Diethylzinc

Diethylzinc (C₂H₅)₂Zn, or DEZ, is an organozinc compound comprised of zinc bonded to two ethyl groups. It is an important reagent in organic chemistry and available commercially as solutions of hexanes, heptane or toluene.

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Synthesis

Edward Frankland prepared the compound in 1848 from zinc and and ethyl iodide, the first organozinc compound discovered.^[1] He improved the synthesis by using diethyl mercury as starting material ^[2] A classic synthesis consists of the reaction between ethyl iodide and ethyl bromide with a zinc / copper couple ^[3]

Reactions

Diethylzinc reacts violently with water and easily catches fire (pyrophoric) when in contact with air. It must therefore be handled under a nitrogen blanket.

Diethylzinc is used in organic synthesis as a nucleophilic ethyl synthon in addition reactions to carbonyl groups (for example in the asymmetric addition to benzaldehyde ^[4]) and imines ^[5]

With diiodomethane it forms a Simmons-Smith reagent.^[6][7]

Other uses

Its reactivity meant that it was used in small quantities as a hypergolic or "self igniting" liquid rocket fuel -- it ignites on contact with oxidiser, so the rocket motor need only contain a pump, without a spark source for ignition.

Diethylzinc was also investigated for a period of many years by the United States Library of Congress as a potential means of mass deacidification of books printed on wood pulp paper. Initial experiments involved placing books within a vacuum chamber and exposing them to diethylzinc vapour. In theory, the vapour would react with acid residues in the paper, neutralizing them and leaving only slightly alkaline zinc oxide residues in the paper. Results were initially promising, showing the pH of the paper to be increased to 7.5. Larger-scale experiments did not go as well; prototypes built for the Library of Congress by Northrup left "tide marks" on the pages, caused the bindings and boards to split and warp, and left behind unpleasant odours. There was also some evidence of the pages being physically weakened, even as their acidity was reduced.

Most infamously, the final prototype suffered damage in a series of explosions from contact between trace amounts of diethylzinc with moisture in the chamber. Engineers assigned to the project were unable to account for large volumes of the chemical after the process was completed and, unable to safely dismantle the device, a demolition team from the United States Army had to be called in to destroy the device with explosives. When the charges were detonated, the "missing" DEZ--which had accreted to the walls of the tubing--caused a cataclysmic explosion, nearly destroying the warehouse that housed the prototype. As a result of this catastrophe, the Library of Congress has abandoned all investigation of DEZ as a potential deacidification agent.^[8]

In microelectronics, diethylzinc is used as a doping agent.^{[citation needed]}

References