacuum gas manifold) is a commonly used chemistry apparatus developed by Wilhelm Schlenk. It consists of a dual manifold with several ports.

Key takeaways

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

Reference excerpt

The Schlenk line (also vacuum gas manifold) is a commonly used chemistry apparatus developed by Wilhelm Schlenk. It consists of a dual manifold with several ports. One manifold is connected to a source of purified inert gas, while the other is connected to a vacuum pump. The inert-gas line is vented through an oil bubbler, while solvent vapors and gaseous reaction products are prevented from contaminating the vacuum pump by a liquid-nitrogen or dry-ice/acetone cold trap. Special stopcocks or Teflon taps allow vacuum or inert gas to be selected without the need for placing the sample on a separate line. Schlenk lines are useful for manipulating moisture- and air-sensitive compounds. The vacuum is used to remove air or other gasses present in closed, connected glassware to the line. It often also removes the last traces of solvent from a sample. Vacuum and gas manifolds often have many ports and lines, and with care, it is possible for several reactions or operations to be run simultaneously in inert conditions. When the reagents are highly susceptible to oxidation, traces of oxygen may pose a problem. Then, for the removal of oxygen below the ppm level, the inert gas needs to be purified by passing it through a deoxygenation catalyst. This is usually a column of copper(I) or manganese(II) oxide, which reacts with oxygen traces present in the inert gas. In other cases, a purge-cycle technique is often employed, where the closed, reaction vessel connected to the line is filled with inert gas, evacuated with the vacuum and then refilled. This process is repeated 3 or more times to make sure air is rigorously removed. Moisture can be removed by heating the reaction vessel with a heat gun.

Techniques The main techniques associated with the use of a Schlenk line include:

counterflow additions, where air-stable reagents are added to the reaction vessel against a flow of inert gas; the use of syringes and rubber septa to transfer liquids and solutions; cannula transfer, where liquids or solutions of air-sensitive reagents are transferred between different vessels stoppered with septa using a long thin tube known as a cannula. Liquid flow is supported by vacuum or inert-gas pressure. Glassware are usually connected by tightly fitting and greased ground glass joints. Round bends of glass tubing with ground glass joints may be used to adjust the orientation of various vessels. Glassware is necessarily purged of outside air by using the purge cycling technique. The solvents and reagents that are used can use a technique called "sparging" to remove air. This is where a cannula needle, which is connected to the inert gas on the line, is inserted into the reaction vessel containing the solvent; this effectively bubbles the inert gas into the solution, which will actively push out trapped gas molecules from the solvent. Filtration under inert conditions poses a special challenge. It is usually achieved using a "cannula filter". Classically, filtration is tackled with a Schlenk filter, which consists of a sintered glass funnel fitted with joints and stopcocks that is sometimes called a Schlenk frit. By fitting the pre-dried funnel and receiving flask to the reaction flask against a flow of nitrogen, carefully inverting the set-up and turning on the vacuum appropriately, the filtration may be accomplished with minimal exposure to air. A glovebox is often used in conjunction with the Schlenk line for storing and reusing air- and moisture-sensitive solvents in a lab.

Dangers The main dangers associated with the use of a Schlenk line are the risks of an implosion or explosion. An implosion can occur due to the use of vacuum and flaws in the glass apparatus. An explosion can occur due to the common use of liquid nitrogen in the cold trap, used to protect the vacuum pump from solvents. If a reasonable amount of air is allowed to enter the Schlenk line, liquid oxygen can condense into the cold trap as a pale blue liquid. An explosion may occur due to reaction of the liquid oxygen with any organic compounds also in the trap.

Gallery

See also Air-free technique gives a broad overview of methods including: Glovebox – used to manipulate air-sensitive (oxygen- or moisture-sensitive) chemicals. Schlenk flask – reaction vessel for handling air-sensitive compounds. Perkin triangle – used for the distillation of air-sensitive compounds.

References

Further reading Sella, Andrea (January 2008). "Schlenk Apparatus". Chemistry World: 69. Retrieved 2008-01-30. Tidwell, Thomas (2001). "Wilhelm Schlenk: The Man Behind the Flask". Angewandte Chemie International Edition. 40 (2): 331–337. doi:10.1002/1521-3773(20010119)40:2<331::AID-ANIE331>3.0.CO;2-E. PMID 11180319. Jürgen Heck. "The Integrated Synthesis Course: Schlenk Technique" (PDF). University of Hamburg. Archived from the original (reprint at Norwegian University of Science and Technology) on 2008-03-09. "Handling Air-Sensitive Reagents" (PDF). Sigma-Aldrich. "Handling Air-Sensitive Reagents" Sigma-Aldrich.

External links Rob Toreki (25 May 2004). "Schlenk Lines and Vacuum Lines". The Glassware Gallery. Interactive Learning Paradigms Incorporated. Preparation of a Manganese oxide column for inert gas purification from oxygen traces

Illustrations

Worked examples

Example 1 — a first encounter with Schlenk line

Start with the simplest possible case. Write down what Schlenk line claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, 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 Schlenk line 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 Schlenk line 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 Schlenk line

In research: Schlenk line appears in science 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 Schlenk line 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: Schlenk line is common in secondary-school and first-year university syllabi. It links to neighbouring topics Air-free techniques, Laboratory equipment, Laboratory glassware, so understanding it makes those chapters shorter.
In everyday life: Look for Schlenk line 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 Schlenk line in 20 minutes

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

Frequently asked questions

What is Schlenk line in simple terms?

The Schlenk line (also vacuum gas manifold) is a commonly used chemistry apparatus developed by Wilhelm Schlenk. It consists of a dual manifold with several ports.

Why does Schlenk line matter?

Because it connects several science 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 Schlenk line?

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 Schlenk line.