# How is the chirality of sidechains written in the IUPAC name?

I circled what I believe to be the chiral centers and I added the locants for the longest carbon chain. One of the chiral centers is in a side chain, so that carbon doesn't have a locant. How should its absolute configuration be included into the IUPAC name?

• Side chain have their locants. Your question is rather how to number them and even more general, how to number/call a molecule and has little to do with chirality. – Alchimista Dec 5 '19 at 7:56
• @AniruddhaDeb look, you can’t just change somebody else’s question like that to fit your answer. – orthocresol Dec 5 '19 at 17:16

The IUPAC name of the given compound without chirality would be $$\text{10-bromo-2-methyl-5-(butan-2-yl)-undec-3-yne}$$
If we want to say that it has an $$\text{R}$$ configuration at locant 5 and 10 and an $$\text{S}$$ configuration at the sec-butyl group, then the name becomes: $$\text{(5} \textit{R}\text{,10}\textit{R}\text{)10-bromo-2-methyl-5-((2}\textit{S}\text{)butan-2-yl)-undec-3-yne}$$