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Alkanes and Cycloalkanes Practice Problems

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By — McGraw-Hill Professional
Updated on Aug 16, 2011

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Alkanes and Cycloalkanes Practice Problems

Practice

Write structural formulas for the five isomeric hexanes and name them by the IUPAC system.

Solution

The isomer with the longest chain is hexane, CH3CH2CH2CH2CH2CH3. If we use a five-carbon chain, a CH3 may be placed on either C2 or C4 to produce 2-methylpentane, or on C3 to give another isomer, 3-methylpentane.

Solved Problem

With a four-carbon chain either a CH3CH2 or two CH3's must be added as branches to give a total of 6 C's. Placing CH3CH2 anywhere on the chain is ruled out because it lengthens the chain. Two CH3's are added, but only to central C's to avoid extending the chain. If both CH3's are introduced on the same C, the isomer is 2,2-dimethylbutane. Placing one CH3 on each of the central C's give the remaining isomer, 2,3- dimethylbutane.

Solved Problem

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