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C2H2 (20% H2SO4, / 1%Hg2+)= A. A(Zn-Pb /HCL(concentrate) = B identify the 'A ' & ' B'?

1 Answer
Mar 8, 2018


A = ethanal; B = ethanol.


A. Hydration of ethyne

Aqueous sulfuric acid with a catalytic amount of #"Hg"^"2+"# is a standard reagent for the addition of water to alkynes.

Thi initially-formed enol rapidly tautomerizes to an aldehyde or a ketone.

#underbrace("H-C≡C-H")_color(red)("ethyne") stackrelcolor(blue)("H"_2"SO"_4"/Hg"^"2+"color(white)(mm))(→) underbrace("H"_2"C=CH-OH")_color(red)("an enol") ⇌ underbrace("H"_3"C-CH(=O)")_color(red)("ethanal")#

B. The Clemmensen reduction

I am guessing that you made a typo and that #"Zn-Pb"# should be #"Zn-Hg"#.

Zinc amalgam and concentrated hydrochloric acid are classic reagents for the reduction of aldehydes and ketones to alcohols.

#"H"_3"C-CH(=O)" stackrelcolor(blue)("Zn(Hg)/HCl"color(white)(mm))(→) underbrace("H"_3"C-CH"_2"-OH")_color(red)("ethanol")#