Which groups make an alcohol primary, secondary or tertiary?

Answer

Dear Alexandra,

To give a short answer: No, in the definition of primary, secondary and tertiary alcohol for respectively two H (one alkyl group), one H (two alkyl groups) and no H (three alkyl groups) on the carbon bearing the OH group there is no version of definition that takes into account that one of the alkyl groups would be slightly different.

The reason is that it is no longer an alcohol functional group. The concept of functional group is very fundamental in organic chemistry. This allows you to understand and map the reactivity and physical properties of organic compounds. A distinction is made here between carbon atoms that have four sigma bonds with other carbon atoms or hydrogen atoms (= alkyl residues) and carbon atoms that are bonded to “heteroatoms” (= Cl, Br, F, I, O, S, N, P on the other hand). most important) and/or be part of an unsaturation (read a double or triple bond). These last kind of carbon atoms are then the functional groups and depending on the bonding pattern we have to deal with another functional group, eg one bond with an O and then an H on O, that is an alcohol group. If there are two OH’s, we speak of a geminal diol. If the O is double bonded to that C, then that is an aldehyde or ketone, depending on whether the C still contains an H or an alkyl group. You can thus divide the functional groups into classes based on the number of bonds that C has with heteroatoms. for example, an alcohol is a functional group of first class = one bond of the C with a heteroatom group (OH). So as soon as you replace an alkyl group with a heteroatom in a tertiary alcohol, you no longer have an alcohol but something of a functional group of second class (C with two bonds with a heteroatom).

Hope this gives you more clarity,

Regards