Introduction to Organic Chemistry: Compounds and Functional Groups

1. Chapter 19 General, Organic, and Biochemistry, 10e John Wiley & Sons, Inc Hein and Pattison Organic Chemistry: Saturated Hydrocarbons Organic chemistry is important in nanotechnology. A carbon nanotube forest is shown here.

2. Organic Chemistry: History and Scope Organic chemistry is the study of compounds containing carbon. These compounds occur naturally but can be prepared in a laboratory. The early history of organic chemistry included an erroneous theory. (i.e. that organic compounds exist only in living organisms). The German chemist Wöhler disproved this theory in 1828 with the laboratory synthesis of urea.

3. Carbon can form a vast array of long chain and ring containing compounds because carbon has the unique ability to bond to itself. Organic compounds include drugs, fuels, toiletries, plastics, and fabrics. You can see why organic chemistry is such an important field of study. What is organic chemistry? Lipstick is made of organic molecules. Cosmetics and perfumes contain organic compounds. 3

4. The Carbon Atom: Bonding and Shape Carbon can form saturatedcompounds(i.e. where all carbon atoms have four single bonds) or unsaturated compounds (i.e. at least one carbon has a double bond (C=C) or a triple bond (C≡C)).

5. The Carbon Atom: Bonding and Shape These are the molecular shapes of carbon compounds predicted by the VSEPR Bonding Theory.

6. The Carbon Atom: Bonding and Shape This figure shows the bonding shape that results when carbon has four single bonds. Figure 19.1Tetrahedral structure of carbon: (a) a regular tetrahedron; (b) a carbon atom with tetrahedral bonds; (c) a carbon atom within a regular tetrahedron; (d) a methane molecule, CH4

7. Your Turn! Estimate the bond angles around 1C and 2C in the following structure. 7

8. Organic Formulas and Molecular Models or in the case of a model. Structural formulas or models are often used in organic chemistry to illustrate molecules. For example,

9. Figure 19.3 Types of formulas and models used to represent organic molecules. Each diagram is a representation of a propane molecule. 9

10. Organic Formulas and Molecular Models This is an example of how to change a condensed structural formula into a line structure. The table on the next slide summarize formulas and models used in organic chemistry.

11. Formula or model Definition

12. Classifying Organic Compounds Functional groups are group of atoms (or one atom) that have specific behavioral characteristics in organic compounds. Organic compounds are classified based on the functional groups that they contain. 12

13. Classifying Organic Compounds The list of common functional groups found in organic compounds are shown here on Table 19.1. 13

14. Classifying Organic Compounds The list of important functional groups found in biological compounds is shown here on Table 19.2. 14

15. Classifying Organic Compounds Ethanol contains the alcohol functional group and dimethyl ether contains the ether functional group. They have the same molecular formula but the boiling point (b.p.) of ethanol is 78C while the b.p. of dimethyl ether is -23C because of the structural differences between the molecules. 15

16. Hydrocarbons Hydrocarbons are organic compounds that contain only carbon and hydrogen atoms. (e.g. propane, CH3CH2CH3 is a hydrocarbon but ethanol, CH3CH2OH is not). Hydrocarbons are classified as either aliphatic (i.e those hydrocarbons without benzene rings in the chemical structure)or aromatic.(i.e those hydrocarbons with benzene rings in the chemical structure) as shown in Figure 19.4 on the next slide. Hydrocarbons are also classified as saturated or unsaturated compounds.

17. Figure 19.4 Classes of Hydrocarbons

18. Hydrocarbons The principal source of hydrocarbons is fossil fuels which include natural gas, petroleum, and coal. Fossil fuels are the primary source of heat and also a primary source of organic chemicals.

19. Saturated Hydrocarbons: Alkanes Alkanes are saturated hydrocarbons that are either straight- chain or branched-chain hydrocarbons.

20. Saturated Hydrocarbons: Alkanes Alkanes form a homologous series of straight-chain molecules as seen in Table 19.3 on the next slide. Members of a homologous series have similar structures but different chemical formulas. The general formula for all non-cyclic alkanes is shown here.

21. Saturated Hydrocarbons: Alkanes 21

22. Your Turn! Write the formula for an alkane that has nine carbon atoms. Write the condensed structural formula for the straight-chain alkane that has nine carbon atoms. 22

23. Isomerism The properties of an organic substance are dependent on its molecular structure. The majority of organic compounds are made up of relatively few elements: carbon, hydrogen, oxygen, nitrogen, and the halogens. The valence bonds or points of attachment may be represented in structural formulas by a corresponding number of dashes attached to each atom. 23

24. Isomerism Carbon can form four single bonds each, nitrogen can form three single bonds, oxygen can only form two single bonds, and hydrogen and the halogens can form one single bond each. 24

25. Isomerism Because carbon can form four single bonds, alkanes with four or more carbon atoms can form isomers. Isomers are molecules that have the same molecular formula but different structural formula.

26. For example, it is possible to write two structural formulas corresponding to the molecular formula C4H10 (i.e., butane and isobutane are isomers of each other). Notice the ball-and-stick models of these molecules on the next slide. Isomerism 26

27. Figure 19.7 Ball-and-stick models illustrating the structural formulas of several alkanes. 27

28. Your Turn! There are several isomers of heptane, C7H16. Draw structural formulas and condensed structural formulas for the two isomers that only have one branching methyl group. 28

29. Naming Organic Compounds How do chemists name organic compounds? Organic compounds are named using the IUPAC System (International Union of Pure and Applied Chemistry). TheIUPAC System was developed at an international science meeting in Geneva in 1892. The IUPAC System is essentially a set of rules that allow for a systematic and uniform method of naming compounds.

30. Naming Alkyl Groups Alkyl groups have one hydrogen less than the respective alkane. The general formula for alkyl groups is shown here and a list of alkyl groups are shown in Table 19.4.

31. Naming Alkyl Groups

32. Naming Organic Compounds Carbon atoms are often classified based on the number of carbon atoms directly attached to them.

33. Naming Organic Compounds Here is an example of a molecule with all three types of carbon atoms. 33

34. Your Turn! Identify all the carbon atoms in the structure below as 1o, 2o or 3o. 34

35. IUPAC Rules for Naming Alkanes 1. Identify and then name the longest continuous chain of carbon atoms. The longest chain in this molecule contains six carbon atoms. 35

36. IUPAC Rules for Naming Alkanes 2. Number the chain so any branch alkyl groups have the lowest possible number. There is only one correct way to number the carbon atoms in the longest chain. 36

37. IUPAC Rules for Naming Alkanes 3. The methyl group is attached to the #3 carbon atom not the #4 carbon atom. The IUPAC name for the molecule is 3-methylhexane. 37

38. IUPAC Rules for Naming Alkanes 4. Use prefixes (i.e. di, tri, tetra etc. ) if two or more of the same alkyl group branches appear on the longest chain. One methyl group is on the #2 carbon atom and another methyl group is on the #3 carbon atom. 38

39. IUPAC Rules for Naming Alkanes 5. When several different groups are attached to the same parent compound, list the groups in alphabetical order (e.g. chloro is listed before isopropyl and isopropyl is listed before methyl). 39

40. Your Turn! Give the IUPAC name for the this alkane. 40

41. Your Turn! Write the structural formula for 5-ethyl-3-methyloctane. 41

42. Introduction to the Reactions of Carbon The importance of organic chemistry is illustrated by the variety of reactions that occur at the carbon atom which include four major types. • Oxidation-reduction • Substitution • Addition • Elimination 42

43. Introduction to the Reactions of Carbon Oxidation involves a higher number of oxygen atoms bonding to carbon. Carbon dioxide is more oxidized than methane so this is an oxidation reaction. 43

44. Introduction to the Reactions of Carbon Reduction is the reverse of oxidation and involves a higher number of hydrogen atoms bonding to carbon. Methanol is more reduced than carbon dioxide so this is a reduction.

45. Introduction to the Reactions of Carbon Substitution is the exchange of one atom for another at the carbon atom. In this reaction a bromine atom changes position with a hydrogen atom in methane. 45

46. Introduction to the Reactions of Carbon Addition is a reaction where two reactants join to form a single product. 46

47. Introduction to the Reactions of Carbon Elimination is the splitting of a single reactant into two products. 47

48. Your Turn! Classify the following reaction as substitution, elimination or addition. 48

49. Reactions of Alkanes Reaction Class Name of Reaction Reactions of alkanes can be classified as shown in this table. 49

50. Reactions of Alkanes Combustion (oxidation) Alkanes are a valuable energy source due to their ability to react with oxygen . Alkanes release a large amount of energy as shown here. Alkanes generally are considered to be unreactive and for reactions other than combustion a catalyst or other special reaction conditions are necessary.