Chapter 25 and 26 Carbon and its Compounds Classes of Organic Compounds

1. Chapter 25 and 26 � Carbon and its Compounds & Classes of Organic Compounds

2. Goals for Chapters 25 and 26 Understand the basics of Organic Chemistry Understand differences between organic and inorganic compounds Identify and name major classes and functional classes of organic compounds Learn a bit about biopolymers and polymers

3. Organic chemistry has a wide reach

4. Organic chemicals make up Foods Flavors and fragrances Medicines Materials, polymers, plastics Plant, animal, and microbial matter; natural products A vast range of manufactured goods adhesives, coatings, packaging, lubricants, cosmetics, films & fibres, etc.]

5. Organic Chemistry � the study of compounds of carbon Organic compounds are made up of carbon and only a few other elements. Chief among these are hydrogen, oxygen, and nitrogen. Also present in some organic compounds are sulfur, phosphorus, and a halogen (fluorine, chlorine, bromine, or iodine). Catenation of carbon is important - ~45 MM compounds known. Remember � carbon can hybridize to form single, double, or triple bonds.

7. Bonding in Unsaturated Hydrocarbons

8. Bonding in Unsaturated Hydrocarbons

9. Organic versus inorganic

10. Organic Structure Structural formula: Shows the atoms present in a molecule as well as the bonds that connect them. (Lewis Structure) VSEPR model: The most common bond angles are 109.5�, 120�, and 180�.

11. Organic Structure Among neutral (uncharged) organic compounds: Carbon normally forms four covalent bonds and has no unshared pairs of electrons. Hydrogen forms one covalent bond and no unshared pairs of electrons. Nitrogen normally forms three covalent bonds and has one unshared pair of electrons. Oxygen normally forms two covalent bonds and has two unshared pairs of electrons. Halogen normally forms one covalent bond and has three unshared pairs of electrons.

12. Functional Groups Functional group: An atom or group of atoms within a molecule that shows a characteristic set of predictable physical and chemical properties. Functional groups are important because: They undergo the same types of chemical reactions no matter in what organic molecule they are found. To a large measure, they determine the chemical and physical properties of a molecule. They are the units by which we divide organic compounds into families. They provide the basis on which we derive names for organic compounds.

13. Functional Groups

14. Carbon Compounds � Many are just C and H Hydrocarbons � compounds containing carbon and hydrogen (saturated or unsaturated). Alkanes � CC single bonds Alkenes � CC double bonds Arenes Alkynes � CC triple bonds

15. Alkanes � C-C single bonds only!

16. The First 10 � know these!

17. Line Angle Formulas � it�s simple

18. Constitutional Isomerism Constitutional isomers: Compounds that have the same molecular formula but different structural formulas (a different connectivity of their atoms). For the molecular formulas CH4, C2H6, and C3H8, only one structural formula is possible. There are no constitutional isomers for these molecular formulas. For the molecular formula C4H10, two constitutional isomers are possible.

19. Try it. Do the structural formulas in each set represent the same compound or constitutional isomers?

20. Solution

21. Try this Draw structural formulas for the five constitutional isomers of molecular formula C6H14.

22. IUPAC Naming System - Alkanes The name of an alkane with a branched chain of carbon atom consists of: a parent name: the longest chain of carbon atoms. substituent names: the groups bonded to the parent chain.

23. IUPAC The IUPAC name of an alkane with an unbranched chain of carbon atoms consists of two parts: (1) A prefix shows the number of carbon atoms in the chain. (2) The suffix - ane: shows that the compound is a saturated hydrocarbon.

24. Alkyl Groups Alkyl group: A substituent group derived from an alkane by removal of a hydrogen atom. Commonly represented by the symbol R- (�R group�). Named by dropping the -ane from the name of the parent alkane and adding the suffix -yl.

25. How it�s done � only 7 simple rules The name for an alkane with an unbranched chain of carbon atoms consists of a prefix showing the number of carbon atoms and the ending -ane. 2. For branched-chain alkanes, the longest chain of carbon atoms is the parent chain and its name is the root name. Name and number each substituent on the parent chain and use a hyphen to connect the number to the name. If there is one substituent, number the parent chain from the end that gives the substituent the lower number. If the same substituent occurs more than once: Number the parent chain from the end that gives the lower number to the substituent encountered first. Indicate the number of times the substituent occurs by a prefix di-, tri-, tetra-, penta-, hexa-, and so forth. Use a comma to separate position numbers. 6. If there are two or more different substituents List them in alphabetical order. Number the chain from the end that gives the lower number to the substituent encountered first. If there are different substituents at equivalent positions on opposite ends of the parent chain, give the substituent of lower alphabetical order the lower number. Do not include the prefixes di-, tri-, tetra-, and so forth or the hyphenated prefixes sec- and tert- in alphabetizing; Alphabetize the names of substituents first, and then insert these prefixes.

26. Let�s try a few Examples (boxed number indicates rule) Know common names

27. Cycloalkanes Cyclic hydrocarbon: A hydrocarbon that contains carbon atoms joined to form a ring. Cycloalkane: A cyclic hydrocarbon in which all carbons of the ring are saturated (has only carbon-carbon single bonds). Cycloalkanes with ring sizes of from 3 to over 30 carbon atoms are found in nature. Five-membered (cyclopentane) and six-membered (cyclohexane) rings are especially abundant in nature.

28. Naming Cycloalkanes To name a cycloalkane, prefix the name of the corresponding open-chain alkane with cyclo-, and name each substituent on the ring. If there is only one substituent on the ring, there is no need to give it a location number. If there are two substituents, number the ring beginning with the substituent of lower alphabetical order.

29. More naming? Cis/Trans Isomers

30. Drawing isomers � lines and wedges

31. Physical Properties of Alkanes The most important physical property of alkanes and cycloalkanes is their almost complete lack of polarity. The electronegativity difference between carbon and hydrogen is 2.5 - 2.1 = 0.4 on the Pauling scale. Given this small difference, we classify a C-H bond as nonpolar covalent. Alkanes are nonpolar compounds and the only interaction between their molecules are the very weak London dispersion forces.

32. Melting Points Boiling points of alkanes are lower than those of almost any other type of compound of the same molecular weight. In general, both boiling and melting points of alkanes increase with increasing molecular weight.

33. Constitutional Isomers have different properties

34. Solubility and Density Solubility: a case of �like dissolves like�. Alkanes are not soluble in water; they are unable to form hydrogen bonds with water. Liquid alkanes are soluble in each other. Alkanes are also soluble in other nonpolar organic compounds, such as toluene and diethyl ether. Density: The average density of the liquid alkanes listed in is about 0.7 g/mL; that of higher-molecular-weight alkanes is about 0.8 g/mL. All liquid and solid alkanes are less dense than water (1.0 g/mL) and, because they are both less dense and insoluble, they float on water.

35. Isolation of Alkanes Natural gas 90 to 95 percent methane. 5 to 10 percent ethane, and A mixture of other relatively low-boiling alkanes, chiefly propane, butane, and 2-methylpropane . Petroleum A thick, viscous liquid mixture of thousands of compounds most of them hydrocarbons formed from the decomposition of marine plants and animals.

36. Where do hydrocarbons come from?

37. Alkenes and Alkynes � unsaturated hydrocarbons Alkene: A hydrocarbon that contains one or more carbon-carbon double bonds. Ethylene is the simplest alkene. Alkyne: A hydrocarbon that contains one or more carbon-carbon triple bonds. Acetylene is the simplest alkyne.

38. VSEPR

39. IUPAC Naming - Alkenes The parent name is that of the longest chain that contains the C=C (sound familiar?). Number the chain from the end that gives the lower numbers to the carbons of the C=C. Locate the C=C by the number of its first carbon. Use the ending -ene to show the presence of the C=C. Branched-chain alkenes are named in a manner similar to alkanes in which substituted groups are located and named. Same rules applies for alkynes � but you must use the suffix �yne.

40. Common Names

41. Examples

42. More than 1 double bond?

43. Examples

44. Cis/Trans Isomerism Because of restricted rotation about a carbon-carbon double bond, an alkene with two different groups on each carbon of the double bond shows cis-trans isomerism.

45. Cycloalkenes Number the carbon atoms of the ring double bond 1 and 2 in the direction that gives the lower number to the substituent encountered first. Note that it is not necessary to explicitly number the position of the double bond in a cycloalkene as in linear alkenes. Number and list substituents in alphabetical order.

46. IUPAC Naming - Alkynes Same as naming alkenes but use �yne to denote the presence of a triple CC bond.

47. Examples

48. Arenes Benzene: A six carbon ring with alternating double bonds.

49. Phenyl group Phenyl group (C6H5- or Ph-): The substituent group derived by removal of an H from benzene.

50. Physical Properties for unsaturated hydrocarbons Alkanes, alkenes, and alkynes are nonpolar compounds. Their physical properties are similar to those of alkanes with the same carbon skeletons. Geometry around the double or triple bond is different however. Alkenes and alkynes are insoluble in water but soluble in one another and in nonpolar organic liquids. Alkenes and alkynes that are liquid or solid at room temperature have densities less than 1.0 g/mL; they float on water.

51. Name these compounds

52. Polymers

53. Poly(mer)

54. Biopolymers

55. Alcohols Contains an �OH (hydroxyl) group bonded to a tetrahedral carbon atom. For example, ethanol:

56. Alcohols Problem: Draw the Lewis structure (and the 3D shape) for the simplest alcohol - methanol.

57. Amines A compound containing an amino group (-NH2, RNH2, R2NH, R3N).

58. Amines Problem: Draw condensed structural formulas for the two primary amines with the molecular formula C3H9N.

59. Aldehydes and Ketones Each contains a C=O (carbonyl) group. Aldehyde: Contains a carbonyl group bonded to a hydrogen; in formaldehyde, the simplest aldehyde, the carbonyl group is bonded to two hydrogens. Ketone: Contains a carbonyl group bonded to two carbon atoms.

60. Aldehydes and Ketones Problem: Draw the structures for methanal, ethanal, and propanone. First draw the functional group of an aldehyde and add the remaining three carbons; these may be bonded in two ways. Then add the six hydrogens necessary to complete the four bonds of each carbon.

61. Carboxylic Acids Carboxylic acid: A compound containing a -COOH (carboxyl: carbonyl + hydroxyl) group. In a condensed structural formula, a carboxyl group may also be written -CO2H.

62. Naming Carboxylic Acids Drop the last �e� and replace it with �oic acid�. You do not need to number the carbon since the carboxyl group will automatically be at carbon #1.

63. Carboxylic Acids Problem: Draw a condensed structural formula for the single carboxylic acid with the molecular formula C2H4O2 Solution: The only way the carbon atoms can be written is three in a chain; the -COOH group must be on an end carbon of the chain.

64. Carboxylic Ester Carboxylic ester: A derivative of a carboxylic acid in which the H of the carboxyl group is replaced by a carbon group. Simply calling these esters is acceptable.

65. Thus far� You know how to name alkanes, alkenes, alkynes, arenes, alcohols, amines, aldehydes, ketones, carboxylic acids, esters. You have seen why these classes are important in nature and materials. You know a bit about the physical properties of the hydrocarbon classes. You need to read about ethers and understand how to name them � think amines. Naming is similar.

66. What�s Next? Chapter 9 � Chemical Reactions and Equations Please R&O Chapter 9 � print off all materials listed for this chapter.