Draw the structures of organic compounds A and B. Indicate stereochemistry where applicable The starting material is ethyne, a carbon carbon triple bond where each carbon is bonded to a hydrogen. Step 1 is N a N H 2 followed by 1 equivalent of C H 3 C H 2 C H 2 B r to form compound A. Compound A reacts with hydrogen and lindlar's catalyst to form compound B. COmpound B reacts with H 2 O and H 3 O Plus to form a 5 carbon chain with a hydroxy substituent on carbon 2.

See explanation below

Explanation:

In this case we have the starting reactant which is the ethine, In the first step reacts with NaNH₂, a strong base. This base will substract the hydrogen from one of the carbon of the ethine, and form a carbanion. This will react with the propane bromide, displacing the bromine and forming a 5 carbon chain with the triple bond on the carbon 1 and 2.

In the second step, reacts with the lindlar catalyst to do a reduction, and form a double bond between carbon 1 and 2. In essence, compound A is similar to compound B.

Finally B reacts with water in acid and makes a addition reaction, and form an alcohol.

The whole process can be seen in the picture below.

Hope this helps

the answers would be

the first one and the second one