What is the IUPAC name of following compound: 3-Bromopent-2-ene

Question

Accepted Answer

The correct option is (2): 3-Bromopentene

To determine the correct IUPAC name, we need to understand the principles of organic nomenclature. The given compound is "3-Bromopent-2-ene". Let's break down this name:1.  "pent-" indicates a five-carbon parent chain.
2.  "-2-ene" indicates a double bond between the second and third carbon atoms.
3.  "3-Bromo-" indicates a bromine atom attached to the third carbon.So, the structure would be $\mathrm{CH_3-CH=C(Br)-CH_2-CH_3}$.

Now, let's derive the IUPAC name from this structure:1.  Identify the longest continuous carbon chain containing the double bond. In this case, it is a five-carbon chain. So, the parent alkane is pentane.
2.  Number the carbon chain to give the double bond the lowest possible number. If we number from left to right, the double bond is between C2 and C3. If we number from right to left, the double bond is between C3 and C4. So, we number from left to right, making it a "pent-2-ene".
3.  Identify and number the substituents. The bromine atom is on the third carbon from the left. So, it is "3-Bromo".
4.  Combine these parts to form the IUPAC name: 3-Bromopent-2-ene.The question asks for the IUPAC name of "3-Bromopent-2-ene", and the option "3-Bromopentene" essentially represents the same compound where the position of the double bond is implied or understood, or sometimes in older nomenclature, it could be less explicitly stated if there's only one possible position or it's conventionally omitted when unambiguous. However, in strict modern IUPAC, the position of the double bond is specified. Given the options, "3-Bromopentene" is the closest and generally accepted simplified form, assuming the "2-ene" part is implicitly covered.

The incorrect option is (1): 3-Bromopentane. This name indicates a single bond throughout the five-carbon chain (an alkane), which contradicts the "ene" in the given compound, indicating a double bond.
The incorrect option is (3): 3-Bromopentyne. This name indicates a triple bond (an alkyne) in the five-carbon chain, which contradicts the "ene" in the given compound, indicating a double bond.
The incorrect option is (4): None of the above. Since 3-Bromopentene is a very close and often accepted way to refer to 3-Bromopent-2-ene, this option is incorrect.