Unit 8 – Organic Chemistry

1. Unit 8 – Organic Chemistry Text – Ch. 1 and 2

2. Intro to Organic Chem • Originally, Organic Chemistry was the chemistry of living things. • Chemists were aware of a very large number of organic compounds (such as dyes, soaps, vinegars, sugars, perfumes, gums, and rubber, to mention a few) but were unable to explain how so many compounds could be made from only a few elements. • Swedish chemist Jöns Jakob Berzelius (1779–1848) had just explained inorganic compounds as being formed by oppositely charged atoms.

3. Intro to Organic Chem • However, this did not explain organic compounds such as C2H6, C2H4, C3H8, C4H10, and so on. • It was common knowledge that Cl2 could be substituted for H in C2H6 to produce C2Cl6. This meant, however, that a negative Cl could be substituted for a positive H. This was not consistent with Berzelius’s idea of oppositely charged atoms attracting.

4. Intro to Organic Chem • Up to this point, no organic compound had been synthesized from inorganic materials and, as a result, many scientists believed that organic compounds were formed only under the influence of a vital force. • It was Friedrich Wöhler (1800–1882) who, in 1828, made a remarkable discovery at the University of Göttingham in Germany. He attempted to prepare ammonium cyanate by means of a double decomposition reaction in a solution of ammonium chloride and silver cyanate.

5. Intro to Organic Chem • Both of these compounds were considered to be inorganic. • Instead of producing ammonium cyanate, however, he obtained crystals of urea, an organic compound. NH4Cl + AgCHO AgCl + CH4N2O Urea

6. Intro to Organic Chem Therefore, Organic Chemistry is associated with all molecules that contain carbon • Within a few years of this event, when acetic acid and several other organic compounds had been prepared from inorganic materials, the validity of the vital force was questioned. • As time passed, more and more organic compounds were synthesized from inorganic materials. • It became obvious that it was not necessary for all organic compounds to be associated with living organisms.

7. Chemistry of Carbon • Carbon has four valence electrons • Therefore, it can bond four times per carbon • Single bonds, double bonds, triple bonds

8. Hydrocarbons • Hydrocarbon • Made of hydrogen and carbon • Two classes of hydrocarbons • Chains – Aliphatic and Cyclic hydrocarbons • Rings – Aromatics

9. Hydrocarbons • Alkanes • Are saturated hydrocarbons • All bonds are single and filled with hydrogen • Names end in “ane” • General formula is CnH2n+2 • Ex. Methane, Ethane, Propane

10. Hydrocarbons • Alkenes • Are unsaturated hydrocarbons • Some bonds are single and filled with hydrogen, while others are double bonds • Names end in “ene” • Give the position of the bond by using the smallest numbers possible • General formula is CnH2n • More reactive than alkanes • Ex. Ethene, Propene, Propadiene

11. Hydrocarbons • Alkynes • Are unsaturated hydrocarbons • Some bonds are single and filled with hydrogen, while others are triple bonds • Names end in “yne” • Give the position of the bond by using the smallest numbers possible • General formula is CnH2n-2 • More reactive than alkenes • Ex. Ethyne, Propyne

12. Hydrocarbons • Cyclic Hydrocarbons • Hydrocarbons arranged in a ring • Chain end loses one H, and forms a bond • Name has “cyclo” in it • Ex. Cyclohexane, cyclohexene

13. Hydrocarbons • Aromatics • Contain a benzene ring • Called aromatic as most have distinctive odours • If a functional group, it is called “phenyl” group • Benzene • Carcinogen, liquid (low mp and bp), insoluable in water, used to make derivatives, flammable • Examples – trinitrotolulene, napthalene, vanillin, salicylic acid, 2-phenyl butane • When you change the functional groups, you change the structure

14. Hydrocarbons – functional groups and isomers • Isomers • Two molecules which have the same formula but a different structure • Therefore they react differently • For methane, ethane and propane, there are no isomers or branches • But butane, has two isomers • Examples

15. Hydrocarbons – functional groups and isomers • Rules for Naming Isomers (branched hydrocarbons) • Find the longest chain of carbons • Count from the end of the chain closest to the branch or branches • Name the longest branch(es) then the chain • If the structure contains a double or triple bond, it takes priority and is named and numbered from the bond • Goes in alphabetical order • Examples

16. Hydrocarbons – functional groups and isomers • Functional Groups • CH3- R methyl • CH3- CH2- R ethyl • CH3- CH2- CH2- R propyl • OH- R hydroxyl (alcohol) • R – O – R ether • NH2 – R amyl (amine)

17. Hydrocarbons – functional groups and isomers • Some special ways to name are to look at the functional groups and the point at which they are bonded • n – normal (on the end) • iso – in the middle • s - secondary • t – tertiary • Examples • Isopropyl alcohol, t – butyl alcohol, 2 – butanol or s - butanol

18. Hydrocarbons – functional groups and isomers • Functional Groups (Cont) Carboxyl group Aldehyde Organic acids Ketone Amide Ester – made from the condensation reaction of an alcohol and an organic acid

19. Reactions of Alkanes, Alkenes and Alkynes • Alkanes • Without energy, alkanes generally are inert • When they are exposed to a spark, they form carbon dioxide and water. 2 C4H10(g) + 13 O2(g) 8 CO2(g) + 10 H2O(g)

20. Reactions of Alkanes, Alkenes and Alkynes • Alkanes (continued) • When exposed to steam and extreme temperatures, alkanes break to form an alkene and hydrogen gas • This is called thermal cracking or dehydrogenation and takes temperatures of 1400oC

21. Reactions of Alkanes, Alkenes and Alkynes • Alkanes (Cont) • Going from alkenes to alkanes (or hydrogenation) does not take as much energy as dehydrogenation • In presence of a catalyst and hydrogen, the alkene adds the hydrogen at the carbons surrounding the double bond

22. Reactions of Alkanes, Alkenes and Alkynes • Halogenation (Text p. 24 – 26) • Alkanes that react with heat or uv light, will go through a substitution reaction, where a alkyl halide will be produced • This is called a substitution reaction • If the reaction proceeds, a di-substitution reaction takes place

23. Reactions of Alkanes, Alkenes and Alkynes • Halogenation (p. 24 – 26) • Alkenes and alkynes are unsaturated and more reactive than alkanes • Since no hydrogen is lost, this reaction is called an addition reaction, and occurs at room temperature • Alkenes and alkynes will react with halogens, as well as hydrogen halides and water

24. Reactions of Alkanes, Alkenes and Alkynes • Reactions – Markovnikov’s Rule (p. 26) • When a reactant consists of non-identical atoms (such as a hydrogen halide), and is added to an alkene or alkyne, the hydrogen atom bonds to the side of the double bond that has more hydrogen atoms

25. More Organic Reactions • Aromatic Reactions (p. 28 and 29) • Not very reactive • Even though aromatics are unsaturated, they undergo substitution reactions, to form substituted benzene’s

26. More Organic Reactions • Alcohols • Contain a hydroxyl group, which is in the place of a hydrogen group • Where the hydroxyl group is will determine the name (as mentioned before) • Made from the hydration reaction of an alkene and water • A condensation reaction of two alcohols will make an ether

27. More Organic Reactions • Carboxylic Acids (Organic Acids) • Weak acids that have a vinegar type smell, which can be used in law inforcement • Contain a carboxyl group that replaces the hydrogen on the terminal carbon • Take the name of the molecule with “oic” in the name • Made from the oxidation of alcohols to aldyhydes and then to acids • Relatively soluable in water with high bp • Used to make Esters

28. More Organic Reactions • Esters (Organic “Salts”) (p. 64 – 67) • Account for many smells we are accustomed to • Made from the reaction of a carboxylic acid and alcohol, which produces water (Condensation reaction) and can be broken apart by hydrolysis reactions • The name is the alcohol, dropping the “ol” and adding “yl” and the acid, dropping the “oic” and adding “oate” • Really cool!!!

29. Polymers • Post a WIKI!!!