Organic Reactions:

C11-5-22 REACTIONS AND POLYMERS OUTCOME QUESTION(S): C11-5-22 REACTIONS AND POLYMERS Outline the transformation of alkanes to alkenes, to alkynes and vice versa. Include: dehydrogenation / hydrogenation Outline the creation of other functional groups through chemical reactions. Include: hydration / dehydration, addition reactions Describe the process of polymerization and identify important natural and synthetic polymers. Vocabulary & Concepts monomer

Thermal cracking: Process of using heat to break long chain-alkanes found in petroleum into shorter alkanes/alkenes. alkane Writing something over the reaction arrow indicates that it is required for the reaction to proceed. CH3CH3 heat () CH3CH2CH2CH2CH3 + long alkane CH2=CHCH3 alkene Remember petroleum is a mix of many short and long chain organic molecules

C C C C Addition Reactions Addition of a functional group at the site of a multiple bond. Reverse reactions are called Elimination Reactions Diverse and useful reactions ? ? C C H addition C C + ? H H elimination H H alkene ?-alkane Multiple bonds welcome addition…we will cover a few important additions

Partial hydrogenation creates trans double bonds – bad fats Hydrogenation (addition reaction) Creates alkanes from reactive alkenes/alkynes by adding hydrogen. Common in food industry to solidify vegetable oils Labelled as “partially hydrogenated "or “hydrogenated” H H C C H C C + H2 Ni,  H H H H alkene alkane Partial hydrogenation creates trans double bonds – bad fats

Needs a platinum catalyst and/or heat Dehydrogenation (elimination reaction) Converts relatively useless alkanes into reactive alkenes/alkynes by removing hydrogen. Alkenes are a precursor to creating other compounds Usually requires high heat (endothermic) or a catalyst H H H H Hydrogen is diatomic… Needs a platinum catalyst and/or heat C C C C H H H Pt,  + H2 H H alkane alkene C C C C H H H + H2 alkyne H H H H alkene

C C C C Hydration (addition reaction) Creates alcohols from reactive alkenes/alkynes by adding water. Reversible elimination reaction – Dehydration reaction Hydrate – to add water HO H C C H C C + H2O acid H H dehydration reaction H H alkene alcohol

H2C CH2 H2C CH2 H2C CH2 H2C CH2 Halogenation (addition reaction) Creates alkyl halides from reactive alkenes/alkynes by adding halogens. Elimination reaction – Dehalogenation reaction H Cl H2C CH2 H2C CH2 + HCl alkene dehalogenation reaction alkyl halide Fluorine reacts violently with organic molecules, iodine reacts the weakest (F>Cl>Br>I) Cl Cl H2C CH2 H2C CH2 + Cl2 alkene dehalogenation reaction alkyl dihalide

This is reversible too… Substitution Reactions Replacement of one functional group in a compound by another. Products can be predicted from the reactivity of the reactants Substitution reactions are versatile and fundamental to creating the variety of compounds in organic chemistry C C H Cl C C H Cl- base + OH- OH alkyl halide alcohol + This is reversible too…

C C C C Halogenation (substitution reaction) Creates alkyl halides from a substitution reaction with the a hydrogen of the alkane. C C H H C C H H hv + Cl2 Cl Cl alkane alkyl halide + Substitutions are common for benzene – switching with a hydrogen on the ring

“poly” – many “mer” – part Polymers are very large molecules made of many smaller repeating units. Each individual part is called a monomer. “poly” – many “mer” – part monomer polymer

Examples: Polypropylene, Teflon, Polyvinyl chloride (PVC) Polymerization is a type of Addition Reaction: Chain Polymerization (addition): Only 1 type of monomer added together to form a long chain polymer. Monomer is usually an alkene Occurs quickly by addition to the end of the growing chain Usually requires an initiator to kick start the reaction Remember what we know of the reactivity of double bonds… Examples: Polypropylene, Teflon, Polyvinyl chloride (PVC)

~ ~ C C C C C C C C Polyethylene H H H H ethene The beginning and ends of the chain will be “capped” with another compound Polyethylene

Examples: Polycarbonate, Polyester, Polyurethane Step Polymerization (condensation): Reactions with two or more different monomers alternatingly linked A-B-A-B… Occurs slowly by multiple smaller chains that eventually link A B Examples: Polycarbonate, Polyester, Polyurethane

Nylon A B B A

More Examples of Synthetic Polymers

C11-5-22 REACTIONS AND POLYMERS CAN YOU / HAVE YOU? C11-5-22 REACTIONS AND POLYMERS Outline the transformation of alkanes to alkenes, to alkynes and vice versa. Include: dehydrogenation / hydrogenation Outline the creation of other functional groups through chemical reactions. Include: hydration / dehydration, addition reactions Describe the process of polymerization and identify important natural and synthetic polymers. Vocabulary & Concepts monomer