How can you identify enantiomers?

Just how do you distinguish your left hand from your right hand? It is something that now is intuitively obvious. Nevertheless, if someone else was coming towards you, you might think twice before identifying his left hand, which of course is on the side of your right hand. I live in the UK at the moment, and given the channel tunnel, there are occasions when you use a right hand drive on left hand lanes, and vice versa when car and trucks come from the continent to Britain. Mistakes often occur with experienced drivers. It is all too easy to do.

Anyway, I can offer you one tip with regard to stereoisomers. Given a model (which you must build!) of a chiral centre that is correct, say #CR_1R_2R_3R_4#. Say that this is correct (and you must satisfy yourself of this!). The interchange of any 2 groups, #R_1# for #R_2#, #R_2# for #R_4#, (I stress any two!) results in the enantiomer. By this reasoning, if we interchange again (of course this may be the original two groups, but not necessarily) we get back the original isomer.

But remember if you don't use models you are shooting yourself in the foot. And you have to practise how to represent these models on the printed page. Good luck.