Indicate whether each of the following pairs represent structural isomers or the same molecule:
a.

Question

Indicate whether each of the following pairs represent structural isomers or the same molecule:

a. Structural isomers comparison showing two molecular structures with labels for each carbon and hydrogen atom.

Accepted Answer

All right. Hello everyone. So this question is asking us are the pair of molecules structural isomers or not. Here we have three methyl pentane and 23 dimethyl butane. Option A says the pair of molecules are structural isomers. And option B says the pair of molecules are not structural isomers. So let's go ahead and get started starting off with the definition of structural isomers. Recall that a pair of molecules are considered structural isomers if they have the same molecular formula, but a different structure. So what that means is that even though both compounds have the same number of atoms, the connections between the atoms are different, which results in different structures. So our first step would be to find the molecular formulas of both compounds to ensure that they are the same. If they are not the same, then they cannot be considered structural isomers starting off with three methyl pentane counting the number of carbons. I have five carbons from the parent chain and one more from my substituent. So that would be six carbons in total. Now, in this case, we are provided the condensed structural formulas in which hydrogen atoms are shown So by counting the hydrogen atoms noted in the structure of three methyl pentane, I get a total of 14. So my formula becomes C six H 14 for three methyl pentane. So now lets do the same thing for 23 dimeo butane, 23 dimethyl butane has four carbons from the parent chain and two more from the two methyl substituents. So that is also six carbons. And if I go ahead and count the number of hydrogens noted in the structure of 23 dimethyl butane, I also get a total of 14. So the the molecular formula of both of these compounds is the same and it is C six H 14. Now notice how when talking about determining the molecular formula, we did point out some differences in their structure because three methyl pentane has a five carbon parent chain and only one methyl substituent, whereas 23 dimethyl butane has a four carbon chain and two methyl substituents. So all this is to say that even though they have the same number of atoms, the connections between them are different, which results in two different structures. Therefore, our answer is going to be option a in the multiple choice because the pair of molecules are in fact structural isomers and there you have. So with that being said, thank you so very much for watching. And I hope you found this helpful

Indicate whether each of the following pairs represent structural isomers or the same molecule:
a.

Verified video answer for a similar problem:

Key Concepts

Structural Isomers

Molecular Formula

Stereoisomers

Indicate whether each of the following pairs represent structural isomers or the same molecule:a.

Verified video answer for a similar problem:

Key Concepts

Structural Isomers

Molecular Formula

Stereoisomers

Indicate whether each of the following pairs represent structural isomers or the same molecule:
a.