Why are E1 reactions generally not used to synthesize alkenes?

Answer 1

E1 reactions proceed through carbonium ions. Carbonium ions resulting from particular carbon skeletons/derivatives are unique. Once the carbonium ion forms, it has a characteristic tendency to eliminate to an olefin, or to hydrate or solvate to an alcohol or an ether. So you can't control how much olefin, alcohol, or ether you'll get.

On the other hand, if the substrate is really cheap, like cyclohexanol, then an E1 reaction is the way to go, because you'll get cheap cyclohexene regardless of what ever else you have to put up with.

Answer 2

In E1 reactions only 1 bond is broken..... remember the formation of an alkene requires the making of a double bond, there fore two bonds need to be broken (eg. in E2 reactions)