Keep coming back to the curly arrow concept, in terms of reinforcing it in different contexts. For a first-year course that’s about 20 lectures, introduce the curly arrow concept in lectures four to seven, then revisit it every lecture thereafter. For 13 or 14 lectures, it would come up in some different form - different examples, different ways of using it, referring back to the original concepts, reiterating the vocabulary, the language that's being used.
Try to encourage active learning in the lecture theatre. Talk about a concept and then ask them to look at some examples and work through them on their own.
There could be five “different” reactions, but actually they are the same core mechanism. If they can identify an electrophile and a nucleophile and how they get together in a particular context, then they understand all five of the reactions and another 55 too, if they choose to. The ultimate goal is that they have a skill-set, a set of tools, that allows them to meet any reaction, even reactions they have not seen before, and apply the concepts, use the tools, and get a handle on what is actually happening.
They're learning a new language as well as new concepts. There's a lot of vocabulary - terms like electrophile and nucleophile and many others. So it’s about learning the language, learning the curly arrow code that we use, and then starting to apply that in half a dozen different contexts.
Explain partial charges, with problems, then link this to bond polarity. Explain the differences in arrows 'language'. Draw organic structures as line structures and no stereochemistry (until you discuss that). Make stoichiometry explicit and link the structures to names to build on the concepts.
Re-teach electronegativity quickly because you don't necessarily trust the person who's taught before you. Make sure that it's reiterated, and then follow through to bond polarity and partial charges. Include all of that information first before going on to do reaction mechanisms. So the first thing to do is draw in partial charges to identify the electrophile and the nucleophile before going on to the next step. It's about doing examples all the way from first principles to build up those concepts.
Do many examples, on the projector or board, from first principles. Start with partial charges and identification of the nucleophile and electrophile, then draw in arrows.
Use a lot of demonstrations - actually doing reactions at the front of the class. You can't actually see the electrons moving when you're doing the reaction, but still it helps to use demonstrations. Beware of possible misinterpretations that could arise when doing demonstrations.
