Chapter 1 Reactions of Organic Compounds. Reactions Involving Hydrocarbons

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1 Chapter 1 Reactions of Organic Compounds Reactions Involving Hydrocarbons Reactions of Alkanes Single bonds (C-C) are strong and very hard to break, therefore these compounds are relatively unreactive Participate in (the reaction of a substance with oxygen, producing oxides and energy) Complete combustion o Produces and only o Dependent upon availability of oxygen (must be in ) C 2 H 8(g) + 5 O 2(g) 3 CO 2(g) + 4 H 2 O (g) Incomplete combustion o Produces,, and because the hydrocarbon is not fully oxidized o 2 C 3 H 8(g) + 7 O 2(g) 2 C (s) + 2 CO (g) + 2 CO 2(g) + 8 H 2 O Alkanes more commonly participate in o A hydrogen atom is substituted with a halogen atom (F 2, Cl 2, Br 2 ) o Require heat or UV light to dissociate the halogen molecule before the substitution can proceed o The product is a halogenated alkane (the halogen atom is a functional group) which is in the family of alkyl halides Substitution Reaction of Alkanes As the reaction above proceeds, the concentration of bromoethane increases causing it to react with Br 2 again to produce 1,2-dibromoethane. NOTE

2 Reactions of Alkene and Alkynes More reactive than alkanes due to Undergo where atoms are added to the molecule with no loss of H atoms Addition reactions can involve halogens ( ), H ( ), hydrogen halides, or water ( ) Addition Reactions of Alkenes and Alkynes NOTE Markovnikov s Rule o When molecules of non-identical atoms are added to an alkene (ie. HBr, H 2 O), 2 possible products may form o However, the hydrogen is added to the carbon with the greater number of hydrogens already bonded to it ( )

3 + HCl + 2 HCl Sample Problem What compound will be produced when water reacts with 2-methyl-1-pentene? 1. Write the structural formula for 2-methyl-1-pentene 2. Identify the C atom within the double bond that has more H atoms attached to it this carbon will accept the H atom, while the other will accept OH 3. Predict and name the products Reactions of Aromatic Hydrocarbons Undergo Reactivity is between that of alkanes and alkenes

4 As reaction (b) proceeds, bromobenzene reacts with Br 2 to substitute another Br and create 3 possible isomers In practice, the 1,3 isomer is favoured A reaction with benzene and nitric acid A reaction with benzene and an alkyl halide (R X) The halide (Cl) joins the H from the benzene ring to produce HCl, while the alkyl group is substituted onto the benzene ring Sample Problem Predict the product or products formed when benzene is reacted with chloromethane, in the presence of a catalyst (AlCl 3 ). Draw structural diagrams of the reactants and products. The methyl group of chloromethane substitutes for one of the H atoms on the benzene ring, forming methyl benzene and releasing the chloride to react with the displaced H.

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6 Reactions Involving Organic Halides (R X) Preparing Organic Halides Can be produced by (See previous section in notes) o Substitution to alkanes and aromatic compounds o Addition to alkene and alkynes Preparing Alkenes from Alkyl Halides This is the opposite process of producing alkyl halides Undergo o Atoms or ions are removed from a molecule and a double bond is put in their place o OH - ion is needed NOTE A metal hydroxide may also be used to assist an elimination reaction (ex. NaOH). In this case, the halide will form a compound with the metal ion (ex. NaCl), and hydrogen with form a compound with the OH- ion (water).

7 Reactions Involving Alcohols Hydration Reactions (Making Alcohols) Alcohols are made by addition reactions of water to unsaturated hydrocarbons Elimination Reactions (Making Alkenes from Alcohols) The above reaction can also proceed in reverse Catalyzed by Removes an H atom and OH group from neighbouring atoms to leave a double bond May also be called because it creates water Combustion of Alcohols Alcohols combust in the presence of oxygen to produce carbon dioxide and water o Sample Problems 1. Draw the structural diagrams to represent the addition reaction of propene to form an alcohol. Draw your reactant: What must be added to produce an alcohol? Draw your reaction: Remember Markovnikov s Rule to determine which C the H and OH will bond to

8 2. Draw the structural diagrams to represent the dehydration reaction of ethanol. Draw the reactant. Eliminate water (H and OH) from neighbouring atoms to leave a double bond between them. Be aware... When a reaction may yield two or more products, you must include all possibilities in the reaction equation. Ex. The dehydration of 2-butanol produces 1-butene, 2-butene and water + + H 2 O 2-butanol 1-butene 2-butene This also applies for previous reactions discussed (another good example is addition to a benzene ring that already has a branch).

9 Reactions Involving Ethers Preparing Ethers Ethers are formed when two alcohols react to eliminate a molecule of water This is known as a because water is released + + H 2 O methanol methanol methoxymethane water Sample Problem Write a balanced equation to show the formation of an ether from 1-propanol. Begin by drawing your reactants. Circle the components that will be eliminated to form water (H from one alcohol, OH from another). Join the alcohols to form an ether.

10 Reactions Involving Aldehydes and Ketones Preparing Aldehydes and Ketones Done by the controlled of Oxidation a gain of oxygen, or a loss of hydrogen In this case, oxygen atoms are supplied by Ex. hydrogen peroxide (H 2 O 2 ), potassium dichromate (K 2 Cr 2 O 7 ), and potassium permanganate (KMnO 4 ) The symbol (O) will be used to indicated the presence of an oxidizing agent Example: The reactive (O) (one from OH and the other from the R group) resulting in a C=O group and H 2 O. When a is oxidized... When a is oxidized... A tertiary alcohol cannot be oxidized!

11 Hydrogenation of Aldehydes and Ketones The carbonyl group (C=O) undergoes an reaction with (only) to create an alcohol ( ) Requires high heat, pressure, and a catalyst Aldehyde Primary Alcohol Ketone Secondary Alcohol

12 Sample Problem 1 Draw the structural formula and write the IUPAC names to represent the controlled oxidation of an alcohol to form butanone. First, draw the structural formula for butanone. What C atom is the carbonyl group attached? What alcohol must be oxidized? Draw the complete reaction. Sample Problem 2 Draw structural diagrams and write IUPAC names to show the hydrogenation of methanal. Draw your reactant. What must be added to hydrogenate the C=O bond? Write the reaction and name all products.

13 Reactions Involving Carboxylic Acids Preparing Carboxylic Acids When an alcohol is oxidized to an aldehyde, a further oxidation can occur to result in a carboxylic acid Example Step 1: Step 2: Sample Problem 1 Write an equation to show the controlled oxidation of an aldehyde to form butanoic acid. Write the structural formula of the product. The aldehyde required must have the same number of carbons, so it must be. Write the reaction.

14 Sample Problem 2 Write a series of equations to show the reactions needed to produce methanoic acid from methanol. Write IUPAC names for all reactants and products. Remember alcohol aldehyde carboxylic acid Step 1: Step 2:

15 Reactions Involving Esters Preparing Esters This condensation reaction is known as Identify acid and alcohol used from the name of the ester (alcohol is the first part of the name, acid is the second part of the name with the suffix -oate ) General Reaction Example Sample Problem 1 Draw a structural diagram and write the IUPAC name for the ester formed in a reaction between 1-propanol and benzoic acid. Write the reactants, and complete the condensation reaction. Name all compounds. Sample Problem 2 Write a condensed structural diagram equation for the esterification reaction to produce the ester CH 3 CH 2 CH 2 COOCH 2 CH 3. Write the IUPAC names for all reactants and products. Identify the acid. Identify the alcohol. Draw the reaction:

16 Hydrolysis of Esters When an ester is treated with an acid or base, the reverse of esterification occurs The ester splits into its acid and alcohol components Also known as General Example (in a basic solution, the products are the sodium salt of the acid and the alcohol)

17 Reactions Involving Amines and Amides Preparing Amines Substitution reaction Examples primary amine The primary amine produced can also react with an alkyl halide to produce a secondary amine secondary amine tertiary amine

18 Preparing Amides Similar to the preparation of esters Condensation reaction carboxylic acid + amide Remember the amide functional group is a carbonyl group (C=O) attached to a N atom (which can only make 2 other bonds to either H or C atoms) o This is why a tertiary amine cannot react with a carboxylic acid Examples amide amide of Amides Like esters, amides can be hydrolyzed in acidic or basic conditions to. This is essentially the reverse of the formation of amides. Remember Carboxylic acids can produce amides and esters

19 Sample Problem Draw a structural diagram of the amide formed from the reaction between 3-methylbutanoic acid and ethylmethyl amine. Name the amide formed. Draw the structural diagram for the reactants. An OH group is eliminated from the carboxyl group of the acid and an H atom from the amine group of the alcohol. A water molecule is eliminated. A bond forms between the C atom of the carboxyl group and the N atom of the amine group. Draw your reaction equation and name the amide formed.

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