# What do the brackets mean in this inline structure representation?

Based on the way the molecular formula is written — $\ce{Br(CH2)4Br}$ — I'm assuming this means that there are $4\ \ce{-CH2}$ groups attached to $\ce{Br}$. Am I correct? I've always thought that $\ce{Br}$ can't accept so many groups though.

• Organic chemistry is starkly different from inorganic, even in the ways of writing the molecular formula. So in fact this is just Br-CH2-CH2-CH2-CH2-Br. – Ivan Neretin Sep 6 '17 at 7:58
• Really? I always thought adding the brackets signified another chain so as to differentiate between isomers. – PhysicsIdiot Sep 6 '17 at 9:10
• Brackets may serve multiple purposes. – Ivan Neretin Sep 6 '17 at 9:31

In the case of $\ce{Br(CH2)4Br}$, organic chemists will know that bromine will typically only form one single bond. Additionally, each $\ce{CH2}$ unit is known to be able to form two bonds — either two single bonds or one double bond. Therefore, an organic chemist will automatically expand the formula to $\ce{Br-CH2-CH2-CH2-CH2-Br}$ or 1,4-dibromobutane.
However, you might also sooner or later encounter inline formulae such as $\ce{BrC(CH3)2CH2Br}$ or $\ce{(CH3)3COH}$. Here, the brackets do actually mean repeated addition of said group to a single common atom. so the first of these two formulae describes 1,2-dibromo-2-methylpropane and could also be written $\ce{H3C-C(CH3)(Br)-CH2Br}$ while the second one represents tert-butanol or 2-methylpropan-2-ol.