krit.club logo

Organic Chemistry - Naming and structural formulae (IUPAC)

Grade 11IGCSEChemistry

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

Homologous Series: A family of organic compounds with the same functional group, the same general formula, and similar chemical properties. Members differ by a CH2CH_2 unit.

IUPAC Nomenclature: A systematic method of naming organic compounds. The prefix indicates the number of carbon atoms: C1C_1 (Meth-), C2C_2 (Eth-), C3C_3 (Prop-), C4C_4 (But-), C5C_5 (Pent-), C6C_6 (Hex-).

Functional Groups: Specific groups of atoms responsible for the characteristic chemical reactions of a molecule, such as the hydroxyl group (OH-OH) in alcohols or the carboxyl group (COOH-COOH) in carboxylic acids.

Saturated vs. Unsaturated: Saturated hydrocarbons (alkanes) contain only single CCC-C bonds. Unsaturated hydrocarbons (alkenes) contain at least one C=CC=C double bond.

Structural Formulae: Can be represented as 'displayed' (showing all atoms and bonds), 'condensed' (e.g., CH3CH2OHCH_3CH_2OH), or 'skeletal' (lines representing carbon-carbon bonds).

Isomerism: Compounds with the same molecular formula but different structural arrangements, such as But-1-ene and But-2-ene.

📐Formulae

CnH2n+2 (Alkanes)C_nH_{2n+2} \text{ (Alkanes)}

CnH2n (Alkenes)C_nH_{2n} \text{ (Alkenes)}

CnH2n+1OH (Alcohols)C_nH_{2n+1}OH \text{ (Alcohols)}

CnH2n+1COOH (Carboxylic Acids)C_nH_{2n+1}COOH \text{ (Carboxylic Acids)}

CnH2nO2 (General formula for Esters and Carboxylic Acids)C_nH_{2n}O_2 \text{ (General formula for Esters and Carboxylic Acids)}

💡Examples

Problem 1:

Provide the IUPAC name for the molecule with the condensed structural formula CH3CH2CH2CH2OHCH_3CH_2CH_2CH_2OH.

Solution:

Butan-1-ol

Explanation:

The molecule has a chain of 4 carbons (prefix 'But-'). It is saturated (suffix '-an-') and contains a hydroxyl functional group (OH-OH) on the first carbon (suffix '-1-ol').

Problem 2:

Identify the name of the alkene with the molecular formula C3H6C_3H_6.

Solution:

Propene

Explanation:

The molecule follows the general formula CnH2nC_nH_{2n} where n=3n=3. Three carbons correspond to the prefix 'Prop-'. Since it is an alkene, the name is Propene.

Problem 3:

What is the name of the ester formed from the reaction between ethanol (CH3CH2OHCH_3CH_2OH) and propanoic acid (CH3CH2COOHCH_3CH_2COOH)?

Solution:

Ethyl propanoate (CH3CH2COOCH2CH3CH_3CH_2COOCH_2CH_3)

Explanation:

In naming esters, the 'alkyl' part comes from the alcohol (ethanol \rightarrow ethyl) and the 'alkanoate' part comes from the carboxylic acid (propanoic acid \rightarrow propanoate).

Naming and structural formulae (IUPAC) Revision - Grade 11 Chemistry IGCSE