DAMIETTA UNIVERSITY. Energy Diagram of One-Step Exothermic Reaction

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1 DAMIETTA UNIVERSITY CHEM-103: BASIC ORGANIC CHEMISTRY LECTURE 5 Dr Ali El-Agamey 1 Energy Diagram of One-Step Exothermic Reaction The vertical axis in this graph represents the potential energy. The transition state is the highest point on the graph, and the activation energy is the energy difference between the reactants and the transition state. Chapter 4 2 1

2 Endothermic and Exothermic Diagrams Chapter 4 3 Energy Diagram for the Chlorination of Methane Chapter 4 4 2

3 Rate-Limiting Step Reaction intermediates (e.g. CH 3 ) are reactive species however, they can be stable (i.e. less reactive) as long as they don t collide with another molecule or atom. Transition states are at energy maximums. Intermediates are at energy minimums. The reaction step with highest E a will be the slowest, therefore rate-determining for the entire reaction. Chapter 4 5 Carbocation Structure Carbon has 6 electrons, positively charged. Carbon is sp 2 hybridized with vacant p orbital. Chapter 4 6 3

4 Carbocation Stability Chapter 4 7 Carbocation Stability (Continued) Stabilized by alkyl substituents in two ways: 1. Inductive effect: Donation of electron density along the sigma bonds. 2. Hyperconjugation: Overlap of sigma bonding orbitals with empty p orbital. Chapter 4 8 4

5 Electrophilic Addition Step 1: Pi electrons attack the electrophile. Step 2: Nucleophile attacks the carbocation. Chapter 8 9 Addition of HX to Alkenes Step 1 is the protonation of the double bond. The protonation step forms the most stable carbocation possible. In step 2, the nucleophile attacks the carbocation, forming an alkyl halide. HBr, HCl, and HI can be added through this reaction. Chapter

6 Mechanism of Addition of HX Step 1: Protonation of the double bond. Step 2: Nucleophilic attack of the halide on the carbocation. Chapter 8 11 Markovnikov s Rule The acid proton will bond to carbon 3 in order to produce the most stable carbocation possible. Chapter

7 13 Mechanism for Hydration Chapter

8 Orientation of Hydration The protonation follows Markovnikov s rule: The hydrogen is added to the less substituted carbon in order to form the most stable carbocation., Chapter 8 15 Regioselectivity Markovnikov s Rule: The addition of a proton to the double bond of an alkene results in a product with the acidic proton bonded to the carbon atom that already holds the greater number of hydrogens. Markovnikov s Rule (extended): In an electrophilic addition to the alkene, the electrophile adds in such a way that it generates the most stable intermediate. Chapter

9 Alcohols 2010, Prentice Hall 17 Structure of Water and Methanol Oxygen is sp 3 hybridized and tetrahedral. The H O H angle in water is The C O H angle in methyl alcohol is Chapter

10 Physical Properties Alcohols have high boiling points due to hydrogen bonding between molecules. Small alcohols are miscible in water, but solubility decreases as the size of the alkyl group increases. Chapter Classification of Alcohols Primary: carbon with OH is bonded to one other carbon. Secondary: carbon with OH is bonded to two other carbons. Tertiary: carbon with OH is bonded to three other carbons. Aromatic (phenol): OH is bonded to a benzene ring. Chapter

11 Examples of Classifications C H 3 C H 3 C H Primary alcohol C H 2 O H * O H C H 3 C H C H 2 C H 3 * Secondary alcohol C H 3 C H 3 C * O H Tertiary alcohol C H 3 Chapter Nomenclature of alcohols IUPAC nomenclature (1) Parent name is alkanol Choose the longest continuous chain containing the hydroxy group. Numbering begins at one end so as to give the hydroxy group the lowest possible number. Alcohols with two OH groups are called diols and Alcohols with three OH groups are called triols

12 Multifunctional Compounds The functional group with the highest priority determines the parent name. Naming Priority: aldehyde > ketone > alcohol > alkene > alkyne Chapter Examples of Nomenclature C H 3 C H 3 C H C H 2 O H C H 3 C H C H 2 C H Methyl-1-propanol 2-Methylpropan-1-ol O H 2-Butanol Butan-2-ol 1C H 3 2 C H 3 C O H 3C H 3 2-Methyl-2-propanol 2-Methylpropan-2-ol O H C H 2 C H C H 2 C H C H penten-2-ol pent-4-en-2-ol Chapter

13 Write the IUPAC name of the following compounds 25 Homework: Write the IUPAC name of the following compounds 26 13

14 Preparation of Alcohols anti-markovnikov addition Markovnikov addition (1) Oxymercuration (2) demercuration Ac = CH 3 CO Markovnikov addition 27 Preparation of Alcohols 28 14

15 Grignard Reagents Formula R Mg X (reacts like R: - + MgX). Ethers are used as solvents to stabilize the complex. May be formed from any halide. Chapter Examples Chapter

16 Reaction with Carbonyl Chapter Preparation of Alcohols 32 16

17 Preparation of Alcohols 33 Reaction of Grignards with Carboxylic Acid Derivatives Chapter

18 Esterification Reactions of Alcohols Reaction of an alcohol and a carboxylic acid produces an ester. Sulfuric acid is a catalyst. Chapter Reactions of Alcohols SOCl 2 : Thionyl chloride 36 18

19 Reactions of Alcohols (as acids) Sodium isopropoxide Metal alkoxide 37 Alkoxide Ions: Williamson Ether Synthesis Sodium alkoxide 1 o alkyl halide ether Ethers can be synthesized by the reaction of alkoxide ions with primary alkyl halides in what is known as the Williamson ether synthesis. Chapter

20 4.32 Homework: Complete the following equations 39 How could you prepare the following compound by three different methods? 40 20