Chemistry A level organic help

Hey everyone, I have a test on organic synthesis in 10 days, and I often get stuck on manny questions. What would you recommend for revision? There’s a lot to memorize, and I find it difficult to keep track of everything since it's all interconnected.

Reply 1

Tamata1

6

I’d recommend going over amines, and aromatics (like benzene), and acyl chlorides, cos the majority of synthesis questions are to do with those reaction types (for AQA at least). so make sure that u know freidal crafts acylation well, electrophillic substitution, nucleophilic addition-elimination mechanisms. I’ve seen free radical substitution come up alot, so if you see that a hydrocarbon chain has just randomly gained a Cl, it’s most likely free radical substitution. I recommend going into chemrevise.org -> AQA revision guides -> organic synthesis. you get a pdf with all the reaction pathways :smile:

Reply 2

Silence22222

OP

10

Original post by Tamata1

I’d recommend going over amines, and aromatics (like benzene), and acyl chlorides, cos the majority of synthesis questions are to do with those reaction types (for AQA at least). so make sure that u know freidal crafts acylation well, electrophillic substitution, nucleophilic addition-elimination mechanisms. I’ve seen free radical substitution come up alot, so if you see that a hydrocarbon chain has just randomly gained a Cl, it’s most likely free radical substitution. I recommend going into chemrevise.org -> AQA revision guides -> organic synthesis. you get a pdf with all the reaction pathways :smile:

Thank you very much! I’ll take some of the advice on board now and save the rest for next year. Sorry, I forgot to mention that I’m in Year 12. I don’t think we’ve covered benzene rings yet. Do you have any specific recommendations for Year 12 organic synthesis?

Reply 3

Tamata1

6

Original post by Silence22222

Thank you very much! I’ll take some of the advice on board now and save the rest for next year. Sorry, I forgot to mention that I’m in Year 12. I don’t think we’ve covered benzene rings yet. Do you have any specific recommendations for Year 12 organic synthesis?

ahhh ok no worries. ok so benzene and amines are part of year 2 so u don’t worry about those. I would recommend going into chemrevise.org -> AQA revision guides -> mechanisms summary AS, and if you scroll to the last page of the pdf, you will see all the reaction pathways that you need to know in year 12. then go to quizlet and for each reaction pathway, make a flash card. For example, if you want to know how to get from a halogenoalkane to an alcohol, on the front of the card write “halogenoalkane -> alcohol” and on the back write “KOH aqueous, nucleophilic substitution”. do this for each pathway, and go over them every morning and evening until ur exam. make sure to learn your mechanisms as well- you can do that by just going on revisely.com and doing some exam questions for each mechanism, refer back to ur chemrevise pdf if u feel like u forgot the mechanism. if u stick to this, an A /A* is VERY achievable. lmk if u have any more questions.

Reply 4

TypicalNerd

18

Original post by Silence22222

Hey everyone, I have a test on organic synthesis in 10 days, and I often get stuck on manny questions. What would you recommend for revision? There’s a lot to memorize, and I find it difficult to keep track of everything since it's all interconnected.

Which exam board are you with?

Reply 5

Silence22222

OP

10

Original post by TypicalNerd

Which exam board are you with?

Ocr

Reply 6

Silence22222

OP

10

Original post by Tamata1

ahhh ok no worries. ok so benzene and amines are part of year 2 so u don’t worry about those. I would recommend going into chemrevise.org -> AQA revision guides -> mechanisms summary AS, and if you scroll to the last page of the pdf, you will see all the reaction pathways that you need to know in year 12. then go to quizlet and for each reaction pathway, make a flash card. For example, if you want to know how to get from a halogenoalkane to an alcohol, on the front of the card write “halogenoalkane -> alcohol” and on the back write “KOH aqueous, nucleophilic substitution”. do this for each pathway, and go over them every morning and evening until ur exam. make sure to learn your mechanisms as well- you can do that by just going on revisely.com and doing some exam questions for each mechanism, refer back to ur chemrevise pdf if u feel like u forgot the mechanism. if u stick to this, an A /A* is VERY achievable. lmk if u have any more questions.

Thank you very much 👑
Thank you for your advice. I shall start from today. And see how things go

Reply 7

TypicalNerd

18

Original post by Silence22222

Ocr

https://www.ocr.org.uk/Images/359182-organic-synthesis-reaction-pathways.pdf

You won’t need absolutely everything from this for year 12 - any reactions of aldehydes, ketones, amines, nitriles, carboxylic acids, acyl chlorides and esters can be ignored (except for the oxidation of aldehydes by K2Cr2O7 and an acid under reflux to give a carboxylic acid). I believe you don’t need to be aware of the synthesis of amines or nitriles by any means, even nucleophilic substitution onto a haloalkane.

You also need not worry about benzene and phenol.

At AS level, you’ll be pleased to know that any synthetic chemistry questions are at most two steps, so the most complex sort of question they could ask is how to convert ethene to ethanoic acid in two steps (i.e. 1. hydrate using steam and conc H3PO4, 2. oxidise by heating under reflux with K2Cr2O7 and H2SO4).

There are a few synthetic techniques being worth aware of. The specification outlines use of separatory funnels to do a liquid-liquid extraction, drying with anhydrous CaCl2 or MgSO4 and redistillation. These are all techniques used to purify an organic liquid and it’s worth learning how they are done and that they often are carried out in conjunction.

(1. After a synthesis is carried out, if the reaction mixture or crude product is a liquid, add an immiscible solvent (often water) and transfer to a separatory funnel. Deduce which layer is which based on density (the upper layer is the least dense - if water is used, 9 times out of 10, the upper layer is the organic layer but halogenated alkanes tend to be denser than water and so comprise the lower layer). Cap, shake and vent the separatory funnel , allow the layers to separate again and then drain off each layer. This is often repeated several times.

(2. Take the organic layer and add a healthy amount of anhydrous MgSO4 or anhydrous CaCl2. Stir and check if the powder is clumpy. If it forms clumps, add more drying agent and stir again until there is no further clumping. Whenever the clumping stops, conduct a gravity filtration and collect the filtrate.

(3. Redistill the filtrate, but only collect anything that comes over within 1 or 2°C of the literature boiling point.

Chemistry A level organic help

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