Problem 17 - Chemistry An Atoms First Approach

Question

Draw a structural formula for each of the following compounds. a. 2 -methylpropane b. 2 -methylbutane c. 2 -methylpentane d. 2 -methylhexane

Step-by-Step Solution

Answer

The structural formulas for the given compounds are as follows: (a) 2-methylpropane: \((CH_3)_2CH-CH_3\) (b) 2-methylbutane: \(CH_3-CH(CH_3)-CH_2-CH_3\) (c) 2-methylpentane: \(CH_3-CH(CH_3)-CH_2-CH_2-CH_3\) (d) 2-methylhexane: \(CH_3-CH(CH_3)-CH_2-CH_2-CH_2-CH_3\)

Step 1: Understand the IUPAC nomenclature

The names provided all follow the IUPAC nomenclature system, which allows us to determine their structure. Each name consists of several parts: - A number specifying the position of a methyl group (this is the number before "methyl"). - The prefix before "methyl" indicating the number of carbon atoms present in the main chain (meth- = 1, eth- = 2, prop- = 3, but- = 4, pent- = 5, hex- = 6, etc.). - The ending "ane," which indicates that we're dealing with single-bonded carbon atoms (alkane compounds). For example, in the case of "2-methylpropane," the name tells us that the compound has a propane backbone (3 carbon atoms) and a methyl group is attached to the second carbon atom in the chain.

Step 2: Draw the main carbon chain

For each compound, draw a horizontal line and place the appropriate number of carbon atoms in the main chain. Label the carbon atoms from left to right as C1, C2, C3, etc. (a) For 2-methylpropane, draw a line with 3 carbon atoms. (b) For 2-methylbutane, draw a line with 4 carbon atoms. (c) For 2-methylpentane, draw a line with 5 carbon atoms. (d) For 2-methylhexane, draw a line with 6 carbon atoms.

Step 3: Attach the methyl group

Attach a methyl group (-CH3) to the indicated carbon atom in each compound. (a) Attach a methyl group to the second carbon atom of 2-methylpropane. (b) Attach a methyl group to the second carbon atom of 2-methylbutane. (c) Attach a methyl group to the second carbon atom of 2-methylpentane. (d) Attach a methyl group to the second carbon atom of 2-methylhexane.

Step 4: Complete the structural formula

Add hydrogen atoms to each carbon atom to complete the structural formulas. In each compound, a carbon atom should have a total of four bonds. After completing these steps, we have the structural formulas for the given compounds: (a) 2-methylpropane: (CH3)2CH─CH3 (b) 2-methylbutane: CH3─CH(CH3)─CH2─CH3 (c) 2-methylpentane: CH3─CH(CH3)─CH2─CH2─CH3 (d) 2-methylhexane: CH3─CH(CH3)─CH2─CH2─CH2─CH3