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Chemistry
INTRO TO ORGANIC CHEM | AQA AS Organic Chemistry
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9 Dec 2025
•
Understanding AQA AS Organic Chemistry: Basics and Key Topics
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Introduction to Organic Chemistry and Naming Rules
Understanding molecular formulae is your first step into organic chemistry. You'll encounter different types: empirical (simplest ratio), molecular (actual numbers of atoms), structural (showing connections), displayed (every bond drawn), and skeletal (simplified diagrams). Think of these as different ways to describe the same molecule - like giving directions using a map versus landmarks.
Homologous series are families of compounds that share the same functional group - the bit that makes them react in similar ways. Each series has its own general formula, making it dead easy to work out molecular formulae once you know the pattern.
The IUPAC naming system follows simple rules that work like a code. Start with the stem based on carbon count, then add the ending based on the functional group .
Quick Tip: Always find the longest carbon chain that includes the functional group - that's your main stem. Number carbons to give the functional group the lowest possible number.
Isomerism - Same Formula, Different Arrangements
Structural isomers have identical molecular formulae but completely different atom arrangements. You'll spot three types: chain isomers (straight vs branched), position isomers (functional group in different spots), and functional group isomers (different functional groups entirely). It's like having the same Lego pieces but building different models.
Stereoisomers are trickier - same formula and functional groups, but atoms arranged differently in 3D space. This happens around double bonds because they can't rotate freely like single bonds.
E/Z isomerism occurs at double bonds where you compare the positions of the largest groups. Z means the big groups are on the "zame zide" (same side), while E means they're on opposite sides. For complex molecules, use CIP rules - rank the four atoms directly attached to the double bond by atomic mass, then see if the top two priorities are together (Z) or apart (E).
Memory Trick: "Z = Zame Zide" - the two highest priority groups are on the same side of the double bond.
Reaction Mechanisms and Free Radicals
Reaction mechanisms show exactly how bonds break and form during chemical reactions. They're like step-by-step instructions for molecular transformations, helping you predict what happens when molecules collide.
Curly arrows are your best mates for showing electron movement. These arrows always show where electron pairs go - either forming new bonds or breaking existing ones. Master these, and you'll understand why reactions happen the way they do.
Free radicals are highly reactive molecules with unpaired electrons, shown with a dot. They're incredibly unstable and will react with almost anything to pair up that lonely electron. Think of them as molecular desperados looking for a partner.
Key Point: Curly arrows always show electron pair movement - never just point randomly between atoms. Follow the electrons, and you'll follow the reaction.
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Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
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This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
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The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
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In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
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very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
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I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
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THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
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.
Stefan S
iOS user
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.
Samantha Klich
Android user
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.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Understanding AQA AS Organic Chemistry: Basics and Key Topics
B
bv
@bv
Organic chemistry might seem overwhelming at first, but it's actually just about learning how to name molecules and understand how they behave. Once you get the hang of the naming rules and can spot different types of isomers, you'll find... Show more
Introduction to Organic Chemistry and Naming Rules
Understanding molecular formulae is your first step into organic chemistry. You'll encounter different types: empirical (simplest ratio), molecular (actual numbers of atoms), structural (showing connections), displayed (every bond drawn), and skeletal (simplified diagrams). Think of these as different ways to describe the same molecule - like giving directions using a map versus landmarks.
Homologous series are families of compounds that share the same functional group - the bit that makes them react in similar ways. Each series has its own general formula, making it dead easy to work out molecular formulae once you know the pattern.
The IUPAC naming system follows simple rules that work like a code. Start with the stem based on carbon count, then add the ending based on the functional group .
Quick Tip: Always find the longest carbon chain that includes the functional group - that's your main stem. Number carbons to give the functional group the lowest possible number.
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Isomerism - Same Formula, Different Arrangements
Structural isomers have identical molecular formulae but completely different atom arrangements. You'll spot three types: chain isomers (straight vs branched), position isomers (functional group in different spots), and functional group isomers (different functional groups entirely). It's like having the same Lego pieces but building different models.
Stereoisomers are trickier - same formula and functional groups, but atoms arranged differently in 3D space. This happens around double bonds because they can't rotate freely like single bonds.
E/Z isomerism occurs at double bonds where you compare the positions of the largest groups. Z means the big groups are on the "zame zide" (same side), while E means they're on opposite sides. For complex molecules, use CIP rules - rank the four atoms directly attached to the double bond by atomic mass, then see if the top two priorities are together (Z) or apart (E).
Memory Trick: "Z = Zame Zide" - the two highest priority groups are on the same side of the double bond.
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Reaction Mechanisms and Free Radicals
Reaction mechanisms show exactly how bonds break and form during chemical reactions. They're like step-by-step instructions for molecular transformations, helping you predict what happens when molecules collide.
Curly arrows are your best mates for showing electron movement. These arrows always show where electron pairs go - either forming new bonds or breaking existing ones. Master these, and you'll understand why reactions happen the way they do.
Free radicals are highly reactive molecules with unpaired electrons, shown with a dot. They're incredibly unstable and will react with almost anything to pair up that lonely electron. Think of them as molecular desperados looking for a partner.
Key Point: Curly arrows always show electron pair movement - never just point randomly between atoms. Follow the electrons, and you'll follow the reaction.
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What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
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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.
Stefan S
iOS user
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.
Samantha Klich
Android user
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.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
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.
Stefan S
iOS user
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.
Samantha Klich
Android user
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.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user