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I am doing the Edexcel Chemistry (Nuffield) exams. I'm about to do my exams in a couple of weeks and have been trying to get to grips with organic chemistry but I'm still very confused. We've been given a flow chart diagram by our teacher but he says it has too much on it and I'm trying to work out what I can cut out of it. Concerning the amines, what reactions do we need to know - is it just the substitution of a primary amine to a primary alcohol and the reaction of a primary amine with a halogenoalkane to form a secondary amine?
Jenkin says:
Essentially, what is in the Nuffield text is examinable (because this represents what is in the specification), but for paper 6 you have the book with you, so you can check reactions. This is, of course, not the case for paper 4 which could include questions on carboxylic acids and their derivatives.
For amines, you should be aware of their alkaline nature and so reactions with acids, their formation of complexes with copper(II) ions and their reactions with halogenoalkanes and with ethanoyl chloride.
Next, the amides .... other than how they are formed from acyl chloride and amine reactions do we actually need to know any reactions of the amides?
Jenkin: No, this all you are expected to know about amides for Chemistry (Nuffield).
Do we need to know about the formation of acyl chlorides from carboxylic acids?
Jenkin: No. But you should revise experiment 15.3 (part 2 deals with reactions of an acyl chloride) and the summary of reactions following this experiment.
Finally, where do acid anhyrdides fit in? What exactly are they and how much do we need to know about them?
Jenkin: The only place in the Nuffield course where you should have encountered acid anhydrides is in the preparation of aspirin (experiment 12.5). Here, ethanoic anhydride is used for the ethanoylation of phenol: it is more reactive than ethanoic acid but less so than ethanoyl chloride so the reaction is more easily controlled.
Acid anhydrides can be thought of molecules formed when 2 molecules of a carboxylic acid eliminate 1 molecule of water between them so that the two acid ‘fragments’ are joined by a - CO – O – OC - linkage. So ethanoic anhydride is CH3-CO-O-CO-CH3.
Check the Edexcel Chemistry (Nuffield) specification and look back at past papers for guidance on what to expect in the exams.
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updated: 02 June 2006
