J McM-OC-Pharmacy-Fm-1-02

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Organic ChemistryOrganic Chemistry

LaboratoriumLaboratorium KimiaKimia OrganikOrganik JurusanJurusan KimiaKimia

FakultasFakultas MatematikanMatematikan dandan IlmuIlmu PengetahuanPengetahuan AlamAlam

UniversitasUniversitas PadjadjaranPadjadjaran

20092009

Dr.Dr. DikdikDikdik KurniaKurnia,, M.ScM.Sc

Alkenes, Alkynes, and Aromatic CompoundsAlkenes, Alkynes, and Aromatic Compounds


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Organic ChemistryOrganic Chemistry

Laboratorium Kimia Organik Jurusan Kimia

Fakultas Matematikan dan Ilmu Pengetahuan Alam

Universitas Padjadjaran

2009

Code of Lecture : D10B. 03E0318

The Unit of Semester credits (SKS) : 2 (2-0)

Semester : Fm/1

Day/Time : Thursday, 13.00 14.40 am


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Alkenes, Alkynes, and Aromatic Compounds

1. What are alkenes, alkyunes, and aromatic compounds?Be able to recognize the structure of members of these three families ofunsaturated organic compounds and give examples of each.

2. How are alkenes, alkyunes, and aromatic compounds named?Be able to name an alkene, alkyune, or simple aromatic compound fromits structure or write the structure, given name.

3. What are cis-trans isomers?Be able to identity cis-trans isomers and predict their occurrence.

4. What are the general properties of alkyunes, and aromatic compounds?Be able to describe and compare such properties as polarity, watersolubility, flammability, bonding, and chemical reactivity.

5. What are the common chemical reactions of alkyunes, and aromatic

compounds?Be able to predict the products of reactions ofalkyunes, and aromaticcompounds.

6. How do organic reactions take place?Be able to show how addition reaction occur and describe the differencebetween additon and substitution reactions.


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Alkenes, Alkynes, and Aromatic Compounds

Compounds in three families described in this chapter all contain carbon-

carbon multiple bonds;

a. Alkenes (ethlene), contain a carbon-carbon double bondb. Alkyunes (acetylene), contain a carbon-carbon triple bond

c. Aromatic compounds (benzene), contain a six-membered ring of carbon

atoms with three double bonds or other rings with similar arrangment of

alternating double bonds.


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Saturated and Unsaturated Hydrocarbons

Alkenes and Alkyunes contain carbon-carbon multiple bonds to which more

hydrogen atoms can be added and are therefore knows as unsaturated

hydrocarbons.

Alkenes are hydrocarbons that contain carbon-carbon doube bonds

Alkyunes are hydrocarbons that contain carbon-carbon triple bonds

CH3CH2CH3

CH3CH=CH3 CH3CH|CH3

The alkanes are often referred to as saturated hydrocarbons because each

carbon atom is fully saturated by bonds to the maximum number of

hydrogen atoms: No more hydrogen atoms can be added.


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Alkenes

Simple Alkenes are made in huge quantities by thermal cracking of natural gasand petroleum and are the basic building block of the vast petrochemical

industri, which produces organic chemicals from petroleum.

CH3(CH2)nCH3 H2 + CH4 + CH2=CH2 + CH2=CH2 + CH3CH2CH=CH2

750-900rC

F-Caroten (a polyalkene)

cis-polyisoprene (Natural rubber)


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Naming Alkenes and Alkynes

1. Name the parent compound

Find the longest chain containing the double or triple bond and name the

parent compound by adding the suffix ene or yne to the root for main chain.


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Naming Alkanes and Alkyunes

2. Number the carbon atoms in the main chain.

Beginning and the end nearer the multiple bond, number each carbon

atom in the chain.

If the multiple bond is an equal distance from the both ends, as in the

middle structure, begin numbering at the end nearer the first branchpoint.


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For the cyclic alkenes, the-ane ending of the cycloalkane is replaced by ene.

No numbers are needed for an unsubstituted cycloalkene.

In substituted cycloalkenes, the double-bond carbon atoms are numbered 1

and 2 so that the first substituent has the lower number:

2. Number the carbon atoms in the main chain.


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3. Write out the full name.

Identify and number branching substituents in the same way as for alkaes:

Assign number to the branching substituents on the chain and list them

alphabetically.

Use commas to separates numbers and use hyphens to separate words from

numbers.


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The Structure of Alkenes: cis-trans Isomerism

Alkenes and Alkyunes differ from alkanes in shapes because of their differet kinds of

bonds

Two carbons and four attached atoms that make up the double-bond functional

group always lie in planar.

Unlike in alkannes where free rotation around the C-C single bond occurs, there is no

free rotation around double bonds a new kind of isomerism is possible for

alkenes


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1-butene and 2-butene are isomers because their double bonds occur at different

positions along the chain.

Because of the rotation cant occur around carbon-

carbon double bonds, there are two different 2-

butenes.

1. The two methyl groups are close togetheron thesame side of the double bond.

2. The two methyl groups are far apart on opposite

sides of the double bond.


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Isomers, cis-trans: Alkenes that have the same formula and connections

between atoms but differ in having pairs of groups on opposite sides of the

double bonds.

cis- isomer: Isomer with a specific pairs of atoms or groups on the same side of

thedouble bond.

trans- isomer: Isomer with a specific pairs of atoms or groups on opposite side

of thedouble bond.


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cis-trans isomers occurs in an alkene whenever each double bond carbon is

bonded to two different substituents groups.If either double-bond carbond is attached to two identical cis-trans

isomerism is not possible.

These compounds are

identical, because the left-

hand carbon of the double

bond has two Hs attached,

cis-trans isomerism is

impossible

These compounds are notidentical, neither carbon of

the double bond has two

identical groups attached to

it


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Properties of Alkenes

Nonpolar: insoluble in water; soluble in nonpolar organic

solvent; less dense than water.

Alkaline-like in melting points, boiling points, and other

physical properties.

Flammable; gaseous alkenes not toxic. Display cis-trans isomerism when each double-bond C atom

has different substituents.

Chemically reactive at double bond, which undergous

addition reactions.


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Properties of Alkenes


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Chemical Reactions of Alkenes and Alkyunes

Most of the reaction carbob-carbon multiple bonds can be grouped under the

category ofaddition reactions, addition of a reactant of the general form X-Yto the multiple bond of an unsaturated compound to yield a saturated poduct.

Alkenes and alkynes react similarity in many ways, but well look at alkenes

because theyre more common and more important


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Chemical Reactions of Alkenes and AlkyunesAddition of Cl2 and Br2 to Alkenes (Halogenation)

Halogenation: The reaction of an alkene (or alkyne) with halogen (Cl2 or Br2) to

yiels a 1,2-dihaloalkane product.

Halogenation: The reaction of an alkene (or alkyne) with halogen (Cl2 or Br2) to

yiels a 1,2-dihaloalkane product.


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Chemical Reactions of Alkenes and AlkyunesAddition of HBr and HCl to Alkenes

An alkyl bromide

An alkyl chloride

Hydrohalogenation: The reaction of an alkene with HCl or HBr to yiels an alkyl

haide product.


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Only one of the two possible addition products is obtained.

This is what usually happens when HBr and HCl add to alkenes with

unsymmetrically substituted double bonds, that is, double bonds in which

one carbon is bonded to more hydrogens than other


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Markovnikovs rule: In the addition of HX to and alkene, the H becomesattached to the carbon that already has the most Hs,

and the X becomes attached to the carbon that has

fewer Hs.


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Chemical Reactions of Alkenes and AlkyunesAddition of H2O to Alkenes (Hydration)

Hydration, alkene: The reaction of an alkene with water (H2O) to yiels an alcohol.

This reaction occurs on treatment of the alkene with water in the presence of

astrong acid catalyst such as H2SO4.


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Chemical Reactions of Alkenes and AlkyunesAddition of H2O to Alkenes (Hydration)

Markovnikovs rule: In the addition of HX to and alkene, the H becomesattached to the carbon that already has the most Hs,

and the X becomes attached to the carbon that has

fewer Hs.

As with the addition of HBr and HCl, Markovnikovs rule can be used to predict

the product when water add to an unsymmetrically substituted alkene.


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How An Alkene Addition Reaction Occurs

Figure 13.2 A reaction mechanism of how the addition of HBr to an alkene occurs.

The reaction takes place in two steps and involves a carbocation intermediate.

Step 1Two electrons from the C-C double bonds are

used to form a new single bond between the

incoming hydrogen ion and one of the carbons.

The other carbon now has only six electrons in its

outer shell and has a positive charge

Step 2The positively charged carbocation then reacts

with the negatively bromide ion, using an

electron pair from bromide to form a single bondbetween carbon and bromine.

The second carbon thus regains an outer-shell

octet

Carbocation:A polyatomic ion with a

positively charged carbon

atom.


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Alkene Polymers

Polymer:

A very large molecule composed of identical repeating units and formed by the

combination of small molecules.

Vinil Monomer:

A compound with the structure CH2=CHZ that undergoes polymerization to give

a polymer with the repeating unit CH2CHZ

Monomer:

A small molecule combined to form a polymer

Polimerization:

A reaction in which monomers combine to form a polymer.

Chain-growth polymer:

A polymer formed by the addition of monomer molecules one by one to the end

of a growing chain.


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Alkene Polymers


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Alkynes


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Aromatic Compounds and The Structure of Benzene

Aromatic compound:A compound that contains a six-membered ring of carbon atoms with three

double bonds or a similarly stable ring.

Resonance:

The exixtance of a molecul in a single structure intermediate among two ormore correct possible double-bond-containing structure that can be drawn.

Benzene, The simplest aromatic compound, is a flat, symmetrical molecule with

the molecular formula C6H6 (cyclohexatriene)


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Aromatic Compounds and The Structure of Benzene


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Naming Aromatic Compounds

Ortho: Indicates 1,2 substituents on a benzene ring



No number is needed for monosubstituted benzene because all the ring

positions are equivalent.


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Number must be included in the name when a benzene ring three or moresubstituents.

In the same manner as for alkane, the numbers are chosen so that substituents

have the lowest possible numbers and the substituents are named in

alphabetical order


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Phenyl group: The name of the C6H5- unit when a benzene ring is considered a

substituent group.

Aryl group: The general name for any substituent derived from an aromatic

compound


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Chemical Reactions of Aromatic CompoundsAromatic Substitution Reactions

Substitution reaction Aromatic:

Substitution of an atom or group for one of the hydrogens on an aromatic ring.


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Nitration


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Halogenation


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Sulfonation


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Polycyclic Aromatic Compounds and Cancer

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