Section 10.2,10.3 and 10.4 (pg ) Hydrocarbon Reactions: Addition, Substitution and Elimination Today’s Objectives: 1)Define, illustrate and provide examples of simple addition, substitution, elimination and esterification (condensation) 2)Predict products and write and interpret balanced equations for the above reations

All Organic Compounds Hydrocarbon Quiz #2

Hydrocarbon Reactions 1. Addition alkenes and alkynes + H 2(g)  alkanes (hydrogenation) alkenes and alkynes + HX (or X 2 )  organic halides 2. Substitution alkanes and aromatics + X 2  organic halides 3. Elimination alcohols  alkenes + water (dehydration) organic halides + OH -  alkenes + halide ion + water 4. Esterification (already covered) carboxylic acid + alcohol  ester + water

1. Addition Reactions: reaction of alkenes and alkynes with hydrogen gas, a halogen compound, or a hydrogen halide compound.  Addition reactions usually occur in the presence of a catalyst a) Addition with H 2(g) (also called hydrogenation)

1. Addition Reactions: reaction of alkenes and alkynes with hydrogen gas, a halogen compound, or a hydrogen halide compound b) Addition of a halogen Since addition reactions involving multiple bonds are very rapid, the alkene product 1,2-dibromoethene can easily undergo a second addition step to produce 1,1,2,2-tetrabromomethane. Excess bromine promotes this second step. 1,2-dichloroethane is a useful solvent and is used to produce chloroethene, the monomer used to make PVC. See Pg. 417 equation

1. Addition Reactions: reaction of alkenes and alkynes with hydrogen gas, a halogen compound, or a hydrogen halide compound c) Addition of an HX (hydrogen halide) molecule Show both possible isomers when predicting the products The addition of hydrogen halides (HF, HCl, HBr or HI) to unsaturated compounds can produce structural isomers, since the hydrogen halide molecules can add in different orientations. However, the type of isomers produced are not always equal. For example only a tiny amount of 1-chloropropane is produced compared to 2-chloropropane in the above reaction.

Practice Addition Reactions  For each of the following questions, draw condensed structural diagrams and name all products 1. ethene + bromine  2. hydrogen chloride + ethene  3. 3-methylbut-1-yne + excess hydrogen  1,2-dibromoethane chloroethane __ 2-methylbutane 

2. Substitution Reactions – breaking of a C-H bond in an alkane or an aromatic ring and replacing it with another atom or group of atoms  Usually occur slowly at room temperature, so light may be necessary as a catalyst  Often substitutes a halogen for a hydrogen  No change in saturation Propane contains hydrogen atoms bonded to end carbons and the middle carbon atom, so two different products (isomers) are formed, in unequal proportions

2. Substitution Reactions – breaking of a C-H bond in an alkane or an aromatic ring and replacing it with another atom or group of atoms Benzene rings are stable, like alkanes, so they react slowly with halogens, even in the presence of light. As with alkanes, further substitution can occur in benzene rings, until all hydrogen atoms are replaced by halogen atoms (in the presence of excess halogens) Would all three isomers be created equally?NO

Practice Substitution Reactions  For each of the following questions, draw condensed structural diagrams and name all products 1. propane + fluorine  2. ethane + chlorine  1-fluoropropane + 2-fluoropropane + hydrogen fluoride chloroethane + hydrogen chloride H - F F - F

3. Elimination Reactions – involves eliminating atoms or groups of atoms from adjacent carbon atoms; decreases the level of saturation a) Alkane cracked into an alkene (uses high temperatures) b) Alcohol is reacted with a catalyst to produce an alkene and water (dehydration – removes a water molecule from the alcohol) a) Alkyl halide reacts with a hydroxide ion (OH - ) to produce an alkene (dehydrohalogenation – removes a hydrogen and halogen atom)

Practice Elimination Reactions  Write a structural formula equation for the preparation of but- 2-ene from chlorobutane, in the presence of a strong base  Write a structural formula equation for the preparation of but- 2-ene from butan-2-ol

Reaction type Complete Combustion AdditionEliminationSubstitutionEsteri- fication Reactants Hydrocarbon* + O 2 ene or yne + HOH, X 2, HX, or H 2 alcohol or alkyl halide alkane or aromatic + X 2 alcohol + carboxylic acid ProductsCO 2 (g) + H 2 O(g) or (l) alcohol, alkyl halide*, alkane alkene + HOH or HX alkyl halideester + water Othertriple or double to single single to double slow; needs uv light acid catalyst needed Othermore bonds*fewer bonds*

Today’s homework  Pg. 422 #7,8 (Addition and Substitution)  Pg. 433 #18-19 (Elimination)  What is coming up tomorrow?  Polymerization  STS Connections