Question

How can you identify primary alcohol?

Answer 1

By the presence of the `CH_2OH` group.

Explanation:

The alcoholic derivative of a primary methyl group is a so-called primary alcohol. Ethyl alcohol, `H_3C-CH_2OH` is certainly a primary alcohol. So if you see 2 hydrogens on the alcoholic ipso carbon, you know you have a primary alcohol. Other examples include `1-"propanol"` and `1-"butanol"`

On the other hand, if there is only the one hydrogen on the ipso carbon, then you have a secondary alcohol: isopropyl alcohol `(H_3C)_2CHOH` is the examplar.

No prizes for guessing that for the tertiary alcohol, the ipso carbon has no hydrogens. Tertiary butanol, `(H_3C)_3C-OH` is an example.

Note that methyl alcohol, `H_3COH` is to all intents and purposes a primary alcohol. Some texts place methyl alcohols, and methyl derivatives, in a special class (which they are because the ipso carbon bears 3 hydrogens!) because they are more reactive than even ethyl alcohol.