One mistake that a lot of students make when learning the A-Level Chemistry organic reactions is focusing too much on the mechanisms and not learning everything else about the reaction, such as the reagents needed, the minor products and the equation.
To stop the students I tutor falling into this trap, I teach them a 6 step framework for learning the A-Level Chemistry organic reactions. This acts as a checklist to make sure they’ve got notes on everything that they need to know about each reaction and organises the key points into memorable ‘chunks’ to make it much easier to remember.
Follow these 6 steps and you’ll be an expert at the A-Level Chemistry organic reactions in no time at all:
1. The name of the mechanism and the type of reaction
The mechanism name describes how the reaction takes place. E.g. Nucleophilic substitution involves a nucleophile bonding to a delta positive carbon, which leads to a group being removed from the carbon.
The type of reaction just describes the outcome, e.g. reduction.
You will need to know either one of these or both of these for each reaction. E.g. for the removal of water from an alcohol to form an alkene the mechanism name is elimination and the type of reaction is dehydration.
In the exam, you’ll often be asked to name the reaction. Double check whether they want the mechanism name of the type of reaction – just putting one or the other without really thinking about it is a really common mistake.
2. The full balanced equation
Be ready to write a full equation or an ionic equation (where relevant) and pay attention to state symbols.
3. The products
Although the products are in the equation I’ve given them a separate category for 2 reasons:
1.The full balanced equation includes products, but that’s not the end of the story. An organic reaction may have possible products that aren’t accounted for in the equation. These may be the products of further substitutions, major and minor products or isomeric products.
2. I often find that students know what the main organic product is but completely forget about the other product (e.g. NaCl) so I include the products category as a reminder.
4. The reagents and conditions
The reagents are any reactants in addition to the organic reactant. A common mistake is to be a little too vague about the reagent. For example, if the reagent is NaOH, students often lose marks for just putting hydroxide. You’ll get away with just putting hydroxide in the equation, but for the reagent you would have to give NaOH to get the mark.
The best way to think about reagents is this: the reagent is the substance you would actually get out of the cupboard and add to the mixture. You couldn’t go to the cupboard and get a bottle of hydroxide ions, you would have to get a bottle of NaOH solution, so that’s the reagent.
The conditions you should look out for any specific temperatures, procedures such as reflux or distillation, catalysts, and solvents.
Make sure you lean these from the exam board endorsed textbook. You’ll see a different combination of reagents and conditions in pretty much every textbook you look in, so it’s important that you learn the ones the exam board expects you to know.
5. The mechanism (equations or curly arrows)
This one speaks for itself. When you’re learning the mechanism try to avoid blinding rote learning them – rote learning them rarely ends well. Make sure you understand why the arrows go the way they’re going and what happens at each step and practice talking yourself through it so that you can work out whether you’ve done it correctly and catch your mistakes.
Not all of the reactions that you need to know about actually have a mechanism (e.g. hydrogenation of alkenes) so make sure you don’t forget about these.
6. Anything else?
In this category, you should include anything else that doesn’t fit into the other categories. For example, if you’re making notes on the nucleophilic substitution of halogenoalkanes with ammonia you may want to include notes on how to prevent further substitutions.
You can also include some notes on exam technique that you’ve noticed from the marks schemes (e.g. which parts of the mechanisms are awarded a mark) and notes to remind you about things you often forget.