Organic Compounds and Carbon's Atomic Properties

1. Chapter 15 Organic Compounds and the Atomic Properties of Carbon

2. Organic Compounds and the Atomic Properties of Carbon 15.1 The Special Nature of Carbon and the Characteristics of Organic Molecules 15.2 The Structures and Classes of Hydrocarbons 15.3 Some Important Classes of Organic Reactions 15.4 Properties and Reactivities of Common Functional Groups 15.5 The Monomer-Polymer Theme I: Synthetic Macromolecules 15.6 The Monomer-Polymer Theme II: Biological Macromolecules

3. Study of C containing compounds. Organic Chemistry

4. The position of carbon in the periodic table. Figure 15.1

5. The Structural Complexity of Organic Molecules Reviewing the atomic structure and properties of carbon, we can get an idea of why organic molecules can be complex. Contributing factors include: • Electron configuration, electronegativity, covalent bonding • 1s2 2s2 2p2 Carbon shares electrons. 2. Bond properties, catenation, and molecular shape. • catenation - two atoms of the same element bound to each other • C forms 4 bonds that point in four different directions. • C forms short strong bonds because of its small size. • It even forms multiple bonds. 3. Molecular stability • atomic size and bond strength – Atomic size increases down a group and bonds become longer and weaker. • Little heat released when C chain reacts • C does not have empty d orbitals that can be attacked.

6. Chemical Diversity Diversity in structure and behavior is due to interrelated factors: 1. Bonding to heteroatoms-atoms other than H and C - See Figure 15.2 2. Electron density and reactivity • C - C bond EN = 0; therefore the C-C bond is nonpolar and in general unreactive. • C - H bond EN ~ 0; therefore the C-H bond is nearly nonpolar and fairly unreactive. • C - O bond EN = 1; therefore the C-O bond is polar and reactive. • bonds to other heteroatoms are usually large and therefore • weak and reactive.

7. The chemical diversity of organic compounds. Figure 15.2 4 carbons linked with single bonds, 1 oxygen and needed hydrogens.

8. The chemical diversity of organic compounds Figure 15.2 continued

9. A specific combination of bonded atoms that reacts in a characteristic way. All reactions take place around the functional group. Table 15.5, P: 639. Functional groups

10. Compounds composed of C-H. Ex: natural gas and gasoline. Hydrocarbons:

11. HYDROCARBONS Carbon Skeletons and Hydrogen Skins When determining the number of different skeletons, remember that Each C can form a maximum of four single bonds, OR two single and one double bond, OR one single and triple bond. The arrangement of C atoms determines the skeleton, so a straight chain and a bent chain represent the same skeleton. Groups joined by single bonds can rotate, so a branch pointing down is the same as one pointing up.

12. C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C C ring Some five-carbon skeletons Figure 15.3 single bonds double bond

13. A C atom single-bonded to one other atom gets three H atoms. A C atom single-bonded to two other atoms gets two H atoms. A C atom single-bonded to three other atoms gets one H atom. A C atom single-bonded to four other atom is already fully bonded (no H atoms). A double-bonded C atom is treated as if it were bonded to two other atoms. A double- and single-bonded C atom or a triple-bonded C atom is treated as if it were bonded to three other atoms. Adding the H-atom skin to the C-atom skeleton Figure 15.4

14. PROBLEM: Draw structures that have different atom arrangements for hydrocarbons with PLAN: Start with the longest chain and then draw shorter chains until you are repeating structures. SOLUTION: (a) Six carbons, no rings SAMPLE PROBLEM 15.1 Drawing Hydrocarbons (a) Six C atoms, no multiple bonds, and no rings (b) Four C atoms, one double bond, and no rings (c) Four C atoms, no multiple bonds, and one ring

15. SAMPLE PROBLEM 15.1 Drawing Hydrocarbons continued (a) continued (b) Four carbons, one double bond (c) Four carbons, one ring

16. Hydrocarbons with single bonds. Saturated hydrocarbons. Bonded to max number of other atoms. CnH2n+2 , Homologous group differs by –CH2 methylene group. C is sp3 hybridized. Alkanes

17. Table 15.1 Numerical Roots for Carbon Chains and Branches PREFIX + ROOT + SUFFIX Number of C atoms Roots meth- 1 eth- 2 prop- 3 but- 4 pent- 5 hex- 6 hept- 7 oct- 8 non- 9 dec- 10

18. Ways of depicting formulas and models of an alkane Figure 15.5

20. It contains one or more rings in structures. CnH2n Cyclopropane has a planar structure. Draw structures for cyclopropane, cyclobutane, cyclopentane, cyclohexane. Cyclic Hydrocarbons

21. Depicting cycloalkanes Figure 15.6 cyclopropane cyclobutane

22. Depicting cycloalkanes Figure 15.6 continued cyclopentane cyclohexane

23. Isomers: Two or more compounds that have same molecular formula but different properties. Constitutional/ Structural isomers: Different arrangement of bonded atoms. Draw isomers of butane and propane and name them. Constitutional Isomerism and Physical Properties of alkanes:

25. Boiling points of the first 10 unbranched alkanes BP increases as chain length increases because dispersion forces increases. Figure 15.7

26. Stereoisomers: Molecules that have same arrangement of atoms but different orientations of groups in space. Optical isomers: Two objects are mirror images and nonsuperimposable. (enantiomers) Chiral: An assymetrical molecule. An organic molecule is chiral if it contains a C atom bonded to 4 different groups. Chiral molecule and optical isomerism:

27. An analogy for optical isomers. Figure 15.8

28. optical isomers of 3-methylhexane optical isomers of alanine Figure 15.9 Two chiral molecules.

29. Polarimeter: Used to measure the angle that the plane is rotated. Optical isomers rotate plane of polarized light in different directions. Dextro-d( +) clockwise. Laveo-l(-) counterclockwise. Racemic: equimolar d+l- does not rotate plane of light. Specific Rotation- It is a characteristic , measurable property at a certain temp, conc and wavelength of light. Chiral molecule and optical isomerism:

30. Figure 15.10 The rotation of plane-polarized light by an optically active substance

31. Hydrocarbons with atleast 1 double bond. Alkenes have general formula: CnH2n. Ethylene is simplest form of alkene. Nomenclature for alkenes: 1) name ends in –ene. 2) Location of double bond is indicated by lowest #. Alkenes (Unsaturated Hydrocarbons)

32. Alkenes exhibit geometric isomers. Alkenes exhibit cis-trans isomerism. Each C atom in C=C should be bonded to two different groups to exhibit cis trans(geometric ) isomerism. Geometric isomers have different properties. Draw structures for cis-2-butene and trans-2-butene. Alkenes

34. Alkynes contain 1 C-C triple bond. Simplest alkyne is acetylene. Name ends with –yne. CnH2n-2 C is sp hybridized Alkenes and alkynes are more reactive than alkanes. Alkynes:

35. PROBLEM: Give the systematic name for each of the following, indicate the chiral center in part (d), and draw two geometric isomers for part (c). PLAN: For (a)-(c), find the longest, continuous chain and give it the base name (root + suffix). Then number the chain so that the branches occur on the lowest numbered carbons and name the branches with the (root + yl). For (d) and (e) the main chain must contain the double bond and the chain must be numbered such that the double bond occurs on the lowest numbered carbon. SAMPLE PROBLEM 15.2 Naming Alkanes, Alkenes, and Alkynes

36. chiral center SAMPLE PROBLEM 15.2 Naming Alkanes, Alkenes, and Alkynes continued SOLUTION: can be numbered in either direction

37. SAMPLE PROBLEM 15.2 Naming Alkanes, Alkenes, and Alkynes continued

38. Planar molecules with one or more rings of 6 C atoms. Simplest form is benzene. Draw structures of toluene, o,m, p,xylene, TNT. Aromatic Hydrocarbons:

39. or Representations of benzene Figure 15.12

41. Types of Organic Reactions An addition reaction occurs when an unsaturated reactant becomes a saturated product: Markovnikov’s Rule. Elimination reactions are the opposite of addition; they occur when a more saturated reactant becomes a less saturated product: A substitution reaction occurs when an atom (or group) from an added reagent substitutes for one in the organic reactant:

42. Figure 15.13 A color test for C=C bonds

43. PROBLEM: State whether each reaction is an addition, elimination, or substitution: PLAN: Look for changes in the number of atoms attached to carbon. SAMPLE PROBLEM 15.3: Recognizing the Type of Organic Reaction • More atoms bonded to C is an addition. • Fewer atoms bonded to C is an elimination. • Same number of atoms bonded to C is a substitution.

44. SAMPLE PROBLEM 15.3: Recognizing the Type of Organic Reaction continued SOLUTION: Elimination: there are fewer bonds to last two carbons. Addition: there are more bonds to the two carbons in the second structure. Substitution: the C-Br bond becomes a C-O bond and the number of bonds to carbon remain the same.

45. The movement of electron density around the C atom determines the oxi-red. 1) C atoms form more bonds to O or fewer to H , oxidation. 2) C atoms form fewer bonds to O or more to H , reduction. Redox process

46. 1) Only single bonds undergo substitution/elimination. 2) Double or triple bonds undergo addition. 3) Both single and double bonds undergo substitution. Functional Groups:

49. Some molecules with the alcohol functional group Figure 15.14

50. the amine functional group primary, 10, amine secondary, 20, amine tertiary, 30, amine General structures of amines Figure 15.15