Substitutes

The alkane series forms the basis of a few other kinds of molecule. One of them is the alcohols. Most of us are familiar with isopropyl rubbing alcohol, ethyl alcohol (the drinky kind), and methyl alcohol (the blindness kind), but did you know that sugars are alcohols too?

When an oxygen has a single hydrogen on it, and a single bond to some other atom, it makes a hydroxy (or hydroxyl) group. An alcohol is a compound whose molecule includes a C-OH group, a carbon single-bonded to a hydroxy group. Methyl alcohol has a molecular structure based on methane, with one of the hydrogens substituted by a hydroxy. Ethyl alcohol is similarly based on ethane. We can take the word for the alkane and change its -ane ending to -anol to get the name of the alcohol: methanol, ethanol, etc.

Propanol, or n-propanol, is a compound whose molecule has all its heavy (i.e. not hydrogen) atoms connected in a straight chain: CH₃CH₂CH₂OH or . This is not the same as rubbing alcohol, which is the isomer of n-propanol: iso-propanol or iso- propyl alcohol, with the formula CH₃CH(OH)CH₃ or . The parentheses mean the -OH is not part of the straight line of atoms, but is branched off to the side. Even though there is no such thing as isopropane, the term "isopropyl" has become the usual way to refer to any CH₃CH(CH₃)- group.

n-Propanol can also be called by its IUPAC name. IUPAC is the International Union for Pure and Applied Chemistry, and they have come up with a way to unambiguously name any organic compound. Unfortunately, their names can get a bit unwieldly, so a great many compounds are known by common names instead. The IUPAC name for n-propanol is 1-propanol or propan-1-ol, with the number 1 referring to the fact that its hydroxy group, its -ol, is attached to one of the terminal (at the end of the chain) carbon atoms. Isopropanol in this naming system is called 2-propanol or propan-2-ol, reflecting the fact that its -ol is attached to the second carbon atom from the end. There is no 3-propanol because that would be the same thing as 1-propanol, but there are various alcohols derived from the larger alkanes, for example from pentane derive 1-pentanol, 2-pentanol, and 3-pentanol, with the hydroxy group progressively farther from the end of the carbon chain, while from octane there are 1-octanol, 2-octanol, 3-octanol, and 4-octanol.

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