What is the IUPAC name of CH3CHO?

(a) Acetal

(b) Methanal

(c) Ethanal

(d) Acetaldehyde

The compound CH3CHO is commonly known by several names, but its IUPAC name is Ethanal. So, the correct answer from your options is (c) Ethanal. Let’s break this down to understand why this is the case.

Understanding the Structure of CH3CHO

To determine the IUPAC name, we first need to analyze the molecular structure of CH3CHO. This compound consists of:

• A methyl group (CH3-)
• A carbonyl group (C=O) attached to a hydrogen atom (H)

When we look at the structure, we can see that it is an aldehyde because the carbonyl group is located at the end of the carbon chain. Aldehydes are characterized by the presence of this functional group, which is crucial for naming the compound.

Identifying the Carbon Chain Length

Next, we count the number of carbon atoms in the longest continuous chain. In CH3CHO, there are two carbon atoms:

• The first carbon is part of the methyl group (CH3).
• The second carbon is part of the carbonyl group (CHO).

Since there are two carbon atoms, we use the prefix "eth-" for the name. The suffix for aldehydes is "-al," which indicates the presence of the carbonyl group at the end of the chain.

Common Names and Their Relevance

In addition to its IUPAC name, CH3CHO is also known as acetaldehyde. This is a common name derived from its historical usage in organic chemistry. While "acetaldehyde" is widely recognized, the IUPAC naming convention prefers "ethanal" for clarity and consistency in scientific communication.

Why Other Options Are Incorrect

Let’s briefly look at the other options you provided:

• Acetal: This term refers to a different class of compounds formed from the reaction of aldehydes or ketones with alcohols, not applicable here.
• Methanal: This is the IUPAC name for formaldehyde (CH2O), which has only one carbon atom.
• Acetaldehyde: While this is a common name for CH3CHO, it is not the IUPAC name.

In summary, the IUPAC name for CH3CHO is Ethanal, reflecting its structure as a two-carbon aldehyde. Understanding the naming conventions helps in accurately identifying and communicating about chemical compounds.