1. Intro to organic chemistry (orgo) SCH4U – Unit B

2. Organic Compounds Organic chemistry: chemistry of carbon compounds ▫Exceptions are oxides of carbon (CO 2 and CO), carbonates, bicarbonates, and cyanides Carbon atoms are generally bonded to: ▫Each other ▫Hydrogen atoms ▫Other specific elements (O, N, S, P and others)

3. Why study organic chemistry? 1.Life is carbon-based. Everyone is made up of organic compounds. There are more known carbon compounds than any other element. 2.There are several million known organic compounds with ~30,000 more being “discovered” each year. 3.Some common organic compounds include plastics, synthetic and natural fibres, dyes, drugs, pesticides, lighter fluid, and gasoline.

4. The carbon atom Carbon has four valence electrons allowing it to form four bonds with other atoms by sharing its electrons ▫This results in a tetrahedral shape Carbon forms covalent bonds (sharing of electrons) with carbon atoms

5. Classification Since organic compounds are composed almost entirely of carbon, they are sometimes referred to as hydrocarbons Hydrocarbons can be divided into: 1.Aliphatics: carbon atoms in an open chain structure; may have branches, but no rings 2.Alicyclics: carbon atoms arranged in a ring structure 3.Aromatics: structures related to benzene (C 6 H 6 )

6. Classification Aliphatics can be further categorized into: 1.Alkanes: contains only single bonds (saturated) 2.Alkenes: contains at least one double bond (unsaturated) 3.Alkynes: contains at least on triple bond

7. Isomers Constitutional Isomers Stereoisomers DiastereomersEnantiomers

8. Isomers Constitutional IsomersStereoisomers Isomers have same molecular formula Atoms bonded in a different sequenceAtoms bonded in same sequence Also known as structural isomersDiffer in 3D orientation of atoms in space

9. Isomers DiastereomersEnantiomers Based on a double bondMirror images of each other around a single carbon atom Carbon atoms with different types of atoms At least one carbon atom bonded to four different types of atoms or groups cis isomer when two identical groups or atoms are on the same side trans isomer when two identical groups or atoms are on the opposite side

10. Diagrams & formulas A number of different (but related) diagrams used to express structures in organic chemistry: ▫Empirical molecular formula ▫Expanded molecular formula ▫Complete structural formula ▫Condensed structural formula ▫Line structural formula ▫3D structural formula

11. Alkanes # of carbonsPrefix# of carbonsPrefix 1Meth-6Hex- 2Eth-7Hept- 3Prop-8Oct- 4But-9Non- 5Pent-10Dec-

12. Alkanes Only single bonds present in the main chain General formula is C n H 2n+2 Form a tetrahedral shape ▫Note: more on shapes in the next unit Create a 109.5° angle between bonds Considered “saturated” because no other hydrogen atoms can be added Always end in “~ane”

13. Nomenclature Three parts to organic chemistry nomenclature: ▫Prefix: indicates number, type and location of branches and/or functional groups (if any) ▫Root: indicates the number of carbon atoms in the main (parent) chain ▫Suffix: indicates the number and location of double or triple bonds (if any) and/or highest priority functional group

14. Let’s draw alkanes! Draw all ten basic alkanes and name them.

15. Alkyl groups and branching Each branch of a hydrocarbon is referred to as an alkyl group (if it contains only C and H) Alkyl groups use the same basic roots as alkanes Alkyls always end in “~yl” Also contain a number and hyphen in front to indicate location on the main carbon chain ▫Example: 2-methyl pentane

16. Alkyl groups and branching Find the longest carbon chain and assign sequential numbers to each carbon ▫Assign these numbers temporarily starting from both ends of the carbon chain ▫Ultimately will select only one set of numbers to use The goal is to use the numbering along the carbon chain that gives the lowest values assigned to branches

17. Alkyl groups and branching Let’s try some! Draw 3-ethyl octane…

18. Alkyl groups and branching

19. When there is more than one branch, they are listed in front of the root and suffix according to alphabetical order of the name of the alkyl group Try naming… 4-ethyl 3-methyl heptane

20. Alkyl groups and branching If there is more than one of any given alkyl group ▫Indicate all the number for the positions using commas to separate the numbers, and ▫Use prefixes (on the prefixes – confused yet?) to indicate the number present

21. Alkyl groups and branching Try naming… 5,6-diethyl-3,3,4-trimethyl nonane

22. Alkenes At least one double bond present in the main chain General formula is C n H 2n Form a trigonal planar shape ▫Note: more on shapes in the next unit Create a 120° angle between bonds Considered “unsaturated” because other hydrogen atoms can be added Always end in “~ene”

23. Nomenclature 1.Identify and name the longest carbon chain that CONTAINS THE DOUBLE BOND(S). 2.Number the carbons in the chain so that the two carbons involved in the double bond have the lowest possible numbers. a)If the double bond is equidistant from both ends, number the chain so that the substituent(s) have the lowest possibly number. 3.Follow same rules for identifying and naming prefixes.

24. Nomenclature Try naming this… 2-ethyl 1-pentene

25. Nomenclature Now let’s draw 1-butene and 2-butene… 1-butene2-butene

26. Nomenclature Let’s try a structure with more than one double bond… 1,3-pentadiene

27. Nomenclature Let’s put everything together and name… 4-ethyl-3,6-dimethyl 1,2,4-octatriene

28. Diastereomers Consider the following compounds… cis-2-butenetrans-2-butene2-methyl- 1-propene

29. Diastereomers Not superimposable upon one another Result from lack of free rotation around the double bond Priorities are assigned to the two groups attached to the carbon atoms on either side of the double bond (starting with the carbon to the left of the double bond) based on atomic number ▫Largest atomic number at the first point of difference has the highest priority

30. Diastereomers If two highest priority groups are on the same side of the double bond (top or bottom)… ▫cis configuration If two highest priority groups are on the opposite side of the double bond… ▫trans configuration

31. Alkynes At least one triple bond present in the main chain General formula is C n H 2n-2 Form a linear shape ▫Note: more on shapes in the next unit Create a 180° angle between bonds Considered “unsaturated” because other hydrogen atoms can be added Always end in “~yne”

32. Nomenclature 1.Identify and name the longest carbon chain that CONTAINS THE TRIPLE BOND(S). 2.Number the carbons in the chain so that the two carbons involved in the triple bond have the lowest possible numbers. a)If the triple bond is equidistant from both ends, number the chain so that the substituent(s) have the lowest possibly number. 3.Follow same rules for identifying and naming prefixes.

33. Nomenclature Try naming this… 3,4-dimethyl 1-hexyne

34. Nomenclature Now let’s draw 1-butyne and 2-butyne… 1-butyne2-butene

35. Nomenclature Let’s try a structure with more than one triple bond… 2,4-hexadiyne

36. Nomenclature Let’s put everything together and name… 4-ethyl-4,5-dimethyl 2,6-octadiyne

37. Alicyclics Connected end-to-end forming a ring Have single and/or double bonds present in the main chain General formula is C n H 2n Can be “saturated” or “unsaturated” Suffix changes depending on presence of double bonds Prefix used is always “cyclo~” before the root

38. Nomenclature Try naming… cyclobutanecyclo-1-pentene cyclopent-1-ene

39. Nomenclature Try drawing… cyclo-1,4-hexadiene2,7-diethyl-4-methyl cyclo-1,3,5-heptatriene

40. Aromatics Based on benzene and the presence of benzene- like rings Benzene is a six-carbon ring with three double bonds ▫Cyclo-1,3,5-hexatriene However, the electrons in the double bonds are actually spread over the whole molecule = delocalized ▫Benzene actually has six identical “1 ½” bonds

41. Aromatics Creates greater stability in the molecule These “1 ½” bonds do not behave/react like double bonds Molecules that have this type of sharing are referred to as aromatic compounds Benzene

42. Aromatics Some common aromatics… benzenenapthalene antracene

43. Nomenclature 1.Number carbons in benzene ring assigning lowest number to a branch. a.If more than one branch exists, start numbering at the branch that contains the group with the highest priority (most complex). 2.Name branches attached to the benzene ring, assigning numbers to each branch. a.If only one branch is present, a number does not need to be assigned. 3.Branches are placed before the root as a prefix.

44. Nomenclature Priority of branches on benzene… Highest priority-OH -NH2 -F, -Cl, -Br, -I -CH2CH2CH3 -CH2CH3 Lowest priority-CH3

45. Nomenclature When benzene has only two branches, position numbers do not have to be used Instead, prefixes ortho-, meta-, and para- replace position numbers 1,2-dimethyl benzene ortho-dimethyl benzene

46. Nomenclature 1,3-dimethyl benzene1,4-dimethyl benzene meta-dimethyl benzenepara-dimethyl benzene

47. Nomenclature IUPAC has retained many of the common names for aromatics…

48. Nomenclature Let’s try naming… 3-ethyl-5-methyl phenol

49. Nomenclature Let’s try drawing… 2,6-diethyl-3-methyl benzaldehyde

50. Nomenclature For use when: ▫Naming compounds with >1 fxn’l group ▫Naming compounds with a complicated substituent

51. Nomenclature Try naming… 3-phenyl hexane

52. Nomenclature Try drawing… 4,6-diphenyl 2-octene

53. Up next That covers the basics of hydrocarbons in organic chemistry. Next we will cover functional groups!