Types of Organic Reactions UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Types of Organic Reactions Learning Goal: I will understand the different kinds of organic reactions (addition, elimination, substitution, condensation, esterification, hydrolysis, oxidation, reduction, combustion) and be able to recognize each, as well as show the products/reactants of each type of organic reaction The material in this section is an overview of important organic reactions. For each type of reaction, students should be able to identify the type of reaction, given a chemical equation predict the products of a reaction, given the reactants identify the reactants, given the product(s)

Summary of Organic Reactions UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Summary of Organic Reactions Important types of organic reactions: addition elimination substitution condensation esterification hydrolysis oxidation reduction combustion The material in this section is an overview of important organic reactions. For each type of reaction, students should be able to identify the type of reaction, given a chemical equation predict the products of a reaction, given the reactants identify the reactants, given the product(s)

Recap: Addition Reactions UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Recap: Addition Reactions Reactions between an alkene or alkyne and a small molecule (HOH, H2, HX, X2) Atoms of a small molecule are added to carbons of a double or triple bond Reactions of alkynes can produce alkenes or alkanes Constitutional isomers may form The general formula for an addition reaction is shown in this slide. An alkene or alkyne reacts with a small molecule, typically H2O, H2, HX, or X2 (where X = F, Br, Cl, or I). For alkynes: bonds with three new atoms can form, leaving a single bond between the two carbon atoms if the amount of the small molecule is limited, an alkene is formed For asymmetric alkenes: more than one product might form (isomers are produced) if the two atoms or groups of atoms being added are different (e.g. HX, HOH), they can be placed on either of the two carbons involved in the double bond The following slide shows an example: pent-2-ene reacting with HCl(g) Carbon atoms of the multiple bond have more atoms bonded to them in the product.

Answer on the next slide UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Learning Check #1 Show how constitutional isomers can form from the following reaction. Answer on the next slide

Learning Check #1: Answer UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Learning Check #1: Answer The chlorine atoms can be added to either carbon 2 or 3 in this addition reaction. For this reaction, both 3-chloropentane and 2-chloropentane are produced.

Addition Reactions (cont’d) UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Addition Reactions (cont’d) One constitutional isomer will predominate. To predict the major product: Markovnikov’s rule: The hydrogen atom of the small molecule will attach to the carbon atom of the double bond that is bonded to the most hydrogens. For reactions involving asymmetric alkenes and small molecules, there is one isomer that will be more abundant. Use Markovnikov’s rule to predict the more abundant isomer that will form: the hydrogen atom of the small molecule will attach to the carbon of the double bond that is already bonded to the most hydrogen atoms. The 2-chloropropane isomer will be the major product.

Elimination Reactions UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Elimination Reactions Two atoms bonded to carbon atoms of an organic molecule are removed and a double bond forms The double bond forms between the carbon atoms that have had the atoms removed Elimination reaction can be thought of as the reverse of an addition reaction The general formula for an elimination reaction is shown in this slide. In this reaction, the organic reactant loses two atoms bonded to carbons and a double bond is formed between the two carbons that have lost those atoms. Alcohols undergo elimination reactions in the presence of a strong acid catalyst, such as sulfuric acid (H2SO4). An alkene and water are the products. Haloalkanes undergo elimination reactions when they are heated in the presence of a strong base, such as sodium ethoxide (NaOCH2CH3). An example is on the following slide. Carbons of the organic product are bonded to fewer atoms than carbons of the reactant.

Answer on the next slide UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Learning Check #2 Draw the product of the following elimination reaction. Answer on the next slide

Learning Check #2: Answer UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Learning Check #2: Answer The product formed is: For this reaction, both 3-chloropentane and 2-chloropentane are produced.

Elimination Reactions (cont’d) UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Elimination Reactions (cont’d) What if an asymmetric molecule undergoes elimination? When asymmetric molecules undergo elimination, there is also a general rule that is used to predict the major product. In the example shown, the hydrogen atom is most likely to be removed from the third carbon. Therefore, but-2-ene is the major product (i.e., it is produced in higher abundance). Note that both the cis and trans isomers are formed. Only the trans form is shown. The minor product is formed by the removal of the hydrogen from the first carbon. General rule: The hydrogen atom is more likely to be removed from the carbon atom with the most C-C bonds.

Substitution Reactions UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Substitution Reactions Reaction in which a hydrogen or functional group has been replaced by another functional group Two compounds react to form two different compounds The same number of atoms are bonded to the carbon atoms of the reactants and products The general formula for a substitution reaction is shown in this slide. In this reaction, a hydrogen or functional group (e.g., –OH, -X) is replaced by a different functional group. Alcohols can react with an acid that contains a halogen (e.g. HCl). The –OH group of the alcohol is replaced by the halogen, producing a haloalkane. Haloalkanes can react with a hydroxide ion to produce an alcohol. Two compounds are converted to two new compounds.

Answer on the next slide UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Learning Check # 3 Draw the products of the following substitution reaction. Answer on the next slide

Learning Check # 3: Answer UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Learning Check # 3: Answer The products formed are: Since it is a substitution reaction of a haloalkane with hydroxide ion, an alcohol is the product.

Condensation Reactions UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Condensation Reactions Two molecules combine to produce a larger organic molecule and another much smaller molecule Water is often the smaller molecule formed Large biomolecules (DNA, fats, carbohydrates, protein) are formed through this type of reaction Production of amides and esters are examples Condensation reactions typically produce water, in addition to the large organic molecule. This is because these reactions usually involve loss of a –OH group from a carboxylic acid and a hydrogen atom from the second reactant molecule (such as an amine). The next two slides discuss reactions that are very important in biological systems. Condensation reactions and a certain type of condensation reaction, called esterification, are carried out by the cell to synthesize large, complex, biologically important molecules, such as proteins, lipids (fats), carbohydrates, and the genetic material, DNA and RNA. For the synthesis of these very large molecules, the reactions occur repeatedly, building up the molecule with the completion of each reaction. A condensation reaction between a carboxylic acid and an amine produces an amide.

Esterification Reactions (A type of condensation reaction) UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Esterification Reactions (A type of condensation reaction) These are a type of condensation reaction A carboxylic acid and an alcohol react to produce an ester and water In what way(s) is an esterification reaction like a condensation reaction? Sample answer to question prompt: a carboxylic acid is one reactant the –OH group of the carboxylic acid becomes part of the second smaller product molecule two molecules combine to form a larger molecule and a much smaller molecule (in this case it is always water) An esterification reaction is between a carboxylic acid and an alcohol.

Hydrolysis Reactions UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Hydrolysis Reactions A molecule is broken apart through the addition of a water molecule (HOH) The –OH is added to one side of a bond, and the H is added to the other side of the bond They are the reverse of condensation reactions The general formula for a hydrolysis reaction is shown in this slide. The term hydrolysis means “splitting apart using water.” This helps to remember that the reaction involves the breaking apart of an organic molecule by water, namely the –OH and –H groups of water. The hydrolysis reaction is the reverse of the condensation reaction (or esterification reaction). Therefore, an ester can undergo hydrolysis to produce a carboxylic acid and an alcohol. In hydrolysis reactions, molecules are broken apart using water as a reactant.

Hydrolysis Reactions are the Reverse of a Condensation Reaction

Answer on the next slide UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Learning Check #4 What are the products of the following reaction? What type of reaction is this? Answer on the next slide

Learning Check #4: Answer UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Learning Check #4: Answer This is an esterification reaction. The products are:

Learning Check #5 The hydrolysis reaction with water is so slow that must be catalysed with dilute acid, so the ester is heated with a dilute acid like dilute hydrochloric acid or dilute sulphuric acid. Show/name the products of hydrolysing ethyl ethanoate:

Oxidation Reactions UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Oxidation Reactions In organic chemistry, the term refers to carbon atoms of the organic reactant forming more bonds to oxygen atoms, or forming fewer bonds to hydrogen atoms Common oxidizing agents, [O], are KMnO4 and K2Cr2O7 Oxidation reactions are always accompanied by reduction reactions. Because of this, these reactions are often referred to as oxidation-reduction reactions. Typically, they are discussed in terms of the transfer of electrons. One reactant is oxidized through the loss of electrons and another reactant is reduced by the gain of electrons. This approach is taken in Unit 5. For this unit, only what is occurring to the organic reactant is considered. Therefore, oxidation and reduction reactions are dealt with separately. Also, oxidation and reduction are defined according to changes in the bonds to the carbons of the organic reactant. Organic compounds that have undergone oxidation can be recognized by an increase in the number of bonds to oxygen atoms or decrease in number of bonds to hydrogen atoms. Organic compounds become oxidized when they react with oxidizing agents, indicated by the symbol [O] Some oxidations of organic compounds may also be classified as elimination (e.g., ones that involve formation of C=O, such as the oxidation of alcohols to aldehydes or ketones). Compare the number of C-H and C-O bonds in the reactant and product.

Reduction Reactions UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Reduction Reactions In organic chemistry, the term refers to carbon atoms of the organic reactant forming fewer bonds to oxygen atoms, or forming more bonds to hydrogen atoms Common reducing agents, [H], are LiAlH4 and H2/Pt Organic compounds that have undergone reduction can be recognized by a decrease in the number of bonds to oxygen atoms or increase in number of bonds to hydrogen atoms. Organic compounds become reduced when they react with reducing agents, indicated by the symbol [H] Often C=C and C=O are reduced to C-C and C-O. Therefore, some may be classified as an addition reaction Aldehydes, ketones, carboxylic acids can be reduced to alcohols Alkenes and alkynes can be reduced to alkanes Compare the number of C-H and C-O bonds in the reactant and product.

Answer on the next slide UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Learning Check #6 What is the product of the following reaction? Is this an oxidation or reduction reaction? + [H] Tips: 1. [H] is shown, which represents a reducing agent. Therefore, this is a reduction reaction. 2. Identify the type of organic compound being reduced. In this case, it is a ketone. 3. What type of organic compound is produced from the reduction of ketones? Alcohols. Therefore, the product must be the alcohol equivalent to the ketone, with the same number of carbon atoms as the ketone. Answer on the next slide

Learning Check #6: Answer UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Learning Check #6: Answer The reaction is a reduction of propanone (acetone) to produce propan-2-ol (isopropanol). There are fewer bonds to O, and more bonds toH

Combustion Reactions UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Combustion Reactions A compound reacts with oxygen to produce oxides of the component elements The products of the complete combustion of a hydrocarbon are carbon dioxide and water If O2 is insufficient, incomplete combustion occurs Regardless of the hydrocarbon, complete combustion always results in production of carbon dioxide and water. If there is insufficient oxygen available, the incomplete combustion occurs and other products are produced, such as soot, indicated by C(s), and the highly toxic carbon monoxide gas. This occurs in situations such as the orange-yellow flame of a Bunsen burner or burning candle, as well as fuel-burning stoves and heaters when used indoors.

Organic Reactions Summary UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 Organic Reactions Summary

HOW DID WE DO? Learning Goal: UNIT 1 Chapter 2: Reactions of Organic Compounds Section 2.1 HOW DID WE DO? Learning Goal: I will understand the different kinds of organic reactions (addition, elimination, substitution, condensation, esterification, hydrolysis, oxidation, reduction, combustion) and be able to recognize each, as well as show the products/reactants of each type of organic reaction The material in this section is an overview of important organic reactions. For each type of reaction, students should be able to identify the type of reaction, given a chemical equation predict the products of a reaction, given the reactants identify the reactants, given the product(s)