Identify any carbon atoms that change hybridization and the change in hybridization during the reactions in Exercise 20.39.

a) 2-butene is an alkene that has 4 carbon atoms in a straight chain while a double bond exists between carbon atoms 2 and \(3.\)

Since there is a double bond and water molecule, we can assume that water will be added to the double bond.

This reaction follows Markovnikov's rule, which says that the H atom is added to the less substituted carbon atom.

Acid serves as a catalyst in this reaction.

Then, the OH group is added to a more substituted carbon atom - in this case, it's either one because alkene is symmetrical and equally substituted.

The reactions with Lewis structures and condensed molecular formulas

Reaction (a)

The two carbon atoms in the middle that share a double bond are\(s{p^2}\)hybridized because of the planar arrangement that the double bond causes.

On the other hand, as they react, they tend to have 4 single bonds around them, like the other two carbon atoms.

The tetrahedral arrangement means \(s{p^3}\)hybridization after the reaction.

b) Let's observe the dehydration reaction of ethanol

Ethanol consists of 2 carbon atoms and one OH group.

Dehydration is a process where water is removed from a molecule.

Here the\(OH\)group will be removed along with the\(H\)atom or carbon atom adjacent to the\(C\)atom that has attached to the\(OH\)group.

Electrons from the C-H bond will be used to form a new \(\pi \)bond and make a double bond between two carbon atoms.

Reaction (b)

In benzene, there is a tetrahedral arrangement which means that\(s{p^3}\)hybridization is present.

By dehydrating ethanol, ethene is made as a product

Ethene has a double bond between its 2 carbon atoms.

This type of structure can only take a planar configuration, which means hybridization is \(s{p^2}.\)