1 Organic Chemistry, Third Edition Janice Gorzynski Smith University of Hawai’i Chapter 3 Lecture Outline Prepared by Layne A. Morsch The University of Illinois - Springfield Copyright © 2011 The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 Functional Groups 1. Organic molecules: R (carbon skeleton) - functional group (Heteroatoms or  bonds: C=C and C=O). 2) Functional group: (1) distinguish one organic molecule from another. (2) determine a molecule’s: geometry physical properties chemical reactivity

3 1.Heteroatoms: 1) electronegative N, O, X 2) have lone 2e - and create e - -deficient sites on C. 2.  bond: react as a base and a nucleophile Functional Groups: Heteroatoms and  bonds

4 An Example of a Functional Group Carbon skeleton

5 1)Ethane: No functional group (no polar bonds, lone pairs, or  bonds)  unreactive. 2)Ethanol: have a functional group (OH) - 2e - (lone pairs) and polar bonds  reactive. Ethane and Ethanol

6 1. Hydrocarbons: Aliphatic or Aromatic. Classification of Hydrocarbons

7 The electronegative heteroatom Z (N, O, X) creates a polar bond  reactive 2. Functional Groups with Carbon– Heteroatom (C–Z)  Bonds

8 Functional Groups with C–Z  Bonds

9 1) e - -deficient C: an electrophile, 2) 2e - (lone pairs) on O: a nucleophile and base. 3)  bond of the carbonyl group : a nucleophile and base. 3. Functional Groups with C=O (carbonyl group) Group

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11 Organic Molecules with Several Functional Groups

12 1)bonding and shape 2)Nomenclature 3)physical properties 4)chemical reactivity 5) type and strength of intermolecular forces Importance of Functional Groups

13 Intermolecular forces: interactions between molecules. cf) Intramolecular forces: within molecules 1. Ion-ion interactions (forces) 2. Covalent compounds 1) van der Waals forces 2) dipole-dipole interactions 3) H-bonding Intermolecular Forces

14 Na + Cl - (oppositely charged particles): extremely strong electrostatic interactions  much stronger than the intermolecular forces in covalent molecules. Ion – Ion Interactions

15 1. van der Waals Forces (London forces) 1) Temporary dipole-temporary dipole interaction. *Temporary dipole: Momentary changes in electron density in a molecule. 2) The only attractive forces present in nonpolar compounds. ex) CH 4 (no net dipole)

16 1) All compounds exhibit van der Waals forces. 2) The larger the surface area of a mol, the stronger the van der Waals forces. van der Waals Forces and Surface Area

17 1)The more polarizable, the stronger the van der Waals Forces. 2)the Polarizability: (1) a measure of how the e - cloud around an atom responds to changes in its electronic environment. (2) Larger atoms (more loosely held valence e - ) are more polarizable than smaller atoms (more tightly held e - ). van der Waals Forces and Polarizability

18 1) Dipole – dipole interactions: the permanent dipole-dipole interactions between polar molecules. 2) much stronger than the van der Waals forces. 2. Dipole – Dipole Interactions

19 1)Very strong dipole-dipole interactions. 2)Between H (bonded to electronegative elements (O, N, X) and a lone pair (2e - ) on an electronegative element. 3. Hydrogen Bonding

20 As the polarity of a mol increases, the strength of its intermolecular forces increases. Intermolecular Forces—Summary

21 Physical Properties—bp & mp Boiling point (bp): liquid mol.  gas. Melting point (mp): solid  liquid. The stronger the intermolecular forces, the higher the bp & mp.

22 For compounds with similar functional groups: The larger the surface area, the higher the bp. The more polarizable the atoms, the higher the bp. Figure 3.2 Other Factors Affecting Boiling Points

23 The more compact and symmetrical the shape (a crystalline lactice), the higher the mp. Ex) Neopentane has a much higher mp than isopentane. Effect of Symmetry on Melting Points

24 Figure 3.3 Distillation Apparatus Separation of Liquids Having Different Boiling Points

25 Solubility: the extent of solute dissolution in a solvent. Hydrophobic and Hydrophilic Hydrophobic: Nonpolar part of a mol, water-insoluble (not attracted to H 2 O). Hydrophilic: Polar part of a mol, water-soluble (H-bond to H 2 O). Solubility

26 “Like dissolves like.” 1) Ionic compounds & polar compounds dissolve in polar solvents. 2) Nonpolar or weakly polar compounds dissolve in: - nonpolar solvents (e.g., CCl 4, hexane). -weakly polar solvents (e.g., diethyl ether) 3) Solubility of organic molecules - Relative size of non-polar portion to a polar portion - Water soluble: ≤ 5 C for one functional group Solubility Trends

27 Dissolve in water by many ion–dipole interactions. Figure 3.4 Solubility of Ionic Compounds

28 Relative size of non-polar portion to a polar portion Water soluble when; ≤ 5 C for one functional group For example, Solubility of Organic Molecules

29 Solubility Properties of Representative Compounds

30 Application—Vitamins Vitamins are organic compounds needed in small amt. for normal cell function. 1)Water insoluble vitamin: Vitamin A (one OH for 20 C atoms). 2)Water soluble vitamin: Vitamin C, ascorbic acid, ( many functional groups, capable of H-bonding with water).

31 Soap molecules have two distinct parts: - Hydrophilic polar head. - Hydrophobic nonpolar tail. Soap Structure

32 Figure 3.7 Phospholipids: ionic or polar head & two long nonpolar hydrocarbon tails. In an aqueous environment, phospholipids form a lipid bilayer, the polar exterior & the hydrophobic interior. Structure of Cell Membrane

33 Ions are impermeable to membrane Ionophores: Polar interior (central cavity) & hydrophobic exterior  Transport polar mol & ions across cell membranes Transport Across the Cell Membrane

34 Ionophores transport ions across cell membrane

35 A synthetic ionophore Crown ethers are cyclic ethers containing several oxygen atoms that bind specific cations depending on the size of their cavity. Crown Ethers

36 Nucleophiles React with Electrophiles Functional groups: heteroatom and  bond. Electron-rich sites (nucleophiles) react with electron poor sites (electrophiles).

37 1) 2e - (lone pair) on a heteroatom  bonds. Nucleophilic Sites in Molecules

38 Electrophiles react with nucleophiles: Nu: - donates 2e - to E + 1) Lone pair (Nu: - ) Reaction of Nucleophiles with Electrophiles  electrons (Nu: - ) donates 2e - to electrophile (E + ).

39 1) Many are relatively small with molecular weights of less than 1000 g/mol. 2) Biomolecules often have several functional groups. Biomolecules