ORGANIC CHEMISTRY CHM 207

CHAPTER 3: ALKENES

NOR AKMALAZURA JANI

SUBTOPICS

• •

Naming alkenes and cycloalkenes.

Physical properties of alkenes: i) boiling points and densities ii)polarity

•

Preparation of alkenes: i) dehydration of alcohols ii) dehydrohalogenation of haloalkanes

•

Reactions of alkenes: i) Addition reaction: a) Catalytic hydrogenation b) Addition of halogens - In inert solvent - In water / aqueous medium c) Addition of hydrogen halides d) Addition reaction with concentrated sulfuric acid: hydration of alkenes e) Addition reaction with acidified water (H 3 O + ): hydration of alkenes ii) Combustion of alkenes iii) Oxidation: a) epoxidation b)hydroxylation c)Ozonolysis iv) Polymerization

•

Unsaturation tests of alkenes: i) Reactions of alkenes with KMnO 4 ii) Reactions of alkenes with bromine.

•

Uses of alkenes: i) PE ii) PVC iii) ethanol

ALKENES

• • • • • •

Also called olefins Contain at least one carbon-carbon double bond (C=C) General formula, C n H 2n (n=2,3,…) Classified as unsaturated hydrocarbons (compound with double or triple carbon-carbon bonds that enable them to add hydrogen atoms.

sp 2 -hybridized For example: C 2 H 4 - ethylene CH 2 CH 2

Naming Alkenes

IUPAC RULES

RULE 1. Select the longest continuous carbon chain that contains a double bond.

This chain contains 6 carbon atoms

RULE 2.

Name this compound as you would an alkane, but change

–ane

to

–ene

for an alkene.

This chain contains 8 carbon atoms Select it as the parent compound.

RULE 3.

Number the carbon chain of the parent compound starting with the end nearer to the double bond.

Use the smaller of the two numbers on the double-bonded carbon to indicate the position of the double bond. Place this number in front of the alkene name.

IUPAC RULES

This end of the chain is closest to the double bond. Begin numbering here.

IUPAC RULES

The name of the parent compound is 1-octene.

4 3 2 1 5 6 7 8

RULE 4.

Branched chains and other groups are treated as in naming alkanes.

Name the substituent group, and designate its position on the parent chain with a number.

IUPAC RULES

3 2 1 5 6 7 8 4-ethyl-1-octene

NEW IUPAC NAMES

• •

Placing numbers (location of double bond) before the part of the name –ene.

Example: 1 CH 2 2 3 C CH 2 H 4 CH 3 1 CH 3 2 C H 3 C H 4 CH 2 5 CH 2 6 CH 3 New naming system: but-1-ene New naming system: hex-2-ene 1 CH 2 2 C H 3 CH 3 C 4 CH 3 H Old naming system: 3-methyl-1-butene New naming system: 3-methylbut-1-ene

• -

A compound with more than one double bond.

Two double bond: diene

-

Three double bond: triene Four double bond: tetraene * Numbers are used to specify the locations of the double bonds.

1 CH 2 2 C H 3 C H 4 CH 2 7 CH 3 6 C 5 C H H 4 C H 3 C H 2 C H IUPAC names: 1,3-butadiene 1,3,5-heptatriene new IUPAC names: buta-1,3-diene hepta-1,3,5-triene 1 CH 2 1 2 8 3 7 4 6 5 IUPAC names: 1,3, 5, 7-cyclooctatetraene new IUPAC names: cycloocta-1,3,5,7-tetraene

ALKENES AS SUBSTITUENTS

• •

Alkenes names as substituents are called

alkenyl

groups.

Can be named systematically as ethenyl, propenyl, etc. or by common names such as vinyl, ally, methylene and phenyl groups.

CH 2 methylene group (methylidene group) 3-methylenecyclohexene -CH=CH 2 vinyl group (ethenyl group) -CH 2 -CH=CH 2 allyl group (2-propenyl group) CH 2 CH=CH 2 CHCHCH 2 CH CH 2 IUPAC name: 3-vinyl-1,5-hexadiene New IUPAC name: 3-vinylhexa-1,5-diene

•

Contains C=C in the ring

CYCLOALKENES

cyclopropene cyclobutene cyclopentene cyclohexene

• -

Nomenclature of cycloalkenes: Similar to that alkenes Number the cycloalkane so that the double bond is between C1 and C2 and so that the first substituent has as low a number as possible.

* Double bond always between C1 and C2.

6 5 1

CH 3

4 2 3 1-methylcyclohexene 4 3 5 2 1 1,5-dimethylcyclopentene 6 1 2

CH 2 CH 3

5 3 4 IUPAC name: 2-ethyl-1,3-cyclohexadiene New IUPAC name: 2-ethylcyclohexa-1,3-diene

NOMENCLATURE OF

cis-trans

ISOMERS

H 3 C CH 2 CH 3 C C H H cis-2-pentene H 3 C H C C H CH 2 CH 3 trans-2-pentene

•

cis

– two particular atoms (or groups of atoms) are adjacent to each other

•

trans

– the two atoms (or groups of atoms) are across from each other

PHYSICAL PROPERTIES OF ALKENES

Boiling points and densities:

- Most physical properties of alkenes are similar to those alkanes.

- Example: the boiling points of 1-butene, cis-2-butene, trans-2-butene and n-butane are close to 0 o C.

- Densities of alkenes: around 0.6 or 0.7 g/cm 3 .

- Boiling points of alkenes increase smoothly with molecular weight.

- Increased branching leads to greater volatility and lower boiling points.

Polarity:

- relatively nonpolar.

- insoluble in water but soluble in non-polar solvents such as hexane, gasoline, halogenated solvents and ethers.

- slightly more polar than alkanes because: i) electrons in the pi bond is more polarizable (contributing to instantaneous dipole moments).

ii) the vinylic bonds tend to be slightly polar (contributing to a permanent dipole moment).

 

Alkyl groups are electron donating toward double bond, helping to stabilize it. This donating slightly polarizes the vinylic bond, with small partial positive charge on the alkyl group and a small negative charge on the double bond carbon atom.

For example, propene has a small dipole moment of 0.35 D. Vinylic bonds H 3 C H C C H H propene, μ = 0.35 D H 3 C H C C CH H 3 Vector sum = propene, μ = 0.33 D cis-2-butene, bp 4 o C H 3 C H C C H CH 3 Vector sum = 0 propene, μ = 0 trans-2-butene, bp 1 o C

• •

In a cis-disubstituted alkene, the vector sum of the two dipole moments is directed perpendicular to the double bond.

In a trans-disubstituted alkene, the two dipole moments tend to cancel out. If an alkene is symmetrically trans-disubstituted, the dipole moment is zero. H 3 C C H C H H H 3 C H C C CH H 3 Vector sum = propene, μ = 0.33 D cis-2-butene, bp 4 o C H 3 C H C C H CH 3 Vector sum = 0 propene, μ = 0 trans-2-butene, bp 1 o C

•

Cis- and trans-2-butene have similar van der Waals attractions, but only cis isomer has dipole-dipole attractions.

•

Because of its increased intermolecular attractions, cis-2-butene must be heated to a slightly higher temperature (4 o C versus 1 o C) before it begins to boil.

H 3 C C H C H H H 3 C H C C CH H 3 Vector sum = propene, μ = 0.33 D cis-2-butene, bp 4 o C H 3 C H C C H CH 3 Vector sum = 0 propene, μ = 0 trans-2-butene, bp 1 o C

PREPARATION OF ALKENES



Dehydration of alcohols



Dehydrohalogenation of haloalkanes

PREPARATION OF ALKENES

•

Alkenes can be prepared in the following ways: i) Dehydration of alcohols conc. H 2 SO 4 R-CH 2 -CH 2 -OH R-CH=CH 2 + H 2 O ii) Dehydrohalogenation of haloalkanes R-CH 2 -CH 2 -X NaOH/ethanol reflux R-CH=CH 2 + HX NaOH can be replaced by KOH

•

Saytzeff rule:

- A reaction that produces an alkene would favour the formation of an alkene that has the greatest number of substituents attached to the C=C group.

Dehydration of alcohols

H +

CH 3 CH 2 -CH-CH 3 OH 2-butanol

H +

CH 3 CH 2 -CH=CH 2 + H 2 O 1-butene CH 3 CH=CH-CH 3 + H 2 O 2-butene major product Dehydrohalogenation of haloalkanes CH 3 CH-CH-CH 2 H Br H 2-bromobutane KOH alcohol reflux CH 3 CH=CH-CH 3 2-butene (major product) CH 3 CH 2 CH=CH 2 1-butene

REACTIVITY OF ALKENES

More reactive than alkanes because: i) ii) iii) A carbon-carbon double bond consists of a σ and a π bond. It is easy to break the π bond while the σ bond remains intact.

The π electrons in the double bond act as a source of electrons (Lewis base). Alkenes are reactive towards electrophiles which are attracted to the negative charge of the π electrons.

π bond will broken, each carbon atom becomes an active site which can form a new covalent bond with another atom. One π bond is converted into 2 σ bonds.

REACTION OF ALKENES

i) Addition reaction:

a) Catalytic hydrogenation b) Addition of halogens - In inert solvent - In water / aqueous medium c) Addition of hydrogen halides d) Addition reaction with concentrated sulfuric acid: hydration of alkenes e) Addition reaction with acidified water (H 3 O + ): hydration of alkenes

ii) Combustion of alkenes iii) Oxidation:

a) epoxidation b)hydroxylation c)Ozonolysis

iv) Polymerization

REACTIONS OF ALKENES

Catalytic hydrogenation:

- hydrogenation: addition of hydrogen to a double bond and triple bond to yield saturated product.

- alkenes will combine with hydrogen in the present to catalyst to form alkanes.

C C H H Pt or Pd 25-90 o C C C H H

-

Plantinum (Pt) and palladium (Pd) – Catalysts Pt and Pd: temperature 25-90 o C Nickel can also used as a catalyst, but a higher temperature of 140 o C – 200 o C is needed.

EXAMPLES: H 2 C CH 2 ethylene H 2 Pt low pressure H 3 C CH 3 ethane CH 3 CH 2 CH 2 CH 2 CH hexene CH 2 H 2 Pt low pressure CH 3 CH 2 CH 2 CH 2 CH 2 CH 3 hexane

Addition of halogens:

i) In inert solvent: - alkenes react with halogens at room temperature and in dark.

- the halogens is usually dissolved in an inert solvent such as dichloromethane (CH 2 Cl 2 ) and tetrachloromethane (CCl 4 ).

- Iodine will not react with alkenes because it is less reactive than chlorine and bromine.

inert solvent - Fluorine is very reactive. The reaction will produced X X explosion. X X = halogen such as Br 2 or Cl 2 Inert solvent = CCl 4 or CH 2 Cl 2

EXAMPLES: H H H C C H ethene Br Br inert solvent (CCl 4 ) H H H C C Br Br H 1,2-dibromoethane * the red-brown colour of the bromine solution will fade and the solution becomes colourless.

cyclohexene CH 3 CH=CH propene Br 2 2 Cl 2 Br CCl 4 CCl 4 Br 1,2-dibromocyclohexane Cl CH 3 CH Cl CH 2 1,2-dichloropropane

Addition of halogens:

ii) In water / aqueous medium: - chlorine dissolves in water to form HCl and chloric (l) acid (HOCl).

Cl 2 (aq) + H 2 O(l) HCl(aq) + HOCl (aq) - same as bromine Br 2 (aq) + H 2 O(l) HBr(aq) + HOBr(aq) * Reaction of alkenes with halogens in water (eg. chlorine water and bromine water) produced halohydrins (an alcohol with a halogen on the adjacent carbon atom).

EXAMPLES: CH 3 CH=CH propene 2 + Br 2 H 2 O CH 3 CH OH CH 2 Br 1-bromo-2-propanol (major product) CH 3 CH Br CH 2 Br 1,2-dibromopropane (minor product) * Br atom attached to the carbon atom of the double bond which has the greater number of hydrogen atoms.

CH 3 CH 2 CH=CH 2 1-butene Cl 2 , H 2 O CH 3 CH 2 CH OH CH 2 Cl 1-chloro-2-butanol

Addition of hydrogen halides:

- Addition reaction with electrophilic reagents.

- Alkenes react with hydrogen halides (in gaseous state or in aqueous solution) to form addition products.

- The hydrogen and halogen atoms add across the double bond to form haloalkanes (alkyl halides).

- General equation: C C HX H X C C alkene haloalkane

-

Reactivity of hydrogen halides : HF < HCl < HBr < HI

* Reaction with HCl needs a catalyst such as AlCl 3 AlCl 3 H 2 C CH 2 HCl CH 3 CH 2 Cl EXAMPLES: cyclopentene H-I CH 3 CH=CHCH 3 + H-Br 2-butene I iodocyclopentane Br CH 3 CH 2 CHCH 3 2-bromobutane

MARKOVNIKOV’S RULE

• •

There are 2 possible products when hydrogen halides react with an unsymmetrical alkene .

It is because hydrogen halide molecule can add to the C=C bond in two different ways.

H H CH 3 C C H H-I H H CH 3 C C H H I 1-iodopropane H H CH 3 C C H H-I H H CH 3 C C H I H 2-iodopropane (major product)

Markovnikov’s rules:

- the addition of HX to an unsymmetrical alkene, the with the hydrogen atom attaches itself to the carbon atom (of the double bond) larger number of hydrogen atoms.

Mechanism of electrophilic addition reactions:

- C=C : electron rich part of the alkene molecule - Electrophiles: electron-seeking

Step 1: Formation of carbocation.

Attack of the pi bond on the electrophile to form carbocation.

C C δ+ E δ Y C C E

carbocation

Step 2: Rapid reaction with a negative ion.

The negative ion (Y addition reaction.

) acts as nucleophile and attacks the positively charged carbon atom to give product of the

Y -

C C E

Y -

C C E Y

ADDITION OF HYDROGEN HALIDES TO UNSYMMETRICAL ALKENES AND MARKOVNIKOV’S RULE 3 2 1 CH 3 CH=CH 2 Propene HCl CH 3 CHCH 2 H Cl 1-chloropropane CH 3 CHCH 2 Cl H 2-chloropropane (major product) according to Markovnikov's rules

MECHANISM: Step 1: Formation of carbocation CH 3 H H C C H H Cl H H H H C C C H or H H less stable carbocation (1 o carbocation) H H H H C C C H H H Cl more stable carbocation (2 o carbocation) - 2 o carbocation is more stable than 1 o carbocation.

- 2 o carbocation tends to persist longer, making it more likely to combine with Cl ion to form 2-chloromethane (basis of Markovnikov's rule).

Step 2: Rapid reaction with a negative ion H H H H C C C H H H Cl H H H H C C C H H Cl H 2-chloromethane (major product)

Addition reaction with concentrated sulfuric acid: hydration of alkenes

- the alkene is absorbed slowly when it passed through concentrated sulfuric acid in the cold (0-15 o C).

- involves the addition of H atom and HSO 4 group across the carbon-carbon double bond.

follows Markovnikov’s rule.

H H H C C H H OSO 3 H (H 2 SO 4 ) H H H C C H H OSO 3 H ethyl hydrogensulphate (CH 3 CH 2 HSO 4 ) When the reaction mixture is added to water and warmed, ethyl hydrogensulphate is readily hydrolysed to ethanol CH 3 CH 2 OSO 3 H + H -OH (H 2 O) CH 3 CH 2 OH + H 2 SO *ethene reacts with concentrated H 2 SO 4 to form ethanol* 4 or *alkene reacts with concentrated H 2 SO 4 to form alcohol*

• • •

Addition reaction with acidified water (H 3 O + ): hydration of alkenes

Hydration : The addition of H atoms and –OH groups from water molecules to a multiple bond.

Reverse of the dehydration reaction.

Direct hydration of ethene: - passing a mixture of ethene and steam over phosphoric (v) acid (H 3 PO 4 ) absorbed on silica pellets at 300 o C and a pressure of 60 atmospheres.

- H 3 PO 4 is a catalyst.

CH 2 =CH 2 (g) ethene H 2 O (g) H 3 PO 4 300 o C, 60 atm CH 3 CH 2 OH (g) ethanol C C alkene H 2 O H + H OH C C alcohol

• •

Markovnikov’s rule is apply to the addition of a water molecule across the double bond of an unsymmetrical alkene.

For examples: CH 3 CH 3 C CH 2 2-methylpropene H OH H + 25 o C CH 3 CH C 3 CH 2 OH H tert-butyl alcohol CH 3 CH=CH 2 + H 2 O propene H + = catalyst H + CH 3 CHCH 3 OH 2-propanol

MECHANISM OF ACID CATALYSED HYDRATION OF ALKENES Step 1: Protonation to form carbocation H H CH 3 C C H H + H H H H C C C H H H more stable carbocation (2 o carbocation) Step 2: Addition of H 2 O to form a protonated alcohol H H H H C C C H H H O H H CH 3 CHCH O H H 3 Step 3: Loss of a proton (deprotonated) to form alcohol CH 3 CHCH 3 O H H CH 3 CHCH OH 3 H + H + = catalyst

ANTI-MARKOVNIKOV’S RULE: FREE RADICAL ADDITION OF HYDROGEN BROMIDE •

When HBr is added to an alkene in the absence of peroxides it obey Markovnikov’s rule.

•

When HBr (not HCl or HI) reacts with unsymmetrical alkene in the presence of peroxides (compounds containing the O O group) or oxygen, HBr adds in the opposite direction to that predicted by Markovnikov’s rule .

•

The product between propene and HBr under these conditions is 1-bromopropane and not 2-bromopropane.

CH 3 CH=CH 2 HBr peroxide CH 3 CH 2 CH 2 Br 1-bromopropane (major product) anti-Markovnikov's orientation

•

Anti Markovnikov’s addition:

- peroxide-catalysed addition of HBr occurs through a free radical addition rather than a polar electrophilic addition. - also observed for the reaction between HBr and many different alkenes.

- not observed with HF, HCl or HI.

Formation of anti-Markovnikov alcohol

•

Alkenes goes to hydroboration reaction to form anti Markovnikov alcohol.

H 2 O 2 , OH C C B 2 H 6 C H C OH anti-markovnikov examples: CH 3 CH=CH propene 2 B 2 H 6 H 2 O 2 , OH CH 3 CHCH 2 -OH propanol CH 3 CH 3 CH C CH 3 CH 2 isobutylene CH 3 C B 2 H 6 CH 3 2-methyl-2-butene H 2 O 2 , OH B 2 H 6 H 2 O 2 , OH CH 3 CH 3 CH CH 2 OH isobutyl alcohol CH 3 CH 3 CHCHCH 3 OH 3-methyl-2-butanol

Combustion of alkenes:



The alkenes are highly flammable and burn readily in air, forming carbon dioxide and water.



For example, ethene burns as follows : C 2 H 4 + 3O 2 → 2CO 2 + 2H 2 O

OXIDATION

•

Oxidation

: reactions that form carbon oxygen bonds.

•

Oxidation reaction of alkenes: i) epoxidation ii)hydroxylation iii)Ozonolysis

EPOXIDATION OF ALKENES

•

Epoxide / oxirane: a three-membered cyclic ether.

C C O R C O O H O C C O R C OH alkene peroxyacid epoxide (oxirane) acid

•

Examples of epoxidizing reagent: O CH 3 C O O H peroxyacetic acid O C O O H peroxybenzoic acid (PhCO 3 H) Cl O H O O m-chloroperoxybenzoic acid (MCPBA)

Examples:

cyclohexene MCPBA CH 2 CI 2 , 25 o C O 1,2-epoxycyclohexane cycloheptene MCPBA CH 2 CI 2 , 25 o C O 1,2-epoxycycloheptane

HYDROXYLATION OF ALKENES

• •

Hydroxylation:

- Converting an alkene to a glycol requires adding a hydroxyl group to each end of the double bond.

Hydroxylation reagents: i) Osmium tetroxide (OsO 4 ) ii)Potassium permanganate (KMnO 4 ) C C OsO 4 H (or KMnO 4 , OH) 2 O 2 C C OH OH glycol

CH 2 CH 2 KMnO 4 (aq), OH cold, dilute ethene CH 3 CH CH 2 propene KMnO 4 (aq), OH cold, dilute CH 2 CH 2 OH OH 1,2-ethanediol MnO 2 CH 3 CH CH 2 OH OH 1,2-propanediol MnO 2 * Also known as Baeyer’s test

OZONOLYSIS OF ALKENES

•

Ozonolysis:

- The reaction of alkenes with ozone (O 3 ) to form an ozonide, followed by hydrolysis of the ozonide to produce aldehydes and /or ketone.

- Widely used to determine the position of the carbon-carbon double bond.

- Ozonolysis is milder and both ketone and aldehydes can be recovered without further oxidation.

R R R' C C H O 3 R R O C O O C ozonide R' H (CH 3 ) 2 S or H 2 O, Zn/H + R C O R ketone R' O C H aldehyde

EXAMPLES: CH 3 O H 3-nonene i) O 3 ii) (CH 3 ) 2 S OCH 3 H i) O 3 ii) (CH 3 ) 2 S CH 3 O O O H O H H O OCH 3 O O H

REACTIONS OF ALKENES WITH HOT, ACIDIFIED KMnO 4 R R' R C C R'' H R' KMnO 4 /H + R'' C C H OH OH R R'' C O ketone R CH=CH 2 R' O C OH acid KMnO 4 /H + R R'' C O ketone R COOH O C R' H aldehyde + CO 2 + H 2 O Example: 4-methyl-4-octene KMnO 4 /H + C O 2-pentanone HO C O butanoic acid

POLYMERIZATION OF ALKENES

•

Polymer : A large molecule composed of many smaller repeating units (the monomers) bonded together.

•

Alkenes serves as monomers for some of the most common polymers such as polyethylene (polyethene), polypropylene, polystyrene, poly(vinyl chloride) and etc.

•

Undergo addition polymerization /chain-growth polymer: - a polymer that results from the rapid addition of one molecule at a time to a growing polymer chain, usually with a reactive intermediate (cation, radical or anion) at the growing end of the chain.

H CI H C C H H CI H C C H vinyl chloride H H C C CI H repeating unit H CI H Cl H Cl C C C C C C H H H H n H poly(vinyl chloride) H

SOME OF THE MOST IMPORTANT ADDITION POLYMERS POLYMER Polyethylene POLYMER USES Bottles, bags, films MONOMER FORMULA CH 2 =CH 2 POLYMER REPEATING UNIT CH 2 CH 2

n

Polypropylene Plastics, olefin fibers H H C C CH 3 H CH 2 CH 3 CH

n

Polystyrene Plastics, foam insulation Poly(isobutylene) Specialized rubbers H H C C H H H C C CH 3 CH 3 H 2 C C H

n

CH 2 CH 3 C CH 3

n

UNSATURATION TESTS FOR ALKENES

1) Reactions of alkenes with KMnO 4 - KMnO 4 is a strong oxidising agent.

- alkenes undergo oxidation reactions with KMnO 4 solution under two conditions: a) Mild oxidation conditions using cold, dilute, alkaline KMnO 4 (Baeyer’s test).

b) Vigorous oxidation conditions using hot, acidified KMnO 4.

a) Reaction of alkenes with cold, dilute, alkaline KMnO 4 (Baeyer’s test)

- the purple colour of KMnO 4 solution disappears and a cloudy brown colour appears caused by the precipitation of manganese (IV) oxide, MnO 2 .

- test for carbon-carbon double or triple bonds.

- a diol is formed (containing two hydroxyl groups on adjacent carbon atoms).

C C KMnO 4 (aq), OH cold, dilute C C OH OH

a diol

MnO 2

2) Reactions of alkenes with bromine - A solution of bromine in inert solvent (CH 2 CI 2 and dilute bromine water are yellow in colour.

or CCI 4 ) - The solution is decolorised when added to alkenes or organic compounds containing C=C bonds.

C C Br 2 CH 2 CI 2 C C Br 2 (aq) H 2 O C Br C Br C C OH Br C Br C Br

DETERMINATION OF THE POSITION OF THE DOUBLE BOND

a) Ozonolysis of alkenes:

- For example, ozonolysis of an alkene produces methanal and propanone.

H CH 3 H C O methanal O C CH 3 propanone remove the oxygen atoms from the carbonyl compounds and joining the carbon atoms with a double bond.

H H C CH C 3 CH 3 H H C CH 3 C CH 3 2-methylpropene

b) Reaction of alkenes with hot, acidified KMnO 4

- by using hot, acidified KMnO 4 , the diol obtained is oxidised further.

- cleavage of carbon-carbon bonds occurs and the final products are ketones, carboxylic acids or CO 2 .

CH 3 CH 3 C CH 2 2-methylpropene KMnO 4 /H + CH 3 CH 3 C O propanone (ketone) CO 2 + H 2 O

•

Example: An alkene with the molecular formula C 6 H 12 hot KMnO 4 is oxidised with solution. The carboxylic acids, butanoic acid (CH 3 CH 2 CH 2 COOH) and ethanoic acid (CH 3 COOH), are produced. Identify the structural formula of the alkene.

i) cleavage of the double bond gives a mixture of carboxylic acids H H R C C R' KMnO 4 /H + R OH C O O OH C R' ii) location of the double bond is done by taking away the oxygen atoms from the carboxylic acids and then joining the carbon atoms by the double bond.

RC OO H and R'C OO H RCH = CHR' CH 3 CH 2 CH 2 C OO butanoic acid H and CH 3 C OO H ethanoic acid CH 3 CH 2 CH 2 CH = CHCH 3 2-hexene

USES OF ALKENES

• •

Ethylene and propylene are the largest-volume industrial organic chemicals.

Used to synthesis a wide variety of useful compounds.

H H C C H H polyethylene n O CH 3 C H acetaldehyde oxidize O CH 3 C OH acetic acid O H 2 C CH 2 ethylene oxide polymerize O 2 Ag catalyst oxidize H C C H ethylene H H Cl 2 CH 2 OH H + H 2 O CH OH 2 ethylene glycol H 2 O catalyst CH 3 CH 2 OH ethanol CH 2 CI CH CI 2 ethylene dichloride H H NaOH CI C C H vinyl chloride

POLYETHENE (PE)

• •

The most popular plastic.

Uses: i) Grocery bags ii)Shampoo bottles iii)Children's toy iv)Bullet proof vests v)Film wrapping vi)Kitchenware

POLYVINYL CHLORIDE (PVC)

H H H C C CI vinyl chloride polymerize H C H CI C H H C H CI C H

n

H C H CI C H poly(vinyl chloride) PVC, "vinyl"

USES OF PVC:



Clothing - PVC fabric has a sheen to it and is waterproof.

 

- coats, shoes, jackets, aprons and bags.

As the insulation on electric wires.

Producing pipes for various municipal and industrial applications. For examples, for drinking water distribution and wastewater mains.

 

As a composite for the production of accessories or housings for portable electronics.

uPVC or Rigid PVC is used in the building industry as a low-maintenance material.



Ceiling tiles.

USES OF ETHANOL

• • • • • • • • • •

Motor fuel and fuel additive.

As a fuel to power Direct-ethanol fuel cells (DEFC) in order to produce electricity.

As fuel in bipropellant rocket vehicles.

In alcoholic beverages.

An important industrial ingredient and use as a base chemical for other organic compounds include ethyl halides, ethyl esters, diethyl ether, acetic acid, ethyl amines and to a lesser extent butadiene. Antiseptic use.

An antidote.

Ethanol is easily miscible in water and is a good solvent. Ethanol is less polar than water and is used in perfumes, paints and tinctures. Ethanol is also used in design and sketch art markers.

Ethanol is also found in certain kinds of deodorants.