Draw a condensed structural formula for each of the following alkanes: a. 3 -ethylpentane b. 3 -ethyl-2-methylpentane c. 4 -ethyl- 2,2 -dimethyloctane d. 2 -bromopropane e. 2,3 -dichloro-2-methylbutane
The Correct Answer and Explanation is:
a. 3-ethylpentane
Condensed Formula: CH₃CH₂CH(CH₂CH₃)CH₂CH₃
b. 3-ethyl-2-methylpentane
Condensed Formula: CH₃CH(CH₃)CH(CH₂CH₃)CH₂CH₃
c. 4-ethyl-2,2-dimethyloctane
Condensed Formula: CH₃CH₂C(CH₃)₂CH(CH₂CH₃)CH₂CH₂CH₂CH₃
d. 2-bromopropane
Condensed Formula: CH₃CHBrCH₃
e. 2,3-dichloro-2-methylbutane
Condensed Formula: CH₃C(Cl)(CH₃)CH(Cl)CH₃
Explanation
A condensed structural formula provides a streamlined way of writing organic molecules by grouping atoms together while still showing how they are connected. It is especially useful for representing complex branched alkanes in a compact format.
For 3-ethylpentane, the parent chain is pentane (five carbon atoms), and an ethyl group (CH₂CH₃) is attached to the third carbon. The chain reads CH₃CH₂CH(CH₂CH₃)CH₂CH₃.
In 3-ethyl-2-methylpentane, the parent is again a five-carbon pentane chain. A methyl group is on the second carbon, and an ethyl group is on the third carbon. The central backbone is adjusted accordingly to CH₃CH(CH₃)CH(CH₂CH₃)CH₂CH₃.
4-ethyl-2,2-dimethyloctane has an eight-carbon chain as the parent. Two methyl groups are attached to the second carbon, and one ethyl group is attached to the fourth carbon. Its structure is more branched, requiring careful placement of substituents.
2-bromopropane is a simple three-carbon propane chain with a bromine atom attached to the second carbon, written as CH₃CHBrCH₃.
For 2,3-dichloro-2-methylbutane, the parent chain is butane. A methyl group is attached to the second carbon along with a chlorine, and another chlorine is on the third carbon. This highly substituted molecule is written with nested parentheses to show the branches.
Each condensed structure reflects carbon bonding rules and helps in predicting physical and chemical behavior.
