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melody!
09/12/2025
Chemistry
carbonyl compounds (ketones and aldehydes) revision notes
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9 Dec 2025
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Comprehensive Revision Notes on Ketones and Aldehydes
melody!
@melodyxmc
1 / 4
Carbonyl Compounds: Aldehydes & Ketones
The carbonyl functional group is like the heart of these compounds, determining their properties and behaviour. Think of it as a molecular hotspot that makes these substances incredibly reactive and useful.
Aldehydes always have their C=O at the end of a carbon chain, with names ending in -al. Methanal (formaldehyde) is probably the most famous example - it's what preserves biological specimens in those jars you see in science labs. The carbonyl carbon is always labelled as carbon-1, making naming straightforward.
Ketones have their C=O sandwiched between two carbon atoms, with names ending in -one. Propanone (acetone) is your everyday nail polish remover and industrial solvent. Unlike aldehydes, you need to number the position of the ketone group in longer chains.
Key Difference: Only aldehydes can be oxidised to carboxylic acids using acidified dichromate - ketones simply won't budge under these conditions!
Nucleophilic Addition Reactions
Here's where carbonyls get really interesting - their polar C=O bond makes them sitting targets for chemical attacks. Unlike alkenes with their non-polar double bonds, carbonyls have a sneaky trick up their sleeve.
Oxygen's higher electronegativity creates a polar bond where oxygen becomes slightly negative (δ-) and carbon becomes slightly positive (δ+). This polarity is like a chemical magnet that attracts nucleophiles to the positive carbon atom.
Reducing carbonyls with NaBH₄ (sodium borohydride) is a classic reaction you'll definitely encounter. Aldehydes become primary alcohols, whilst ketones become secondary alcohols. The reaction happens when you warm the carbonyl with NaBH₄ in water - simple but effective.
Remember: Aldehydes → Primary alcohols, Ketones → Secondary alcohols. The pattern never changes!
This nucleophilic addition mechanism explains why carbonyls are so reactive compared to their alkene cousins.
Hydrogen Cyanide Addition
Adding HCN (hydrogen cyanide) to carbonyls might sound scary (it's extremely poisonous!), but it's actually a brilliant way to extend carbon chains. In the lab, we use H₂SO₄ and NaCN to generate the HCN safely.
The product is always a hydroxynitrile - a molecule containing both a hydroxyl group and a nitrile group . This dual functionality makes these compounds incredibly versatile for further reactions.
The nucleophilic addition mechanism follows a predictable pattern. The electron-deficient carbon in C=O acts like a molecular vacuum, sucking in nucleophiles. With NaBH₄, the hydride ion (H⁻) does the attacking.
Mechanism Tip: Always remember the three steps - nucleophile attacks δ+ carbon, π bond breaks, then protonation occurs!
The intermediate formed is negatively charged and unstable, desperately seeking a proton to become a stable alcohol product.
Cyanide Addition Mechanism
The cyanide ion (CN⁻) mechanism is slightly trickier than the hydride reduction, but follows the same fundamental pattern. The cyanide's lone pair of electrons can't resist that electron-deficient carbon atom.
Step-by-step: CN⁻ donates its lone pair to the δ+ carbon, forming a dative covalent bond. The C=O π bond breaks through heterolytic fission, creating a negatively charged intermediate that's eager for stabilisation.
Protonation is the final step where the intermediate grabs a hydrogen ion, transforming into the final hydroxynitrile product. The beauty of this reaction is that you've successfully added an extra carbon to your chain whilst introducing two new functional groups.
Pro Tip: The negative charge in the intermediate is actually on the carbon atom of the cyanide group - this detail often trips students up in exams!
This mechanism demonstrates why carbonyls are such versatile starting materials in organic synthesis - their predictable reactivity makes them perfect building blocks for more complex molecules.
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Comprehensive Revision Notes on Ketones and Aldehydes
melody!
@melodyxmc
Ever wondered why nail polish remover works so effectively, or what makes certain chemicals smell so distinctive? Welcome to the world of carbonyls and carboxylic acids - organic compounds that contain the powerful C=O double bond and play crucial roles... Show more
Carbonyl Compounds: Aldehydes & Ketones
The carbonyl functional group is like the heart of these compounds, determining their properties and behaviour. Think of it as a molecular hotspot that makes these substances incredibly reactive and useful.
Aldehydes always have their C=O at the end of a carbon chain, with names ending in -al. Methanal (formaldehyde) is probably the most famous example - it's what preserves biological specimens in those jars you see in science labs. The carbonyl carbon is always labelled as carbon-1, making naming straightforward.
Ketones have their C=O sandwiched between two carbon atoms, with names ending in -one. Propanone (acetone) is your everyday nail polish remover and industrial solvent. Unlike aldehydes, you need to number the position of the ketone group in longer chains.
Key Difference: Only aldehydes can be oxidised to carboxylic acids using acidified dichromate - ketones simply won't budge under these conditions!
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Nucleophilic Addition Reactions
Here's where carbonyls get really interesting - their polar C=O bond makes them sitting targets for chemical attacks. Unlike alkenes with their non-polar double bonds, carbonyls have a sneaky trick up their sleeve.
Oxygen's higher electronegativity creates a polar bond where oxygen becomes slightly negative (δ-) and carbon becomes slightly positive (δ+). This polarity is like a chemical magnet that attracts nucleophiles to the positive carbon atom.
Reducing carbonyls with NaBH₄ (sodium borohydride) is a classic reaction you'll definitely encounter. Aldehydes become primary alcohols, whilst ketones become secondary alcohols. The reaction happens when you warm the carbonyl with NaBH₄ in water - simple but effective.
Remember: Aldehydes → Primary alcohols, Ketones → Secondary alcohols. The pattern never changes!
This nucleophilic addition mechanism explains why carbonyls are so reactive compared to their alkene cousins.
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Hydrogen Cyanide Addition
Adding HCN (hydrogen cyanide) to carbonyls might sound scary (it's extremely poisonous!), but it's actually a brilliant way to extend carbon chains. In the lab, we use H₂SO₄ and NaCN to generate the HCN safely.
The product is always a hydroxynitrile - a molecule containing both a hydroxyl group and a nitrile group . This dual functionality makes these compounds incredibly versatile for further reactions.
The nucleophilic addition mechanism follows a predictable pattern. The electron-deficient carbon in C=O acts like a molecular vacuum, sucking in nucleophiles. With NaBH₄, the hydride ion (H⁻) does the attacking.
Mechanism Tip: Always remember the three steps - nucleophile attacks δ+ carbon, π bond breaks, then protonation occurs!
The intermediate formed is negatively charged and unstable, desperately seeking a proton to become a stable alcohol product.
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Cyanide Addition Mechanism
The cyanide ion (CN⁻) mechanism is slightly trickier than the hydride reduction, but follows the same fundamental pattern. The cyanide's lone pair of electrons can't resist that electron-deficient carbon atom.
Step-by-step: CN⁻ donates its lone pair to the δ+ carbon, forming a dative covalent bond. The C=O π bond breaks through heterolytic fission, creating a negatively charged intermediate that's eager for stabilisation.
Protonation is the final step where the intermediate grabs a hydrogen ion, transforming into the final hydroxynitrile product. The beauty of this reaction is that you've successfully added an extra carbon to your chain whilst introducing two new functional groups.
Pro Tip: The negative charge in the intermediate is actually on the carbon atom of the cyanide group - this detail often trips students up in exams!
This mechanism demonstrates why carbonyls are such versatile starting materials in organic synthesis - their predictable reactivity makes them perfect building blocks for more complex molecules.
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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
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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