The Schlenk line (also vacuum gas manifold) is a commonly used chemistry apparatus developed by Wilhelm Schlenk.[1] It consists of a dual manifold with several ports.[2] 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.[3]
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.[4] 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. [5]
- ^ The prototype of what became the "Schlenk line" appears in: Schlenk, Wilhelm; Thal, Alexander (1913). "Über Metallketyle, eine große Klasse von Verbindungen mit dreiwertigem Kohlenstoff. II" [On metal ketyls, a large class of compounds with trivalent carbon. II.]. Berichte der Deutschen Chemischen Gesellschaft (in German). 46 (3): 2840–2854. doi:10.1002/cber.19130460356. See illustrations on pp. 2844–2845.
- The illustrations from Schlenk's 1913 paper are reproduced on pp. 960-963 of: Schlenk, Wilhelm (1924). "Organometallverbindungen [Organometallic compounds]". In Weyl, Josef (ed.). Die Methoden der Organischen Chemie [Methods of Organic Chemistry] (in German). Vol. 4 (2nd ed.). Leipzig, Germany: Georg Thieme. pp. 720–978.
- See also: Tidwell, Thomas T. (2001). "Wilhelm Schlenk: The Man Behind the Flask" (PDF). Angewandte Chemie International Edition. 40 (2): 331–337. doi:10.1002/1521-3773(20010119)40:2<331::AID-ANIE331>3.0.CO;2-E.
- ^ Craig M. Davis and Kelly A. Curran (November 2007). "Manipulation of a Schlenk Line: Preparation of Tetrahydrofuran Complexes of Transition-Metal Chlorides" (abstract page). Journal of Chemical Education. 84 (11): 1822–3. Bibcode:2007JChEd..84.1822D. doi:10.1021/ed084p1822.
- ^ Borys, Andryj M. (2023). "An Illustrated Guide to Schlenk Line Techniques". Organometallics. 42 (3): 182–196. doi:10.1021/acs.organomet.2c00535. S2CID 256409354.
- ^ C. R. McIlwrick and C. S. Phillips The removal of oxygen from gas streams: applications in catalysis and gas chromatography, Journal of Physics E: Scientific Instruments, 1973, 6:12, 1208–10.
- ^ James, Michael J.; Clarke, George E.; Lee, Charlotte; Fairlamb, Ian J. S. (2022-07-12). "Safe Handling of Air-Sensitive Organometallic Reagents Using Schlenk Line Techniques: Negishi Cross-Couplings for Trainee Graduate Students". Journal of Chemical Education. 99 (7): 2656–2660. doi:10.1021/acs.jchemed.2c00134. ISSN 0021-9584.