Question

Draw all aldehydes and ketones with the formula \(\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}\)

Short answer

Pentanal, 3-methylbutanal, pentan-2-one, pentan-3-one, 2-methylbutan-2-one.

Step-by-step solution

Identify the molecular formula components

The molecular formula \(\text{C}_5 \text{H}_{10} \text{O}\) contains carbon (C), hydrogen (H), and oxygen (O). Aldehydes and ketones typically have a carbonyl group (C=O). Since the formula needs to fit into the structure of either an aldehyde or a ketone, we will consider all possible structures.

Draw possible aldehyde structures

Aldehydes have the general structure \(\text{R-CHO}\), where \(\text{R}\) is an alkyl group. Given the formula, we can have CHO as a part of the molecule and the remaining carbons forming alkyl chains. Possible structures are: (1) \(\text{CH}_3-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CHO}\) (pentanal), (2) \(\text{CH}_3-\text{CH}_2-\text{CH(CH}_3\text{)-CHO}\) (3-methylbutanal).

Draw possible ketone structures

Ketones have the general structure \(\text{R-CO-R'}\), where \(\text{R}\) and \(\text{R'}\) are alkyl groups. Given the formula, possible structures are: (1) \(\text{CH}_3-\text{CO}-\text{CH}_2-\text{CH}_2-\text{CH}_3\) (pentan-2-one), (2) \(\text{CH}_3-\text{CH}_2-\text{CO}-\text{CH}_2-\text{CH}_3\) (pentan-3-one), (3) \(\text{CH}_3-\text{CO}-\text{CH}(\text{CH}_3)-\text{CH}_3\) (2-methylbutan-2-one).

Key concepts

Molecular Formula

A molecular formula represents the types and numbers of atoms in a molecule. In the given problem, \(\text{C}_5 \text{H}_{10} \text{O}\), we have 5 carbons (C), 10 hydrogens (H), and 1 oxygen (O). This molecular formula can correspond to different structures. Here, we focus on aldehydes and ketones. Both types have a carbonyl group (C=O). The specific arrangement of atoms will differentiate aldehydes from ketones.

Aldehyde Structures

Aldehydes contain the formyl group (\text{CHO}), where the carbonyl group (C=O) is attached to at least one hydrogen atom. This can be symbolized as \text{R-CHO}, with \text{R} representing an alkyl group. For \(\text{C}_5\text{H}_{10}\text{O}\), potential aldehyde structures include:
\begin{itemize}

\(\text{CH}_3-\text{CH}_2-\text{CH}_2-\text{CH}_2-\text{CHO}\) (pentanal)

\(\text{CH}_3-\text{CH}_2-\text{CH}(\text{CH}_3)-\text{CHO}\) (3-methylbutanal)

these structures consist of the formyl group bonded to a chain of carbons (alkyl groups).

Ketone Structures

Ketones feature the carbonyl group (C=O) bonded to two alkyl groups, symbolized as \text{R-CO-R'}. Unlike aldehydes, the carbonyl carbon is not at the end of the carbon chain. With the molecular formula \(\text{C}_5\text{H}_{10}\text{O}\), possible ketone structures are:

• \(\text{CH}_3-\text{CO}-\text{CH}_2-\text{CH}_2-\text{CH}_3\) (pentan-2-one)
• \(\text{CH}_3-\text{CH}_2-\text{CO}-\text{CH}_2-\text{CH}_3\) (pentan-3-one)
• \(\text{CH}_3-\text{CO}-\text{CH}(\text{CH}_3) -\text{CH}_3\) (2-methylbutan-2-one)

Carbonyl Group

The carbonyl group (C=O) is a fundamental functional group in organic chemistry. It's characterized by a carbon double-bonded to an oxygen. This group defines both aldehydes and ketones but in distinct contexts.

• Aldehydes: Here, the carbonyl carbon is bonded to at least one hydrogen atom. This makes the carbonyl group terminal in the structure.
• Ketones: In ketones, the carbonyl carbon is bonded to two carbon atoms, making it more internal in the structure.

Understanding the behavior and reactivity of the carbonyl group is key to mastering organic chemistry.