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Chapter 22: Problem 45

If one hydrogen in a hydrocarbon is replaced by a halogen atom, the number of isomers that exist for the substituted compound depends on the number of types of hydrogen in the original hydrocarbon. Thus there is only one form of chloroethane (all hydrogens in ethane are equivalent), but there are two isomers of propane that arise from the substitution of a methyl hydrogen or a methylene hydrogen. How many isomers can be obtained when one hydrogen in each of the compounds named below is replaced by a chlorine atom? a. \(n\) -pentane c. 2,4 -dimethylpentane b. 2 -methylbutane d. methylcyclobutane

Short Answer

Expert verified
In summary, when one hydrogen in each of the compounds is replaced by a chlorine atom, the total number of isomers for each hydrocarbon are as follows: a. n-pentane: 3 isomers b. 2-methylbutane: 4 isomers c. 2,4-dimethylpentane: 4 isomers d. Methylcyclobutane: 3 isomers

Step by step solution

01

a. n-pentane

In n-pentane, there are three types of hydrogen atoms: two methyl hydrogens (at the ends of the chain) and three methylene hydrogens (in the middle of the chain). Each methyl group has 3 equivalent hydrogens, and each methylene group has 2 equivalent hydrogens. The total number of unique hydrogen atoms in n-pentane is 3 (2 methyl + 1 methylene). Therefore, when one hydrogen is replaced by a chlorine atom, there are 3 possible isomers for chlorinated n-pentane.
02

b. 2-methylbutane

In 2-methylbutane, there are the following types of hydrogen atoms: - Two methyl hydrogens in the main chain - Two methylene hydrogens in the main chain - One tertiary (central) hydrogen - One methyl hydrogen in the branched group The total number of unique hydrogen atoms in 2-methylbutane is 4 (2 methyl + 2 methylene + 1 tertiary). Therefore, when one hydrogen is replaced by a chlorine atom, there are 4 possible isomers for chlorinated 2-methylbutane.
03

c. 2,4-dimethylpentane

In 2,4-dimethylpentane, there are the following types of hydrogen atoms: - Two methyl hydrogens in the main chain - One methylene hydrogen in the main chain - Two tertiary (central) hydrogens - Two methyl hydrogens in the branched groups The total number of unique hydrogen atoms in 2,4-dimethylpentane is 4 (2 methyl + 1 methylene + 1 tertiary). Therefore, when one hydrogen is replaced by a chlorine atom, there are 4 possible isomers for chlorinated 2,4-dimethylpentane.
04

d. Methylcyclobutane

In methylcyclobutane, there are the following types of hydrogen atoms: - One methylene hydrogen in the main ring - Two methine hydrogens in the main ring - One methyl hydrogen in the branched group The total number of unique hydrogen atoms in methylcyclobutane is 3 (1 methylene + 2 methine + 1 methyl). Therefore, when one hydrogen is replaced by a chlorine atom, there are 3 possible isomers for chlorinated methylcyclobutane.

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Most popular questions from this chapter

Draw structural formulas for each of the following alcohols. Indicate whether the alcohol is primary, secondary, or tertiary. a. 1 -butanol c. 2 -methyl-l-butanol b. 2 -butanol d. 2 -methyl-2-butanol

Consider the following reactions. For parts \(\mathrm{b}-\mathrm{d}\), see Exercise \(62 .\) a. When \(\mathrm{C}_{5} \mathrm{H}_{12}\) is reacted with \(\mathrm{Cl}_{2}(g)\) in the presence of ultraviolet light, four different monochlorination products form. What is the structure of \(\mathrm{C}_{5} \mathrm{H}_{12}\) in this reaction? b. When \(\mathrm{C}_{4} \mathrm{H}_{8}\) is reacted with \(\mathrm{H}_{2} \mathrm{O}\), a tertiary alcohol is produced as the major product. What is the structure of \(\mathrm{C}_{4} \mathrm{H}_{8}\) in this reaction? c. When \(\mathrm{C}_{7} \mathrm{H}_{12}\) is reacted with \(\mathrm{HCl}\), 1 -chloro-1-methylcyclohexane is produced as the major product. What are the two possible structures for \(\mathrm{C}_{7} \mathrm{H}_{12}\) in this reaction? d. When a hydrocarbon is reacted with \(\mathrm{H}_{2} \mathrm{O}\) and the major product of this reaction is then oxidized, acetone (2-propanone) is produced. What is the structure of the hydrocarbon in this reaction? e. When \(\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O}\) is oxidized, a carboxylic acid is produced. What are the possible structures for \(\mathrm{C}_{5} \mathrm{H}_{12} \mathrm{O}\) in this reaction?

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