The oxidation of ethyne to ethanal in Wacker process is catalysed by…

The correct answer is Option (1) → PdCl₂

In the Wacker process, an alkene is oxidised by air to a carbonyl compound in aqueous solution, with palladium(II) chloride as the catalyst and copper(II) chloride to regenerate it. Ethene gives ethanal:

    \( \displaystyle \ce{2CH2=CH2 + O2} \xrightarrow[\ce{H2O}]{\ce{PdCl2},\ \ce{CuCl2}} \ce{2CH3CHO} \)

Palladium(II) oxidises the alkene and is reduced to palladium metal; copper(II) chloride oxidises the palladium back to palladium(II), and air oxidises the copper(I) formed back to copper(II). So the catalyst for the oxidation to ethanal is \( \ce{PdCl2} \).

Note 1: It seems that there is a mistake in the original NTA paper, which prints “oxidation of ethyne to ethanal” when it should read “oxidation of ethene to ethanal”. The NCERT textbook prints the same slip in this sentence; the Wacker process oxidises ethene, as in the equation above.

NCERT (2026-27 edition):
Some Applications of d- and f-Block Elements – “… Many of the metals and/or their compounds are essential catalysts in the chemical industry. V₂O₅ catalyses the oxidation of SO₂ in the manufacture of sulphuric acid. TiCl₄ with Al(CH₃)₃ forms the basis of the Ziegler catalysts used to manufacture polyethylene (polythene). Iron catalysts are used in the Haber process for the production of ammonia from N₂/H₂ mixtures. Nickel catalysts enable the hydrogenation of fats to proceed. In the Wacker process the oxidation of ethyne to ethanal is catalysed by PdCl₂.”

Note 2: The same/similar question has been asked in different years by NTA as per the details given below: