12.7 Addition Reactions for - PowerPoint Presentation

Slide1

12.7 Addition Reactions for Alkenes

The commercial processof hydrogenation is usedto convert the double bondsin vegetable oils to saturatedfats such as those in margarine. Learning Goal Draw the condensed or line-angle structural formulas and give the names for the organic products of addition reactions of alkenes. Draw a condensed structural formula for a section of a polymer.Slide2

Addition Reactions

In alkenes and alkynes, the double and triple bonds are very reactive and undergo hydrogenation, addition ofH — H, and hydration, addition of H — OH to the carbons in the double or triple bond.undergo polymerization at high temperatures and pressure.are easily broken, providing electrons to form new bonds.Slide3

Hydrogenation

In hydrogenation, hydrogen atoms add to the carbon atoms of a double bond or triple bond.a catalyst such as Pt, Ni, or Pd is used to speed up the reaction.Core Chemistry Skill Writing Equations for Hydrogenation, Hydration, and PolymerizationSlide4

Study Check

Write an equation for the hydrogenation of 1-butene using a platinum catalyst.Slide5

Solution

Write an equation for the hydrogenation of 1-butene using a platinum catalyst. Pt CH2=CH−CH2−CH3 + H2  CH3−CH2−CH2−CH3 Slide6

Vegetable oils are unsaturated fats composed of fatty acids that contain double bonds.

Adding H2 to double bonds in vegetable oils producescompounds with higher melting points.solids at room temperature, such as margarine, soft margarine, and shortening.Chemistry Link to Health: Hydrogenation of Unsaturated FatsSlide7

Study Check

Write the product of each the following: PtA. CH3−CH=CH−

CH

3

+ H

2



B.

Pt

+ H

2

 Slide8

Solution

Write the product of each the following: PtCH3−CH=CH−

CH

3

+ H

2



CH

3

−

CH

2

−

CH

2

−

CH

3

B.

Pt

+ H2

 Slide9

Hydration Reactions

In hydration reactions, an alkene reacts with water, H — OH, to form an alcohol.A hydrogen atom (H —) from water forms a bond with the carbon atom in the double bond with more hydrogen atoms.The — OH from water forms a bond with the second carbon atom in the double bond with fewer hydrogen atoms.These reactions are catalyzed by a strong acid such as H2SO4.Slide10

Study Check

Predict the product of the addition of H — OH to the following alkene:Slide11

Solution

Predict the product of the addition of H — OH to the following alkene:Slide12

Markovnikov’s Rule

When H2O adds to a double bond in an asymmetrical alkene, two products are possible. Markovnikov’s rule states the following: The H — from H — OH attaches to the carbon that has the greater number of H atoms, and the — OH adds to the more substituted carbon atom.Slide13

Addition of Alkenes: Polymerization

A polymer is a large molecule that consists of small, repeating units called monomers. Many of these polymers are produced by addition reactions of alkenes.In the past hundred years, the plastics industry has made synthetic polymers such as those used in carpeting, plastic wrap, nonstick pans, plastic cups, and rain gear. Slide14

Addition of Alkenes: Polymerization

In medicine, synthetic polymers are used to replace diseased or damaged body parts such as hip joints, pacemakers, teeth, heart valves, and blood vessels.Slide15

Addition of Alkenes: Polymerization

In medicine, synthetic polymers are used to replace diseased or damaged body parts such as hip joints, pacemakers, teeth, heart valves, and blood vessels.Slide16

Polymerization

Many of the synthetic polymers are made by addition reactions of small alkene monomers. Often, many polymerization reactions requirehigh temperature.a catalyst.high pressure (over 1000 atm).In an addition reaction, a polymer grows longer as each monomer is added at the end of the chain. Slide17

Polymerization: Polyethylene

A polymer may contain as many as 1000 monomers. Polyethylene, a polymer made from ethylene monomers, is used in plastic bottles, film, and plastic dinnerware.Low-density polyethylene (LDPE) is flexible, breakable, less dense, and more branched than high-density polyethylene (HDPE). High-density polyethylene is stronger and more dense than LDPE, and it melts at a higher temperature than LDPE.Slide18

Polymers

Table 12.9 lists several alkene monomers that are used to produce common synthetic polymers.Slide19

Polymers

The alkane-like nature of these plastic synthetic polymers makes them unreactive. They do not decompose easily.are not biodegradable.have become significant contributors to pollution, on land and in the oceans.Efforts are being made to make them more degradable.Slide20

Polymers: Recycling

Each type of polymer used to manufacture a plastic item can be identified by looking for the recycling symbol (arrows in a triangle) found on the label or on the bottom of the plastic container.The number 5 or the letters PP inside the triangle is the code for a polypropylene plastic.There are now many cities that maintain recycling programs to reduce the amount of plastic materials that are transported to landfills.Slide21

Study Check

A firefighter/EMT arrives at a home where a premature baby has been delivered. To prevent hypothermia during transport to the neonatal facility, she wraps the baby in cling wrap. Draw and name the monomer unit, and draw the polymer of three monomer units for cling wrap, polydichloroethylene (ethene).Slide22

Solution

A firefighter/EMT arrives at a home where a premature baby has been delivered. To prevent hypothermia during transport to the neonatal facility, she wraps the baby in cling wrap. Draw and name the monomer unit, and draw the polymer of three monomer units for cling wrap, polydichloroethylene (ethene).