Parentheses confusion

[Naiomi Desai]

I have come across a lot of practice problems where a hydrocarbon is placed in parentheses but the confusing part is deciding whether they are a substituent or part of a parent chain. I read in the chapter that a way to figure out which is which is to draw it out and see if each carbon has four bonds. What does that mean actually? I am still having a difficult time deciding how to draw the line structure if the formula is condensed or if it is a substituent. Help please??

[Renee Crippen 2I]

Hi Naiomi,

The parentheses are usually used to denote groups of substituents.

When the book tells you to draw out a structure and see if the carbon has four bonds, they are asking you to consider the structure of the molecule when looking for the longest chain.

Hope this helps!

Renee Crippen 2I

[Crystal Eshraghi 2L]

If, for example, you have the formula CH3CH2CH(CH3)C(CH3)3, you would be able to see clearly the the CH3 in parenthesis in the middle of the formula is a substituent, since a single carbon can't have four bonds (3 H's and 2 of the C's right next to it). Also, you would always include ONE of the molecules indicated in parenthesis in the parent chain if these parentheses are at the very beginning or very end of the formula, and leave the rest as substituents. So for this structure, you would have a parent chain of 5 carbons, with 2 CH3s as substituents off of the second C and another CH3 as a substituent off of the third C. The IUPAC name of the structure would then be: 2,2,3-trimethylpentane.