Question

R-X can be reduced to R-H by Zn - Cu couple / C₂H₅OH as a result of:

• A. Hydride ion
• B. Molecular activated hydrogen
• C. Electron transfer from the metal to the substrate followed by H⁺ addition from the solvent
• D. All of the above

Answer 1

The correct option is C

Electron transfer from the metal to the substrate followed by H⁺ addition from the solvent

In this particular case the reaction happens as:

$Zn⟶Z{n}^{2+}+2e^{-}$

The above two steps could be combined as $R\stackrel{\curvearrowright }{-}X+2e^{-}⟶R^{-}+X^{-}$

$R{:}^{-}+C_2{H}_{5}O-H⟶C_2{H}_5{O}^{-}+RH$

The process happens due to electron transfer by the metal onto the substrate followed by proton transfer from ethanol.

Other methods to carry out reduction are:

a) Zn $\&$ Acetic acid; Z and NaOH

b) Zn $\&$ HCl

c) Al-Hg (amalgam) in ethanol

d) Red phosphorus and Hydrogen iodide $\left(plus△\right)$

All these methods produce Nascent Hydrogen to facilitate reduction.