2. - Organic Reactions Mr. ShieldsRegents Chemistry U17 L03

3. 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 - Addition- Esterification - Fermentation- Saponification - Polymerization (Condensation & Addition)

4. 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

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

6. Substitution Rxns Another example of a substitution reaction is The replacement of a halogen with a hydroxyl group CH 3 CH 2 CL + NaOH(aq)  CH 3 CH 2 OH + NaCl Or the replacement of a halogen with an amine group CH 3 CH 2 CL + NH 3  CH 3 CH 2 NH 2 + HCl

7. Elimination Rxns Any reaction in which atoms are eliminated from another molecule This can be done by –Elimination of H 2 –Elimination of HX

8. Elimination Rxns -L-Loss of H 2 - This process is often referred to as Dehydrogenation H H H-C-C-H  H 2 C=CH 2 + H 2 H H Heat, catalyst

9. Elimination Rxns -L-Loss of HX (X = a halogen) -A-Also known as dehydrohalogenation H H H-C-C-H (g) + Heat  H 2 C=CH 2 + HX (g) H X

10. 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–X2 –H2–H2 –HX –H2O–H2O

11. Addition Addition of halogen –Normally occurs dissolved in a solvent such as CCL 4 –Alkenes form dihaloalkanes –Alkynes produce dihaloalkenes or tetrahaloalkanes 1,2-dichloroethane

12. Addition Addition of Hydrogen –Catalysts normally used such at Pt, Pd or Ni Known as Hydrogenation –Alkene becomes an alkane H 2 C=CH 2 + H 2  Heat, catalyst H H H-C-C-H H H

13. 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 H 2 C=CH 2 + HX  H H H-C-C-H H X HC=CH + HX  H-C-C-H H X H-C-C-H H X + HX 

14. 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 H 2 C=CH 2 + H-OH  H H H-C-C-H H OH HC=CH + H-OH  H-C-C-H H OH H H H-C-C-H HO OH + HOH 

15. 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 propyl ethanoate From the acid From the alcohol alcohol acid

16. Aspirin – Made by Esterification H-O-C-CH 3 O +  HO C=O OH HO C=O O-C-CH 3 O Salicylic Acid Acetyl Salicylic Acid (Common Name) “Aspirin” (An alcohol and acid) Acetic acid

17. CH 3 CH 2 OH + HCOOH  CH 3 CH 2 COOH + CH 3 CH 2 CH 2 OH  Name the Esterification Products

18. Fermentation 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 is Zymase (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 C 6 H 12 O 6  2C 2 H 5 OH + 2CO 2 Glucose Ethanol Carbon dioxide Zymase

19. Saponification 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 CH 2 -0-C-(CH 2 ) 14 CH 3 | O CH 2 -O-C-(CH 2 ) 14 CH 3 | O CH 2 -0-C-(CH 2 ) 14 CH 3 + 3KOH  O CH 2 -0H K + - O-C-(CH 2 ) 14 CH 3 | O CH 2 -OH K + - O-C-(CH 2 ) 14 CH 3 | O CH 2 -0H K + - O-C-(CH 2 ) 14 CH 3 A TRIGYCERIDE GLYCEROL 3 SOAP MOLECULES + 1,2,3-propanetriol Carboxylate salt An ester

20. 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

21. Monomers a b a b a b a a a a a a a a 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)

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

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

24. 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

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

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

27. 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 …

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

29. Condensation Polymerization - Nylon Formed by loss of water An amide groupA Polyamide

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