Question

What functional group characterizes an alcohol? What ending is added to the name of the parent hydrocarbon to show that a molecule is an alcohol?

Short answer

The functional group characterizing an alcohol is the hydroxyl group (-OH). To show that a molecule is an alcohol, the ending "-ol" is added to the name of the parent hydrocarbon.

Step-by-step solution

Identifying the Functional Group of Alcohols

A functional group is an atom or a group of atoms that is responsible for the specific properties of a molecule. In the case of alcohols, the functional group is the hydroxyl group (-OH) bonded to an alkyl group (R). The general structure for an alcohol can be represented as R-OH.

Naming Alcohols: Adding the Ending

To name an alcohol, we first need to identify the parent hydrocarbon, which is the longest carbon chain containing the -OH group. The ending of the parent hydrocarbon's name has to be changed to indicate the presence of an alcohol. This is done by replacing the "-e" ending of the parent hydrocarbon with the suffix "-ol." For example, if the parent hydrocarbon is methane (CH4), the alcohol derived from methane would be methanol (CH3OH). Remember to also include the position of the hydroxyl group on the carbon chain when there are multiple carbons in the molecule. For example, if the -OH group is attached to the second carbon in a three-carbon chain (propane), the alcohol should be named as 2-propanol. In conclusion, the functional group that characterizes an alcohol is the hydroxyl group (-OH), and the ending "-ol" is added to the name of the parent hydrocarbon to indicate that a molecule is an alcohol.

Key concepts

Functional Groups

Functional groups are fundamental components in organic chemistry. They determine the characteristics and reactions of molecules. A functional group is a specific group of atoms within a molecule that is responsible for the distinctive chemical reactions of that molecule. One of the reasons functional groups are so critical is because they behave in consistent ways in different organic molecules. For instance, when you see the hydroxyl group in an unknown molecule, you can predict certain properties and behaviors based on known alcohol reactions. This predictability is why functional groups are a primary focus when studying organic compounds.

Hydroxyl Group

The hydroxyl group, denoted as -OH, is the defining functional group of alcohols. It consists of an oxygen atom bonded to a hydrogen atom. This group is polar, which means it has a slight positive charge on the hydrogen and a slight negative charge on the oxygen. This polarity is crucial because it allows alcohols to form hydrogen bonds with other molecules, leading to higher boiling points compared to similar-sized hydrocarbons. Alcohols are further categorized based on the carbon atom to which the hydroxyl group is attached:

• Primary (1°) alcohols - The -OH group is attached to a carbon atom that is only bonded to one other carbon.
• Secondary (2°) alcohols - The -OH group is attached to a carbon atom that is bonded to two other carbons.
• Tertiary (3°) alcohols - The -OH group is attached to a carbon atom that is bonded to three other carbons.

These classifications influence the reactivity and types of reactions that the alcohols can participate in. Moreover, the ability to form hydrogen bonds makes alcohols useful in many applications, from solvents to antiseptics.

Naming Organic Compounds

Naming organic compounds is a systematic process crucial for universal understanding within the scientific community. The primary system used is IUPAC (International Union of Pure and Applied Chemistry) nomenclature. For alcohols, the naming involves identifying the longest carbon chain that contains the hydroxyl -OH group, known as the parent hydrocarbon. Once identified, the suffix -"e" of the parent hydrocarbon's name is replaced with -"ol" to signify the presence of an alcohol. For example:

• Methane (CH4) becomes Methanol (CH3OH) when it has an -OH group.
• Propane (C3H8) becomes Propanol (C3H7OH) when an -OH group is introduced.

Additionally, when the carbon chain contains more than one carbon, it is essential to number the chain to indicate the position of the hydroxyl group. This numbering helps ensure clarity, especially with isomers where the -OH group's location creates different compounds. For example, 2-Propanol indicates that the -OH group is on the second carbon of the three-carbon propane chain. Through this systematic approach, organic chemists can effectively communicate complex molecular structures universally.