Question

But-2-yne is reacted separately with one mole of Hydrogen as shown below: 

 

A. A is more soluble than B
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 $A$ 
Identify the incorrect statements from the options given below:

• A. A, C & D only
• B. A and B only
• C. B, C & D only
• D. B and C only

Answer 1

The Correct Option is C

To solve this problem, we need to analyze the given chemical reaction and the properties of the resulting compounds A and B.

The chemical reaction involves but-2-yne reacting with one mole of hydrogen. The reaction conditions are:

• Reaction with Pd/C catalyst produces compound A.
• Reaction with sodium in liquid ammonia produces compound B.

1. Identify A and B:

• A: The reaction of but-2-yne with H₂ in the presence of Pd/C leads to the formation of cis-2-butene.
• B: The reaction of but-2-yne with H₂ using sodium in liquid ammonia results in trans-2-butene.

2. Evaluate each statement:

• Statement A: "A is more soluble than B." This statement is incorrect as both are alkenes with similar molecular weights and non-polarity, leading to similar solubility in organic solvents.
• Statement B: "The boiling point & melting point of A are higher and lower than B respectively." This is incorrect because trans-2-butene typically has a lower boiling point but a higher melting point compared to cis-2-butene due to better packing in the solid state.
• Statement C: "A is more polar than B because the dipole moment of A is zero." This is incorrect because cis isomers (A) generally have a higher dipole moment than trans isomers (B).
• Statement D: "Br₂ adds easily to B than A." This is incorrect as the addition of bromine to alkenes is stereospecific; hence the relative reactivity does not vary significantly between stereoisomers.

3. Conclusion:

The incorrect statements from the options given are B, C, and D only. Therefore, the correct answer is the statement list B, C & D only.