Provide the name(s) for the branched constitutional isomer(s) with the molecular formula C7H16 that have three methyl groups.
To find the branched constitutional isomers with the molecular formula C7H16 that have three methyl groups, we can follow these steps:
Step 1: Determine the number of carbons in the main chain.
Since the formula is C7H16, we know there are 7 carbons.
Step 2: Calculate the number of hydrogens in the main chain.
Each carbon in the main chain (except for the terminal carbons) is connected to two hydrogens, so the total number of hydrogens in the main chain is 7 x 2 = 14.
Step 3: Subtract the number of hydrogens in the main chain from the total number of hydrogens.
The formula has 16 hydrogens in total, so 16 - 14 = 2 hydrogen atoms must be outside of the main chain.
Step 4: Determine the possible locations for the three methyl groups.
Since there are only 2 hydrogen atoms available outside of the main chain, only two methyl groups can be attached to the carbon atoms outside of the main chain.
Step 5: Place the three methyl groups on the different carbon atoms outside of the main chain.
There are several possible ways to arrange the three methyl groups on the two available positions. Let's go through the possibilities:
- Methyl group on the first carbon atom outside of the main chain and two methyl groups on the second carbon:
CH3 - C(CH3)2 - CH2 - CH2 - CH2 - CH3
This is known as 2,3-dimethylheptane.
- One methyl group on each carbon atom outside of the main chain and one methyl group on a carbon within the main chain:
CH3 - CH(CH3) - CH(CH3) - CH2 - CH2 - CH2 - CH3
This is known as 2,4-dimethylheptane.
- Two methyl groups on the first carbon atom outside of the main chain and one methyl group on the second carbon:
CH3 - C(CH3)3 - CH2 - CH2 - CH2 - CH3
This is known as 2,2,3-trimethylpentane.
So, there are three branched constitutional isomers with the molecular formula C7H16 and three methyl groups: 2,3-dimethylheptane, 2,4-dimethylheptane, and 2,2,3-trimethylpentane.