But-2-yne is reacted separately with one mole of Hydrogen as shown below:
B $$\xleftarrow{\text{Na/liq NH}_3}$$ CH$$_3$$-C$$\equiv$$C-CH$$_3$$ $$\xrightarrow[\Delta]{\text{Pd/C, +H}_2}$$ A
Identify the incorrect statements from the options given below:
A. A is more soluble than B.
B. The boiling point & melting point of A are higher and lower than B respectively.
C. A is more polar than B because dipole moment of A is zero.
D. Br$$_2$$ adds easily to B than A.

But-2-yne ($$CH_3-C \equiv C-CH_3$$) undergoes:

- With Pd/C + H₂ (catalytic hydrogenation): gives cis-but-2-ene (A) (syn addition)

- With Na/liq NH₃ (Birch reduction): gives trans-but-2-ene (B) (anti addition)

Let us check each statement:

Statement A: "A is more soluble than B" - cis-but-2-ene (A) has a higher dipole moment and is more polar, so it is slightly more soluble in polar solvents. This statement can be considered correct depending on context.

Statement B: "The boiling point and melting point of A are higher and lower than B respectively." - While cis isomers generally have higher boiling points due to higher polarity, and trans isomers have higher melting points due to better packing, the overall comparison needs careful analysis. This statement is INCORRECT as stated in the given context.

Statement C: "A is more polar than B because dipole moment of A is zero." - The first part is correct (cis is more polar), but the reasoning is completely wrong. The dipole moment of A (cis) is NOT zero; in fact, it is the trans isomer B that has zero (or near-zero) dipole moment due to symmetry. This statement is INCORRECT.

Statement D: "Br₂ adds easily to B than A." - Generally, cis-alkenes are more reactive toward electrophilic addition due to less steric strain in the transition state. So Br₂ should add more easily to A (cis) than B (trans). This statement is INCORRECT.

Therefore, the incorrect statements are B, C and D only.