Organic chemistry might seem overwhelming at first, but it's actually...
Understanding Organic Chemistry - AQA High School Guide







Basic Concepts and Formulae
Ever wondered why petrol burns differently than cooking oil? It's all about hydrocarbons - compounds made only of carbon and hydrogen atoms. These molecules form the backbone of organic chemistry and everything from fuels to plastics.
Saturated hydrocarbons contain only single bonds between carbons, making them quite stable. Unsaturated hydrocarbons have double bonds , which makes them more reactive and useful for making other chemicals.
You'll encounter several types of formulae in your exams. The molecular formula shows exactly how many of each atom you have (like C₄H₁₀), whilst the empirical formula gives the simplest ratio. Structural formulae show how atoms connect, and displayed formulae reveal every single bond - essential for understanding reactions.
Top Tip: When drawing organic molecules, remember each carbon must have exactly 4 bonds. If you can't see 4 bonds to other atoms, the missing ones are to hydrogen atoms!

Homologous Series and Functional Groups
Think of homologous series as chemical families - groups of compounds that behave similarly because they share the same functional group. Just like family members share traits, these compounds share chemical properties whilst differing by CH₂ units.
Alkanes (like butane) are your basic hydrocarbons with only single bonds. Alkenes contain double bonds, making them perfect for creating plastics. Alcohols have an -OH group, which is why they mix with water unlike pure hydrocarbons.
Each family has its own naming pattern. Alkanes end in "-ane", alkenes in "-ene", and alcohols in "-ol". Aldehydes end in "-al", ketones in "-one", and carboxylic acids in "-oic acid". Learning these patterns makes naming compounds much easier.
Remember: The functional group determines how a molecule behaves chemically - it's like the molecule's personality!

Naming Rules and Priority System
Naming organic compounds follows a clear hierarchy, just like deciding who gets served first in a queue. Carboxylic acids have the highest priority, followed by aldehydes, ketones, alcohols, alkenes, and finally halogenoalkanes.
Start by finding the longest carbon chain and use the appropriate stem (meth=1, eth=2, prop=3, but=4, etc.). The highest priority functional group gets the suffix and the lowest possible number on the carbon chain.
Branch chains and lower priority groups become prefixes. For example, in 3,5-dimethylheptane, you've got a 7-carbon chain with methyl groups on carbons 3 and 5. Multiple identical groups get prefixes like "di-", "tri-", or "tetra-".
Exam Strategy: Always identify the longest carbon chain first, then find the highest priority functional group - this determines your base name and numbering system.

Alkenes and Haloalkanes
Alkenes are unsaturated hydrocarbons with the general formula CₙH₂ₙ, and that double bond makes all the difference. They're much more reactive than alkanes and can form polymers like polythene. When naming, the number indicates where the double bond starts (but-2-ene has the double bond between carbons 2 and 3).
Multiple double bonds get special treatment - "diene" for two, "triene" for three. Sometimes you'll see E or Z prefixes, which describe the arrangement of groups around the double bond (stereoisomers).
Haloalkanes are simply alkanes with halogen atoms (F, Cl, Br, I) replacing some hydrogens. Name them using prefixes: fluoro-, chloro-, bromo-, or iodo-. For example, 2-bromobutane has a bromine on the second carbon of a 4-carbon chain.
Key Point: When multiple functional groups are present, list prefixes in alphabetical order, ignoring any "di-" or "tri-" prefixes.

Alcohols and Aldehydes
Alcohols contain the -OH functional group, which makes them polar and able to form hydrogen bonds. This explains why ethanol mixes with water but hexane doesn't. Simple alcohols end in "-ol" (like butan-2-ol), whilst multiple -OH groups create diols or triols.
When alcohols appear alongside higher priority groups, they become "hydroxy-" prefixes instead of taking the suffix. For instance, 2-hydroxypropanoic acid has both alcohol and carboxylic acid groups, but the acid takes priority.
Aldehydes always have their C=O group on carbon 1, so you don't need to specify its position - it's ethanal, not ethan-1-al. This carbonyl group makes aldehydes quite reactive and gives them distinctive smells (vanilla contains vanillin, an aldehyde).
Memory Trick: ALdehydes are ALways on carbon 1 - the carbonyl carbon must be at the end of the chain.

Ketones, Carboxylic Acids, and Reaction Mechanisms
Ketones have their C=O group somewhere in the middle of the carbon chain, unlike aldehydes. For chains with 5 or more carbons, you need to specify the position (pentan-2-one). Acetone (propanone) is the most common ketone - it's nail polish remover.
Carboxylic acids always sit at the end of carbon chains, so numbering always starts from the acid group. These compounds are weak acids (like ethanoic acid in vinegar) and can form salts with metals or bases.
Homolytic fission introduces reaction mechanisms - when bonds break, each atom keeps one electron, forming free radicals. These highly reactive species have unpaired electrons (shown with a dot) and are crucial in many organic reactions, including combustion and polymerisation.
Mechanism Tip: Use single-headed arrows (→) to show single electron movement in free radical reactions - this is different from the double-headed arrows used in other mechanisms.
We thought you’d never ask...
Similar content
Most popular content: Alcohols
9AQA A-Level Chemistry Tests
Explore comprehensive AQA A-Level Chemistry tests covering functional groups, transition metals, and ion tests. This resource includes detailed observations and reactions for various chemical tests, ideal for exam preparation and revision. Perfect for students seeking to enhance their understanding of laboratory techniques and chemical nomenclature.
Electrophilic Addition & Fuels
Explore the mechanisms of electrophilic addition reactions in organic chemistry, focusing on alkenes and their derivatives. This summary covers key concepts such as carbocation formation, isomerism, and the environmental impact of various fuels, including biofuels and hydrogen. Ideal for OCR A-Level Chemistry students seeking to understand the relationship between organic reactions and fuel development.
Organic Chemistry Essentials
Explore key concepts in organic chemistry, including the structure and properties of alkenes, polymerization processes, hydrocarbon cracking, and the characteristics of carboxylic acids. This summary covers essential reactions, the homologous series, and the combustion of hydrocarbons, providing a comprehensive overview for GCSE Chemistry students.
Organic Chemistry Overview
Explore key concepts in organic chemistry, including reaction rates, properties of alcohols and carboxylic acids, thermochemistry, halogenoalkanes, and hydrocarbons. This comprehensive summary is essential for understanding enthalpy and the behavior of organic compounds in various reactions.
Organic Reaction Mechanisms
Explore key organic reaction mechanisms including electrophilic addition, electrophilic substitution, and nucleophilic substitution. This summary covers the reactions of alkenes, benzene, carbonyl compounds, and halogenoalkanes, detailing reactants, products, and conditions necessary for each mechanism. Ideal for OCR A-level chemistry students.
Natures Chemistry Overview
Explore key concepts in Natures Chemistry with this comprehensive summary covering esters, alcohols, oxidation, homologous series, proteins, and soaps. Ideal for higher chemistry students preparing for exams, this resource provides essential insights into chemical reactions, functional groups, and the properties of organic compounds.
Organic Chemistry Essentials
Explore key concepts in organic chemistry with this comprehensive overview. Covering functional groups, structural formulas, and reaction mechanisms, this resource is perfect for A-level students. Includes insights on alcohols, carboxylic acids, alkenes, and spectroscopy techniques. Ideal for exam preparation and understanding organic synthesis.
Reactions of Alcohols
Explore the key reactions of alcohols, including combustion, substitution with halogens, dehydration to form alkenes, and oxidation to aldehydes and carboxylic acids. This summary covers essential tests for aldehydes and the reactivity of different alcohol types. Ideal for chemistry students preparing for exams.
Advanced Organic Chemistry Concepts
Explore key concepts in organic chemistry, including esters, carboxylic acids, oxidation-reduction reactions, and the chemistry of fats and proteins. This comprehensive summary covers essential topics such as saponification, emulsifiers, and the role of functional groups in molecular structure. Ideal for students preparing for higher chemistry exams.
Most popular content in Chemistry
9GCSE AQA Chemistry Topic 1- The Atom
The Atom
chem paper 1
higher
Chemistry paper 2
Chem paper 2 notes
A-level OCR A Chemistry summary sheets
Everything from snaprevise for OCR chemistry a-level
chem paper 1
Unlock the secrets of chemical reactions with this comprehensive flashcard set designed to help you conquer complex concepts and ace your Chemistry exams.
AQA GCSE Chemistry 4.4 Chemical changes
4.4 Reactions of acids with bases or carbonates
Essential Chemistry Practicals
Explore key AQA GCSE Chemistry practicals, including flame tests, titration, and gas identification. This resource covers essential techniques for analyzing ions, making salts, and understanding reaction kinetics. Perfect for students preparing for exams and practical assessments.
Atomic Mass and Atomic Number Calculations
Calculate the number of protons, neutrons, and electrons for different elements and isotopes.
Chemistry Topic 1
ATOMIC STRUCTURE AND THE HISTORY OF THE PERIODIC TABLE
Most popular content
9Sociology of Families: Comprehensive Revision
Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.
Comprehensive Crime & Deviance Overview
Explore an extensive revision of crime and deviance topics, including theories, types of crime, and the impact of media. This resource covers key concepts such as Marxism, functionalism, gender and crime, and the influence of globalization on criminal behavior. Ideal for students seeking a thorough understanding of criminology and its various theories. Type: Full Topic Revision.
Criminology: Crime & Punishment Overview
Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.
Sociology of Education Overview
Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.
Cell Biology and Cell structure
cell structures
WJEC Unit 4 Criminology
Criminology unit 4 detailed revision note
Language Paper 1 Strategies
Master the AQA English Language Paper 1 with this comprehensive guide. Explore key strategies for language and structural analysis, critical evaluation, and creative writing. Learn how to effectively analyze texts, utilize literary techniques, and enhance your writing skills to excel in your exams.
Media Studies: Key Concepts & Theories
Dive into the essential concepts and theories of media studies for AQA A-level Sociology. This comprehensive revision guide covers topics such as media influence, representations, globalization, and sociological perspectives, ensuring you grasp the critical elements needed for your exams. Perfect for students seeking to enhance their understanding of media's role in society.
Sociological Theories Overview
Comprehensive revision of key sociological theories including Functionalism, Marxism, Feminism, and Interpretivism. Explore concepts like value freedom, identity formation, and the critique of social control. Ideal for AQA A-Level Sociology students preparing for exams. This summary covers essential theories and their implications in sociology, providing a clear understanding of each perspective.
Students love us — and so will you.
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Understanding Organic Chemistry - AQA High School Guide
Organic chemistry might seem overwhelming at first, but it's actually just about understanding how carbon and hydrogen atoms connect to form different molecules. Once you grasp the basic naming rules and functional groups, you'll be able to identify and draw...

Basic Concepts and Formulae
Ever wondered why petrol burns differently than cooking oil? It's all about hydrocarbons - compounds made only of carbon and hydrogen atoms. These molecules form the backbone of organic chemistry and everything from fuels to plastics.
Saturated hydrocarbons contain only single bonds between carbons, making them quite stable. Unsaturated hydrocarbons have double bonds , which makes them more reactive and useful for making other chemicals.
You'll encounter several types of formulae in your exams. The molecular formula shows exactly how many of each atom you have (like C₄H₁₀), whilst the empirical formula gives the simplest ratio. Structural formulae show how atoms connect, and displayed formulae reveal every single bond - essential for understanding reactions.
Top Tip: When drawing organic molecules, remember each carbon must have exactly 4 bonds. If you can't see 4 bonds to other atoms, the missing ones are to hydrogen atoms!

Homologous Series and Functional Groups
Think of homologous series as chemical families - groups of compounds that behave similarly because they share the same functional group. Just like family members share traits, these compounds share chemical properties whilst differing by CH₂ units.
Alkanes (like butane) are your basic hydrocarbons with only single bonds. Alkenes contain double bonds, making them perfect for creating plastics. Alcohols have an -OH group, which is why they mix with water unlike pure hydrocarbons.
Each family has its own naming pattern. Alkanes end in "-ane", alkenes in "-ene", and alcohols in "-ol". Aldehydes end in "-al", ketones in "-one", and carboxylic acids in "-oic acid". Learning these patterns makes naming compounds much easier.
Remember: The functional group determines how a molecule behaves chemically - it's like the molecule's personality!

Naming Rules and Priority System
Naming organic compounds follows a clear hierarchy, just like deciding who gets served first in a queue. Carboxylic acids have the highest priority, followed by aldehydes, ketones, alcohols, alkenes, and finally halogenoalkanes.
Start by finding the longest carbon chain and use the appropriate stem (meth=1, eth=2, prop=3, but=4, etc.). The highest priority functional group gets the suffix and the lowest possible number on the carbon chain.
Branch chains and lower priority groups become prefixes. For example, in 3,5-dimethylheptane, you've got a 7-carbon chain with methyl groups on carbons 3 and 5. Multiple identical groups get prefixes like "di-", "tri-", or "tetra-".
Exam Strategy: Always identify the longest carbon chain first, then find the highest priority functional group - this determines your base name and numbering system.

Alkenes and Haloalkanes
Alkenes are unsaturated hydrocarbons with the general formula CₙH₂ₙ, and that double bond makes all the difference. They're much more reactive than alkanes and can form polymers like polythene. When naming, the number indicates where the double bond starts (but-2-ene has the double bond between carbons 2 and 3).
Multiple double bonds get special treatment - "diene" for two, "triene" for three. Sometimes you'll see E or Z prefixes, which describe the arrangement of groups around the double bond (stereoisomers).
Haloalkanes are simply alkanes with halogen atoms (F, Cl, Br, I) replacing some hydrogens. Name them using prefixes: fluoro-, chloro-, bromo-, or iodo-. For example, 2-bromobutane has a bromine on the second carbon of a 4-carbon chain.
Key Point: When multiple functional groups are present, list prefixes in alphabetical order, ignoring any "di-" or "tri-" prefixes.

Alcohols and Aldehydes
Alcohols contain the -OH functional group, which makes them polar and able to form hydrogen bonds. This explains why ethanol mixes with water but hexane doesn't. Simple alcohols end in "-ol" (like butan-2-ol), whilst multiple -OH groups create diols or triols.
When alcohols appear alongside higher priority groups, they become "hydroxy-" prefixes instead of taking the suffix. For instance, 2-hydroxypropanoic acid has both alcohol and carboxylic acid groups, but the acid takes priority.
Aldehydes always have their C=O group on carbon 1, so you don't need to specify its position - it's ethanal, not ethan-1-al. This carbonyl group makes aldehydes quite reactive and gives them distinctive smells (vanilla contains vanillin, an aldehyde).
Memory Trick: ALdehydes are ALways on carbon 1 - the carbonyl carbon must be at the end of the chain.

Ketones, Carboxylic Acids, and Reaction Mechanisms
Ketones have their C=O group somewhere in the middle of the carbon chain, unlike aldehydes. For chains with 5 or more carbons, you need to specify the position (pentan-2-one). Acetone (propanone) is the most common ketone - it's nail polish remover.
Carboxylic acids always sit at the end of carbon chains, so numbering always starts from the acid group. These compounds are weak acids (like ethanoic acid in vinegar) and can form salts with metals or bases.
Homolytic fission introduces reaction mechanisms - when bonds break, each atom keeps one electron, forming free radicals. These highly reactive species have unpaired electrons (shown with a dot) and are crucial in many organic reactions, including combustion and polymerisation.
Mechanism Tip: Use single-headed arrows (→) to show single electron movement in free radical reactions - this is different from the double-headed arrows used in other mechanisms.
We thought you’d never ask...
Similar content
Most popular content: Alcohols
9AQA A-Level Chemistry Tests
Explore comprehensive AQA A-Level Chemistry tests covering functional groups, transition metals, and ion tests. This resource includes detailed observations and reactions for various chemical tests, ideal for exam preparation and revision. Perfect for students seeking to enhance their understanding of laboratory techniques and chemical nomenclature.
Electrophilic Addition & Fuels
Explore the mechanisms of electrophilic addition reactions in organic chemistry, focusing on alkenes and their derivatives. This summary covers key concepts such as carbocation formation, isomerism, and the environmental impact of various fuels, including biofuels and hydrogen. Ideal for OCR A-Level Chemistry students seeking to understand the relationship between organic reactions and fuel development.
Organic Chemistry Essentials
Explore key concepts in organic chemistry, including the structure and properties of alkenes, polymerization processes, hydrocarbon cracking, and the characteristics of carboxylic acids. This summary covers essential reactions, the homologous series, and the combustion of hydrocarbons, providing a comprehensive overview for GCSE Chemistry students.
Organic Chemistry Overview
Explore key concepts in organic chemistry, including reaction rates, properties of alcohols and carboxylic acids, thermochemistry, halogenoalkanes, and hydrocarbons. This comprehensive summary is essential for understanding enthalpy and the behavior of organic compounds in various reactions.
Organic Reaction Mechanisms
Explore key organic reaction mechanisms including electrophilic addition, electrophilic substitution, and nucleophilic substitution. This summary covers the reactions of alkenes, benzene, carbonyl compounds, and halogenoalkanes, detailing reactants, products, and conditions necessary for each mechanism. Ideal for OCR A-level chemistry students.
Natures Chemistry Overview
Explore key concepts in Natures Chemistry with this comprehensive summary covering esters, alcohols, oxidation, homologous series, proteins, and soaps. Ideal for higher chemistry students preparing for exams, this resource provides essential insights into chemical reactions, functional groups, and the properties of organic compounds.
Organic Chemistry Essentials
Explore key concepts in organic chemistry with this comprehensive overview. Covering functional groups, structural formulas, and reaction mechanisms, this resource is perfect for A-level students. Includes insights on alcohols, carboxylic acids, alkenes, and spectroscopy techniques. Ideal for exam preparation and understanding organic synthesis.
Reactions of Alcohols
Explore the key reactions of alcohols, including combustion, substitution with halogens, dehydration to form alkenes, and oxidation to aldehydes and carboxylic acids. This summary covers essential tests for aldehydes and the reactivity of different alcohol types. Ideal for chemistry students preparing for exams.
Advanced Organic Chemistry Concepts
Explore key concepts in organic chemistry, including esters, carboxylic acids, oxidation-reduction reactions, and the chemistry of fats and proteins. This comprehensive summary covers essential topics such as saponification, emulsifiers, and the role of functional groups in molecular structure. Ideal for students preparing for higher chemistry exams.
Most popular content in Chemistry
9GCSE AQA Chemistry Topic 1- The Atom
The Atom
chem paper 1
higher
Chemistry paper 2
Chem paper 2 notes
A-level OCR A Chemistry summary sheets
Everything from snaprevise for OCR chemistry a-level
chem paper 1
Unlock the secrets of chemical reactions with this comprehensive flashcard set designed to help you conquer complex concepts and ace your Chemistry exams.
AQA GCSE Chemistry 4.4 Chemical changes
4.4 Reactions of acids with bases or carbonates
Essential Chemistry Practicals
Explore key AQA GCSE Chemistry practicals, including flame tests, titration, and gas identification. This resource covers essential techniques for analyzing ions, making salts, and understanding reaction kinetics. Perfect for students preparing for exams and practical assessments.
Atomic Mass and Atomic Number Calculations
Calculate the number of protons, neutrons, and electrons for different elements and isotopes.
Chemistry Topic 1
ATOMIC STRUCTURE AND THE HISTORY OF THE PERIODIC TABLE
Most popular content
9Sociology of Families: Comprehensive Revision
Dive into an extensive overview of family dynamics, perspectives, and patterns in sociology. This resource covers key concepts such as family diversity, gender roles, marriage, and the impact of social policies on family structures. Perfect for A-Level Sociology students preparing for Paper 2.
Comprehensive Crime & Deviance Overview
Explore an extensive revision of crime and deviance topics, including theories, types of crime, and the impact of media. This resource covers key concepts such as Marxism, functionalism, gender and crime, and the influence of globalization on criminal behavior. Ideal for students seeking a thorough understanding of criminology and its various theories. Type: Full Topic Revision.
Criminology: Crime & Punishment Overview
Comprehensive mindmaps covering key concepts in the Crime and Punishment topic for WJEC Criminology Unit 4. This resource includes detailed insights into the Criminal Justice System, crime prevention strategies, sentencing models, and the roles of various agencies. Ideal for A-Level revision, ensuring you grasp essential theories and legislative processes to excel in your exams.
Sociology of Education Overview
Explore comprehensive A-Level Sociology notes on the education system, covering key theories, policies, and sociological perspectives. This resource includes insights on marketisation, gender roles, cultural deprivation, and educational inequalities, providing a thorough understanding of how education shapes social stratification and individual achievement. Ideal for exam preparation and in-depth study.
Cell Biology and Cell structure
cell structures
WJEC Unit 4 Criminology
Criminology unit 4 detailed revision note
Language Paper 1 Strategies
Master the AQA English Language Paper 1 with this comprehensive guide. Explore key strategies for language and structural analysis, critical evaluation, and creative writing. Learn how to effectively analyze texts, utilize literary techniques, and enhance your writing skills to excel in your exams.
Media Studies: Key Concepts & Theories
Dive into the essential concepts and theories of media studies for AQA A-level Sociology. This comprehensive revision guide covers topics such as media influence, representations, globalization, and sociological perspectives, ensuring you grasp the critical elements needed for your exams. Perfect for students seeking to enhance their understanding of media's role in society.
Sociological Theories Overview
Comprehensive revision of key sociological theories including Functionalism, Marxism, Feminism, and Interpretivism. Explore concepts like value freedom, identity formation, and the critique of social control. Ideal for AQA A-Level Sociology students preparing for exams. This summary covers essential theories and their implications in sociology, providing a clear understanding of each perspective.
Students love us — and so will you.
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.