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Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
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Chemistry
9 Dec 2025
141
2 pages
Isabelle @isabelle_study
Halogenoalkanes are organic compounds where halogens replace hydrogen atoms, creating polar molecules that undergo two key reactions. Understanding... Show more
Ever wondered why some organic reactions happen so predictably? Halogenoalkanes contain polar bonds because halogens are more electronegative than carbon atoms. This creates regions with partial positive (δ+) and negative (δ-) charges that make reactions possible.
Nucleophiles are your best friends in organic chemistry - they're molecules or ions with lone electron pairs that love attacking positive regions. Common ones include CN⁻, NH₃, and OH⁻, and they're absolutely essential for making new compounds.
Nucleophilic substitution lets you transform halogenoalkanes into useful products like alcohols and amines. The nucleophile simply replaces the halogen atom, creating entirely new functional groups. This reaction only works with primary and secondary halogenoalkanes - tertiary ones behave differently.
Key Point The polar C-X bond is what makes nucleophilic substitution possible - without it, nucleophiles wouldn't be attracted to attack the carbon atom.
Sometimes halogenoalkanes don't substitute - they eliminate instead! Under high temperature with alcoholic conditions, nucleophiles act as bases rather than substitution agents. They grab a hydrogen atom, forcing the molecule to form a carbon-carbon double bond and create an alkene.
This elimination mechanism only occurs with secondary and tertiary halogenoalkanes. The base removes a proton whilst the halogen leaves, resulting in a new double bond formation.
But here's the environmental twist - halogenoalkanes like CFCs are seriously damaging our ozone layer. When UV radiation breaks their carbon-halogen bonds, free radicals form that catalyse ozone destruction. Just one chlorine radical can destroy thousands of ozone molecules!
Thankfully, CFC-free solvents are now being developed to prevent atmospheric damage. This shift helps minimise both ozone depletion and global warming - showing how chemistry directly impacts environmental protection.
Environmental Alert The same UV absorption that makes CFCs useful also makes them incredibly destructive to our protective ozone layer.
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.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
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Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the mechanisms of electrophilic substitution in benzene, including nitration, halogenation, Friedel-Crafts alkylation, and acylation. This summary covers key reactions, catalysts, and general equations essential for understanding aromatic chemistry. Ideal for students studying organic chemistry.
ChemistryExplore 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.
ChemistryExplore essential organic synthesis techniques including nucleophilic addition, reduction, and esterification. This summary covers key reactions involving hydrogen halides, sodium cyanide, and various reagents like NaBH4 and KrCrO7, tailored for OCR A Level Chemistry students. Enhance your understanding of organic chemistry with practical examples and reaction mechanisms.
ChemistryExplore the key mechanisms of electrophilic and nucleophilic reactions in benzene, including Friedel-Crafts acylation and alkylation. This summary covers essential organic reactions and their mechanisms, tailored for A-Level Chemistry students, particularly those following the OCR B Salters syllabus.
ChemistryExplore the key concepts of aromatic chemistry, including the structure and reactivity of benzene, electrophilic substitution mechanisms, and the role of delocalized electrons. This summary covers nitration and Friedel-Crafts reactions, comparing the reactivity of alkenes and arenes, and the unique properties of phenols. Ideal for A-Level organic chemistry students.
ChemistryExplore the mechanisms of nucleophilic substitution reactions in haloalkanes, including hydrolysis processes and bond enthalpy. This summary covers primary, secondary, and tertiary haloalkanes, common nucleophiles, and environmental impacts of organohalogen compounds. Ideal for A Level organic chemistry students.
ChemistryApp Store
Google Play
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
Isabelle
@isabelle_study
Halogenoalkanes are organic compounds where halogens replace hydrogen atoms, creating polar molecules that undergo two key reactions. Understanding these reactions and their environmental impact is crucial for A-level chemistry success.
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ever wondered why some organic reactions happen so predictably? Halogenoalkanes contain polar bonds because halogens are more electronegative than carbon atoms. This creates regions with partial positive (δ+) and negative (δ-) charges that make reactions possible.
Nucleophiles are your best friends in organic chemistry - they're molecules or ions with lone electron pairs that love attacking positive regions. Common ones include CN⁻, :NH₃, and :OH⁻, and they're absolutely essential for making new compounds.
Nucleophilic substitution lets you transform halogenoalkanes into useful products like alcohols and amines. The nucleophile simply replaces the halogen atom, creating entirely new functional groups. This reaction only works with primary and secondary halogenoalkanes - tertiary ones behave differently.
Key Point: The polar C-X bond is what makes nucleophilic substitution possible - without it, nucleophiles wouldn't be attracted to attack the carbon atom.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Sometimes halogenoalkanes don't substitute - they eliminate instead! Under high temperature with alcoholic conditions, nucleophiles act as bases rather than substitution agents. They grab a hydrogen atom, forcing the molecule to form a carbon-carbon double bond and create an alkene.
This elimination mechanism only occurs with secondary and tertiary halogenoalkanes. The base removes a proton whilst the halogen leaves, resulting in a new double bond formation.
But here's the environmental twist - halogenoalkanes like CFCs are seriously damaging our ozone layer. When UV radiation breaks their carbon-halogen bonds, free radicals form that catalyse ozone destruction. Just one chlorine radical can destroy thousands of ozone molecules!
Thankfully, CFC-free solvents are now being developed to prevent atmospheric damage. This shift helps minimise both ozone depletion and global warming - showing how chemistry directly impacts environmental protection.
Environmental Alert: The same UV absorption that makes CFCs useful also makes them incredibly destructive to our protective ozone layer.
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.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
8
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the mechanisms of electrophilic substitution in benzene, including nitration, halogenation, Friedel-Crafts alkylation, and acylation. This summary covers key reactions, catalysts, and general equations essential for understanding aromatic chemistry. Ideal for students studying organic chemistry.
ChemistryExplore 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.
ChemistryExplore essential organic synthesis techniques including nucleophilic addition, reduction, and esterification. This summary covers key reactions involving hydrogen halides, sodium cyanide, and various reagents like NaBH4 and KrCrO7, tailored for OCR A Level Chemistry students. Enhance your understanding of organic chemistry with practical examples and reaction mechanisms.
ChemistryExplore the key mechanisms of electrophilic and nucleophilic reactions in benzene, including Friedel-Crafts acylation and alkylation. This summary covers essential organic reactions and their mechanisms, tailored for A-Level Chemistry students, particularly those following the OCR B Salters syllabus.
ChemistryExplore the key concepts of aromatic chemistry, including the structure and reactivity of benzene, electrophilic substitution mechanisms, and the role of delocalized electrons. This summary covers nitration and Friedel-Crafts reactions, comparing the reactivity of alkenes and arenes, and the unique properties of phenols. Ideal for A-Level organic chemistry students.
ChemistryExplore the mechanisms of nucleophilic substitution reactions in haloalkanes, including hydrolysis processes and bond enthalpy. This summary covers primary, secondary, and tertiary haloalkanes, common nucleophiles, and environmental impacts of organohalogen compounds. Ideal for A Level organic chemistry students.
ChemistryApp Store
Google Play
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
Sociology