Question

Draw the structures of organic compounds A and B. Indicate stereochemistry where applicable.

Draw the structures orga C Compounds A ama P. Indicate StereoChemistry where applicao 1) NaNH2 H--C C- 2) CH3CH2CH2Br CH2 (1 equiv.) CH3 CH2 H2 Lindlar cat H20, OH H2O CH3 H3C

Answer 1

Concepts and reason

The concept used is to draw the structures of A and B in the given reaction for the conversion of alkynes to the desired alcohol.

Fundamentals

${\rm{NaN}}{{\rm{H}}_2}$ is a strong base that abstracts the acidic protons. Alkynes have two acidic protons.

Terminal alkynes on reaction with ${\rm{NaN}}{{\rm{H}}_2}$ produce the corresponding acetylide ion followed by the reaction with alkyl halide produces the corresponding internal alkynes.

Alkynes undergo cis-hydrogenation upon reaction with Lindlar’s catalyst. The two H atoms are added on the same side producing cis-alkenes.

Hydration of alkenes produce the corresponding alcohols. The reaction follows Markovnikov’s rule.

Acetylene reacts with ${\rm{NaN}}{{\rm{H}}_2}$ followed by alkyl halide produces the internal alkyne.

The reaction is as follows:

Hydrogenation of alkyne A produces the corresponding cis-alkene B.

The reaction is as follows:

Hydration of the alkene produces the desired alcohol.

The reaction is as follows:

Ans:

Therefore, the structures of A and B are as follows: