I don't understand why the answer is "C". Isn't it true that an E2 reactions typically require primary or secondary alkyl halides, then why would the tertiary halide be the most reactive?!
please help! Thanks 🙂
Edit: Quick thing, E2 can react with tertiary, secondary, or primary alkyl halides, typically they react with tertiary > secondary though. Explanation below.
First off, we aren't going to worry about what might be reacting with our substrates, our reactivity will solely be based on the substrate and its leaving group in this problem (assume a strong base, since it is required).
Okay, our substrate or electrophile. What do we want with E2? We want to form the most substituted alkene possible (most stable). So looking at our choices, "A" clearly forms the most substituted alkene (more substituted alkyl halide, more substituted alkene usually). So we automatically know "A" is most reactive.
Remember we aren't worried about attacking like in Sn2, thus we aren't worried about steric hindrance. Next are our two secondary alkyl halides (B and C), which has the better leaving group? Iodine, so our order is now A>B>C. Same thing with choices D and E, Bromine is the better leaving halide than Chlorine, so our answer is "C".
Anyway, the key point to remember here is that with E2 you want the most substituted alkene product possible.
Cheers
