Chapter Thirteen Unsaturated Hydrocarbons

13 | 2 Unsaturated Hydrocarbons AlkANES –Hydrocarbons in which all of the carbon-carbon bonds are _____________ bonds AlkENES –Hydrocarbons in which at least one of the carbon- carbon bonds is a ____________ bond AlkYNES –Hydrocarbons in which at least one of the carbon- carbon bonds is a ______________ bond

13 | 3 Properties of Alkenes and Alkynes Similar to those of alkanes –..

13 | 4 Alkenes Draw the structures of the monounsaturated alkenes with 4, 5, and 6 carbons What is the relationship between the number of carbons and the number of hydrogens in these alkenes? –.

13 | 5 Alkynes Draw the structures of the monounsaturated alkynes with 4, 5, and 6 carbons What is the relationship between the number of carbons and the number of hydrogens in these alkenes? –.

13 | 6 Bond Angles in Alkenes and Alkynes According to VSEPR theory: –The four groups bonded to carbon atoms in single bonds are at angles of ____________________ –The three groups bonded to carbon atoms in a double bond are at angles of ______________________ –The two groups bonded to carbon atoms in a triple bond are at angles of _____________________

13 | 7 →Fig In ethene, the atoms are in a flat rather than a tetrahedral arrangement. Note the shapes using space filling molecular models. Unsaturated Hydrocarbons cont’d

13 | 8 σ and π Bonds A single bond between 2 carbon atoms is called a sigma (σ) bond. The second bond that forms in a double bond is called the pi (π) bond. The third bond that forms a triple bond is also called the pi (π) bond. There is π bonding in all double and triple bonds between two carbon atoms. π bonds are more reactive than sigma bonds.

13 | 9  Carbon-carbon double bonds  Names end in -___________ H 2 C=CH 2 H 2 C=CH-CH 3 Alkenes

13 | 10  Carbon-carbon triple bonds  Names end in _____________ HC  CH HC  C-CH 3 Alkynes

13 | 11 Naming Step 1: –Name ___________________________. Find the longest continuous carbon chain that contains the multiple bond. Name that chain with the __________ suffix if it has a double bond. Name the chain with the _______ suffix if it has a triple bond. CH 3 CH 2 CH 2 CH 3 CH 2 CH 2 C

13 | 12 Naming Step 2: –Number the carbon atoms. Begin numbering _____________________________ CH 3 CH 2 CH 2 CH 3 CH 2 CH 2 C

13 | 13 Naming Step 2: –Number the carbon atoms. If the multiple bond is the same distance from each end of the molecule, begin _________________________ CH 3 CHCH CHCH 2 CH 3 CH ???

13 | 14 Naming Step 3: –Use ___________________________________ _________________to designate multiple bond position. –List the substituents ________________(with numbers to designate position). CH 3 CH 2 CH 2 CH 3 CH 2 CH 2 C

13 | 15 Naming Step 3: –Use “di”, “tri”, “tetra”, etc. to designate _________ _____________________________ CH 3 CH 2 CH 2 CH 3 CH 2 CH 2 C pentene 2-ethyl 1-

13 | 16 Name these alkenes. CH 3 CHCH CHCH 2 CH 3 CH 3 CH 3 CH 2 CH 2 CH 3 CH CH C CH 2 CCH CH 2 CH 3

13 | 17 Name These Alkynes

13 | 18 Naming cycloalkenes Number the double bond ______________. The first substituent possesses __________ ______________________.

13 | 19 Name these cycloalkenes.

13 | 20 Write the IUPAC name for each of the following unsaturated compounds: A.CH 3 CH 2 C  CCH 3 CH 3 B. CH 3 C=CHCH 3 C. Learning Check

13 | 21 Learning Check Draw the structures that correspond to the following names –4-methyl-1-hexene –1,3-cyclohexadiene –4,4,5-trimethyl-2-heptene –4-chloro-1-pentyne –5-fluoro-4-ethyl-2-hexyne

13 | 22 Isomerism in Alkenes Alkenes have many possible structural isomers –Isomers depend not only on the position of the carbons, but on where the double bond is

13 | 23 A comparison of structural isomerism possibilities for four- and five-carbon alkane and alkene systems.

13 | 24 Cis-Trans Isomerism Another kind of isomerism exists in alkenes: _____ _________________________________________ –. C CH 3 HH C CH 3 H H C CH 3 HH C CH 3 H H CisTransHHHH

13 | 25 Cis-Trans Isomerism Two isomers are possible when groups are attached to the double bond –In a cis isomer, groups are attached ______________ of the double bond –In a trans isomer, groups are attached _____________ ______________________ of the double bond. –Cis-trans isomerism is not possible when ___________ _______________________ _______________________ cis trans

13 | 26 Draw the cis and trans isomers of 1- chloro-2-pentene. trans-1-chloro-2-pentene cis-1-chloro-2-pentene Review: How many hydrogens on each carbon?

13 | 27 Learning Check Determine whether each of the following substituted alkenes can exist in cis-trans isomeric forms. If they can, draw and name them. –1-chloropropene –2-chloropropene

13 | 28 Learning Check Name each, using cis-trans prefixes when needed

13 | 29 Cis-Trans Isomers in Nature Insects emit tiny quantities of pheromones, which are chemicals that send messages The silkworm moth attracts other moths by emitting bombykol, which has one cis and one trans double bond.

13 | 30 Terpenes---the basis for cholesterol, steroids and many other biologically active compounds

13 | 31 Chemical Reactions of Alkenes and Alkynes. Types of alkene reactions: –.. –.. –.

13 | 32 Addition Reactions. –In the process, __________________________ ______________________________________ C H HH H + HCl

13 | 33 In an addition reaction, the atoms provided by an incoming molecule are attached to the carbon atoms originally joined by a double bond. In the process, the double bond becomes a single bond.

13 | 34 Adds __________________ to each carbon atom of a double bond (catalyst: Pt or Ni) H H Ni H–C=C–H + H 2 ethene Hydrogenation

13 | 35 Adding H 2 to vegetable oils produces compounds with higher melting points (ie. can convert a liquid to a solid) Margarines Soft margarines Shortenings (solid) Products of Hydrogenation

13 | 36 Fatty acids in vegetable oils are omega-6 acids (the first double bond occurs at carbon 6 counting from the methyl group) A common omega-6 acid is linoleic acid CH 3 CH 2 CH 2 CH 2 CH 2 CH=CHCH 2 CH=CH(CH 2 ) 7 COOH 6 linoleic acid, a fatty acid Unsaturated Fatty Acids

13 | 37  In vegetable oils, the unsaturated fats usually contain cis double bonds.  During hydrogenation, some cis double bonds are converted to trans double bonds (more stable) causing a change in the fatty acid structure  If a label states “partially” or “fully hydrogenated”, the fats contain trans fatty acids. Trans Fats

13 | 38  In the US, it is estimated that 2-4% of our total Calories is in the form of trans fatty acid.  trans fatty acids behave like saturated fatty acids in the body.  Several studies reported that trans fatty acids raise LDL- cholesterol. Some studies also report that trans fatty acid lower HDL-cholesterol  The trans fatty acids controversy will continue to be debated. Trans Fats

13 | 39 Inuit people of Alaska have a high fat diet and high blood cholesterol levels, but a very low occurrence of atherosclerosis and heart attacks. Fat in the Intuit diet was primarily from fish such as salmon, tuna and herring rather than from land animals (as in the American diet). Fats and Atherosclerosis

13 | 40 Fatty acids in the fish oils are mostly the omega-3 type (first double bond occurs at the third carbon counting from the methyl group). linolenic acid 18 carbon atoms CH 3 CH 2 CH=CHCH 2 CH=CHCH 2 CH=CH(CH 2 ) 7 COOH  eicosapentaenoic acid (EPA) 20 carbon atoms CH 3 CH 2 (CH=CHCH 2 ) 5 (CH 2 ) 2 COOH Omega-3 Fatty acids

13 | 41 Plaques of cholesterol adhere to the walls of the blood vessels Blood pressure rises as blood squeezes through smaller blood vessels Blood clots may form Omega-3 fatty acids decrease the “sticking” of blood platelets (fewer blood clots) Omega-3 fatty acids can increase bleeding time Atherosclerosis

13 | 42 What is the product of adding H 2 (Ni catalyst) to 1-butene? Learning Check

13 | 43 ____________ also add to the carbons in a double or triple bond H 2 C  CH 2 + Cl 2 CH 3 C=CCH 2 CH 3 + 2Br 2 Halogenation

13 | 44 Using Bromination to Test for Double Bonds Bromine in water has a reddish brown color If another compound with a double bond reacts with the bromine, ______________________ –The reddish color persists ______________________________ ___________________________________________________

13 | 45 Write the product of the following addition reactions: CH 3 CH=CHCH 3 + H 2 Learning Check

13 | 46 Hydrohalogenation A _________________ is incorporated into the carbons involved in a multiple bond –The _____________ adds to one carbon –The ______________ adds to the other carbon Markovnikov’s rule: –. H 3 C CH CH 2 + H X

13 | 47 Where does the halide add to these double bonds (alkenes)?

13 | 48 Hydration A ______________ is incorporated into the carbons involved in a multiple bond –The ___________ adds to one carbon –The ___________ adds to the other carbon. H 3 C CH CH 2 + H OH

13 | 49 Learning Check Write the products of each reaction CH 3 -CH=CH 2 + Cl 2  CH 3 -CH=CH-CH 3 + H 2 O  Cyclopentene + H 2 

13 | 50 Addition Reactions: Polymers Polymers are large molecules built up by repetitive bonding of many smaller molecules called ____________________. May have thousands of monomer units in one polymer molecule. The monomers are __________ C H HH H Radical Catalyst C C C C C C C C C C HH HHHHHHHHHH HHHHHHHH

Synthetic Polymers

13 | 52 What is the monomer?

13 | 53 What is the monomer?

Aromatic Compounds Aromatic compounds contain _____________. Benzene has:. Have many properties similar to alkanes

13 | 55 Structure of Benzene: Resonance Two resonance structures. Neither resonance form is correct by itself. The true structure is a combination. –.

Benzene Structure The structure for benzene is also written as one formula with a circle within the ring to represented the alternating double bonds. The circle shows: Benzene structure

Aromatic Compounds in Nature and Health Many aromatic compounds are common in nature and in medicine. Aspirin Vanillin Ibuprofen

Naming Aromatic Compounds Aromatic compounds are named, With ________________ as the parent chain. Side chains are named:

Naming Aromatic Compounds When two groups are attached to benzene, the ring is numbered to give _________________ _____________________________________. ( para- chloromethylbenzene) ( meta- dichlorobenzene) ( ortho- dimethylbenzene) 1,2-dimethylbenzene 1,3-dichlorobenzene 1-chloro-4-methylbenzene Cl CH 3 Cl Cl CH 3 CH 3

13 | 60 Naming Aromatic Compounds Disubstituted benzenes are named using prefixes: –.

13 | 61 Naming Aromatic Compounds ortho- (o) meta- (m) para- (p)

13 | 62 Naming Aromatic Compounds Some aromatic compounds have common names.

Some Common Names Some substituted benzenes use common names. toluene 3-chlorotoluene phenol

Learning Check Select the correct name for each structure: 1) chlorocyclohexane 2) chlorobenzene 3) 1-chlorobenzene 1) 1,2-dimethylbenzene 2) 1,4-dimethylbenzene 3) 1,3-dimethylbenzene

Learning Check Write the structural formulas for each of the following: A. 1,3-dichlorobenzene B. 2-chlorotoluene

13 | 66 Naming Aromatic Compounds Tri- or higher-substituted benzenes. Number ________________________________ Use ____________________________________. Name substituents listed __________________. If any “common named” monosubstituted parent is used the principle substituent is on ____________

13 | 67 Naming Aromatic Compounds

13 | 68 Chemical Reactions of Aromatic Hydrocarbons Aromatic compounds can undergo substitution reactions –Alkylation. –Halogenation. –Nitration. –Sulfonation.

13 | 69 Learning Check Write the reaction for the bromination of benzene, including the catalyst.

13 | 70