when dealing with the hydrocarbon compounds, the branch is a carbon atom attached to one of the canter carbon atoms of the chain, but not on the end carbons as that would still be a straight chain. In the derivatives, the functional group is a part of that carbon chain and is considered when determining branching of the compound. The types of branches will be shown in this section because they occur commonly with the alcohol compounds. However, branching can occur in any of the hydrocarbon-derivative groups. Figure 5.56 shoes examples of branches of a four-carbon alcohol. The branch is determined by the location of the functional group on the carbon chain. The first structure is the straight-chained compound butyl alcohol with a molecular formula of C4H9OH. Straight-chained compounds are sometimes referred to as the “normal” form. Normal butyl alcohol is represented by a small “n” in front of the molecular formula and the word normal in front of the name. The next structure is isobutyl alcohol. The “iso” branch is determined by locating the –O-H of the alcohol functional group and using it as an entry point into the structure. Then go to the first carbon that is attached to the –O-H. See how many carbon atoms are attached to the first carbon. In the case of the “iso” branch, only one carbon atoms is attached. The third structure is secondary butyl alcohol. The –O-H is attached to a carbon that is attached to two other carbons. In the final structure, the compound is called tertiary butyl alcohol. The functional group is attached to a carbon atom, which is attached to three other carbon atoms. Notice that all of the compounds have the same molecular formula. To distinguish between them, it is necessary to include a small letter. A small “I” is used for “iso” branches, a small “s” for secondary, and a small “t” for tertiary branches. In front of the names, insert iso, sec or secondary, or tert or tertiary.