Unit 2: Organic Chemistry (Hebden-Unit X p.213)Warm Up Questions, Org Bkt p.26#1-3

IntroductionDef: Chemistry of carbon compounds

Some compounds are produced synthetically, some occur naturally, some are beneficial, some are hazardous.

Where are they found?Fossil fuels(petroleum by-products, natural gas), all living things (trees, grasses, vegetables, insects, animals, people)

Petrochemicals industry: largest industry involving organic chemistry Petroleum is separated through fractionated distillation for every day use’s products such as foods, cosmetics, plastics, clothing fibres, pharmaceuticals and fuels.

Carbon is tetravalent, it has a valence of 4 and can form: .4 single bonds (alkanes) .1 double bond and 2 single bonds (alkenes) .1 triple bond and 1 single bond (alkynes)

Hydrocarbons: containing only carbon and hydrogen atoms. .simplest type of organic compounds

There are 6 ways to represent an hydrocarbon formula:Let’s use butane molecule (lighter fuel) as an example (Edvantage p.403, 405)Table 8.1.2, Org Bkt p.27 1) Molecular formula C4H102) Structural formula H H H H

| | | |H-C-C-C-C-H | | | | H H H H

3) Condensed structural formula CH3-CH2-CH2-CH34) Carbon skeleton formula C C

/ \ / orC C

5) Ball and stick model Org Bkt p. 27

6) Space filling model Org Bkt p.27

1

Practice Problem#1- Org Bkt p.28 (Using Structural Formulas EI p.40)Org Bkt p.30#1

There are 5 types of hydrocarbons (contains hydrogen and carbon):alkanes, cycloalkanes, alkenes, alkynes, and aromatic compounds.

1) AlkanesThey contain only single bonds.They are saturated, meaning that there is no room for other atoms to combine with the carbon skeleton.General formula: CnH(2n+ 2)Naming: compound ends in “-ane”#C 1 2 3 4 5 6 7 8 9 10prefix meth- eth- prop- but- pent- hex- hept- oct- non- dec-

For example, hexane means six carbons bonded in a chain.Hex is the Greek word for six.

Hebden p.215Table 8.1.2: 10 Straight-Chain Alkanes You Need to Know (EI p.405) Org Bkt p.27

In addition to form a straight chain, a hydrocarbon chain has “side branches” called alkyl groups that are attached to its main skeleton.

Ex: CH3-CH2-CH-CH2-CH2-CH3 I CH2 I ethyl branch

CH3

Rules for Naming Branched Alkanes1) Find the longest continuous chain of carbon atoms. It does not have to be in

a straight line. This is the “parent” chain. State the number of carbon atoms using the appropriate prefix and the ending “ane”.

2) Number the carbon atoms in the parent chain starting at the end closest to the branches.

3) Name each branch with a prefix according to the number of carbon atoms it contains. Branch names end in “yl” instead of “ane”. A branch containing one carbon atom is called a methyl branch and a branch containing 2 carbon atoms is called an ethyl branch.

4) If two,three or four branches have the same number of carbon atoms, use the prefixes “di” (two), “tri” (three), and “tetra” (four). For example if there are two branches each with three carbons, they are called “dipropyl”.

2

5) State the name of the alkane by first listing the “address” of each branch, then naming the branches, then naming the parent. Use commas between numbers and hyphens between a number and a branch name.

6) Always use the lowest possible number for a branch.

The correct name for the above hydrocarbon is: 3-ethylhexane (p.2)Alkyl group: alkane which has lost one hydrogen atom

Unused bond can be connected to another hydrocarbon chainNaming Rule: changing the “ane” ending to “yl”

Alkane Molecule( parent ) Alkyl Group ( branch ) methane = CH4 methyl = CH3-ethane = CH3-CH3 ethyl = CH3-CH2-propane = CH3-CH2-CH3 propyl = CH3-CH2-CH2-butane = CH3-CH2-CH2-CH3 butyl = CH3-CH2-CH2-CH2-

Naming Rules:1-number a carbon at which an alkyl group is attached2-add a dash3-name the alkyl group4-name the longest hydrocarbon chain to which the alkyl is attached

To find longest chain: look at every “branch point” carbon and decide which two branches create the longest overall path. (Only carbons are shown to make various branches easier to see

a) C – C – C – C – C – C Longest path: 7 carbons; heptane I C – C – C

b) C – C C –C No “unique” path” exists. I I Longest path: 6 carbons; hexane C – C – C – C I I C – C C –C

c) C – C – C – C C – C – C Longest path: 9 carbons; nonane I I C – C – C – C – C – C I C – C

Example:1 2 3 4 5CH3 – CH – CH2 – CH2 – CH3 2-methylpentane I

3

CH3

Examples:8 7 6 5 4 3 2 1CH3 – CH2 – CH2 – CH2 – CH2 – CH – CH2 - CH3 3-methyloctane I 6-methyloctane(incorrect) CH3

1 2 3 4 5 6 7 8CH3 – CH2 – CH2 – CH – CH2 – CH2 – CH2 - CH3 4-ethyloctane I 5-ethyloctane(incorrect) CH2 – CH3

3 4 5 6 7 CH3 – CH – CH2 – CH2 – CH2 – CH3 3-methylheptane I 5-methylheptane(incorrect) CH2 – CH3 2 1

Practice Problems-2: Naming Simple Alkanes, Org Bkt p.28Exercise Heb p. 218 #2, p.219 #3, p. 220 #4-6

Rules: Organic bkt p.5If there are more than one different alkyl group attached to a hydrocarbon;

.list the alkyl groups alphabetically

.precede each alkyl group by its number

.put a dash between each alkyl group and its number

Practice Problems4-ethyl-2-methyloctane3-ethyl-3-methyloctane (2 groups can be attached to same carbon)5-ethyl-3-methyl-6-propyldecane (tricky!!)

Examples Heb p. 220

Rules:If an alkyl group is repeated, then

.list each carbon number where the repeated group is attached, separated by commas.prefix the repeated group name by di, tri, tetra, etc, to show how many identical groups are attached.

Examples Heb p. 221

4

2,4,6-trimethyloctane4,4-diethyl-2,2,7-trimethyl-7-propyldecaneExercises Heb p.221 #7, 8-9:a,c,e…

Structural Isomers Org Bkt p.5Compounds which have the same molecular formula but a different arrangement of atoms.

Example: C4H10 can refer to either:

CH3 - CH2 - CH2 –CH3 or CH3 - CH - CH3 I

CH3 Butane 2-methylpropane

Each structural isomer has chemical/physical properties different from other isomers with the same chemical formula.

As the number of carbon atoms in a molecule increases, the number of possible isomers increases dramatically.

C5H12 has three structural isomersC6H14 has five structural isomersC7H16 has nine structural isomersC20H42 has more than 300 000 structural isomers

Activity 8.1: Building/Naming Structural Isomers, Org Bkt p.29

Quick Check#1, Org Bkt p.51. What is the molecular formula for an alkane that has 12 carbon atoms? 2. Draw condensed structural formulas for three of the structural isomers of

C7H163. Name the three structural isomers you drew in question 2.

Hebden p.222#10-13Org Bkt p.30#2

5

2) Cycloalkanes Org Bkt p.6Cyclic hydrocarbons: chains where the head connects to the tail. The carbon atoms bond to each other and form a cyclic structure called a ring.General formula: CnH(2n)

Examples: cyclopropane cyclobutane cyclopentane cyclohexane

C3H6 C4H8 C5H10 C6H12

Alkyl CycloalkanesRules:.Same rule as for a chain alkanes. .Single substituent doesn’t use a number since all carbons in the cycloalkyl are identical.More than one substituent: the first substituent is given the “1” position and remaining substituents are numbered to have the lowest set of overall values..If the ring structure is not the longest continuous carbon chain, then it is named as a branch with the prefix “cyclo” and ends in “yl”.

Examples: methylcyclohexane1-ethyl-2-methylcyclohexane1,1-dimethylcyclopentane1-butylcyclopentane

Figure 8.1.5 (p.410 EI)Exercises Heb p.223-224 #15-16: a-e

Alkyl Halides Org Bkt p. 11Halogens: fluorine, chlorine, bromine and iodine

Alkyl Halides Naming:.Same manner as akyl groups.Attached F, Cl, Br and I atoms are called “fluoro”, “chloro”, “bromo” and “iodo” groups.

The general term for an attached halogen atom is a “halo” group.

.Use a number to indicate the attachment position on the hydrocarbon chain.

6

.If more than one of the same kind of halogen is present, use the prefixes di, tri, etc..If a compound contains both alkyl and halo groups, list the attached groups in alphabetical order. Start numbering from the end which gives the lowest set of numbers.

Examples: CH3-Cl = chloromethaneCCl3-CF3 = 1,1,1-trichloro-2,2,2-trifluoroethane2,2-dibromo-3-methylhexanefluorocyclopentane

Hebden p.225#17-18

3) AlkenesOrg Bkt p.7Hydrocarbons containing a double bond that is unsaturated.This means that the double bond is a reactive site where other atoms could attach to the carbon skeleton.General formula: CnH(2n)

Rules:.If a double bond is present, change the “ane” ending to “ene”..The parent chain must contain the double bond..The position of the double bond is indicated in the name by stating the number of the carbon atom in the parent chain that the double bond follows..The parent chain carbon atoms are numbered starting at the end closest to the double bond.

Alkenes can also have geometric isomers where they have the same structure and a different orientation of the groups across the double bond. This is called Cis-Trans Isomerism Example: 2-pentene forms cis-2-pentene and trans-2-penteneExample: cis-2-butene and trans-2-butene (EI p. 411)

Cis isomer: 2 groups are on the Same Side of double bond

Trans isomer: 2 groups are Transverse(opposite sides of double bond) to each other

Quick Check #2 (EI p. 411), Org Bkt p.81. What is the molecular formula for an alkene containing one double bond and

seven carbon atoms?2. Draw a cycloalkane containing seven carbon atoms. What is its molecular

formula?3. Name the compound shown here.

7

4. Draw cyclohexane and write its molecular formula. Beside it, draw the 2 geometric isomers of 2-hexene, and write their molecular formulas. Classify each molecule as saturated or unsaturated.

5. Unsaturated fats such as those found in olive oils and avocados are healthier than saturated fats found in cocconut oil and butter. What do the words “unsaturated” and “saturated”mean in terms of organic molecular structure?

Org Bkt p.30#3-6

4) AlkynesHydrocarbon containing a triple bond. They are also unsaturated.General formula: CnH2n-2

Rules:.If a triple bond is present, change the “ane” ending to “yne”..The parent chain must contain the triple bond..The position of the triple bond is indicated in the name by stating the number of the carbon atom in the parent chain that the triple bond follows..The parent chain carbon atoms are numbered starting at the end closest to the triple bond.Example: 3-methyl-1-pentyne (EI p. 412)

Easy way to remember bond endings:Use alphabetical order: Single bonds Double bonds Triple BondsAne Ene Yne

Writing Condensed Structure of Alkenes and Alkynes1-Write the condensed formula2-Write all the carbons in a row with spacing in between them3-Number each carbon atom4-Insert the specific bonds5-Write the correct number of hydrogen for each carbon, knowing that carbon is tetravalent.

Examples: Heb p.227-Class Activity (done in pairs)2-hexene 1-pentyne ethene or ethylene propene2-butene 2-methyl-1-butene3,3-dimethyl-1-pentene ethyne or acetylene

8

propyne 2-butyne4-methyl-1-pentyne 3,3-dimethyl-1-cyclopentyne

Quick Check#31. What is the molecular formula for an alkyne containing one triple bond and 8

carbon atoms in a chain?2. Do alkynes exhibit cis and trans isomerism? Explain3. Draw the condensed structural formula for 3,4-dimethyl-1-hexyne.

Exercises Heb p.228 #21-25: a,c,e…Org Bkt p.30#6-7

5) Aromatic CompoundsBenzene C6H6 has the following structure

Ring-like structure has 2 resonance structures, consisting of alternating single and double bonds between carbon atoms

Actual arrangement of electrons in carbon ring is a mixture of both resonance structures. Benzene is represented as follow:

Benzene’s resonance structures gives it unusual stability and is highly resistant to chemical reactions.Atoms attached to benzene ring can be replaced.

9

An aromatic molecule contains one or more benzene rings.Its compounds are fragrant and have pleasant scents (aroma)

Aromatic Naming:Identical to naming procedure used for cyclic hydrocarbons.We label the first substituted carbon as 1 and proceed either clockwise or counterclockwise in such a way as to give the lowest combination of numbers of substituted carbons.

For benzenes where only two branches exists on the ring, there are three possiblepositions: 1,2-, 1,3-, and 1,4- . These prefixes describe how close the branches are to each other on the benzene ring. (Figure 8.1.10, p. 413-Edvantage Interactive 2011)

A benzene ring with one methyl branch is commonly called toluene.A benzene ring with two methyl branches is commonly called xylene.Some organic compounds have benzene as a branch and in this case this branch is called a “phenyl”. (EI p. 413, Figure 8.1.11)

Structures and names of some common aromatic compoundsEI p.413, Figures 8.1.12

Examples: 1,4-dichlorobenzene or paradichlorobenzeneExercises Heb p.232 #29-31: a,c,e…Org Bkt p.30#8, p.31

6) Functional Groups

Warm Up#2Every day, you use products that contain organic compounds. In the list below, place a checkmark beside each product that you have in your home.Product Product☐vanilla flavouring ☐fuels (gasoline)☐nail polish remover ☐cosmetics☐insecticide ☐glue☐acetaminophen (Tylenol) ☐asphalt☐antifreeze ☐nylon☐wax ☐Teflon☐plastics ☐paint thinner

Org Bkt p.11The number of isomers for large hydrocarbons is enormous. There would be even more possible isomers if we included atoms of oxygen, nitrogen, sulphur or other elements. In a Chemistry Handbook, organic compounds greatly outnumber inorganic compounds. All the products in the Warm Up#2 contain organic compounds. We are surrounded by organic chemistry!!

10

Several organic compounds have a functional group which is an atom, group of atoms, or organization of bonds in an organic molecule that react in a characteristic manner. Organic compounds with the same functional group react in a similar manner.

By adding functional groups to hydrocarbons a chemist can:.make molecule act as acid, base or both.give molecule a particular solubility.give molecule a pleasant or unpleasant smell.make molecule react with specific chemicals.make molecule explosive

Chemists use a shorthand to represent carbon and hydrogen atoms that are not part of the functional group. We use the symbol R to represent the hydrocarbon fragment that is not part of the functional group. R’ (r prime) is used for different hydrocarbon fragment in the same molecule. We will learn to identify functional groups as well as the rules given to name these types of compounds.

a)Alkyl Halides (halogens): R-X (where X =F, Cl, I or Br) def: Organic compounds with halogens (F, Cl, Br or I)F = fluoro Cl = chloro Br = bromo I = iodo

Alkyl Halides Naming: .Same manner as alkyl groups.Attached F, Cl Br or I atoms are called: fluoro, chloro, bromo and iodo groups.Use a number to indicate the attachment position on the hydrocarbon chain..If more than one of same kind of halogen is present, use prefixes di, tri, etc..If compound contains both alkyl and halo groups, list the attached groups in alphabetical order. Start numbering from the end which gives the lowest set of numbers.

Examples:ChloromethaneFluorobenzene1,1,1-trichloro-2,2,2-trifluoroethane3-bromo-1,6-diiodononane2,2-dibromo-3-methylhexanefluorocyclopentane2-bromo-4-chloropentane

b) Alcohols: R-OH (Org Bkt p.12)Compound containing an OH group

11

Naming Rule.Number the hydrocarbon chain to give the lowest possible number to (–OH) group.Place the number immediately before the name of the parent hydrocarbon, separated by a dash. Alkyl groups and their numbers are placed in front of the number for the OH.Indicate the presence of an OH group by changing the “e” ending of the hydrocarbon chain to “ol”. (ending “ol” comes from “alcohol”)

Examples:CH3 – OH methanol or methyl hydrateCH3 – CH2 – OH ethanol (drinking alcohol)

CH3 – CH – CH2 – CH3 2-butanol I OH

CH3 – CH – CH2 – CH – CH2 – CH3 5-methyl-3-hexanol I I CH3 OH

Application:2-propanol or isopropanol or isopropyl alcohol (electronics cleaner, sterilizing soln)“Isopropyl” refers to the branch of three carbons. This branch is attached at the second carbon in the chain of three carbon atoms.

Quick Check #4 (EI p. 419) Org Bkt p. 32Hedben p.234#32-33

Oc) Ethers: / \

R R’Def: two hydrocarbon fragments are attached by an oxygen atom. NB: You do not need to know how to name ethers.

Ether Name Application Structuremethoxymethane(dimethyl ether)

Aerosol spray propellant O / \H3C CH3

Ethoxyethane(diethyl ether)

Early anesthetic H3C O CH3 \ / \ / CH2 CH2

Methoxybenzene(methylphenyl ether)

Anise (licorice) flavoring Draw structure

12

O IId) Aldehydes: R-C-HOrganic compound containing a carbonyl group at the end of the carbon chain. A carbonyl group is a carbon atom double bonded to an oxygen atom.Uses: dyes, organic acids, formaldehyde (biological preservative)

O IIAldehyde group: - C - HNB: You do not need to know how to name aldehydes.

Examples: O IIH – C - H formaldehyde (common name), methanalCH3 – CHO ethanalCH3 – CH2 – CH2 – CH – CHO 2-methylpentanal I

CH3

benzaldehyde

O e) Ketones: ||

C / \

R R’Organic compound containing a carbonyl group at a position other than at the end of a hydrocarbon chain.Uses: as solvents, to make polymers, Nail polish remover: acetonePolymer: a very large molecule that is produced by linking together many smaller molecules.

NB: You do not need to know how to name ketones.Examples: O II C or CH3COCH3 acetone(common name), propanone / \ H3C CH3

13

O ||H3C C 3-hexanone \ / \ CH2 CH2 -CH2 -CH3

cyclohexanoneQuick Check #5, Org Bkt p.32

Of) Carboxylic Acids: ||

R--C \ O- H

Compound containing a carboxyl (-COOH) groupUses: organic acids, food preservativesUnpleasant odour, vinegar…NB: You do not need to know how to name most carboxylic acids.

O II C / \ R OH

Examples: CH3COOH Acetic acid (common name), ethanoic acidHCOOH Formic acid (common name), methanoic acid

Found in red ant venom, fourmis (French)CH3-CH2- CH2- COOH Butyric acid (common name), butanoic acid

Responsible for odour of smelly feet Cat’s pheromones: when cat rubs its cheeks on your leg, you’re being marked as safe territory.Cat’s facial secretions: mix of fatty acids including oleic acid, azelaic acid, pimelic acid, palmitic acid, butyric acid, caproic acid, 5-aminovaleric acid, para-hydroxyphenylacetic acid and trimethylamine.

O ||g) Esters: C / \

R OR’Compound in which a –COO- group joins 2 hydrocarbon chainsUses: Strong fruity odours, used in perfumes and flavoringsDNA, some plastics and explosives.NB: You do not need to know how to name esters.

14

H3C CH3CH2CH2 \ \

C=O C=O / /

CH3CH2CH2CH2CH2CH2CH2CH2O CH3CH2OOctyl acetate (orange flavoring) ethyl butanoate(pineapple flavouring)

Ester Synthesis:Reaction an organic acid (carboxylic) and an alcohol in the presence of an inorganic acid such as HCl or H2SO4.

Acetic acid methanol methyl acetate water O O II IICH3 – C- O –H + CH3 -OH CH3 – C- O – CH3 + H2O

Demo: Ester PreparationFew ml of carboxylic acid + few mL of alcohol + few drops of acid + heat

h) Amines: R-NH2 or R-NH-R’ or R-N-R’ Nitrogen is trivalent |

R’’Compound containing only single bonds and a nitrogen atom is attached to a carbon atom.Uses: dyes and drugs, chlorpheniramine (antihistamine)ephedrine, phenyllephrine: decongestants.Have “fish-like” odourNB: You do not need to know how to name amines.

Examples CH3-NH2 methylamine

H3C CH3 dimethylamine \ / N | H

i) Amides:Compound containing a nitrogen atom bonded to a carbonyl group.

15

O II C R’’ / \ / R N | R’Uses: plastics, rubber, inks, cosmetics, nylon, KevlarAcetominophen: pain killerAmide group linking amino acids together in a peptide chain that makes up proteins.NB: You do not need to know how to name amides.

Examples: O || ethanamide C / \ H3C NH2 O || butanamide C / \CH3CH2CH2 NH2 Quick Check#6, Org Bkt p. 33

j) Amino Acids:Compound that contains carboxylic acid and amine groups20 amino acids: building blocks essential to life

Example: CH3- CH – COOH 2-aminopropanoic acid (common name: alanine) I NH22 important properties of amino acids:a) Highly soluble in waterb) Link with other amino acids to form dipeptides and polypeptides forming proteins.

O O O O II II II IIH–N-CH2-C-OH + H-N-CH2-C-OH H–N-CH2-C- N-CH2-C-OH + H2O

16

I I I I H H H H a “dipeptide”

k) Summary of Functional GroupsTable 8.2.3, Org Bkt p.34Heb p. 240-241#37Review Questions 8.2, Org Bkt p.35-37

l) Reactions of Organic Molecules

(i) Warm Up1) Unsaturated fats such as those found in olive oils and avocados are healthier

than saturated fats found in coconut oil and butter. What do the words “unsaturated” and “saturated” mean in terms of organic molecular structure?

Answer: unsaturated means the presence of a double bond while saturated means the absence of a double bond2) Earlier in this unit, you learned about the types of chemical reactions. What

are the products of the combustion of a hydrocarbon or carbohydrate?Answer: carbon dioxide and water

3) The chemical reactivity of an organic compound largely depends on the type of organic compound involved. Match the functional group in the column on the left to the correct description from the column on the right. Draw lines to connect each pair.

(a) alcohol (iii) (i) contains a carboxyl group(b) alkyne (vi) (ii) contains a halogen(c) carboxylic acid (i) (iii) contains a hydroxyl group(d) alkyl halide (ii) (iv) contains a double bond between 2 carbon atoms(e) alkene (iv) (v) contains a –COOR group(f) ester (v) (vi) contains a triple bond between 2 carbon atoms

Examples of Simple Organic Reactions.Respiration, reproduction, digestion, and circulation.Production of proteins, carbohydrates, nucleic acid (DNA, RNA).Products of organic rxns: fabrics, building materials, food, drugs, paints, fuels, greases, perfumes, explosives, plastics, dyes and soaps.

We will look at the following reactions with organic molecules:(ii) Combustion Reactions(iii) Substitution Reactions(iv) Addition Reactions(v) Elimination and Condensation Reactions(vi) Polymerization(vii) Addition Polymerization

17

(ii) Combustion ReactionsHydrocarbon reacting with oxygen, also known as an oxidation reaction.During a complete combustion, in excess oxygen, the products are water and carbon dioxide.Ex: combustion of octane (car fuel):2 C8H18(l) + 25 O2(g) 16 CO2(g) + 18 H2O(g) + EnergyDuring an incomplete combustion, there is a limited amount of oxygen and the products may be carbon monoxide or carbon and water.

Carbon: solid, sooty material present in blackened smokeCO: colourless, odorless and very poisonous gas.

It is dangerous to run a car in an enclosed space such as a garage.

Example of complete combustion:2 CH4(g) + 2 O2(g) CO2(g) + 2 H2O(g) + Energy

Example of incomplete combustion: CH4(g) + O2(g) C(s) + 2H2O(g) + Energy

or2 CH4(g) + 3 O2(g) 2 CO(g) + 4 H2O(g) + Energy

Quick Check#7: (E.I. p.431)1) Some cars are powered by propane. Write the balanced chemical equation

for the complete combustion of propane.C3H8 + 5O2 3CO2 + 4H2O + energy

2) Find out if your home has a carbon monoxide detector. Why might a carbon monoxide detector be a good idea?

A carbon monoxide detector might indicate the presence of toxic carbon monoxide obtained for incomplete combustion in a fireplace or in candles.

3) Write a balanced chemical equation to represent the incomplete combustion of propane.

C3H8 + 2O2 3C + 4H2O + energyOr 2C3H8 + 7O2 6CO + 8H2O + energy

(iii) Substitution ReactionsAn atom from a reactant takes the place of an atom on an organic molecule.Ex: When exposed to ultraviolet light (catalyst), methane reacts with chlorine to produce chloromethane. H H | | H – C + Cl-Cl H – C + H-Cl / \ / \ H H H Cl

One hydrogen atom is replaced by a chlorine atom.

18

NB: Carbon remains tetravalent.

This reaction can go further when another chlorine atom replaces a hydrogen atom and, produces dichloromethane.

CH3Cl + Cl2 CH2Cl2 + HClDrawing on the board.

Aromatic compounds can also undergo substitution reactions. p.432 (EI) fig 8.3.2Ex: benzene + chlorine chlorobenzene + hydrochloric acidEx: chlorobenzene + chlorine dichlorobenzene + hydrochloric acidDrawing on the board.

(iv) Addition ReactionsWhen an unsaturated compound becomes saturated.

A double bond becomes a single bond.A triple bond becomes a double bond.

General Equation:H H H H \ / | | C=C + X-Y H – C – C - H / \ | |H H X Y

Halogenation: Halogens reacting with alkenes and alkynes.H H Cl Cl \ / | | C=C + Cl-Cl H –C – C -H / \ | |H H H H Ethanol is a common additive to gasoline and is synthetically produced by adding ethene(ethylene) and water in the presence of a catalyst: phosphoric acid or sulfuric acid.H H H H \ / H3PO4 | | C=C + H-O-H --------- H-C – C – O – H / \ or H2SO4 | |H H H HHydrogenation: Adding hydrogen atoms to the unsaturated site.H H H H \ / Ni | | C=C + H-H --------- H -C – C – H / \ catalyst | |

19

H H H H

Alkynes can also undergo addition reactions: Br Br Br Br

| | | |HC Ξ CH + Br2 --------- C = C + Br2 ----- H – C - C - H

| | | | H H Br Br

Quick Check #8 (EI p.434)1) How can the number of atoms bonded to the carbon assist your classification

of a reaction as addition or substitution?Carbon is always tetravalentA triple bond will become double bond, and a double bond will become saturated2) Classify the following as substitution or addition reactions:

a) H3C-CH3 + Br2 --------- H3C-CH2 + HBr addition |

Br

b) H3C CH3 Cl \ / | C=C + HCl --------- H3C-CH2-CH-CH3 substitution / \ H H3) Using structural formulas, draw reactions showing the following. For each

reaction, write the ame of the reactants and products under the appropriate molecule.

a) Formation of bromoethane H H H H

\ / | | C = C + HBr Br – C – C - H / \ | |

H H H H

b) Reaction between trichloromethane and fluorineCl Cl | |

Cl – C – Cl + F2 Cl – C – Cl + HF | | H F

4) Can an alkane undergo an addition reaction? Explain.

No, because an alkane is not unsaturated.

20

(v) Elimination ReactionsAn elimination reaction is the opposite of an addition reaction. A small molecule such as H2O or HX is eliminated.

H Br H H | | alcoholic \ /H - C –C – H --------- C = C + HBr (H and Br are eliminated) | | KOH / \ H H H HNB: In an elimination reaction, the number of atoms that a carbon atom is bonded to, decreases. In the above reaction, each carbon atom in the reactant is bonded to four other atoms. In the products, each carbon atom is only bonded to three other atoms.

Dehydration or condensation reaction: if water is eliminated (dehydration) or produced (condensation).(EI p.435: fig 8.3.10)

Esterification: process of reacting an organic acid and an alcohol to produce an ester. This is a type of dehydration or elimination reaction.(EI p.435: fig 8.3.10)The –OH group on the carboxylic acid combines with the H atom from the alcohol group to make water. The name of the ester is derived from the names of the alcohol and carboxylic acid. The first part of the name comes from the alcohol. The alcohol portion of the ester is named by removing the “-ol” ending and changing it to “-yl”. The name of the carboxylic acid part is changed by dropping the “-oic acid” part and adding “-oate”.Ester example: ethyl butanoate (sweet pineapple smell)

Produced when ethanol and butanoic acid are reacted:Butanoic acid + ethanol ethyl butanoate + water(EI p.435: fig 8.3.11)Animal and vegetable fats and oils are esters.Saturated fats: molecules where the organic acid part of the carbon chain does not contain any double bonds.Unsaturated fat: contains double bonds in the carbon parent chain.Fats: important nutrient for your body where they supply energy and help in the absorption of fat-soluble vitamins. (Vitamins A,D,E,K)People on a Mediterranean diet (fruits, vegetable, fish and whole grains) consume more unsaturated fats than saturated fats. This could be a reason why people on this diet have healthier lives.

Sample Problem: Writing Equations for Simple Organic Reactions, Org Bkt p.38Ex: Reaction between methanol and acetic acid where the product is airplane glue.

21

Practice Problems: Writing Equations for Simple Organic Reactions1) Oil of wintergreen contains the ester formed when methanol and salicyclic

acid react. What is the name of the ester responsible for this pleasant odor?Answer: Methyl salicylioate2) Ehtyl heptanoate smells like apricots. Draw structural diagrams to represent

the reaction that produces ethyl heptanoate.

3) Cholorofluorocarbons (CFCs) in the stratosphere are molecules that use up Earth’s protective ozone layer. Ozone molecules at this level absorb harmful UV-B and UV-C radiation. One such CFC is called chlorodifluoromethane. Draw structural diagrams to represent how this CFC is produced. Assume that methane reacts with chlorine, and then the product reacts with excess fluorine. What type of reactions are these?H H F | | |

H – C – H + Cl2 H – C – Cl + F2 F – C – Cl | | | H H HReaction Type: Substitution

(vi) Polymerization, Org Bkt p.38Macromolecules: very large molecules containing tens of thousands of atoms each.Polymers are long molecules made by stringing together smaller parts called “monomers”.

Polymer: many parts Monomer: one partNatural polymers: DNA, starch, proteins, celllulose, rubber, silkSynthetic polymers: plastics, nylon, styrofoam, pharmaceuticals, Teflon, paints, PlexiglasCellulose: several hundred to over ten thousand glucose molecules linked together

The name of a polymer depends on the monomer that it was made from.We represent a polymer by showing the monomer in brackets, with “n” representing some large number of repeating units.Homopolymer: one repeating monomer

Ex: vinylidene polyvinylidene (EI p.438 fig 8.3.14)

Copolymer: mixture of repeating units. (EI p.438 fig 8.3.15)

Addition PolymerizationPolyethylene: most common plastic

.Formation of polyethylene: repeating units of ethylene

H H \ /

22

n C=C ethylene / \ H H

polymerization

H H H H H H H H H H H H | | | | | | | | | | | |

R – C – C – C – C – C – C – C – C – C –C – C – C –R | | | | | | | | | | | | H H H H H H H H H H H H

H H | |

Simplified: - C – C - where n = a very large integer | | H H n

HDPE (high-density polyethylene): linear carbon backbone with few branches.Such long strands of these molecules fit very closely together.

LDPE(low-density polyethylene): the carbon backbone has many polyethylene branches and these chains of polymer cannot be packed tightly together.Ex: Rayon/viscose(artificial silk) is a long chain of glucose molecules broken into shorter chains.(regenerated cellulose)

HDPE LDPEProperties Stronger and stiffer Softer, filmsExamples Milk jugs, plastic garbage cans,

shampoo bottles, water pipesPlastic films, food wrap, garbage bags

UHMWPE (ultra-high molecular weight polyethylene): bulletproof vests, artificial joints Molar Mass (MM): millions of gram/molPolyethylenes are thermoplastic since they can be melted and molded into other shapes. Polyethylenes are not biodegradable and should be recycled. Examples of Polymers Formed by Addition Reactions Name Formula Monomer ApplicationsPolypropylene(PP)

-[CH2-CH(CH3)]n- PropyleneCH2 = CHCH3

Carpet (indoor/outdoor)Plastic bottles, Upholstery

Poly(vinyl chloride)

-(CH2-CHCl)n- Vinyl chlorideCH2 = CHCl

Pipes, Siding, Flooring

23

(PVC)Polystyrene(PS)

-[CH2-CH(C6H5)]n- StyreneCH2 = CHC6H5

Insulation, Furniture, Car’s Bumper, Packing Materials

Polytetrafluoro-ethylene(PTFE, Teflon)

-(CF2-CF2)n- Tetrafluoroethylene CF2=CF2

Non-Stick Surface on Cooking Ustensils, Engines’ Lining, Electrical Insulation

Polychloeoprene(cis + trans)(Neoprene)

-[CH2CH=CCl-CH2]n-

ChloropreneCH2CH=CCl=CH2

Synthetic rubber products for wetsuits, insulation

Starch: mixture of 2 polymers; amylose(straight chains) and amylopectin(many branches) of shorter glucose(C6H12O6) chains.Modified starch:

.obtained by treatment with acids, enzymes or oxidizing agents

.approved food additive

.used to thicken sauces

.prevent French dressing from separating

.fat substitute

.drying agent

Quick Check #9 (EI p.440)1) Polytetrafluoroethylene, commonly called Teflon, is a non-stick substance used in kitchen products, the aerospace industry, electronics, and communications. It is a polymer that can b represented by the diagram below.

Is this a homopolymer or a copolymer? Homopolymer(repeating monomer)

Circle the repeating unit on the diagramF F F F F F F F F F F F

| | | | | | | | | | | | … C – C – C – C – C – C – C – C – C – C – C – C … | | | | | | | | | | | | F F F F F F F F F F F F2) On a molecular level, how does HDPE differ from LDPE?

HDPE: long molecular strandsLDPE: several branches of molecules

3) Many plastics pipes, siding, and flooring are made of polyvinyl chloride or PVC. The reaction for its formation is shown below. What type of reaction is this? On the diagram below, circle the repeating unit in this polymer.

Cl H Cl H Cl H \ / \ / \ /

24

C = C + C = C + C = C / \ / \ / \ H H H H H H

Cl H Cl H Cl H | | | | | | - C – C – C – C – C - C – | | | | | | H H H H H H4) The symbols shown here are used to distinguish HDPE from LDPE. List two products in your home that are made up of HDPE and two products made up of LDPE.

HDPE LDPEExamples Shampoo bottle

“Thick” Water bottleGarbage bagFood wrap

Condensation Reactions1) Nylon Production:Hexamethylenediamine reacts with adipic acid. For each amine that reacts with a carboxylic acid, water is eliminated. The monomer is highlighted.

H H O O H H O | | || || | | ||- N – (CH2)4 – N – C – (CH2)4 – C – N – (CH2)4 – N – C - (CH2)4

2) Protein ProductionBuilding block: amino acidsAmino acid: organic molecule containing at least one amino group (-NH2) and one carboxyl group (-COOH).In our body: 20 different amino acidsHow?When an amino group on one amino acid reacts with the carboxyl group of another amino acid.Dipeptide: When two amino acids combine

amino acid + amino acid dipeptide + water Fig 8.3.19, Org Bkt p.39

Polypeptide (protein): many amino acids combine. A water molecule is eliminated with the formation of a new peptide bond.

Protein: natural polymer H R H R H R H R H R | | | | | | | | | | N – CH – C – N –CH – C – N – CH…- C – N – CH – C – N – CH –COOH

25

|| || || || O O O O

DNA or RNA: natural proteinsDNA: deoxyribonucleic acid, largest molecules knownActivity 8.3: Organic Molecules In Every Day Life, Org Bkt p.39-Optional8.3 Review Questions #1-12, Org Bkt p.40-41

26