Question

A chiral C5H10O ether reacts with excess hot HI to give a C5H10I2 product. When this product is treated with KOH, 1,3-pentadiene is produced. What is the structure of the starting ether

Answer 1

Answer:

See answer and picture below

Explanation:

In this case, the key to get an idea of how is the starting ether is with the final product and the empirical formula of the ether.

First, the empirical formula of the ether gives us information of the structure of the ether. This ether could be either an alkene, alkane or cycloalkane.

Alkane cannot be because alkane's formula is CnH(2n+2), so it's either an alkene or cycloalcane (CnH2n).

However, as we can see, it reacts with HI in excess, so, it cannot be an alkene because in this case the acid will react with the double bond of the ether too forming another product. This discart the fact that the ether has a double bond. So it has to be a cycloalkane.

As the innitial structure it's an ether, it should be either a cyclohexane or cyclopentane with a methyl group attached. So, how can we know which of these structures is? well, we can actually do the reaction with both reactants and see which match. In the attached picture you have the answer.

Hope this helps.