# Aldehydes and Ketones Organic compounds containing the **carbonyl functional group** ($>C=O$) are called aldehydes and ketones. This section outlines their key characteristics, differences, and structures. ### Comparison of Aldehydes and Ketones The primary distinction between aldehydes and ketones lies in the atoms bonded to the carbonyl carbon. | Feature | Aldehydes | Ketones | | :--- | :--- | :--- | | **Functional Group** | The carbonyl carbon is directly attached to at least one **hydrogen atom**. The functional group is the **formyl group** ($-CHO$). | The carbonyl carbon is bonded to two other **carbon atoms**. The functional group is the **keto group** ($>C=O$). | | **General Formula** | The homologous series of aliphatic aldehydes has the general formula: $$C_n H_{2n} O$$ | The homologous series of aliphatic ketones has the same general formula: $$C_n H_{2n} O$$ | | **Structural Formula** | Represented by the general structure $R-CHO$, where $R$ can be a hydrogen atom or an alkyl/aryl group.

$$\begin{array}{c} \Large O \\ \large \parallel \\ R - C - H \end{array}$$ | Represented by the general structure $R-CO-R'$, where $R$ and $R'$ are alkyl or aryl groups.

$$\begin{array}{c} \Large O \\ \large \parallel \\ R - C - R' \end{array}$$ | | **Examples** | **(i) Methanal (Formaldehyde):** $HCHO$

**(ii) Ethanal (Acetaldehyde):** $CH_3CHO$ | **(i) Propanone (Acetone):** $CH_3COCH_3$

**(ii) Butanone:** $CH_3COC_2H_5$ | --- ## Possible Questions/Answers **Q:** What is the key structural difference between an aldehyde and a ketone? **A:** In an aldehyde, the carbonyl carbon ($C=O$) is bonded to at least one hydrogen atom. In a ketone, the carbonyl carbon is bonded to two other carbon atoms. **Q:** Do aldehydes and ketones have the same general formula? **A:** Yes, for aliphatic (non-cyclic) structures, both share the general formula $C_n H_{2n} O$. This means they can be functional isomers. For example, propanal ($CH_3CH_2CHO$) and propanone ($CH_3COCH_3$) both have the formula $C_3H_6O$. - **Carbonyl Compounds:** Both aldehydes and ketones are characterized by the carbonyl functional group ($>C=O$). - **Structural Difference:** - **Aldehydes:** Have a terminal carbonyl group ($R-CHO$). - **Ketones:** Have an internal carbonyl group ($R-CO-R'$). - **General Formula:** Aliphatic aldehydes and ketones are functional isomers and share the general formula $C_n H_{2n} O$. - **Nomenclature:** Aldehydes typically end with the suffix *-al* (e.g., methanal), while ketones end with *-one* (e.g., propanone). - **Significance:** Aldehydes and ketones are important in both biology and industry. Formaldehyde is used as a preservative, acetone is a common solvent, and many sugars (like glucose) contain an aldehyde functional group.

19.1 Organic Compounds Containing The Carbonyl Functional Group Are Called Aldehydes And Ketones. | Carbonyl Compounds | Chemistry 11