Butyfyl Molecules
Butyl alcohol also has some isomers that I want to make sure to cover.
n-Butanol or 1-butanol is CH3CH2CH2CH2OH or .
2-butanol CH3CH2CH(OH)CH3 or is also called sec-butanol, with the prefix meaning secondary.
A secondary alcohol is one where the carbon of the C-OH is single-bonded to two other carbons, i.e. it has a C-CH(OH)-C group in the molecule. 1-butanol is a primary alcohol; it has only one other carbon bonded to the C of its C-OH group.
There are also tertiary alcohols like tert-butanol or t-butanol, which has the formula CH3C(CH3)2OH or .
In a tertiary alcohol, the C-OH is bonded to three other carbons, e.g. C-C(OH)(-C)-C.
Then there is isobutanol which is CH3CH(CH3)CH2OH or , which is branched at the last possible position. In this case it is not only an isomer of n-butanol, it is also an alcohol based on isobutane. Isobutanol is a primary alcohol.
The default for most iso- compounds is to have the branch right at the end of the molecule, such as isopentyl alcohol CH3CH(CH3)CH2CH2OH or , also called isoamyl alcohol. Isoamyl alcohol's molecule is as close to the structure of n-amyl alcohol (n-pentyl alcohol or 1-pentanol) as possible while still being an isomer.
You will sometimes see skeletal formulas or names of compounds with n-butyl, isobutyl, sec-butyl, tert-butyl, n-amyl, or isoamyl groups as substituents, so it's helpful to know what they are.
Alcohols with more than one hydroxy group are called polyols. One example of a polyol is table sugar. Its formula is famously C12H22O11, but that doesn't tell us anything about its molecular structure, only how many atoms of each element it has. Later on we'll see that several of its eleven oxygen atoms are part of hydroxy groups.
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