Alkenes and AlkynesAlkenes and Alkynes UnsaturatedUnsaturated

contains a carbon-carbon double or contains a carbon-carbon double or triple bond to which takes away from triple bond to which takes away from the maximum number of hydrogen the maximum number of hydrogen possible. possible.

Alkenes: carbon-carbon Alkenes: carbon-carbon doubledouble bonds bonds Alkynes: carbon-carbon Alkynes: carbon-carbon tripletriple bonds. bonds.

AlkenesAlkenes Members of the alkene group Members of the alkene group

have a double bond between have a double bond between two carbon atoms.two carbon atoms.

General formula is CGeneral formula is CnnHH22nn

““-ane” suffix changes to “--ane” suffix changes to “-ene”ene”

Section 14.3

14 | 14 | 33

Naming AlkenesNaming Alkenes When assigning numbers to the When assigning numbers to the

chain, the chain, the double bond double bond gets priority gets priority over over anyany side chain. Give it the side chain. Give it the lowest number possible!lowest number possible!

The number preceding the final The number preceding the final name indicates the Carbon atom on name indicates the Carbon atom on which the double bond which the double bond startsstarts..

AlkynesAlkynes Members of the alkyne group Members of the alkyne group

have a triple bond between two have a triple bond between two carbon atoms.carbon atoms.

General formula is CGeneral formula is CnnHH22nn-2-2

Suffix changes to “-yne”Suffix changes to “-yne”

Section 14.3

Naming Alkenes and Naming Alkenes and AlkynesAlkynes

IUPAC nomenclature rules for alkenes IUPAC nomenclature rules for alkenes and alkynes are similar to alkanes. and alkynes are similar to alkanes.

Step 1Step 1. Find the longest chain . Find the longest chain containing the double or triple containing the double or triple bondbond..This will be the main parent chain. Pick This will be the main parent chain. Pick the correct suffix by adding the correct suffix by adding –ene or –ene or –yne–yne to the end of the name. to the end of the name.

Step 2:Step 2: Number the carbon so the Number the carbon so the double or triple bond is the lowest double or triple bond is the lowest carbon possible. carbon possible. They gets priority They gets priority over all side chains!over all side chains!

If the multiple bond is an equal If the multiple bond is an equal distance from both ends, begin distance from both ends, begin numbering at the end closest to the numbering at the end closest to the first branch point.first branch point.

Naming Alkenes and Naming Alkenes and AlkynesAlkynes

CHCH22=CHCH=CHCH22CHCH33 1-butene1-butene but-1-enebut-1-ene

CHCH33CH=CHCHCH=CHCH33 2-butene2-butene but-2-enebut-2-ene

CHCH33CCCCHCCH33 2-butyne2-butyne but-2-ynebut-2-yne

Learning CheckLearning Check

Write the IUPAC name for each of the Write the IUPAC name for each of the following following unsaturatedunsaturated compounds: compounds:

A.A. CHCH33CHCH22CCCCHCCH33

CHCH33

B. B. CHCH33C=CHCHC=CHCH33 C. C.

CH3

Step 3:Step 3: If more than one multiple bond is If more than one multiple bond is present, identify the position of each present, identify the position of each multiple bond. Name by alphabetical suffix multiple bond. Name by alphabetical suffix and include prefixes if there is more than and include prefixes if there is more than one of the same type of bond. (diene, one of the same type of bond. (diene, triene) triene)

1,3-pentadiyne1,3-pentadiyne

Practice ProblemsPractice Problems Name the following Compounds:Name the following Compounds:

4,4-difluoro-3-methyl-1-butene4,4-difluoro-3-methyl-1-butene

5-methyl-1,3-5-methyl-1,3-cylcopentadienecylcopentadiene

Write these molecules:Write these molecules: 1-bromo-4,4-dimethyl-2-1-bromo-4,4-dimethyl-2-

pentenepentene

4-sec-butyl-3-isopropyl-3-4-sec-butyl-3-isopropyl-3-methyl-1-cylcobutenemethyl-1-cylcobutene

Assigning PriorityAssigning Priority Alkenes and alkynes have equal Alkenes and alkynes have equal

priority.priority. In a molecule with In a molecule with bothboth a double a double

and a triple bond, whichever is closer and a triple bond, whichever is closer to the end of the chain determines to the end of the chain determines the direction of numbering. the direction of numbering.

In the case of a tie, the double bond In the case of a tie, the double bond takes the lower number. takes the lower number.

In naming, “ene” comes before In naming, “ene” comes before “yne” because of alphabetization.“yne” because of alphabetization.

Name these compoundsName these compounds

3-penten-1-ynePent-3-en-1-yne

1-penten-4-ynePent-1-en-4-yne

Draw these moleculesDraw these molecules 6-methyl-4-octen-1-yne6-methyl-4-octen-1-yne

3,3-dimethyl-2-tertbutyl-1-3,3-dimethyl-2-tertbutyl-1-penten-4-ynepenten-4-yne

Cis-Trans IsomersCis-Trans Isomers

Cis- and Trans- terminologyCis- and Trans- terminology If alkenes have two different side

chains at each end of the C=C double bond, then they can exist as stereoisomers.

This happens because the double bond is fixed and can not rotate.

Think of it as having a “top” and “bottom” of a molecule.

You can model this You can model this by making a by making a “double bond” “double bond” with your index with your index and middle and middle fingers locked fingers locked together. There together. There are two possible are two possible ways to do this, ways to do this, and your thumbs and your thumbs are either on the are either on the same side or same side or opposite from opposite from each other.each other.

Cis-Trans Isomerism 2-butene can exist in two different isomers. The methyl groups can be on the same side of the molecule or opposite sides. The formulas are the same, but the tops and bottom are different, and we call these “steroisomers”.

“Top” is both

Hydrogen

“Top” is a H and CH3 group

“Bottom” is both methyl groups

“Bottom” is a hydrogen and methyl group

In a In a cis isomercis isomer, the two groups , the two groups (Anything not Hydrogen)(Anything not Hydrogen)are close together and on the are close together and on the same side of the double bond. same side of the double bond.

(Both on top or both on bottom)(Both on top or both on bottom)

In the trans isomer, the two groups (Anything not Hydrogen) In the trans isomer, the two groups (Anything not Hydrogen) are far apart and on opposite side of the double bond.are far apart and on opposite side of the double bond.

(One on top, and one on bottom)(One on top, and one on bottom)

2222

When it’s not a cis- or trans- When it’s not a cis- or trans- isomerisomer

• Alkenes cannot have cis-trans isomers if a Alkenes cannot have cis-trans isomers if a carbon atom in the double bond is attached carbon atom in the double bond is attached to to identical groupsidentical groups on the same carbon on the same carbon atom!atom!

IdenticalIdentical Identical Identical

2-bromopropene2-bromopropene 1,1dibromoethene 1,1dibromoethene (not cis or trans)(not cis or trans) (not cis or trans) (not cis or trans)

C C

H Br

H CH3

C C

H Br

BrH

H

H

H Br

Practice: Identify if these are Cis- Trans- isomers and if so, name them

correctly

C C

CH3 H

CH3H

C C

Br Br

H H

A.

B.

C C

CH3 Cl

ClH

C.

Practice: Identify if these are Cis- Trans- isomers and if so, name them

correctly

C C

CH3 H

CH3H

C C

Br Br

H H

A.

B.

C C

CH3 Cl

ClH

C.

cis-1,2-dibromoethene

trans-2-butene

1,1-dichloropropene

Unsaturated Fatty AcidsUnsaturated Fatty Acids

Fatty acids in vegetable oils are omega-6 Fatty acids in vegetable oils are omega-6 acids (the first double bond occurs at acids (the first double bond occurs at carbon 6 counting from the methyl group)carbon 6 counting from the methyl group)

A common omega-6 acid is linoleic acidA common omega-6 acid is linoleic acid

CHCH33CHCH22CHCH22CHCH22CHCH22CH=CHCHCH=CHCH22CH=CH(CHCH=CH(CH22))77COOHCOOH

66

linoleic acid, a fatty acid linoleic acid, a fatty acid

TransTrans Fats Fats

In vegetable oils, the unsaturated fats In vegetable oils, the unsaturated fats usually contain usually contain ciscis double bonds. double bonds.

During hydrogenation, some During hydrogenation, some cis cis double double bonds are converted to bonds are converted to trans trans double double bonds (more stable) causing a change bonds (more stable) causing a change in the fatty acid structure in the fatty acid structure

If a label states “partially” or “fully If a label states “partially” or “fully hydrogenated”, the fats contain hydrogenated”, the fats contain transtrans fatty acids. fatty acids.

TransTrans Fats Fats

In the US, it is estimated that 2-4% of In the US, it is estimated that 2-4% of our total Calories is in the form of our total Calories is in the form of transtrans fatty acid. fatty acid.

trans trans fatty acids behave like saturated fatty acids behave like saturated fatty acids in the body. fatty acids in the body.

Several studies reported that trans Several studies reported that trans fatty acids raise LDL-cholesterol. Some fatty acids raise LDL-cholesterol. Some studies also report that trans fatty acid studies also report that trans fatty acid lower HDL-cholesterollower HDL-cholesterol

The trans fatty acids controversy will The trans fatty acids controversy will continue to be debated. continue to be debated.

Fats and AtheroschlerosisFats and Atheroschlerosis

Inuit people of Alaska have a high fat Inuit people of Alaska have a high fat

diet and high blood cholesterol levels, diet and high blood cholesterol levels,

but a very low occurrence of but a very low occurrence of

atherosclerosis and heart attacks. atherosclerosis and heart attacks. Fat in the Intuit diet was primarily Fat in the Intuit diet was primarily

from fish such as salmon, tuna and from fish such as salmon, tuna and

herring rather than from land animals herring rather than from land animals

(as in the American diet). (as in the American diet).

Omega-3 Fatty AcidsOmega-3 Fatty Acids

Fatty acids in the fish oils are mostly the Fatty acids in the fish oils are mostly the omega-3 type (first double bond occurs at the omega-3 type (first double bond occurs at the third carbon counting from the methyl group). third carbon counting from the methyl group).

linolenic acid 18 carbon atoms linolenic acid 18 carbon atoms

CHCH33CHCH22CH=CHCHCH=CHCH22CH=CHCHCH=CHCH22CH=CH(CHCH=CH(CH22))77COOHCOOH

eicosapentaenoic acid (EPA)eicosapentaenoic acid (EPA) 20 carbon atoms 20 carbon atoms

CHCH33CHCH22(CH=CHCH(CH=CHCH22))55(CH(CH22))22COOH COOH

AtherosclerosisAtherosclerosis

Plaques of cholesterol adhere to the walls of Plaques of cholesterol adhere to the walls of

the blood vessels the blood vessels Blood pressure rises as blood squeezes Blood pressure rises as blood squeezes

through smaller blood vessels through smaller blood vessels Blood clots may formBlood clots may form Omega-3 fatty acids decrease the “sticking” Omega-3 fatty acids decrease the “sticking”

of blood platelets (fewer blood clots) of blood platelets (fewer blood clots) Omega-3 fatty acids can increase bleeding Omega-3 fatty acids can increase bleeding

timetime

Name TheseName These

C CCH3

H

CH3

CH2CH3

C CCl

H

CH2

Cl

CH3

Aromatic Compounds and Aromatic Compounds and BenzeneBenzene

Aromatic compounds contain benzene.Aromatic compounds contain benzene.

Benzene, CBenzene, C66HH6 6 , is represented as a six , is represented as a six

carbon ring with 3 double bonds.carbon ring with 3 double bonds.

Two possible can be drawn to show Two possible can be drawn to show benzene in this form.benzene in this form. H

H

H

H

H

H

HH

H

H

H

H

Aromatic Compounds Aromatic Compounds and the Structure of Benzeneand the Structure of Benzene

In the early days the word In the early days the word aromaticsaromatics was was used to described many fragrant used to described many fragrant molecules isolated from natural sources. molecules isolated from natural sources. Today the term Today the term aromatic aromatic is used to is used to describe benzene like molecules.describe benzene like molecules.

Benzene is a flat, symmetrical molecule Benzene is a flat, symmetrical molecule with the molecular formula Cwith the molecular formula C66HH66..

It has alternating three carbon-carbon It has alternating three carbon-carbon double and three single bonds.double and three single bonds.

Benzene’s relatively lack of chemical Benzene’s relatively lack of chemical reactivity is due to its structure. reactivity is due to its structure.

There are two possible structures There are two possible structures with alternating double and single with alternating double and single bonds.bonds.

Experimental evidence suggest that all six Experimental evidence suggest that all six carbon-carbon bonds in benzene are identical.carbon-carbon bonds in benzene are identical.

The properties, including the above one, of The properties, including the above one, of benzene can only be explained by assuming benzene can only be explained by assuming that the actual structure of benzene is an that the actual structure of benzene is an average of the above two possible equivalent average of the above two possible equivalent structures-known as structures-known as resonanceresonance..

Simple aromatic compounds like benzene are Simple aromatic compounds like benzene are non-polar, insoluble in water, volatile, and non-polar, insoluble in water, volatile, and flammable.flammable.

Unlike alkenes, several aromatic Unlike alkenes, several aromatic hydrocarbons are toxic. Benzene itself is hydrocarbons are toxic. Benzene itself is implicated as a cancer causing chemical.implicated as a cancer causing chemical.

Aromatic Compounds in Aromatic Compounds in Nature and HealthNature and Health

Many aromatic compounds are common in Many aromatic compounds are common in nature and in medicine.nature and in medicine.

COOH

COOCH3

CHO

OCH3

OH

Aspirin Vanillin

CHCOOH

CH3

CH3CHCH2

CH3

Ibuprofen

Naming Aromatic Naming Aromatic CompoundsCompounds

Aromatic compounds are named with Aromatic compounds are named with benzene as the benzene as the parent chain. parent chain. One side group is named in front of One side group is named in front of the name the name benzene.benzene. - No number is needed for mono-substituted - No number is needed for mono-substituted

benzene since all the ring positions are identical.benzene since all the ring positions are identical.

methylbenzenemethylbenzene chlorobenzenechlorobenzene (toluene)(toluene)

CH3 Cl

Naming Aromatic Naming Aromatic CompoundsCompounds

When two groups are attached to benzene, When two groups are attached to benzene, the ring is numbered to give the lower the ring is numbered to give the lower numbers to the side groups. The prefixes numbers to the side groups. The prefixes ortho (1,2), meta (1,3-) ortho (1,2), meta (1,3-) andand para (1,4-) para (1,4-) areare also used.also used.

CH3

CH3

Cl

Cl

Cl

CH3

1,2-dimethylbenzene 1,3-dichlorobenzene 1-chloro-4-methylbenzene

(ortho-dimethylbenzene) (meta-dichlorobenzene) (para-chloromethylbenzene)

Some Common NamesSome Common Names

Some substituted benzene rings also use a Some substituted benzene rings also use a common name. Then naming with additional common name. Then naming with additional more side groups uses the more side groups uses the ortho-, meta-, ortho-, meta-, para-para- system. system.CH3

Cl

CH3 OH

Toluene meta-chlorotoluene phenol(Methylbenzene) (meta-chloromethylbenzene) (hydroxybenzene)

Many substituted aromatic compounds Many substituted aromatic compounds have common names in addition to have common names in addition to their systematic names.their systematic names.

Learning CheckLearning Check

Select the names for each structure:Select the names for each structure:

a. Chlorocyclohexanea. Chlorocyclohexaneb. Chlorobenzeneb. Chlorobenzenec. 1-chlorobenzenec. 1-chlorobenzene

a. a. Meta-Meta-xylenexyleneb. b. Meta-Meta-dimethylbenzenedimethylbenzenec. 1,3-dimethylbenzenec. 1,3-dimethylbenzene

Cl

CH3

CH3

Learning CheckLearning Check

Write the structural formulas for each of the Write the structural formulas for each of the following:following:

A. 1,3-dichlorobenzeneA. 1,3-dichlorobenzene

B. B. Ortho-Ortho-chlorotoluenechlorotoluene

New Attached GroupsNew Attached Groups

PhenylPhenyl

BenzylBenzyl

Nitro -NONitro -NO22

2,4,6-trinitrotoluene2,4,6-trinitrotoluene

Benzyl alcohol

4-phenyl-1-butene

Refer to your chart for order of priority!

PCBsPCBs(Polychlorinated Biphenyls)(Polychlorinated Biphenyls)

There are 209 There are 209 varieties of PCBs, varieties of PCBs, known individually known individually as congeners. A as congeners. A congener may congener may have between 1 have between 1 and 10 chlorine and 10 chlorine atoms, which may atoms, which may be located at be located at various positions various positions on the PCB on the PCB molecule. molecule.

PCBsPCBs PCBs are mixtures of man-made PCBs are mixtures of man-made

chemicals with similar chemical chemicals with similar chemical structures. PCBs can range from structures. PCBs can range from oily liquids to waxy solids. Due to oily liquids to waxy solids. Due to their non-flammability, chemical their non-flammability, chemical stability, high boiling point and stability, high boiling point and electrical insulating properties, electrical insulating properties, PCBs were used in hundreds of PCBs were used in hundreds of industrial and commercial industrial and commercial applications including electrical, applications including electrical, heat transfer, and hydraulic heat transfer, and hydraulic equipment; as plasticizers in equipment; as plasticizers in paints, plastics and rubber paints, plastics and rubber products; in pigments, dyes and products; in pigments, dyes and carbonless copy paper and many carbonless copy paper and many other applications. More than 1.5 other applications. More than 1.5 billion pounds of PCBs were billion pounds of PCBs were manufactured in the United States manufactured in the United States prior to cessation of production in prior to cessation of production in 1977.1977.