Question

Deduce the structures of compounds A-D Draw the structures that show stereochemistry where appropriate

Answer 1

Compound A (4-ethyl-2,4-dimethylhept-2-en-5-yne) reacts with Li in ethyl amine and ammonium chloride to form (E)-4-ethyl-2,4-dimethylhepta-2,5-diene. In this reaction, the triple bond is selectively reduced to double bond with trans geometry.
Compound A (4-ethyl-2,4-dimethylhept-2-en-5-yne) on ozonolysis followed by reduction gives compound C (2-formyl-2-methylbutanoic acid) which is optically active.
Compound A (4-ethyl-2,4-dimethylhept-2-en-5-yne) on treatment with alkaline potassium permanganate solution gives compound D (2-ethyl-2-methylmalonic acid, optically inactive) alongwith acetone and acetic acid.
Compound A (4-ethyl-2,4-dimethylhept-2-en-5-yne) on hydrogenation with Lindlar's catalyst gives compound B ((Z)-4-ethyl-2,4-dimethylhepta-2,5-diene) which is
optically active.