Condensed structural formula

[Austin Qiu 1A]

So for this formula: (CH3)2CHCH(CH2CH3)2, how do you know which carbons are part of the main chain and which ones are substituents?

[Hannah Markovic 3C]

The ones that are part of the main chain will be the ones in the chain that has the largest amount of carbon atoms. The other carbons will be substituents coming off the main chain. If there are two equally long longest chains, you can use either one for naming and it will not matter which you choose.