Define the following terms: 1.1 homologous series 1.2 functional group write down the structural formula of the functional group for the following homologous series: 2.1 alcohols 2.2 aldehydes 2.3 carboxylic acids 2.4

Certainly! Here's a detailed explanation of the requested terms and their corresponding structural formulas: --- ### **1. Definitions** #### **1.1 Homologous Series** A **homologous series** is a group of organic compounds that share the same general formula, exhibit similar chemical properties, and show a gradual change in physical properties (such as boiling point and melting point) as the molecular size increases. Each successive member of the series differs from the previous one by a specific structural unit, typically a **—CH₂—** (methylene) group. * **Example:** In the alkane series, methane (CH₄), ethane (C₂H₆), propane (C₃H₈), etc., form a homologous series where each successive molecule has one more **—CH₂—** unit than the previous one. #### **1.2 Functional Group** A **functional group** is a specific group of atoms within a molecule that is responsible for the characteristic chemical reactions of that molecule. Functional groups determine the class of organic compounds and provide sites for chemical transformations. * **Examples of Functional Groups:** - **Hydroxyl Group (–OH)** in alcohols - **Carbonyl Group (C=O)** in ketones and aldehydes - **Carboxyl Group (–COOH)** in carboxylic acids --- ### **2. Structural Formulas of Functional Groups** Below are the structural formulas for the functional groups of the specified homologous series: #### **2.1 Alcohols** - **Functional Group:** Hydroxyl Group (**–OH**) - **Structural Formula:** ``` H | R—C—OH | H ``` - **Simplified Representation:** **R–OH** Here, **R** represents an alkyl group (a chain of carbon atoms). The hydroxyl group (**–OH**) is attached to the carbon atom, making the compound an alcohol. - **Example:** Ethanol (CH₃CH₂OH) ``` H H | | H—C—C—OH | | H H ``` #### **2.2 Aldehydes** - **Functional Group:** Carbonyl Group with a Hydrogen (**–CHO**) - **Structural Formula:** ``` O || R—C—H ``` - **Simplified Representation:** **R–CHO** The carbonyl group (**C=O**) is bonded to a hydrogen atom and an alkyl group (**R**), characterizing aldehydes. - **Example:** Formaldehyde (H₂C=O) ``` H | H—C=O | H ``` #### **2.3 Carboxylic Acids** - **Functional Group:** Carboxyl Group (**–COOH**) - **Structural Formula:** ``` O || R—C—OH ``` - **Simplified Representation:** **R–COOH** The carboxyl group consists of a carbonyl group (**C=O**) bonded to a hydroxyl group (**–OH**). This functional group is responsible for the acidic properties of carboxylic acids. - **Example:** Acetic Acid (CH₃COOH) ``` H | H—C—C—OH | O || O ``` --- ### **Summary Table** | **Homologous Series** | **Functional Group** | **Structural Formula** | |-----------------------|----------------------|------------------------| | **Alcohols** | Hydroxyl (–OH) | R–OH | | **Aldehydes** | Formyl (–CHO) | R–CHO | | **Carboxylic Acids** | Carboxyl (–COOH) | R–COOH | *Where **R** represents an alkyl group (a chain of carbon atoms).* --- If you have any further questions or need more examples, feel free to ask!