Addition Reactions of Alkenes Section 12 4 Pages

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Addition Reactions of Alkenes Section 12. 4 Pages 332 -339

Addition Reactions of Alkenes Section 12. 4 Pages 332 -339

Addition Reaction n Addition of two atoms or groups of atoms to a double

Addition Reaction n Addition of two atoms or groups of atoms to a double bond. n R can be carbon or hydrogen.

Types of Addition Reactions n The major alkene addition reactions include n Addition of

Types of Addition Reactions n The major alkene addition reactions include n Addition of hydrogen (H 2) – hydrogenation n Addition of halogens (Cl 2 or Br 2) – halogenation n Addition of water (H 2 O) – hydration n Addition of hydrogen halides (HBr or HCl) – hydrohalogenation n Note: Double bond becomes a single bond.

Hydrogenation: Adding H 2 n Double bond is broken n H atom added to

Hydrogenation: Adding H 2 n Double bond is broken n H atom added to both sides of double bond n Platinum, palladium, or nickel catalyst required n Heat and/or pressure may also be needed

Examples of Hydrogenation n Hydrogenation of 1 -propene to propane n Hydrogenation of trans-2

Examples of Hydrogenation n Hydrogenation of 1 -propene to propane n Hydrogenation of trans-2 -butene

YOU TRY THESE! n Write hydrogenation reactions for: n 1 -pentene n 2 -methyl-2

YOU TRY THESE! n Write hydrogenation reactions for: n 1 -pentene n 2 -methyl-2 -butene n ethene

Halogenation: Adding Br 2 or Cl 2 n This reaction occurs easily and does

Halogenation: Adding Br 2 or Cl 2 n This reaction occurs easily and does not require a catalyst.

Examples of Halogenation n Bromination of 1 -propene to form 1, 2 - dibromopropane

Examples of Halogenation n Bromination of 1 -propene to form 1, 2 - dibromopropane n Chlorination of trans-2 -butene to form 2, 3 - dichlorobutane

YOU TRY THESE! n Write halogenation reactions for: n 1 -pentene with bromine n

YOU TRY THESE! n Write halogenation reactions for: n 1 -pentene with bromine n 2 -methyl-2 -butene with chlorine n Ethene with chlorine

Hydration: Addition of H 2 O n Requires a trace of acid (H+) as

Hydration: Addition of H 2 O n Requires a trace of acid (H+) as a catalyst n The product is an alcohol n Markovnikov’s rule applies

Markovnikov’s Rule n A mixture of products is formed when an unsymmetrical alkene is

Markovnikov’s Rule n A mixture of products is formed when an unsymmetrical alkene is hydrated. n One product is always favored over the other. n Vladimir Markovnikov came up with a rule to determine the major product formed. n The carbon of the carbon-carbon double bond that originally has more hydrogen atoms receives the hydrogen atom being added. n “The rich get richer. ”

Example of Markovnikov’s Rule n Hydration of 1 -propene to form 2 -propanol (major)

Example of Markovnikov’s Rule n Hydration of 1 -propene to form 2 -propanol (major) and 1 -propanol (minor)

YOU TRY THESE! n Write the hydration equation for each of the following molecules.

YOU TRY THESE! n Write the hydration equation for each of the following molecules. Indicate the major and minor products for the reactions where applicable. 1 -pentene n 2 -methyl-2 -butene n ethene n

Hydrohalogenation: Adding HCl or HBr n Follows Markovnikov’s rule

Hydrohalogenation: Adding HCl or HBr n Follows Markovnikov’s rule

Examples of Hydrohalogenation n Hydrobromination of 1 -propene to form 2 - bromopropane (major)

Examples of Hydrohalogenation n Hydrobromination of 1 -propene to form 2 - bromopropane (major) and 1 -bromopropane (minor)

YOU TRY THESE! n Write the hydrohalogenation equation for each of the following molecules.

YOU TRY THESE! n Write the hydrohalogenation equation for each of the following molecules. Indicate the major and minor products for the reactions where applicable. 1 -pentene with HCl n 2 -methyl-2 -butene with HBr n Ethene with HCl n