P ROPERTIES 2 OF O RGANIC C OMPOUNDS C HOLESTEROL
2.1 STRUCTURE AND PHYSICAL PROPERTIES Dipole-Dipole Forces Blue arrow: direction of net dipole moment Cl Cl C C Cl Cl H Cl Cl H Tetrachloromethane Dichloromethane Te bond moments cancel Te bond moments do not and there is no net polarity cancel and there is a net polarity Section 2.1 Structure and Physical Properties Dipole-Dipole Forces
Figure 2.1 Physical Properties of Isobutane and Acetone Te physical properties of these two molecules refmect their dipole moments. Isobutane, which has a dipole moment near zero, has a low boiling point of -11.7 o C. Acetone, however, has a large dipole moment of 2.91 D and a boiling point of 56–57 o C. H O CH 3 C C CH 3 CH 3 CH 3 CH 3 Isobutane, bp –11.7 o C Acetone, bp 56-57 o C Section 2.1 Structure and Physical Properties Figure 2.1
London Forces CH 3 CH 2 Br CH 3 CH 2 Cl Boiling point 38.4°C 12.3°C Molecular weight 109 amu 64.5 amu CH 3 H 2 CH 2 CH 2 CH 3 CH 3 CH 2 CH 2 CHvCH 2 CH 3 pentane hexane (bp 36 °C) (bp 69 °C) Section 2.1 Structure and Physical Properties London Forces
Figure 2.2 London Forces (a) T e approach of one nonpolar molecule induces a transient dipole in its neighbor “end-to-end”. (b) Several nonpolar molecules interacting side-by-side by London interactions. induced dipoles induced dipoles δ + δ - δ - δ - δ + δ + δ + δ + δ - δ + δ - δ - δ - δ + δ - δ + δ + δ - (b) (a) CH 3 CH 3 C CH 3 CH 3 CH 2 CH 2 CH 2 CH 3 CH 3 pentane, bp 36 o C 2,2-dimethylpropane, bp 10 o C Section 2.1 Structure and Physical Properties Figure 2.2 London Forces
Figure 2.3 London Forces Molecular models show how the difg erence in surface contact depends on molecular shapes. 2,2-dimethylpropane (neopentane) n -pentane small area of surface contact large area of surface contact Section 2.1 Structure and Physical Properties Figure 2.3 London Forces
Hydrogen-Bonding Forces H H H H O H N H N H H H H O Hydrogen bond Hydrogen bond H H O C H H H H O C Hydrogen bond H H CH 3 CH 2 OH CH 3 CH 3 O ethanol, bp 78.5 o C dimethyl ether, bp -24 o C Section 2.1 Structure and Physical Properties Hydrogen Bonding Forces
Figure 2.4 Hydrogen Bonding in Ethanol Section 2.1 Structure and Physical Properties Figure 2.4 Hydrogen Bonding in Ethanol
Solubility Hydrogen bond H CH 2 O CH 3 H H O Hydrogen bond H O H Section 2.1 Structure and Physical Properties Solubility
Figure 2.5 Water-and Fat-Soluble Vitamins OH HO OH NH 2 OH O O OH CH 3 N O OH HO N OH OH CH 3 N N Vitamin C Riboflavin O Vitamin B 6 Water-soluble vitamins OH Vitamin A (retinol) O H CH 3 (CH 2 ) 3 C (CH 2 ) 3 (CH 2 ) 7 C CH 3 HO CH 3 CH 3 Vitamin E HO Vitamin D 3 Fat-soluble vitamins Section 2.1 Structure and Physical Properties Figure 2.5 Water Soluble and Fat Soluble Vitamins
2.3 BRØNSTED-LOWRY ACIDS AND BASES this bond forms H + H + H O O H Cl Cl this bond H H breaks H + + H N H O H H O H H N H H H H H O O H + + H H H CH 3 C O O CH 3 C O O H H acetate, hydronium ion, acetic acid water, a base conjugate base conjugate acid H H + + CH 3 N H O H O H CH 3 N H H H H H methylamine hydronium ion methylammonium ion, water, conjugate acid conjugate base Section 2.2-2.3 Chemical Reactions: Acid-Base Reactions Brønsted-Lowry Acids
2.3 LEWIS ACIDS AND BASES Cl F Aluminum can accept Al Cl B F Boron can accept an electron pair an electron pair Cl F aluminum trichloride boron trifluoride + FeBr 3 Br FeBr 3 Br Br Br Lewis base Lewis acid F F H F B O CH 3 F B O CH 3 CH 3 F F CH 3 Section 2.2-2.3 Chemical Reactions: Acid-Base Reactions Lewis Acids
2.4 OXIDATION-REDUCTION REACTIONS H O O [O] [O] OH H C H C H C H OH H methanol methanal methanoic acid (formaldehyde) (formic acid) CH 3 CH 3 O K 2 Cr 2 O 7 CH 3 C CH 2 O H CH 3 C C OH H 2 SO 4 CH 3 CH 3 H H H H Pt + H 2 C C H C C H H OH H H H H + H 2 O C C H H H C C H ethene ethane H H H H H H ethene ethanol Pt + 2 H 2 H C C H H C C H H H ethyne Section 2.4 Redox Reactions Examples of Redox Reactions
Biochemical Redox Reactions NAD + + 2H + + 2e - NADH + H + oxidized form reduced form + 2H + + 2e - FAD FADH 2 oxidized form reduced form OH O NAD + + + H + + NADH CO 2 H CH 2 C CO 2 H CO 2 H CH 2 C CO 2 H H oxaloacetic acid malic acid H H CH 3 (CH 2 ) 6 CH 2 CH 2 (CH 2 ) 6 CO 2 H enzyme CH 3 (CH 2 ) 6 CH 2 C C CH 2 (CH 2 ) 6 CO 2 H C C H H H H FAD FADH 2 stearic acid oleic acid Cyt P450 + H + NADP + + OH + H 2 O H + + NADPH O 2 R R reduced form oxidized form Section 2.4 Redox Reactions, II Examples of Biochemical Redox Reactions
2.5 CLASSIFICATION OF ORGANIC REACTIONS addition H Br H H + C C H Br H C C H H H H H bromoethane ethene elimination H OH H H + H C C CH 3 C C H OH H 2 SO 4 H CH 3 H H propene 2-propanol substitution X + Y + Y X R R substitution Br + + OH Br CH 3 CH 3 OH bromomethane methanol Section 2.5 Classifjcation of Organic Reactions Examples of Addition, Elimination, and Substitution Reactions
2.5 CLASSIFICATION OF ORGANIC REACTIONS this bond breaks this bond breaks these bonds form O O hydrolysis + HO + H CH 3 C O CH 3 CH 3 C OH H O CH 3 methyl acetate acetic acid methanol these bonds break this bond forms this bond forms O O condensation + + HO CH 3 C OH CH 3 C O CH 3 H H O CH 3 acetic acid methanol methyl acetate H rearrangement CH 3 C CH CH 2 CH 3 CH CH CH 2 Br Br Section 2.5 Classifjcation of Organic Reactions, II Examples of Hydrolysis, Condensation, and Rearrangement Reactions
2.6 CHEMICAL EQUILIBRIUM AND EQUILIBRIUM CONSTANTS forward reaction m A + n B p X + q Y reverse reaction [X] p [Y] q K equilibrium = [A] m [B] n K eq + HBr CH 2 CH 2 CH 3 CH 2 Br ethene [CH 3 CH 2 Br] = 10 8 K equilibrium = [CH 2 =CH 2 ][HBr] O O K eq + + CH 3 CH 2 OH H 2 O C C CH 3 OH CH 3 OCH 2 CH 3 ethanoic acid ethanol ethyl ethanoate [CH 3 CO 2 CH 2 CH 3 ] [H 2 O] K equilibrium = = 4.0 [CH 3 CO 2 H] [CH 3 CH 2 OH] Section 2.6 Chemical Equilibrium and Equilibrium Constants Equations for Equilibrium Constants
Le Châtelier’s Principle H H O O H C + CH 3 CH 2 OH + C O H H C C OCH 2 CH 3 H 2 O Adding ethanol pushes Removing water H H the reaction to the right pulls the reaction to the right Section 2.6 Chemical Equilibrium and Equilibrium Constants Le Châtelier’s Principle
2.7 EQUILIBRIA IN ACID-BASE REACTIONS K eq Table 2.1 A - + H 3 O + K a and pK a Values of + H 2 O HA Common Acids Acid K a pK a [H 3 O + ][A - ] HBr 10 9 -9 K equilibrium = 10 7 HCl -7 [HA][H 2 O] H 2 SO 4 10 5 -5 10 1 HNO 3 -1 [H 3 O + ][A - ] HF 6 x 10 -4 3.2 K a = K eq [H 2 O] = [HA] 2 x 10 -5 CH 3 CO 2 H 4.7 (CF 3 ) 3 COH 2 x 10 -5 4.7 3 x 10 -11 CH 3 CH 2 SH 10.6 CF 3 CH 2 OH 4 x 10 -13 12.4 3 x 10 -16 CH 3 OH 15.5 (CH 3 ) 3 COH 1 x 10 -18 18 10 -25 CCl 3 H 25 10 -25 25 HC ≡ CH 10 -36 NH 3 36 CH 2 =CH 2 10 -44 44 10 -49 CH 4 49 Section 2.7 Equilibria in Acid-Base-Reactions Table 2.1 Acidity of Common Acids
2.7 EQUILIBRIA IN ACID-BASE REACTIONS, II weaker acid stronger base than H 3 O + than H 2 O conjugate acid-base pair + H 3 O + H 2 O CH 3 CO 2 CH 3 CO 2 H conjugate acid-base pair weaker base than stronger acid CH 3 CO 2- than CH 3 CO 2 H A - + H 2 O HA + OH - [HA][OH - ] K b = K eq [H 2 O] = [A - ] K b + OH – CH 3 CO 2– + H 2 O CH 3 CO 2 H strong base weak base Section 2.7 Equilibria in Acid-Base-Reactions, II Weak and Strong Acids, Conjugate Acids and Bases
2.7 EQUILIBRIA IN ACID-BASE REACTIONS, III Table 2.2 K b and pK b Values of Common Bases Acid K b pK b 4 x 10 -10 9.4 K b NH 2 CH 3 NH 3+ + OH - + H 2 O CH 3 NH 2 weak base strong base CH 3 CO 2 – 5 x 10 -10 9.3 1.6 x 10 -5 4.8 C ≡ N – 1.7 x 10 -5 NH 3 4.8 4.3 x 10 -4 CH 3 NH 2 3.4 CH 3 O – 3 x 10 -16 -1.5 weaker base stronger acid than OH - than H 2 O conjugate acid-base pair + + CH 3 NH 3 CH 3 NH 2 H 2 O OH conjugate acid-base pair weaker acid stronger base than CH 3 NH 3+ than CH 3 NH 2 Section 2.7 Equilibria in Acid-Base-Reactions, III Table 2.2 Basicity of Common Bases
2.8 EFFECT OF STRUCTURE ON ACIDITY O O H O S O H CH 3 O S OH O O sulfuric acid, methane sulfonic acid, a strong acid a strong acid H N H H N CH 2 CH 3 H H ethylamine ammonia pK b 4.74 pK b 3.25 (weak base) (weak base) K a = 10 -16 CH 3 O - H 3 O + + + H 2 O CH 3 OH O O K a = 1.8 � 10 -5 C C CH 3 CO 2- H 3 O + + CH 3 CO 2 H + H 2 O CH 3 O CH 3 O H H H O O O Cl C C H C C C C Cl O H O H H H H O H pK a = 2.9 pK a = 4.7 Section 2.8 Efgect of Structure on Acidity Efgect of Structure on Acidity, Resonance, and Inductive Efgects
2.9 INTRODUCTION TO REACTION MECHANISMS A P reactant product Step 1 A M intermediate reactant Step 2 M P intermediate product Section 2.9 Introduction to Organic Reaction Mechanisms Reactions Tat Proceed Trough an Intermediate
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