Another way of saying the same thing is that the O-H bond has a strong “dipole”. We say that electron density in the O-H bond is strongly “polarized” toward oxygen. This means that oxygen will be more “electron rich” (more negative) and hydrogen more “electron poor” (more positive) than they would be in a bond where electrons were shared perfectly equally. Oxygen, being “greedier” for electrons than hydrogen, will have more than its “share” of the two electrons in the O-H bond. Oxygen has an electronegativity of 3.5 and hydrogen 2.2. The key to understanding the physical properties of alcohols – and as we shall see later, their reactivity – is to appreciate just how polarized the hydroxyl group is. Physical Properties of Alcohols: Hydrogen Bonding Here’s an example by Leah Fisch, for example.Ģ. There are all kinds of fantastic videos and resources on the internet that describe the naming of alcohols in detail, and I will happily refer you to those for now. The deeper nomenclature of alcohols is not something I’m going to discuss on this blog at the present. And there are other funky functional groups such as hydrates (“geminal diol”) that really belong in a separate category from alcohols themselves. OH attached to an alkene is called an “enol” (ene + ol). If the OH is attached to a carbonyl (C=O), that functional group is called a “carboxylic acid”. Note that not all functional groups containing OH are alcohols. Hydroxyl groups attached to aromatic rings are called, “phenols”. If zero carbons and three hydrogens (a unique situation) it is methanol. If that carbon is attached to one carbon, the alcohol is primary two, secondary three, tertiary. To determine if an alcohol is primary, secondary, or tertiary, examine the carbon attached to OH.
The carbinol carbon (carbon attached to OH), however, is the key to understanding the most common classifications we use for alcohols, that being “primary”, “secondary”, and “tertiary” alcohols. The carbon directly attached to OH is technically called the “carbinol” carbon, although this nomenclature is often not introduced in introductory classes. Structure and Nomenclature Of Alcohols: Primary, Secondary, and TertiaryĪlcohols are organic molecules containing the “hydroxyl” functional group, “OH” directly bonded to carbon.
#Alcohol functional group series
In this next series of posts we are going to discuss the reactions of alcohols.Īs a functional group, alcohols are introduced fairly early in organic chemistry.
Alcohol Nomenclature, Properties, and Structure