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Outline the steps involved in the following transformation: $\ce{C2H4}$ to $\ce{(COOC2H5)2}$ (diethyl oxalate).

I am familiar with the transformation of $\ce{C2H4}$ to ethyl acetate $\ce{CH3COOC2H5}$ by first converting to ethanol using water and acid, then using an oxidising agent such as $\ce{KMnO4}$ to convert ethanol to ethanoic acid and subsequently reacting ethanol and ethanoic acid together.

I'm not sure if the process needed to get to the diethyl oxalate is similar to this.

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  • $\begingroup$ For future reference: Within the body of questions, answers, and comments, on chemistry.se using mhchem is recommended. It is something special not all web browsers know to trade with, thus, do not use this syntax in the title of an question. $\endgroup$
    – Buttonwood
    May 14 at 21:07
  • $\begingroup$ Oxidise ethene to ethylene oxide (peracids will do this), treat with aqueous acid to form ethylene glycol, oxidise to oxalic acid, esterify. $\endgroup$
    – Waylander
    May 14 at 21:17
  • $\begingroup$ Or treat ethene with bromine $\ce{Br2}$, then hydrolyze dibromoethane to glycol with $\ce{NaOH}$ and oxidize glycol to oxalic acid, before esterification by ethanol. $\endgroup$
    – Maurice
    May 15 at 8:11
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Conversion 1

  1. Convert ethene to ethanol.

    Ethene is mixed with steam and passed over a catalyst consisting of solid silicon dioxide coated with phosphoric(V) acid. The temperature used is 300 °C and the pressure is about 60 to 70 atmospheres (chemguide — The mechanism for the acid catalysed hydration of ethene).

    $$\ce{CH2=CH2 + H2O <=>[H3PO4] CH3CH2OH}$$

  2. React the ethanol with oxalic acid to get diethyl oxalate.

    $$\ce{(COOH)2 + 2C2H5OH ->[CCl4,\Delta] (COOC2H5)2 + 2 H2O}$$

    The details of this reaction is given on Organic Syntheses — Ethyl Oxalate and in the paper by Jewel and Butts [1].

Conversion 2

Convert ethene to oxalic acid by first converting to ethyne and then making oxalic acid from it. Use the oxalic acid to make diethyl oxalate by reacting it with absolute alcohol.

$$\ce{CH2=CH2 ->[Br2][CCl4] Br-CH2-CH2-Br ->[alc. KOH][\Delta] CH#CH ->[alc. KMnO4] (COOH)2}$$

Reference

  1. Jewel, P. W.; Butts, J. S. A Method for the Preparation of Diethyl Oxalate. J. Am. Chem. Soc. 1931, 53 (9), 3560–3561. DOI: 10.1021/ja01360a052.
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  • $\begingroup$ Don't you think the oxalic acid might also be produced from ethene ? $\endgroup$
    – Maurice
    May 15 at 8:49
  • $\begingroup$ @Maurice Yes, we can. Added in my answer $\endgroup$ May 15 at 9:45
  • $\begingroup$ I don't think alcoholic $\ce{KOH}$ will do the job in conversion 2, reaction 2. You will need $\ce{NaNH2}$ in liquid $\ce{NH3}$. $\endgroup$ May 15 at 11:21
  • $\begingroup$ @NisargBhavsar Both works fine. $\endgroup$ May 15 at 11:52

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