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The Clemmensen reduction involves the reduction of a ketone to its corresponding alkane, by removing the double bonded oxygen atom and replacing it with two hydrogens.
The reaction is not suitable for substances sensitive to acids. Also, carboxylic acid groups cannot be reduced by this method.
The reduction involves adding the target ketone to a solvent resistant to this reduction process, where a Zn-Hg amalgam is present. Hydrochloric acid is added to the reaction mass, which causes the zinc to react with the acid, releasing hydrogen.
While the exact mechanism is still debated, it is known that no alcohols are formed as intermediates, as OH groups cannot be reduced via this method.
Replacing Zn-Hg with zinc powder has been shown to be similar in effectiveness. Suspensions of Zn powder in ethanol with hydrogen chloride are capable of dechlorinating halocarbons, such as chloroform to dichloromethane, while aqueous suspensions of Zn powder will reduce said chlorocarbons to their alkanes.
The Clemmensen reduction can be used to reduce ketones to their corresponding alkanes