McMurry (Kap. 6,5) - Alkene polar reaction (electrophilic addition reaction)

Question 1

What happens when you add water to a double bond (alkene) for instance Ethylene, and heat it up, and use a strong acid catalyst such as H2SO4?

Answer 1

You will get an electrophilic addition reaction.

Question 2

Is the electrophilic addition reaction an polar reaction?

Answer 2

YES, the reactions take place between electron poor sites and electron rich sites and involve donating an electron pair from a nucleophile to an electrophile - see exact mechanism (Electrophilic addition reaction of ethylene and H2O - acid catalyzed) on page 158.

Question 3

Why are alkanes more inert then alkenes?

Answer 3

1) its electrons are tied up in strong C-C and C-H bonds.

2) The bonding electrons are inaccessible, because they are sheltered in sigma bonds between nuclei (pi bonds are more accessible).

Question 4

Why are alkenes more reactive?

Answer 4

1) Double bonds have greater electron density then single bonds (more nucleophilic).

2) The electrons in pi bonds (double bonds - 1 pi bond and 1 sigma bond), are more accessible, because they are located below and above the plane rather then being sheltered.

Question 5

What are the chemistry of alkenes dominated by?

Answer 5

By reactions with electrophiles, because they acts as nucleophilic.