Chapter 3:

1. Chapter 3: Alkanes and Their Stereochemistry

2. Functional Groups • Functional groups are a group of atoms that has similar characteristic chemical behavior in every molecules where it occurs. • Think of functional groups as individuals in a team. They bring their special abilities yet they all function as a unit or team. • There are many functional groups with different properties.

3. Carbon – Carbon Functional Groups • When a carbon is bound to a second carbon only 4 possibilities arise. • Alkane – Carbon –Carbon (Single Bond - SP3) • Alkene – Carbon – Carbon (Double Bond – SP2) • Alkyne – Carbon – Carbon (Triple Bond – SP) • Arene – Carbon – Carbon (Aromatic Ring – Resonance Structures) • Properties: Covalent Bonds (Oil Soluble)

4. Basic Carbon Structures: Carbon

5. Carbon – Oxygen (Single Bond) • When a carbon is singly bound to a oxygen the most common functional possibilities are: • Alcohol (C-OH) are used as antiseptic, beverage, etc … • Ether (C-O-C) are used as solvents for synthesis. • Phosphate (C-O-PO3) found in DNA, RNA, and many biological molecules. • Properties: Polar Covalent Bonds (Water Soluble)

6. Basic Carbon Structures: Oxygen

7. Carbon – Oxygen (Double Bond) • When a carbon is doubly bound to a oxygen called a carbonyl the most common functional possibilities are: • Aldehyde C-(C=O)-H • Ketone C-(C=O)-C • Carboxylic Acid C-(C=O)-O-H • Carboxylic Acid Ester C-(C=O)-O-C • Carboxylic Acid Anhydride C-(C=O)-O-(C=O)-C • Properties: Polar Covalent Bonds (Water Soluble) • Carboxylic Acid is a strong acid

8. Basic Carbon Structures: Carboxyl

9. Carbon – Nitrogen • When a carbon is singly bound to a nitrogen the most common functional possibilities are: • Amine- (C-N) single bond • Imine- (C=N) double bond • Nitrile (C=N) triple bond • Nitro (C-NO2) • Amide (C=O)-N- • Properties: Polar Covalent Bonds (Water Soluble) • Can be strongly basic (accepts a proton)

10. Basic Carbon Structures: Nitrogen

11. Carbon – Sulfur • When a carbon is singly bound to a sulfur the most common functional possibilities are: • Thiol (C-S-H) single bond to carbon and one to hydrogen • Sulfide (C-S-C) 2 single bond to carbon(s) • Sulfoxide C-(S=O)-C double bond • Sulfone C-(O=S=O)-C 2 double bonds • Properties: Polar Covalent Bonds (Water Soluble)

12. Basic Carbon Structures: Sulfur

13. Common Functional Groups

14. Basic Carbon Structures: Alkane

15. Basic Carbon Structure: Alkene

16. Basic Carbon Structure: Alkyne

17. Basic Carbon Structure: Alcohol

18. Basic Carbon Structure: Ether

19. Basic Carbon Structure: Carboxyl • Carboxyl is found in a number of functional groups. • It is reactive and is often used in organic reactions.

20. Basic Carbon Structure: Aldehyde

21. Basic Carbon Structure: Ketone

22. Basic Carbon Structure: Carboxylic Acid

23. Basic Carbon Structure: Ester

24. Basic Carbon Structure: Amine

25. Basic Carbon Structure: Imine

26. Basic Carbon Structure: Nitrile

27. Basic Carbon Structure: Nitro

28. Basic Carbon Structure: Amide

29. Basic Carbon Structure: Sulfide

30. Basic Carbon Structure: Sulfoxide

31. Basic Carbon Structure: Sulfone

32. Basic Carbon Structure: Thiol

33. What are Alkanes? • Alkanes are chains of carbon(s) and hydrogen(s) that are SP3 hybridized. • Remember: Carbon and hydrogen maintain similar electronegativies so that they have a covalent bond (even distrubtion of electrons). Non-polar molecules.

34. Properties of Alkanes • Alkane chains are nonpolar molecules single bonded (SP3) carbon chains. You can think of them as oils. • Alkanes are saturated hydrocarbon (also aliphatic) because they only contain carbons and hydrogens. • Octane is an alkane chain of 8 carbons and 18 hydrogens that you use as fuel in your gas tank. • Cooking oils are also alkane chains.

35. Types of Alkane Chains • There are two different types of alkane chains. 1) Straight chain alkanes (normal alkanes) 2) Branched-chain alkanes

36. Different Structures that Represent Alkanes All of these structures represents C4H10 butane

37. Alkane Isomers • Isomers are compounds that have the same number and kind of atoms but are arranged differently. They can be applied to most organic structures. • Constitutional Isomers – have the same molecular formula but have different arrangements. See below (C4H10) They both have the same number of carbons and hydrogens.

38. Naming Carbon Backbones • To name carbon chains we determine the number of the longest connected carbons to get a proper name. • For example if we had a 5 carbon chain we would have Pent- • And if the carbon chain were all single bonds we would have an –ane ending. • The Name would be :Pentane

39. Naming Carbons Skeletons Methane Ethane Propane Butane Pentane Hexane Heptane Octane Nonane Decane • 1 (Carbon) Meth- • 2 (Carbons) Eth- • 3 (Carbons) Prop- • 4 (Carbons) But- • 5 (Carbons) Pent- • 6 (Carbons) Hex- • 7 (Carbons) Hept- • 8 (Carbons) Oct- • 9 (Carbons) Non- • 10 (Carbons) Dec-

40. Carbons as Substitutents • If carbon chains are part of a branched alkane chain then the branches would be the same parent (backbone) name but you would add a –yl to the end of the name. • Methyl • Propyl • Octyl • Decyl

41. Naming Carbon Chains (Alkyl) Prefix – Locant – Parent – Suffix What is the primary group functional group. Additional functional groups and placements. How many carbons are in the longest chain. Where is the primary group (number).

42. Steps to Naming Alkane Chains • Step 1. Find the longest carbon chain (Parent hydrocarbon). YOU HAVE TO REALLY LOOK. • Step 2. Number the atoms in the main chain. Make sure that if anything is bound to this chain it is at the lowest carbon number. • Step 3. Identify and number the substitutents. • Step 4. Write the name as a single word. Use hyphens to separate the groups and comma for the numbers. • Step 5. Name a complex substitutents as though it were itself compound.

43. Example 1 Find the longest carbon chain By counting carbons. Number the carbons in the chain substitutents with the lowest number. Seven carbons - Hept Identify the number and name of the substitutents Methyl on 3 carbon Write the name on one line 3-Methylheptane

44. Types of Carbons These are the types of SP3 carbons, Primary, Secondary, Tertiary, Quaternary carbons.

45. Other Branched Alkane Group Names

46. Properties of Alkanes • Alkanes are normally chemically inert (normally does not easily react with anything except with O2) • Both the melting point and boiling point increases with the length of the carbon chain. • Increased branching decrease the boiling point when compared to the straight chains.

47. Conformation of Ethane • Stereochemistry is the branch of chemistry that is concerned with the three dimensional aspects of molecules. • Carbons that are singly bond rotate in space (just like an umbrella). Newman Projections looks directly down the carbon – carbon bond.

48. Torsional Strain • Torsional Strain describes how atoms or groups move between single bonds as they rotate. • When 2 atoms or groups overlap then the energy increases (eclipsed), when they move apart (staggered) the energy decreases. • This happens three times in a rotation of 360o.

49. Conformation Energies • Energies of Ethane changes not only in the staggered and eclipsed forms but with the size of the additional groups bound. • The bigger the groups the more energy it takes to pass each other when rotating. • The lowest energy called the anti-conformation places the two bulk groups on the other side of the bond.

50. Take Home Message • Know Functional Groups • Know Naming of Alkanes • Know Properties of Alkanes • Understand Conformation and its Energies.