Reaksi KimiaReaksi KimiaReaksi KimiaReaksi Kimia

Faktor-faktor yang mempengaruhi1. Kolisi2. Luas permukaan3. Konsentrasi4. Tekanan5. Temperatur6. Katalis

a. Heterokatalisb. Homokatalisc. Autokatalis

Order ReaksiJenis-jenis rekasiReaksi radikal bebasReaksi addisi dan substitusi elektrofilikReaksi addisi dan substitusi nukleofilikReaksi eliminasi

1. 1. KolisiKolisi

2. Luas Permukaan2. Luas Permukaan

3. Konsentrasi3. Konsentrasi

4. Tekanan4. Tekanan

5. Temperature5. Temperature

SummaryIncreasing the temperature increases reaction rates because of the disproportionately large increase in the number of high energy collisions

6. Katalis6. Katalis

.

a. Heterogenus katalisa. Heterogenus katalis

The reaction between persulphate ions and iodide The reaction between persulphate ions and iodide ionsions

Persulphate ions (peroxodisulphate ions), S2O82-, are very

powerful oxidising agents. Iodide ions are very easily

oxidised to iodine. And yet the reaction between them in

solution in water is very slow.If you look at the equation, it is easy to see why that is:

S2O82-+ 2I- 2SO4

2-+ I2 The reaction needs a collision between two negative ions. The catalysed reaction avoids that problem completely. The catalyst can be either iron(II) or iron(III) ions which are added to the same solution.

S2O82-+ 2Fe2+ 2SO4

2-+ 2Fe3+

2Fe3+ + 2I- 2Fe2+ + I2

b. Homogenus katalisb. Homogenus katalis

The destruction of atmospheric ozoneThe destruction of atmospheric ozone

O2 UV .O. + .O.

The oxygen radicals can then combine with ordinary oxygen molecules to make ozone.

O2 + .O. O3

Ozone can also be split up again into ordinary oxygen and an oxygen radical by absorbing ultraviolet light.

O3 UV O2 + .O.

Chlorofluorocarbons (CFCs) like CF2Cl2 slow breakdown

in the atmosphere produces chlorine atoms - chlorine

free radicals

Cl. + O3 O2 + ClO.

ClO. + .O. ClO. + O2

In autocatalysis, the reaction is catalysed by one of its products.In autocatalysis, the reaction is catalysed by one of its products. One of the One of the simplest examples of this is in the oxidation of a solution of ethanedioic acid simplest examples of this is in the oxidation of a solution of ethanedioic acid (oxalic acid) by an acidified solution of potassium manganate(VII) (potassium (oxalic acid) by an acidified solution of potassium manganate(VII) (potassium permanganate).permanganate).

The reaction is very slow at room temperature. It is used as a titration to find the The reaction is very slow at room temperature. It is used as a titration to find the concentration of potassium manganate(VII) solution and is usually carried out at a concentration of potassium manganate(VII) solution and is usually carried out at a temperature of about 60°C. Even so, it is quite slow to start with.temperature of about 60°C. Even so, it is quite slow to start with.The reaction is catalysed by manganese(II) ions. There obviously aren't any of The reaction is catalysed by manganese(II) ions. There obviously aren't any of those present before the reaction starts, and so it starts off extremely slowly at those present before the reaction starts, and so it starts off extremely slowly at room temperature. However, if you look at the equation, you will find room temperature. However, if you look at the equation, you will find manganese(II) ions amongst the products. More and more catalyst is produced as manganese(II) ions amongst the products. More and more catalyst is produced as the reaction proceeds and so the reaction speeds up.the reaction proceeds and so the reaction speeds up.You can measure this effect by plotting the concentration of one of the reactants You can measure this effect by plotting the concentration of one of the reactants as time goes on. You get a graph quite unlike the normal rate curve for a reaction.as time goes on. You get a graph quite unlike the normal rate curve for a reaction.

c. Auto katalisc. Auto katalis

CATALYSTS IN INORGANIC INDUSTRIAL PROCESSESCATALYSTS IN INORGANIC INDUSTRIAL PROCESSES

The Contact Process for the manufacture of sulphuric acidAt the heart of the Contact Process is a reaction which converts

sulphur dioxide into sulphur trioxide. Sulphur dioxide gas is passed together with air (as a source of oxygen) over a solid vanadium(V) oxide catalyst. This is therefore an example of heterogeneous catalysis.

The Haber Process for the manufacture of ammoniaThe Haber Process combines hydrogen and nitrogen to make

ammonia using an iron catalyst. This is another reversible reaction, and another example of heterogeneous catalysis.

CATALYSTS IN THE PETROCHEMICAL INDUSTRYCATALYSTS IN THE PETROCHEMICAL INDUSTRY

Catalytic crackingCracking is the name given to breaking up large hydrocarbon

molecules into smaller and more useful bits. This is achieved by using high pressures and temperatures without a catalyst, or lower temperatures and pressures in the presence of a catalyst.

CATALYSTS IN THE PETROCHEMICAL INDUSTRYCATALYSTS IN THE PETROCHEMICAL INDUSTRY

IsomerisationHydrocarbons used in petrol (gasoline) are given an octane rating

which relates to how effectively they perform in the engine. A hydrocarbon with a high octane rating burns more smoothly than one with a low octane rating. Molecules with "straight chains" have a tendency to pre-ignition.

CATALYSTS IN THE PETROCHEMICAL INDUSTRYCATALYSTS IN THE PETROCHEMICAL INDUSTRY

ReformingReforming is another process used to improve the octane rating of

hydrocarbons to be used in petrol, but is also a useful source of aromatic compounds for the chemical industry. Aromatic compounds are ones based on a benzene ring. Reforming uses a platinum catalyst suspended on aluminium oxide together with various promoters to make the catalyst more efficient. The original molecules are passed as vapours over the solid catalyst at a temperature of about 500°C.

ACID CATALYSIS IN ORGANIC CHEMISTRY

The nitration of benzeneBenzene is treated with a mixture of concentrated nitric acid and

concentrated sulphuric acid at a temperature not exceeding 50°C. As the temperature increases there is a greater chance of getting more than one nitro group, -NO2, substituted onto the ring.

Nitrobenzene is formed.

ACID CATALYSIS IN ORGANIC CHEMISTRY

The hydration of ethene to make ethanolEthene is mixed with steam and passed over a catalyst consisting of

solid silicon dioxide coated with phosphoric(V) acid. The temperature used is 300°C and the pressure is about 60 to 70 atmospheres.

ACID CATALYSIS IN ORGANIC CHEMISTRY

Making esters - the esterification reactionEsters are what is formed when an organic acid

reacts with an alcohol in the presence of concentrated sulphuric acid as the catalyst. Everything is present in a single liquid phase, and so this is an example of homogeneous catalysis. For example, ethanoic acid reacts with ethanol to produce ethyl ethanoate.

ACID CATALYSIS IN ORGANIC CHEMISTRY

The acid catalysed hydrolysis of estersIn principle, this is the reverse of the esterification reaction but, in

practice, it has to be done slightly differently. The ester is heated under reflux with a dilute acid such as dilute hydrochloric acid or dilute sulphuric acid.

You would normally hydrolyse esters quite differently by heating them with sodium hydroxide solution (alkaline hydrolysis). This isn't an example of a catalytic reaction because the hydroxide ions are used up during the reaction.

MORE EXAMPLES OF CATALYSIS IN ORGANIC CHEMISTRY

Epoxyethane is manufactured by reacting ethene with a limited amount of oxygen in the presence of a silver catalyst at a temperature of about 250 - 300°C and a pressure of less than 15 atmospheres. Because the solid silver is catalysing a gas reaction, this is an example of heterogeneous catalysis.

The halogenation of benzeneBenzene reacts with chlorine or bromine in the presence of a

catalyst. The catalyst is either aluminium chloride (or aluminium bromide if you are reacting benzene with bromine).

MORE EXAMPLES OF CATALYSIS IN ORGANIC CHEMISTRY

The Friedel-Crafts alkylation of benzeneBenzene is treated with a chloroalkane (for example, chloromethane

or chloroethane) in the presence of aluminium chloride as a catalyst. The equation shows the reaction using a methyl group, but any other alkyl group could be used in the same way

The Friedel-Crafts acylation of benzeneAn acyl group is an alkyl group attached to a carbon-oxygen double

bond. Acylation means substituting an acyl group into something - in this case, into a benzene ring. The most commonly used acyl group is CH3CO-. This is called the ethanoyl group .

Order Order reaksireaksi

A + B productsA + B products 1. The rate of reaction is proportional to the concentration of A

Rate = k [A]Rate = k [A]

2. The rate of reaction is proportional to the square of the concentration of A

Rate = k [A]Rate = k [A]22

By doing experiments involving a reaction between A and B, you would find that the rate of the reaction was related to the concentrations of A and B in this way

Rate = k [A]Rate = k [A]a a [B][B]bb

a= order reaksi Ab= order reaksi B

Total order reaksi = a + b

ORDERS OF REACTION AND MECHANISMSORDERS OF REACTION AND MECHANISMS

Monomolecular reactionMonomolecular reaction Here is the mechanism we have already looked at. How do we Here is the mechanism we have already looked at. How do we know that it works like this?know that it works like this?

By doing rate of reaction experiments, you find this rate By doing rate of reaction experiments, you find this rate equation:equation:

ORDERS OF REACTION AND MECHANISMSORDERS OF REACTION AND MECHANISMS

Bimolecular reactionBimolecular reaction Here is the mechanism we have already looked at. How do we Here is the mechanism we have already looked at. How do we know that it works like this?know that it works like this?

By doing rate of reaction experiments, you find this rate By doing rate of reaction experiments, you find this rate equation:equation:

Methoda untuk mempelajari reaksi organicMethoda untuk mempelajari reaksi organicNERS-M (NERS-M (Name - Example - Regiochemistry - Stereochemistry – Name - Example - Regiochemistry - Stereochemistry –

Mechanism)Mechanism)

Reaksi Asam-BasaReaksi Asam-BasaReaksi asam/basa adalah meliputi transfer proton.

Asam/basa Lewis

Note : Seluruh reaksi asam/basa yang tidak melibatkan serah terima proton adalah reaksi asam/basa Lewis. Reagen berlaku sebagai electrophiles dan nucleophiles.

Reaksi Organik DasarReaksi Organik Dasar

Reaksi Substitusi dan EliminasiReaksi Substitusi dan EliminasiNama: SN2 Reaction Example:

CH3Br + NaOH -> CH3OH + NaBr

Regiochemistry: NAStereochemistry: Inversion of configurationComments: Reaksi ini adalah reaksi bimolecular: kecepatan reaksi akan

meningkat ketika konsentrasi electrophile and nucleophile ditingkatkan.

Reaktifitas dari electrophile: MeX > allylic, benzylic > 1° > 2° (No 3° ) MsO-, TsO-, I- > Br- > Cl-

Leaving groups that form stable, basa yang tidak reaktif adalah bagus sebagai leaving groups.

Reaksi Organik DasarReaksi Organik Dasar

HO BrH3C

H

H HHO Br H3C OH+ Br+

Reaktifitas dari nucleophile: Reaktifitas dari nucleophile: Kuat > Sedang >> lemah (unreactive) Kuat > Sedang >> lemah (unreactive)

Reaksi ini bersaingan degan reaksi E2 .Reaksi ini bersaingan degan reaksi E2 .examples:examples:Enolate alkylation:Enolate alkylation:

Tosylation/STosylation/SNN22

Reaksi Organik DasarReaksi Organik Dasar

Example:

Regiochemistry:Saytzeff's rule applies to reactions using small bases.Hofmann elimination occurs when large sterically bulky

bases are used (tBuO-).Stereochemistry: stereospecific

Name: E2 ReactionName: E2 Reaction

Mechanism:

Comments:Reactivity of acid: 3° > 2° > 1° Competes with SN2 reaction. E2 favored at

higher T.

Name: E2 ReactionName: E2 Reaction

Stereospecific examples:

Name: E2 ReactionName: E2 Reaction

Example:

Regiochemistry: NAStereochemistry: RacemizationMechanism: Comments:Reaksi Unimolecular. Kecepatan reaksi tergantung pada

konsentrasi dari nucleophile. Reaktifitas dari electrophile: 3° > benzylic, allylic > 2° >

1° >> MeIntermediate Carbocation terbentukRacemization b) Rearrangements

Reaksi SReaksi SNN11

Example:

Regiochemistry: NAStereochemistry: Racemization

Acid-Catalyzed SAcid-Catalyzed SNN11

Mechanism:

Comment: E1 reaction is major competitor.

Acid-Catalyzed SAcid-Catalyzed SNN11

Example:

Regiochemistry: Saytzeff's rule: the more highly substituted alkene will be

the dominant product.Stereochemistry: nonspecific (cis and trans alkenes will

form)

E1 Reaction E1 Reaction

Mechanism:

Comments:Reactivity of electrophile: 3° > 2° Carbocation intermediates are formed. Reaction competes with SN1. E1 is preferred at higher

temperature

E1 Reaction E1 Reaction

Example:

Regiochemistry: Saytzeff rule applies.Stereochemistry: nonspecific

Acid Catalyzed EliminationAcid Catalyzed Elimination

Mechanism:

Competes with acid catalyzed SN1.

Acid Catalyzed EliminationAcid Catalyzed Elimination

Example:

Regiochemistry: Markovnikov's rule: the hydrogen adds to the

carbon with the greatest number of hydrogens.

Stereochemistry: nonspecific

Markovnikov AdditionMarkovnikov Addition

Mechanism:

Comments:Carbocation intermediates are formed.

Markovnikov AdditionMarkovnikov Addition

Example:

Regiochemistry: Anti-MarkovnikovStereochemistry: nonspecific

Anti-Markovnikov addition Anti-Markovnikov addition

Mechanism:

Comments:Radical intermediates are formed. Relative reactivity: 3° > 2° > 1° . Related reaction: Hydroboration

Anti-Markovnikov addition Anti-Markovnikov addition

DEFINITIONS OF OXIDATION AND REDUCTION (REDOX)This page looks at the various definitions of oxidation and

reduction (redox) in terms of the transfer of oxygen, hydrogen and electrons. It also explains the terms oxidising agent and reducing agent.

Oxidation and reduction in terms of oxygen transferDefinitions• Oxidation is gain of oxygen.• Reduction is loss of oxygen.For example, in the extraction of iron from its ore:

REDOXREDOX

Oxidising and reducing agentsOxidising and reducing agentsAn oxidising agent is substance which oxidises something else. An oxidising agent is substance which oxidises something else.

In the above example, the iron(III) oxide is the oxidising In the above example, the iron(III) oxide is the oxidising agent.agent.

A reducing agent reduces something else. In the equation, the A reducing agent reduces something else. In the equation, the carbon monoxide is the reducing agent.carbon monoxide is the reducing agent.

• Oxidising agents give oxygen to another substance.Oxidising agents give oxygen to another substance.• Reducing agents remove oxygen from another substance.Reducing agents remove oxygen from another substance.Oxidation and reduction in terms of hydrogen transferOxidation and reduction in terms of hydrogen transferThese are old definitions which aren't used very much nowadays. These are old definitions which aren't used very much nowadays.

The most likely place you will come across them is in organic The most likely place you will come across them is in organic chemistry.chemistry.

DefinitionsDefinitions• Oxidation is loss of hydrogen.Oxidation is loss of hydrogen.• Reduction is gain of hydrogen.Reduction is gain of hydrogen.

REDOXREDOX

An update on oxidising and reducing agentsAn update on oxidising and reducing agents• Oxidising agents give oxygen to another substance or remove Oxidising agents give oxygen to another substance or remove

hydrogen from it.hydrogen from it.• Reducing agents remove oxygen from another substance or Reducing agents remove oxygen from another substance or

give hydrogen to it.give hydrogen to it.

Oxidation and reduction in terms of electron Oxidation and reduction in terms of electron transfertransfer

This is easily the most important use of the terms oxidation and This is easily the most important use of the terms oxidation and reduction at A' level.reduction at A' level.

DefinitionsDefinitions• Oxidation is loss of electrons.Oxidation is loss of electrons.• Reduction is gain of electrons.Reduction is gain of electrons.

REDOXREDOX

OXIDATION OF ALCOHOLSOXIDATION OF ALCOHOLS Oxidising the different types of alcoholsOxidising the different types of alcoholsThe oxidising agent used in these reactions is normally a solution The oxidising agent used in these reactions is normally a solution

of sodium or potassium dichromate(VI) acidified with dilute of sodium or potassium dichromate(VI) acidified with dilute sulphuric acid. If oxidation occurs, the orange solution sulphuric acid. If oxidation occurs, the orange solution containing the dichromate(VI) ions is reduced to a green containing the dichromate(VI) ions is reduced to a green solution containing chromium(III) ions.solution containing chromium(III) ions.

The electron-half-equation for this reaction isThe electron-half-equation for this reaction is

REDOXREDOX

Primary alcohols Primary alcohols Primary alcohols can be oxidised to either aldehydes or carboxylic Primary alcohols can be oxidised to either aldehydes or carboxylic

acids depending on the reaction conditions. acids depending on the reaction conditions. Partial oxidation to aldehydesPartial oxidation to aldehydes You get an aldehyde if you use an excess of the alcohol, and distil You get an aldehyde if you use an excess of the alcohol, and distil

off the aldehyde as soon as it forms.off the aldehyde as soon as it forms.The excess of the alcohol means that there isn't enough oxidising The excess of the alcohol means that there isn't enough oxidising

agent present to carry out the second stage. Removing the agent present to carry out the second stage. Removing the aldehyde as soon as it is formed means that it doesn't hang aldehyde as soon as it is formed means that it doesn't hang around waiting to be oxidised anyway! around waiting to be oxidised anyway!

OXIDATIONOXIDATION

Primary alcohols Primary alcohols Full oxidation to carboxylic acidsFull oxidation to carboxylic acids You need to use an excess of the oxidising agent and make sure You need to use an excess of the oxidising agent and make sure

that the aldehyde formed as the half-way product stays in the that the aldehyde formed as the half-way product stays in the mixture.mixture.

The alcohol is heated under reflux with an excess of the oxidising The alcohol is heated under reflux with an excess of the oxidising agent. When the reaction is complete, the carboxylic acid is agent. When the reaction is complete, the carboxylic acid is distilled off. distilled off.

OXIDATIONOXIDATION

Secondary alcoholsSecondary alcoholsSecondary alcohols are oxidised to ketones - and that's it. Secondary alcohols are oxidised to ketones - and that's it.

For example, if you heat the secondary alcohol propan-2-For example, if you heat the secondary alcohol propan-2-ol with sodium or potassium dichromate(VI) solution ol with sodium or potassium dichromate(VI) solution acidified with dilute sulphuric acid, you get propanone acidified with dilute sulphuric acid, you get propanone formed.formed.

OXIDATIONOXIDATION

Using these reactions as a test for the different types of Using these reactions as a test for the different types of alcoholalcohol

You would need to show that it was a neutral liquid, free of water You would need to show that it was a neutral liquid, free of water and that it reacted with solid phosphorus(V) chloride to and that it reacted with solid phosphorus(V) chloride to produce a burst of acidic steamy hydrogen chloride fumes.produce a burst of acidic steamy hydrogen chloride fumes. You You would then add a few drops of the alcohol to a test tube would then add a few drops of the alcohol to a test tube containing potassium dichromate(VI) solution acidified with containing potassium dichromate(VI) solution acidified with dilute sulphuric acid. The tube would be warmed in a hot water dilute sulphuric acid. The tube would be warmed in a hot water bath. Results for the various kinds of alcohol. bath. Results for the various kinds of alcohol. Picking out the Picking out the tertiary alcoholtertiary alcohol

In the case of a primary or secondary alcohol, the orange solution In the case of a primary or secondary alcohol, the orange solution turns green. With a tertiary alcohol there is no colour change.turns green. With a tertiary alcohol there is no colour change.

After heating: After heating:

OXIDATIONOXIDATION

Distinguishing between the primary and secondary Distinguishing between the primary and secondary alcoholsalcohols

You need to produce enough of the aldehyde (from You need to produce enough of the aldehyde (from oxidation of a primary alcohol) or ketone (from a oxidation of a primary alcohol) or ketone (from a secondary alcohol) to be able to test them. There are secondary alcohol) to be able to test them. There are various things which aldehydes do which ketones don't. various things which aldehydes do which ketones don't. These include the reactions with Tollens' reagent, These include the reactions with Tollens' reagent, Fehling's solution and Benedict's solution. A Fehling's solution and Benedict's solution. A muchmuch simpler but fairly reliable test is to use simpler but fairly reliable test is to use Schiff's reagentSchiff's reagent. . Schiff's reagent is a fuchsin dye decolourised by Schiff's reagent is a fuchsin dye decolourised by passing sulphur dioxide through it. In the presence of passing sulphur dioxide through it. In the presence of even small amounts of an aldehyde, it turns bright even small amounts of an aldehyde, it turns bright magenta.It must, however, be used absolutely cold, magenta.It must, however, be used absolutely cold, because ketones react with it very slowly to give the because ketones react with it very slowly to give the same colour. same colour.

OXIDATIONOXIDATION

What is formed when aldehydes are oxidised?What is formed when aldehydes are oxidised?

OXIDATION ALDEHYDE AND KETONEOXIDATION ALDEHYDE AND KETONE

Using Tollens' reagent (the silver mirror test)Using Tollens' reagent (the silver mirror test)Tollens' reagent contains the diamminesilver(I) ion, Tollens' reagent contains the diamminesilver(I) ion,

[Ag(NH[Ag(NH33))22]]

++..

This is made from silver(I) nitrate solution. You add a drop This is made from silver(I) nitrate solution. You add a drop of sodium hydroxide solution to give a precipitate of of sodium hydroxide solution to give a precipitate of silver(I) oxide, and then add just enough dilute ammonia silver(I) oxide, and then add just enough dilute ammonia solution to redissolve the precipitate.solution to redissolve the precipitate.

OXIDATION ALDEHYDE AND KETONEOXIDATION ALDEHYDE AND KETONE

Using Fehling's solution or Benedict's solutionUsing Fehling's solution or Benedict's solution

Fehling's solutionFehling's solution contains copper(II) ions complexed with contains copper(II) ions complexed with tartrate tartrate ions in sodium hydroxideions in sodium hydroxide solution. Complexing the copper(II) solution. Complexing the copper(II) ions with tartrate ions prevents precipitation of ions with tartrate ions prevents precipitation of copper(II) copper(II) hydroxide.hydroxide.

Benedict's solutionBenedict's solution contains copper(II) ions complexed with contains copper(II) ions complexed with citrate citrate ions in sodium carbonate solutionions in sodium carbonate solution. Again, complexing the . Again, complexing the copper(II) ions prevents the formation of a precipitate - this time copper(II) ions prevents the formation of a precipitate - this time of of copper(II) carbonatecopper(II) carbonate..

Both solutions are used in the same way. A few drops of the Both solutions are used in the same way. A few drops of the aldehyde or ketone are added to the reagent, and the mixture is aldehyde or ketone are added to the reagent, and the mixture is warmed gently in a hot water bath for a few minuteswarmed gently in a hot water bath for a few minutes

OXIDATION ALDEHYDE AND KETONEOXIDATION ALDEHYDE AND KETONE