Chapter 22 Organic and Biological Molecules

1. Chapter 22Organic and Biological Molecules

2. 22.1 – Alkanes: saturated hydrocarbons • Uses of organic chemistry: • Biochemistry • Medicinal chemistry • Molecular biology • Synthetics • Industry (petroleum) • And more!

3. 22.1 – Alkanes: saturated hydrocarbons • Hydrocarbons: compounds containing carbon and hydrogen • Saturated: hydrocarbons where each carbon is bound to four atoms • Unsaturated: hydrocarbons that contain carbon-carbon multiple bonds (double or triple)

4. 22.1 – Alkanes: saturated hydrocarbons • The simplest saturated hydrocarbon is methane (CH4)

5. 22.1 – Alkanes: saturated hydrocarbons Number of carbons IUPAC prefix 1 meth- 2 eth- 3 prop- 4 but- 5 pent- 6 hex- 7 hept- 8 oct- 9 non- 10 dec-

6. 22.1 – Alkanes: saturated hydrocarbons • If you add the suffix –ane, to any of those prefixes, you have generated their alkanes. • If that is all you add, they are called straight-chained alkanes, or unbranchedalkanes • For all alkanes, the general formula is given by: CnH2n+2

7. 22.1 – Alkanes: saturated hydrocarbons

8. 22.1 – Alkanes: saturated hydrocarbons • Isomerism: • In organic chemistry, isomers are chemical compounds with the same molecular formula, but a different structural formula

9. 22.1 – Alkanes: saturated hydrocarbons • Isomerism:

10. 22.1 – Alkanes: saturated hydrocarbons • Isomerism: • C4H10 and up all exhibit structural isomerism, also known as constitutional isomerism. In this form of isomerism, the molecules have the same number of atoms, but different bonds

11. 22.1 – Alkanes: saturated hydrocarbons • Nomenclature 1. Find the longest uninterrupted carbon chain. Depending on how many carbons there are, this determines the prefix (here, it is ______hexane)

12. 22.1 – Alkanes: saturated hydrocarbons • Nomenclature 2. Branches are named by dropping the -ane suffix and adding an -yl suffix

13. 22.1 – Alkanes: saturated hydrocarbons • Nomenclature 3. The position of the branch must be indicated by finding its position on the main carbon chain. The goal is to always have the lowest numbering possible

14. 22.1 – Alkanes: saturated hydrocarbons • Nomenclature We could call this 3-ethylhexane or 4-ethylhexane. Since the numbering is smaller in 3-ethylhexane, it is the suitable name

15. 22.1 – Alkanes: saturated hydrocarbons • Nomenclature 4. The naming goes alphabetically. If there are more than one of a substituent (branch), the prefixes –di and –tri are used. They do not count when alphabetizing.

16. 22.1 – Alkanes: saturated hydrocarbons • Nomenclature

17. 22.1 – Alkanes: saturated hydrocarbons • Nomenclature

18. 22.1 – Alkanes: saturated hydrocarbons • Nomenclature

19. 22.1 – Alkanes: saturated hydrocarbons • Reactions • Combustion • Common in the petroleum industry (methane, propane, butane, octane, etc…) • In a perfect world, the products are CO2 and H2O (incomplete combustion leads to CO and others)

20. 22.1 – Alkanes: saturated hydrocarbons • Reactions • Substitution • Primarily seen when halogens (F, Cl, Br, I) replace hydrogen atoms in an alkane • Example, the free radical halogenation of CH4 with Cl2

21. 22.1 – Alkanes: saturated hydrocarbons • Reactions • Dehydrogenation • Is the creation of double bonds in an alkane (turning it into an alkene)

22. 22.1 – Alkanes: saturated hydrocarbons • Cyclic alkanes • Simplest cyclic alkane is cyclopropane, C3H6. • These alkanes follow CnH2n

23. 22.1 – Alkanes: saturated hydrocarbons • Naming Cyclic alkanes • Just add the prefix –cycloto the alkane • If there is only one substituent coming off of the cyclic hydrocarbon, you do not need to number it

24. 22.1 – Alkanes: saturated hydrocarbons • Stability of cyclic alkanes • Cyclohexane

25. 22.2 – Alkenes and Alkynes • Alkenes • The carbons involved have sp2 hybridization, and adopt a trigonal planar shape (flat!)

26. 22.2 – Alkenes and Alkynes • Alkenes • Recall from chapter 9 that a C=C has a sigma bond (from overlapping sp2 orbitals) and a pi bond (from overlapping pi orbitals).

27. 22.2 – Alkenes and Alkynes • Alkenes • Naming alkenes: • Instead of an –ane suffix, use a –enesuffix • IUPAC name for the simplest alkene is: ethene (although it is often called acetylene)

28. 22.2 – Alkenes and Alkynes • Alkenes • Naming alkenes: • In longer alkenes, you must number the parent chain to figure out the location of the double bond. Since it exists in two carbons, put the lower number carbon in the name

29. 22.2 – Alkenes and Alkynes • Alkenes • Cis-trans (Z/E) isomerism: • Only occurs if both carbons involved in double-bonding have two different substituents coming off of them Cannot have isomers

30. 22.2 – Alkenes and Alkynes • Alkenes • Cis-trans (Z/E) isomerism: • Example, 2-pentene cis-2-pentene trans-2-pentene (Z)-2-pentene (E)-2-pentene

31. 22.2 – Alkenes and Alkynes • Alkenes • Cis-trans (Z/E) isomerism • Cahn-Ingold-Prelog rules for assigning E/Z: 1. The higher priority goes to the higher atomic number

32. 22.2 – Alkenes and Alkynes • Alkenes • Cis-trans (Z/E) isomerism • Cahn-Ingold-Prelog rules for assigning E/Z: 2. If there is a tie, you go to the next atom in the line (count double bonds as two single bonds to the same atom )

33. 22.2 – Alkenes and Alkynes • Alkenes • Properties: • More reactive than alkanes • Usually have a strong odor

34. 22.2 – Alkenes and Alkynes • Alkenes • Reactions: • Alkenes are synthesized through elimination reactions (because two atoms are eliminated)

35. 22.2 – Alkenes and Alkynes • Alkenes • Reactions: • Addition reaction

36. 22.2 – Alkenes and Alkynes • Alkenes • Reactions: • Hydrogenation

37. 22.2 – Alkenes and Alkynes • Alkynes • Have sphybridization (linear)

38. 22.2 – Alkenes and Alkynes • Comparing properties of alkanes, alkenes, and alkynes Alkanes Alkenes Alkynes Low BP Less acidic Less energy in bonds High BP More energy in bonds More acidic

39. 22.3 – Aromatic Hydrocarbons • Aromatic hydrocarbons are extremely stable (unreactive) cyclic hydrocarbons • They are planar molecules (all atoms in the cyclic structure are sp2 hybrids) • They have delocalized pi electrons

40. 22.3 – Aromatic Hydrocarbons • Examples

41. 22.3 – Aromatic Hydrocarbons • Benzene is a commonly studied aromatic compound.

42. 22.3 – Aromatic Hydrocarbons • Naming the positions • Ortho-, meta-, para-

43. 22.3 – Aromatic Hydrocarbons • As a substituent, benzene is called a phenyl group

44. 22.3 – Aromatic Hydrocarbons • Some notable benzene derivatives: Hydroxybenzene (phenol)

45. 22.3 – Aromatic Hydrocarbons • Reactions: • Substitution

46. 22.4 – Hydrocarbon Derivatives

47. 22.4 – Hydrocarbon Derivatives • Alcohols and ethers • Alcohols have an -OH group • Has hydrogen bonding, therefore has a higher boiling point • Methanol boils at 65oC • Ethane boils at -89oC Same molar mass, difference in BP’s come from the H-bonding!

48. 22.4 – Hydrocarbon Derivatives • Alcohols and ethers • Naming alcohols: • Uses the suffix –ol • This can be named as either 2-butanol or butan-2-ol • This is a secondary alcohol

49. 22.4 – Hydrocarbon Derivatives • Alcohols and ethers • Naming alcohols: • Uses the suffix –ol • This name is 6-bromo-2-methyl-2-hexanol or 6-bromo-2-methylhexan-2-ol

50. 22.4 – Hydrocarbon Derivatives • Alcohols and ethers • Ethers are two organic compounds joined by an oxygen atom • They generally do not experience hydrogen bonding (low BP’s)