Passage IITwo isomeric alkynes A and B have molecular formula C8H14 A ...
Explanation:
Alkynes are hydrocarbons that contain at least one triple bond between carbon atoms. Isomeric alkynes have the same molecular formula but different structural arrangements. In this case, isomeric alkynes A and B have the molecular formula C8H14.
AgNO3 Test:
When alkynes are treated with ammoniacal silver nitrate (AgNO3), a white precipitate is formed if the alkyne is terminal (i.e., the triple bond is at the end of the carbon chain). In this case, alkene A forms a white precipitate, indicating that it is a terminal alkyne. On the other hand, alkene B does not form a precipitate, suggesting that it is not a terminal alkyne.
Chirality:
Chirality refers to the property of a molecule that is non-superimposable on its mirror image. Both alkynes A and B are chiral, meaning that they exist as two non-superimposable mirror image forms. Chirality is often associated with the presence of asymmetric carbon atoms, which are carbon atoms bonded to four different groups. However, the passage does not provide information about the presence of asymmetric carbon atoms in A and B.
Hydrogenation:
Hydrogenation is a chemical reaction in which hydrogen (H2) is added across a double or triple bond to form a saturated compound. When either alkene A or B is hydrogenated with H2/Pt, the same achiral hydrocarbon C(C8H18) is obtained. This means that the double bond in both A and B is converted to a single bond, resulting in the formation of an alkane.
HgSO4 /H2SO4 Test:
When alkynes are treated with HgSO4 /H2SO4 (aqueous), an enol intermediate is formed, which can rearrange to form a ketone or aldehyde. In this case, alkene A gives the major product D(C8H16O), indicating that it undergoes rearrangement to form a ketone. On the other hand, alkene B forms a mixture of D and E in comparable amounts, suggesting that it undergoes both ketone and aldehyde formation.
Conclusion:
Based on the information given in the passage, the correct statement regarding alkynes A and B is that they are positional isomers. Positional isomers have the same molecular formula but different positions of functional groups or multiple bonds. In this case, A and B have the same molecular formula but differ in the position of the triple bond, which is at the end of the carbon chain for A (terminal alkyne) and in the middle of the carbon chain for B (internal alkyne).
Passage IITwo isomeric alkynes A and B have molecular formula C8H14 A ...
B is correct.
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