[WilliamYWT]

I've come across this question when I was studying.

The chlorination of propane under diffuse sunlight gave four dichloro products C₃H₆Cl₂ - A, B, C and D. Each of the products was further chlorinated and the trichloro products C₃H₅Cl₃ were formed and analysed. It was found that A gave one trichloro product, B gave two, while C and D gave three. Nevertheless, compound C is optically active while D is not. Suggest the structural formulae and names of A-D.

I've found that A is 2,2-dichloropropane, B is 1,3-dichloropropane and C and D would be 1,1-dichloropropane or 1,2-dichloropropane, one or another, so I want to ask what does optically active really mean so I can figure out the answer of this question, thank you for reading this.

P.S. If you don't mind, I want to know what is the fastest way to come across such questions, e.g. how many structural isomers would C₃H₅Cl₃ have, drawing the structures one by one would be too time-consuming in exam.

[Dan]

If something is optically active, it is chiral.