Naming Alcohols - Online Tutor, Practice Problems & Exam Prep

Alcohols are organic compounds characterized by the presence of a hydroxyl group (–OH) attached to an sp³ hybridized carbon. They are named by modifying the alkane name, replacing the suffix "e" with "ol" (e.g., pentane becomes pentanol). Alcohols can be classified as primary, secondary, or tertiary based on the number of carbon groups attached to the carbon bearing the hydroxyl group. Understanding these classifications is essential for proper naming and recognizing the structure of alcohols in organic chemistry.

Rules for Naming Alcohols Concept 1

Now, before we delve into naming alcohols, recall that alcohols possess a hydroxyl group. The hydroxyl group is the OH group, and it's connected to an sp³ hybridized carbon. Here, the set of rules for naming alcohols are similar to alkanes, plus a modifier ending. Now here, what exactly is a modifier? Well, the modifier is the change to the suffix or ending because of the presence of a functional group. As we go from functional group to functional group, we're going to have different types of modifiers. Now, here for alcohols, the modifier modifies the ending of the alkane name of e to ol. So instead of like pentane, we have pentanol. Here the naming convention is we have to give still the locations of our different substituents, remember those are our branch groups, the location of our parent in terms of our OH group, and then the modification to the ending. In this case, going from an e ending to ol. So keep this in mind when we're naming different types of alcohols.

Naming Alcohols Example 1

Here in this example question, it says, "Name the following alcohol compound." Alright. So, we're going to use the following steps in order to name this particular alcohol. Here, step 1 says that we have to find the longest carbon chain. That longest carbon chain represents our parent chain. And we're going to assign a name according to the prefixes and now modifier. Now, the parent chain should include the OH group, since we're talking about an alcohol, and have the greatest number of carbons. Now, if a tie exists between the longest chains, choose the chain with more substituents. This one is pretty straightforward. Our longest chain we can see is this portion right here, and we can see that the OH and the Cls act as our substituents. So this leads us into step 2, assign a name to all the substituents. Alright. So here our chlorines would be chloro. The alcohol itself is going to be a modifier, so we don't have to name it here. Next, we're going to say start numbering the chain from the end closest to the OH group. If a tie, number from the end closest to the next substituent. If still a tie, number in alphabetical order. Now, assign the numerical location to the carbon with the OH group. So here we've identified the two substituents in terms of chlorine, we've looked at the longest chain, we know that OH is going to be our functional group that's going to modify the end of the name. So here, I've already numbered the chain for us. We're numbering it from this end 1 because, going 1, 2, we get to our first substituent. If we had numbered it from the other end, it would take us 1, 2, 3 before we get to a substituent. That takes too long. Alright. So now, let's finally name this. We're going to say here that a 6 carbon chain is hexane, but remember the presence of the OH changes the ending from 'e' to 'ol,' so it becomes hexanol. We have to state on what carbon the OH is for the alcohol; it's on carbon 3, so this would be 3-hexanol. Remember, we use a dash to separate numbers from letters. Next, we said that these chlorines are chloro, there are two of them, so that would be dichloro. And finally, we have to state on what carbons those two chlorines are found. They're found on carbons number 2 and 4. So this would be 2,4-dichloro-3-hexanol. So "2,4-dichloro-3-hexanol" will be the name of this particular alcohol compound.

Provide the systematic name for the following alcohol.

• A. 1-methyl-1-hydroxycyclohexane
• B. 1-methylcyclohexanol
• C. 1-methyl-1-hydroxyhexane
• D. 1-methylhexanol

Provide the formal name for the following alcohol. 

• A. 3-isopropyl-4,5,6-trimethyloctanol
• B. 2-isopropyl-1,3,4,5-tetramethylheptanol
• C. 3-isopropyl-4,5,6-trimethyl-2-octanol
• D. 6-isopropyl-3,4,5-trimethyl-2-octanol

Which structure represents 2-bromo-2,3-dichloro-1-heptanol?

• A.
• B.
• C.
• D.

Name the following dialcohol.

• A. hexane-3,6-diol
• B. hexane-3,6-ol
• C. heptane-3,6-diol
• D. heptane-2,5-diol

Provide IUPAC name for the following trialcohol.

• A. 1,1-dibromohexane-1,3,5-triol
• B. 1,1-dibromopentane-1,2,4-triol
• C. 1,1-dibromopentane-2,4-diol
• D. 5,5-dibromopentane-2,4,5-triol

Alcohol Classification Concept 2

Alcohols can be classified based on how many carbon groups are attached to the OH-bearing carbon atom. So here we have classifications of primary, which is 1º, secondary, which is 2º, and tertiary which is 3º. If we take a look here at the first one, we have a carbon with our OH group. We'd say that the carbon with the OH group, let's say it's connected to just one carbon here. That would mean that this is a primary alcohol. Now, here let's put 2 carbons. So now that the carbon that bears the OH group is connected to 2 carbons, it's secondary. And then finally, we can say in this last image, the carbon possessing the OH group, it's directly connected to 3 carbons, meaning that it is a tertiary alcohol. So, remember, in our exploration to name different types of alcohols, you're going to come into contact with primary, secondary, tertiary alcohols, including also methyl alcohols, which don't belong to any of these categories. Right? So just keep this in mind when looking at different types of alcohols.

Alcohol Classification Example 2

Here it says that we need to classify the following alcohols. So let's look to see where is the carbon with the OH group. So here's the carbon with the OH group, and here's the carbon with the OH group. In the first image, that carbon possessing the OH group is connected to 2 other carbons which we don't see, here and here. Since it's connected directly to 2 carbons, it is a secondary alcohol. And then for this other one, this carbon with the OH group, it is directly connected to 1 carbon here. So here it's connected directly to one carbon, so this would represent a primary alcohol. The first compound is secondary, and the second one here is primary.

Label each alcohol as primary, secondary, or tertiary.

• A.
• B.
• C.
• D.

Here’s what students ask on this topic:

What is the general rule for naming alcohols in organic chemistry?

In organic chemistry, alcohols are named by modifying the name of the parent alkane. The suffix 'e' in the alkane name is replaced with 'ol'. For example, 'pentane' becomes 'pentanol'. Additionally, the position of the hydroxyl group (–OH) must be indicated by a number placed before the name. For instance, if the hydroxyl group is on the second carbon of pentane, it is named '2-pentanol'. The numbering of the carbon chain should start from the end nearest to the hydroxyl group to give it the lowest possible number.

How are primary, secondary, and tertiary alcohols classified?

Alcohols are classified based on the number of carbon groups attached to the carbon bearing the hydroxyl group (–OH). A primary alcohol has the hydroxyl-bearing carbon attached to only one other carbon (e.g., ethanol). A secondary alcohol has the hydroxyl-bearing carbon attached to two other carbons (e.g., isopropanol). A tertiary alcohol has the hydroxyl-bearing carbon attached to three other carbons (e.g., tert-butanol). This classification helps in understanding the reactivity and properties of different alcohols.

What is the significance of the hydroxyl group in alcohols?

The hydroxyl group (–OH) is the defining feature of alcohols and significantly influences their chemical properties. It is attached to an sp³ hybridized carbon. The presence of the hydroxyl group makes alcohols polar, which affects their solubility in water and their boiling points. The hydroxyl group also participates in hydrogen bonding, which further influences the physical properties of alcohols. Additionally, the hydroxyl group is reactive and can undergo various chemical reactions, making alcohols important intermediates in organic synthesis.

Why is it important to indicate the position of the hydroxyl group in alcohol nomenclature?

Indicating the position of the hydroxyl group in alcohol nomenclature is crucial because it determines the specific structure and properties of the alcohol. Different positions of the hydroxyl group can result in different compounds with distinct chemical and physical properties. For example, 1-propanol and 2-propanol (isopropanol) are both alcohols with three carbon atoms, but their properties differ due to the position of the hydroxyl group. Properly indicating the position ensures clear communication and accurate identification of the compound.

How does the presence of a hydroxyl group affect the physical properties of alcohols?

The presence of a hydroxyl group (–OH) in alcohols significantly affects their physical properties. The hydroxyl group is polar and can form hydrogen bonds with water molecules, making many alcohols soluble in water. This solubility decreases as the carbon chain length increases. The ability to form hydrogen bonds also raises the boiling points of alcohols compared to hydrocarbons of similar molecular weight. For example, ethanol has a higher boiling point than ethane due to hydrogen bonding. These properties are essential for understanding the behavior of alcohols in various chemical and biological contexts.