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Organic Chemistry

Organic Chemistry. - Organic Reactions. Mr. Shields Regents Chemistry U17 L03. Organic Reaction Types. There are in fact so many types of organic rxn’s It would be impossible to review them all. Therefore we’re going to focus on just 7 : Substitution - Elimination

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Organic Chemistry

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  1. Organic Chemistry - Organic Reactions Mr. Shields Regents Chemistry U17 L03

  2. OrganicReaction Types • There are in fact so many types of organic rxn’s • It would be impossible to review them all. • Therefore we’re going to focus on just 7: • Substitution - Elimination • Addition - Esterification • - Fermentation - Saponification • - Polymerization (Condensation & Addition)

  3. Substitution Rxns • Any reaction in which one atom is replaced by another • Used to place a halogen onto an alkane • The products always are a halocarbon and the acid of the halogen (ex: hydrobromic acid) • Need ultraviolet light to initiate the reaction • Provides the energy of activation needed to form the excited state

  4. 2. R-H + Br  H-Br + R 1. Br-Br  2Br uv A free radical 3. R + Br2 R-Br + Br Substitution Rxns What are the products formed in the following rxn? CH3CH3 + Br2 sunlight CH3 CH2Br + HBr (What is the purpose of the sunlight?) Let’s look at how this reaction occurs?

  5. Substitution Rxns Another example of a substitution reaction is The replacement of a halogen with a hydroxyl group CH3CH2CL + NaOH(aq)  CH3 CH2OH + NaCl Or the replacement of a halogen with an amine group CH3CH2CL + NH3 CH3 CH2NH2 + HCl

  6. Elimination Rxns • Any reaction in which atoms are eliminated from another molecule • This can be done by • Elimination of H2 • Elimination of HX

  7. H H H-C-C-H  H2C=CH2 + H2 H H Heat, catalyst Elimination Rxns • Loss of H2 • - This process is often referred to as Dehydrogenation

  8. H H H-C-C-H (g) + Heat  H2C=CH2 + HX (g) H X Elimination Rxns • Loss of HX (X = a halogen) • Also known as dehydrohalogenation

  9. Addition • Takes place with unsaturated compounds which are usually more reactive than saturated compounds • Can take place with both Double and Triple bonds • Two atoms are added across the electron rich double bond • What are some examples of molecules that can be added? • X2 • H2 • HX • H2O

  10. Addition • Addition of halogen • Normally occurs dissolved in a solvent such as CCL4 • Alkenes form dihaloalkanes • Alkynes produce dihaloalkenes or tetrahaloalkanes 1,2-dichloroethane

  11. H2C=CH2 + H2  H H H-C-C-H H H Heat, catalyst Addition • Addition of Hydrogen • Catalysts normally used such at Pt, Pd or Ni • Known as Hydrogenation • Alkene becomes an alkane

  12. H H H-C-C-H H X H X H-C-C-H H X H2C=CH2 + HX  H-C-C-H H X HC=CH + HX  + HX Addition • Addition of Hydrogen Halides (HX) • HX = HCl, HBr, HI (Not HF!) • Alkene becomes an alkyl Halide • Alkynes form Monohalo alkenes or dihaloalkanes with the halogens on the same carbon

  13. H H H-C-C-H HOH H2C=CH2 + H-OH  HC=CH + H-OH  H-C-C-H H OH H H H-C-C-H HO OH + HOH Addition • Addition of Water • Water adds across a double bond to form an alcohol • Water can add across a triple bond to form a diol

  14. Esterification • Alcohol + Organic Acid = Water + Ester • Used to make perfumes, scents and flavors • Combination rxn which involves dehydration (Loss of water). • The alcohol becomes the alkyl group & the acid becomes -oate alcohol propyl ethanoate acid From the alcohol From the acid

  15. HO C=O H-O-C-CH3 O OH HO C=O O-C-CH3 O Aspirin – Made by Esterification +  Acetic acid Salicylic Acid (An alcohol and acid) Acetyl Salicylic Acid (Common Name) “Aspirin”

  16. Name the Esterification Products CH3CH2OH + HCOOH  CH3CH2COOH + CH3CH2CH2OH 

  17. Fermentation is the process by which glucose is broken down by an enzyme (a catalyst) in the absence of oxygen into an alcohol and carbon dioxide One enzyme used isZymase (Found in baker yeast) If Zymase is used the alcohol produced is ethanol The oldest chemical reaction practiced by man Dates back to at least 6000 B.C. In place of glucose, starches from grains can be used. Hence the name grain alcohol C6H12O6  2C2H5OH + 2CO2 Glucose Ethanol Carbon dioxide Fermentation Zymase

  18. Another very old chemical reaction practiced by man The hydrolysis of the ester bonds (back to acid + alcohol) in triglycerides using an aqueous sol’n of a strong base to form carboxylate salts and glycerol Triglycerides,from fats, and a strong base (KOH or NaOH) Products are soap and glycerol (a triol) O CH2-0-C-(CH2)14CH3 | O CH2-O-C-(CH2)14CH3 | O CH2-0-C-(CH2)14CH3 Saponification Carboxylate salt An ester 1,2,3-propanetriol O CH2-0H K+ -O-C-(CH2)14CH3 | O CH2-OH K+ -O-C-(CH2)14CH3 | O CH2-0H K+ -O-C-(CH2)14CH3 + 3KOH  + A TRIGYCERIDE GLYCEROL 3 SOAP MOLECULES

  19. Polymers The joining together of many smaller repeating Units to form a very high MW molecule - Polymers range from 10,000 amu to more than 1,000,000 amu The small repeating units used to build the polymer are known as monomers

  20. a b a b a b a a a a a a a a Monomers Sometimes just one monomer is used to make the Polymer (example: ethylene (a) to form polyethylene) And sometimes two monomers alternate are used to form an alternating polymer (ex: Nylon or Polyesters)

  21. Natural polymers Example of “natural” polymers in nature abound: Some examples are: Wool Cotton Starch Protein Cellulose

  22. Polymerization There are two methods we’ll look at for the Production of Polymers: - Addition polymerization - Condensation polymerization

  23. Addition Polymerization • All the atoms present in the monomer are • retained in the polymer in Addition Polymerization • This type of reaction involves monomers with • double or triple bonds • An initiator is required to produce a free radical • A very reactive substance having a free e- • Peroxides are typically used to produce this free radical Peroxide  Rad

  24. Rad Rad Free radical induced addition polymerization of Ethylene to form polyethylene

  25. Free radical induced addition polymerization of Styrene to form polystyrene Monomer Notice loss of electron pair to form Connecting bonds in polymer AdditionPolymer

  26. Condensation Polymerization • Monomers that join together by the loss of water • each monomer has two functional groups that are • the same • monomer 1 and monomer have functional groups • that are different • reaction occurs between the two pairs of • dissimilar functional groups Let’s look at some examples …

  27. Di-Acid Di-Alcohol Formed by loss of water One example of Condensation Polymerization - Dacron Monomer B Monomer A A polyester

  28. Formed by loss of water Condensation Polymerization - Nylon An amide group A Polyamide

  29. I’m Done! You’re Done! WE Made it to the End! Only the regents is left !!

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