Select the correct IUPAC name for the following cycloalkane: 1- rnethyl-2-methylcyclohexane 1 – ethyl-2,2-dimethylcyclobutane 1- ethyl-2,3–dimethylcyclobutane 1,2-dimethyl-3-ethylcyclobutane
The correct answer and explanation is:
The correct IUPAC name for the compound is 1-Ethyl-2,3-dimethylcyclobutane.
Explanation:
To determine the correct IUPAC name for the given compound, we need to follow the systematic rules for naming cycloalkanes:
- Identify the Parent Chain:
- The base name of the compound is determined by the largest continuous carbon ring. In this case, the ring structure has four carbon atoms, so the base name is butane, referring to a four-carbon cycloalkane, cyclobutane.
- Identify the Substituents:
- The substituents attached to the ring are methyl (–CH₃) and ethyl (–CH₂CH₃) groups.
- The term “dimethyl” indicates two methyl groups, while “ethyl” indicates an ethyl group.
- Numbering the Ring:
- The numbering of the ring should be done in such a way as to give the substituents the lowest possible numbers. Starting at one substituent, we number the ring such that the first substituent (ethyl) gets the number 1, and the second substituent (dimethyl) gets the lowest possible set of numbers.
- The ethyl group is placed at position 1, while the two methyl groups are positioned at positions 2 and 3. This results in the name 1-ethyl-2,3-dimethylcyclobutane.
Why Not the Other Options?
- 1-methyl-2-methylcyclohexane: This is incorrect because the parent chain here is incorrectly identified as cyclohexane (a six-membered ring), which doesn’t match the given structure of the cycloalkane.
- 1-ethyl-2,2-dimethylcyclobutane: This is incorrect because both methyl groups are positioned at the same location (2), which is inconsistent with the structure described (having one methyl at position 2 and the other at position 3).
- 1,2-dimethyl-3-ethylcyclobutane: This is incorrect because the ethyl group should take priority in numbering (as it is a larger substituent), meaning it should be at position 1, not 3.
Therefore, the correct IUPAC name is 1-ethyl-2,3-dimethylcyclobutane.