Question

In the presence of manganese acetate, ethyne produces:
(a)- Acetic acid
(b)- Propanoic acid
(c)- Butanoic acid
(d)- Methanoic acid

Answer 1

The formula of manganese acetate is $Mn{{(C{{H}_{3}}COO)}_{2}}$ and it is an organometallic compound. Ethyne is a compound of alkynes having 2 carbon atoms and its formula is $HC\equiv CH$. When they react with each other there is the formation of an organic acid having the same number of carbon atoms as in the alkyne taken in the reaction.

Complete step by step solution:
- The formula of manganese acetate is $Mn{{(C{{H}_{3}}COO)}_{2}}$ and it is an organometallic compound. Since it is an organometallic compound it behaves the same as that Grignard reagent. When the manganese acetate reacts with compounds having electronegative hydrogen then that acidic hydrogen will get attached to the manganese acetate.
- Let us first know about electronegative hydrogen, when the hydrogen is attached to an electronegative atom then that hydrogen is called electronegative hydrogen and we can say this hydrogen is acidic hydrogen. If the hydrogen is not attached to any electronegative atom, then hybridization is considered. If the carbon atom is $sp$ hybridized then the hydrogen attached with that carbon atom then this hydrogen is also electronegative hydrogen.
- Ethyne is a compound of alkynes having 2 carbon atoms and its formula is $HC\equiv CH$.
So, when manganese acetate and ethyne reacts with each other then the acidic hydrogen gets attach with acetate forming acetic acid and the reaction is given below:
$Mn{{(C{{H}_{3}}COO)}_{2}}+HC\equiv CH\to 2C{{H}_{3}}COOH+Mn{{C}_{2}}$
So, the correct answer is “Option A”.

Note: When the atom is attached with a triple bond then that compound is $sp$ hybridized. If manganese acetate reacts with alkanes or alkenes then acid will not be formed because they don't have acidic hydrogen.