Functional Groups & Organic Reactions

30min Part 4 / Ch7 / Lesson 2

Prerequisites: 4-7-1

Objectives

Identify major functional groups and their properties
Understand the relationship: alcohol → aldehyde → carboxylic acid
Distinguish addition, substitution, and elimination reactions

Functional Groups

Functional groups: specific atom groups that determine the chemical properties of organic compounds. Compounds with the same functional group share similar reactivity.

Group	Name	Compound class	Example
-OH	Hydroxyl	Alcohol	Ethanol CH₃CH₂OH
-CHO	Aldehyde	Aldehyde	Acetaldehyde CH₃CHO
-CO-	Carbonyl	Ketone	Acetone CH₃COCH₃
-COOH	Carboxyl	Carboxylic acid	Acetic acid CH₃COOH
-COO-	Ester linkage	Ester	Ethyl acetate CH₃COOC₂H₅
-NH₂	Amino	Amine	Methylamine CH₃NH₂

Major functional groups

Oxidation Stages

Oxidation: alcohol → aldehyde → carboxylic acid

Esterification

Esterification: a carboxylic acid and alcohol lose water to form an ester (condensation).

$\mathrm{R\text{-}COOH + R'\text{-}OH \rightleftharpoons R\text{-}COOR' + H_2O}$

The reverse reaction is hydrolysis (saponification when using a base).

Types of Organic Reactions

Reaction type	Description	Example
Addition	Atoms/molecules add across a double bond	Ethylene + Br₂ → 1,2-dibromoethane
Substitution	An atom/group replaces another	Methane + Cl₂ → chloromethane + HCl
Elimination	Loss of a small molecule (e.g., H₂O)	Ethanol → ethylene + H₂O

Check Your Understanding

Q1 An organic compound containing -COOH is classified as:

Q2 Mild oxidation of ethanol (CH₃CH₂OH) produces:

Q3 Adding bromine water to ethylene is an example of:

Q4 The reaction of acetic acid with ethanol to form an ester is:

Exercises

Q1. Classify each compound by functional group: (a) CH₃OH (b) HCHO (c) CH₃COOH (d) CH₃COOCH₃ (e) CH₃NH₂

Solution

Compound	Functional group	Class
(a) CH₃OH	-OH (hydroxyl)	Alcohol
(b) HCHO	-CHO (aldehyde)	Aldehyde
(c) CH₃COOH	-COOH (carboxyl)	Carboxylic acid
(d) CH₃COOCH₃	-COO- (ester linkage)	Ester
(e) CH₃NH₂	-NH₂ (amino)	Amine