Question

The IUPAC name of acraldehyde is (1) prop-2-en-1-al (2) propenylaldehyde (3) but-2-en-1-al (4) propanal

Short answer

The IUPAC name is (1) prop-2-en-1-al.

Step-by-step solution

Identify the Compound

First, recognize that acraldehyde is a common name for an organic compound. It is essential to deduce the structure of the compound.

Determine the Structure

The structure of acraldehyde is CH2=CH-CHO. It consists of a carbon-carbon double bond adjacent to an aldehyde group (-CHO).

Determine the Parent Chain

The longest chain including the aldehyde group has three carbon atoms, hence the name will be based on 'prop'.

Identify the Double Bond Position

The double bond starts from the second carbon. Numbering starts from the aldehyde carbon (C1), making the position of the double bond at carbon 2.

Formulate the IUPAC Name

Combine the elements together. The name for three carbons with a double bond at carbon 2 and an aldehyde group is 'prop-2-en-1-al'.

Verify the Correct Answer

Compare the formulated name with the options given: (1) prop-2-en-1-al, (2) propenylaldehyde, (3) but-2-en-1-al, (4) propanal. The correct IUPAC name is 'prop-2-en-1-al'.

Key concepts

Organic Compound Naming

Naming organic compounds systematically requires understanding the structure and functional groups present. The International Union of Pure and Applied Chemistry (IUPAC) has established rules for this purpose. These rules help ensure that each compound has a unique and consistent name. Here, we focus on naming a compound with an aldehyde group and a carbon-carbon double bond. The parent chain, functional group position, and double bond position all influence the final name.
For example, in the exercise, the compound acraldehyde is named 'prop-2-en-1-al' by following these steps. The alphabetic order of substituents, the longest chain selection, and correct numbering are crucial for proper naming.

Aldehyde Group

The aldehyde group is a vital functional group in organic chemistry. It is represented as -CHO and consists of a carbon atom double-bonded to an oxygen atom and single-bonded to a hydrogen atom. When naming a compound, if it contains an aldehyde group, it is necessary to include it in the parent chain. The aldehyde carbon is always assigned the position number 1 in the chain to prioritize its position.
In the exercise, the aldehyde group is at the end of a three-carbon chain. Therefore, the longest chain containing the aldehyde is the 'prop' chain (three carbons), and the aldehyde carbon is numbered as 1, giving rise to the suffix '-al' in the name.

Carbon-Carbon Double Bond

A carbon-carbon double bond is a type of covalent bond where two carbon atoms share two pairs of electrons. In the IUPAC naming system, the presence of a double bond is recognized by the suffix '-en'. The position of the double bond is stated with the lowest possible numbers. Numbering always starts from the end closest to the double bond.
In acraldehyde, the double bond is between the second and third carbons when numbered from the aldehyde group, resulting in '-2-en' in the name. Thus, combining it all, we get 'prop-2-en-1-al', indicating a three-carbon chain (prop), a double bond starting at carbon 2 (2-en), and an aldehyde group at carbon 1 (1-al). This precise naming helps in identifying the exact structure of the compound.