C11 TAHAP 3 RUSLI

4541/CHEMISTRY MODUL P3T ( TAHAP 2)

11 CARBON COMPOUNDS

11.1 ORGANIC COMPOUNDS

Carbon compounds are compounds that contain the carbon element.

HYDROCARBON

Hydrocarbons are organic compounds that contain ……..…………., C

and……………….., H.

The main source of hydrocarbons are ………………..gas and ……………………. It is formed as a result of decomposition of plants and animals that died million years ago.

JPNT 2009 CHAPTER 2 : CARBON COMPOUNDS

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Carbon compounds

Organic compoundscarbon compounds that are obtained from living things (plants and animals) such as sugar/glucose (C6H12O6), starch, protein, vitamin, enzym etc.

Inorganic compoundscarbon compounds that are usually do not contain carbon to carbon bonds such as carbon monoxide (CO), carbon dioxide (CO2), calsium carbonate (CaCO3) etc.

Hydrocarbons Non-Hydrocarbons

Hydrocarbons

Saturated Hydrocarbonscontain only …………….covalent bonds between ………atoms. C - C

Unsaturated Hydrocarbonscontain at least one ……………or ………..covalent bond between carbon atoms. C = C C = C


11.2 ALKANES

1 Alkanes are ……………….hydrocarbons.

2 The general formula of alkanes:……………………………………

3 Each carbon atom is bonded to four other atoms(carbon or hydrogen atoms) by

…………..covalent bonds.

4 Naming of Alkanes (IUPAC)

The names of straight chain alkanes (all the carbon atoms are joined in a continuous chain) are made up of two component parts :

Stem / root

indicates the number of carbon atoms in the longest continuous carbon chain.The names of stems for the first ten straight alkanes are :

Number of carbon atom

1 2 3 4 5 6 7 8 9 10

Stem Meth Eth Prop But Pent Hex Hept Oct Non Dec

Suffix / ending

indicates the family of the compound. For alkane, the suffix is ‘ane’ because it belongs to the alkane group.

Number of carbon atoms,

n

Name of alkane

Molecular Formula, CnH2n+2

Structural Formula

1 Methane CH4

2 Ethane C2H6


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– C –



n

Name of alkane

Molecular Formula, CnH2n+2

Structural Formula

3 Propane C3H8

4 Butane C4H10

5 Pentane C5H12

6 Hexane

7 Heptane

8 Octane

9 Nonane

5 Physical properties of alkanes

Alkanes are covalent compound which consist of molecules. These molecules are held together by …………………intermolecular forces.


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Covalent bond (strong covalent bond) Intermolecular force


Alkanes have physical properties similar to other covalent compounds.

Physical property Explaination

1 Low ……………………points

The molecules are held together by …………..intermolecular forces. ……………..amount of heat required to overcome the forces.

2

……………….in water but ……………….in organic solvents (ether, benzene, tetrachloromethene)

3…………………conduct electricity

4 ……………dense than water ……………on top of water

Name of members

Molecular Formula

Molar mass/ g mol-1

Melting and Boiling point

Density

Methane CH4 16Ethane C2H6 30PropaneButane C4H10 58PentaneHexane 86Heptane

6 Chemical properties of alkanes

Alkanes are saturated hydrocarbon (have single covalent bonds, C – C and C –H) Hence, alkanes are generally chemically………………………..

Combustion


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………..

Gradually

………..

Gradually

CH2


Alkanes undergo complete combustion in the presence of excess oxygen to form carbon dioxide and water .

Alkane + oxygen → carbon dioxide + water

Step 1 : Balance C → Step 2 : Balance H → Step 3 : Balance O

(i) CH4 + 2O2 → CO2 + 2H2O

(ii) C2H6 + O2 → 2CO2 + 3H2O ..X 2

2C2H6 + 7O2 → 4CO2 + 6H2O

Balance the equations :

(iii) C3H8 + O2 → CO2 + H2O

(iv) C4H10 + O2 → CO2 + H2O

(v) C5H12 + O2 → CO2 + H2O

Alkanes undergo incomplete combustion when there is insufficient oxygen to form carbon dioxide gas, carbon monoxide gas carbon (in the form of soot) and water.

Substitution Reaction

Alkanes react with halogens (Cl2 and Br2) in the presence of ……………..or ………………..light

In this reaction, each hydrogen atoms in the alkane molecule are substituted one by one by halogen atoms.

Example :When methane reacts with chlorine gas in the presence of ultraviolet light, a variety of substituted products are formed :

Step 1


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UV

UV


CH4 + Cl2 CH3Cl + HCl

(methane) (chloromethane)

Step 2

CH3Cl + Cl2 CH2Cl2 + HCl

(dichloromethane)

Step 3

CH2Cl2 + Cl2 CHCl3 + HCl

(trichloromethane)

Step 4

CHCl3 + Cl2 CHCl4 + HCl

( tetrachloromethane)

11.3 ALKENES


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UV

UV


1 Alkenes are unsaturated hydrocarbons.

2 General formula : …………………………………………

3 The functional group of the alkene ………………………………

Example : ethene

4 Naming of Alkenes (straight chain) (IUPAC)

(i) Determine the longest carbon chain containing double bond, give the stem name according to the number of carbon atoms ; eth, prop, but, pent, hex, hept, oct, non and dec.

(ii) Add the suffix “ene” at the end of the name.

(iii) Number the carbon atoms from the end nearer to the double bond and give the double bond the smaller number.

(iv) The first member of alkenes has two carbon atoms in a molecule

because : …………………………………………………………………..


n

Name of alkaneMolecular Formula,

CnH2n

Structural Formula

2 Ethene C2H4

3 Propene C3H6

4 But-1-ene

5 Pent-1-ene


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n

Name of alkaneMolecular Formula,

CnH2n

Structural Formula

6 Hex-1-ene

7 Hept-1-ene

8 Oct-1-ene

5 Physical properties of alkenes

Physical properties of Alkenes are similar to alkanes.

i …………………….melting and boiling points,

ii ……………………in water but ………………….in organic solvents,

iii …………………….conduct electricity and Less dense than water

6 Chemical properties of alkenes

Alkenes are chemically more ……………….than alkanes because of the existence of ……………….covalent bond between two carbon atoms.

Almost all of the chemical reactions of alkene occur at the double bond.

Combustion Reaction

Alkene burns completely in the excess oxygen to produce carbon dioxide and water.


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Alkene + oxygen → carbon dioxide + water

Example : C2H4 + 3O2 → 2CO2 + 2H2O

Balance the following equations :

(i) C3H6 + O2 → CO2 + H2O

(ii) C4H8 + O2 → CO2 + H2O

(iii) C5H10 + O2 → CO2 + H2O

Alkene burns incompletely in limited supply of oxygen to form carbon dioxide, carbon monoxide, carbon (in the form of soot) and water.

Addition Reaction

As alkenes are unsaturated hydrocarbon, they undergo addition reaction.

An addition reaction is a reaction in which other atoms are added to each

carbon atom of the double bond, [C = C ] to form single covalent bond

product [ C-C ].

C = C + AB C C

A B (i) Addition of Hydrogen (Hydrogenation)

Alkenes react with hydrogen at ……………..C in the presence of

………………………. as a catalyst to produce……………………..

Example :

H H H H


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Ni / Pt

180 C


H C C H + H2 H C C H

Ethene H H Ethane

(ii) Addition of Halogen (Halogenation)

Alkenes react with halogens such as chlorine and bromine at room conditions.(no catalyst or ultraviolet light needed)

Example :

H H H H

H C C H + Br2 H C C H

Ethene (bromine water) Br Br 1,2-dibromoethane

When ethene gas is passed through bromine water, brown colour of bromine water is…………………………….

This reaction is used to distiguish a saturated hydrocarbon and unsaturated hydrocarbon.

(iii) Addition of Hydrogen Halide [ HX ]

Alkenes react with hydrogen halide such as hydrogen chloride, HCl or hydrogen bromide, HBr at room temperature to form haloalkane.

Example :

C2H4 + HCl → C2H5 Cl Ethene Hydrogen chloride Chloroethane

C3H6 + HBr → Propene Hydrogen bromide ………………….

(iv) Addition of hydroxyl groups (Acidified Potassium manganate(VII), KMnO4 // Potassium dicrhoromate(VI), K2Cr2O7 solution)


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In this reaction, two hydroxyl, -OH groups are added to the

carbon-carbon double bond in an alkene molecule.

An alkene …………………the purple solution of acidified

potassium manganate(VII) // the ……………solution of acidified

Potassium dicrhoromate(VI), K2Cr2O7 turns to……………...

This reaction is used to distiguish a saturated hydrocarbon and

unsaturated hydrocarbon.

Example :

C2H4 + H2O + [O] → C2H4(OH)2

Ethene Ethane-1,2-diol

Complete the following equation :

C3H6 + H2O + [O] →

H H H C = C H + H2O + [O] →

(v) Addition of Water (Hydration)

Alkenes react with water (in the form of steam) at high temperature and pressure in the presence of ……………….acid as a catalyst to produce alchohols.

Alkene + H2O Alcohol

Example :

C2H4 + H2O C2H5OH

Ethene ethanol


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H3PO4

300 C / 60 atm

H3PO4

300 C / 60 atm


Complete the following equation :

C3H6 + H2O

H H H C = C H + H2O

Addition of steam to alkene is one way to manufacture alcohol in industry:

CnH2n + H2O(g) CnH2n+1OH Alkene Alcohol

Polymerisation reaction

In this reaction, small alkene molecules undergo addition reaction at a

high pressure of 1000 atm and temperature of 200 C. Thousands of

alkene molecule join together to form long chain giant molecules

called………………………………..

The small repeating units of molecules that join together to form polymer

are called ………………………….

Example : Polymerisation of ethene

Polythene Polymerisation of propene:


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H3PO4

300 C / 60 atm

H3PO4

300 C / 60 atm

H H

H C C H

Ethene

H H

C C

H H

n is large number up to a few thousands

n

n

H3PO4

300 C / 60 atm


COMPARING PROPERTIES OF ALKANE WITH ALKENE

Alkanes Alkenes

Similar(physical properties)

……………..melting and boiling points ………………….melting and boiling points

……………..in water but ………………in organic solvents

……………..in water but ………………….in organic solvents

……………………..conduct electricity ……………………………conduct electricity

……………….dense than water …………………………dense than water

Different(chemical properties)

unreactive

Burn in air to produce ……………….flame Burn in air to produce very sooty flame

Undergo subtitution reaction Undergo ………………………reaction

…………………react with bromine………………….with bromine (brown colour of bromine ……………………….

……………..react with acidified potassium manganate(VII) solution

…………………..with acidified potassium manganate(VII) solution (purple colour

……………………)

7 HOMOLOGOUS SERIES

Homologous series are groups of carbon compounds that have the following general characteristics :


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(a) Members having the same ………………………… properties because they

have the same ………………………. (group that takes part in a reaction).

(b) Members of the series can be represented by a …………………………

formula.

(c) Members of the series can be prepared by the …………………………

(d) Two consecutive members in the series have a difference in relative atomic

mass of 14, a difference of CH2.

(e) Members of the series have physical properties that …………………………

gradually as the number of carbon atoms in a molecule

…………………………

1. Example of homologous series :

Homologous Series

General FormulaFunctional

groupExample of members

AlkaneCnH2n+2

n = 1, 2, 3, …

C – CSingle bond

Propane

Alkene

AlcoholCnH2n+1 OH

n = 1, 2, 3, …

-OHHydroxyl

group

Carboxylic acidCnH2n+1 COOH

n = 0, 1, 2, 3, …

-COOHCarboxyl

group

Ester

CnH2n+1 COO Cn’H2n’+1

n = 0, 1, 2, 3, …n’ = 1, 2, 3,…

-COOC-

8 ISOMERISM


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Number of carbon in the longest chain

(4 carbon atoms)

Homologous series

(alkene)


Method of writing the Name of organic compound using IUPAC nomenclature

Prefix

(Branch)

Stem

( number of carbon atoms in the longest carbon

chain)*

Suffix

(functional group / homologous series)

* for alkenes, the smallest number is given to the carbon with the double bond.

Example :

2,3-dimethylbut-1-ene

(a) Name the following compounds.

(i) (ii)

………………………………… …………………………………

(iii) (iv)

Name : ……………………………… Name : …………………..……

(v) (vi)


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SuffixStem

Branch

Prefix

CH3

H3C CH CH2 CH2 CH3

H3C CH CH2 CH2 CH3

CH2 CH3

CH3

H3C CH = CH CH CH3


Name : …………………………… Name : ……………………………

(b) Draw the structural formula for the following molecules :

(i) 2,-methylhexane (ii) 2,4-dimethylpentane

(iii) 3-methylpent-2-ene (iv) 2,3-dimethylhex-2-ene

Isomerism is phenomenon where a compound has the ………….

molecular formula but ……………………..structural formulae.

Molecular formula shows the type and number of atoms in a molecular compound.

Structural formula shows the type and number of atoms for each element, and how the atoms are ………………..to one another in a compound.

Molecular Formula

Structural Formula & IUPAC nameNumber of

IsomersC4H10

Butane


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…………………….

C5H12

C4H8

C5H10

11.5 ALCOHOL

1 Alcohols are organic compounds that contain……………., ………………….and

………………………….atoms.

2 The general formula for alcohol is :……………………………………………………

3 Functional group :…………………………………………………………..


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4 Naming alcohol using IUPAC nomenclature :

Determine the number of carbon atoms in the longest carbon chain which contains the hydroxyl group ( –OH ) obtain the name of alkane with the same number of carbon atom as alcohol.

Replace the ending “e” from the name of alkane with “ol”

Example :

Methane MethanolEthane EthanolPropane ?Butane ?

Number the carbon atom in the longest carbon chain which is joined to the hydroxyl group -OH with the smallest number the number is placed in front of the “ ol ” to indicate which carbon atom the hydroxyl group is attached to.

Example :

Butan-2-ol

Name : ………………….. Name : ………………….

Name : ………………….. Name : ………………….. Name : …………………..


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4 carbon atoms -OH

-OH at the 2nd C


5 Isomerism in alcohol :

Isomers are molecules that have …………. molecular formula but …………………structural formula.

Methanol and ethanol do not have isomers. Isomerism in alcohol begins with propanol

Complete the following table :

Name of alcohol

Molecular Formula

Structural Formula & IUPAC name

Number of isomers

Propanol C3H7OH 2

Butanol 4


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6 Preparation of Ethanol

Two methods of preparation of Ethanol

(i) Preparation of ethanol, C2H5OH in the laboratory ( Fermentation of glucose)

7 Physical properties of alcohol

Alcohols with one to eleven carbon atoms exist as……………………..

Methanol, ethanol and propanol mix with water in all……………………... Solubility in water decreases with increasing of molecular size.

Physical properties of ethanol, C2H5OH :


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Preparation of Ethanol

In the laboratory

Process : ………………………

………………..is a process in which microorganism such as yeast act on

…………………..(sugar or starch) to produce ………………..and …………………

C6H12O6 → 2C2H5OH + 2CO2 Glucose Ethanol

In industry :

Process : ………………………………

Alkene is reacted with …………… at temperature; ……….. oC and pressure; …………atm in presence of

……………………………… as a catalyst.

C2H4 + H2O → C2 H5OHEthene steam ethanol


Colour : ………………………..

mixes with water in all ………………..

………dense than water

boiling point is ………. ....... at 1 atm.

8 Chemical properties of ethanol, C2H5OH

(a) Combustion of ethanol

(i) Ethanol burns in air to produce …………..and…………………...

(ii) Ethanol burns readily with a …………flame and …………….producing soot.

C2H5OH + 3O2 → 2CO2 + 3H2O

(ii) Combustion of ethanol releases …………….amount of heat (ethanol is suitable for use as a fuel)

Balance the following equations :

2C3H7OH + 9O2 → 6CO2 + 8H2O

C4H9OH + O2 → CO2 + H2O

C5H11OH + O2 → CO2 + H2O

C6H13OH + 9O2 → 6CO2 + 7H2O

(b) Oxidation of ethanol

(i) Ethanol is oxidised by an oxidising agent such

as……………………………………………………, KMnO4

or……………………………………………………., ………….7 solution


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produce ………………………………….

Example :

C2H5OH + 2[O] → CH3COOH + H2O

Ethanol Ethanoic acid water

or

H H H

H C C H + 2[O] → H C C + H2O

H OH H

Complete the following equations :

C3H7OH + 2[O] → C2H5 COOH + H2O

or

CH3CH2 CH2OH + 2[O] → ……………………… + H2O

Propanol propanoic acid

or

H H H

H C C C H + 2[O] → + H2O

H H OH

……………………..

(c) Dehydration of ethanol

(i) Dehydration of an alcohol involves the removal of ……………molecule from each of alcohol molecule.

(ii) Water molecule from the alcohol molecule is removed by a


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O

OH

From oxidising agent


dehydration agents such as ……………………/ ………………………/

concentrated ……………..acid / concentrated phosphoric acid.

(iii) There are two ways to carry out the dehydration of ethanol in the laboratory :1 Hot vapour of ethanol is passed over a heated catalyst such as

porcelain chips /aluminium oxide.1 Ethanol is heated under reflux with excess of concentrated

sulphuric acid / concentrated phosphoric acid.

Draw a labelled diagram to show the set-up of apparatus to carry out the dehydration of ethanol.

(iv) Dehydration of ethanol produces ………………and…………………...

Equation for the reaction :

H H H H porcelain

H C C H H C C H + H2O ∆

H OH

or

C2H5OH → C2H4 + H2O Ethanol Ethene


(a) C3H7OH → + H2O

……….. …………


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∆

∆


(b) → + H2O

Butanol …………

9 Uses of alcohol

Uses Example/explanation1 As a fuel

releases a …………of heat energy

2 As a solvent

3 Antiseptic

4

11.6 CARBOXYLIC ACID [ ORGANIC ACID ]

1 CARBOXYLIC ACID Consists of elements :…………., C ; ……………., H ;

and…………………, O.

2 The general formula of the carboxylic acid is :………………………………………


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∆

STARCH

GLUCOSE

……………. ETHENE PETROLEUM

Combustion in excess oxygen

Oxidationby an oxidising agent

Dehydrationby a dehydrating agent

…………………. and

………………….

Fermentation

Hydration

…………………. and

………………….

…………………. and

………………….


3 Functional group is the …………………group :

4 For straight chain carboxylic acid molecules, the name ends with ‘oic’ and acid.


Number of carbon

atoms

Molecular FormulaCnH2n+1COOH

Structural Formula Name

1HCOOH

methanoic acid

2CH3COOH

ethanoic acid

3 CH3COOH Propanoic acid

4 CH3COOH

5 CH3COOH

6 CH3COOH

.

For branched chain carboxylic acid molecules :


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C

O

OH

C

O

OHH

C

O

OH


the name and position of the branched group is written as prefix

the smallest number is given to the carbon atom that is joined to the functional carboxyl group.

Example :

H H H O | | | // H – C – C – C – C | | | \ H H CH3 OH

2-methylbutanoic acid

Name: ……………………… Name: ………………………

5 Preparation of ethanoic acid :

Laboratory preparation through ………………of ethanol by ………………KMnO4 / K2Cr2O7 solution

H H H O | | | // H - C - C - OH + 2[O] → H - C - C + H2O | | | \ H H H OH ethanol ethanoic acid


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Name: ………………………


Draw the set-up of apparatus for the preparation of ethanoic acid by reflux method.(preparation of ethanoic acid in laboratory)

6 Chemical properties of carboxylic acid

(i) Reacts as an acid with…………, …………………………and …………..that are more electropositive than hydrogen.

(a) Carboxylic acid + metal → carboxylate salt + hydrogen gas

(b) Carboxylic acid + base → carboxylate salt + water

(c) Carboxylic acid + metal carbonate → carboxylate salt + water + carbon

dioxide


(a) HCOOH + Mg →

(b) C2H5COOH + KOH → + H2O

(c) CH3COOH + Na2CO3 → CH3COONa + H2O + CO2

(d) C2H3COOH + K2CO3 → + + CO2


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(e) C2H5COOH + NaOH →

(f) C5H11COOH + K →

(ii) Carboxylic acid react with alcohol to produce ……………and………………..

with the presence of concentrated ……………..acid as a catalyst

(…………………reaction).

Carboxylic acid + Alcohol → Ester + Water

(a) C2H5COOH + → C2H3COOC2H5 + H2O

propanoic acid ethanol ethyl propanoate

(b) + C3H7OH → C2H3COOC2H5 + H2O

butanoic acid propanol propyl butanoate

(c) HCOOH + → + H2O

methanoic acid ethanol ethyl methanoate

11.7 ESTERS

1 Esters are non-hydrocarbon organic compounds containing……………,

…………………and oxygen.

2 General formula of ester : …………………………………………….

3 Functional group : ………………………………………….

O ||


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R – C - O : Derived from carboxylic acid, name ending with ‘oate’. R is alkyl group with general formula CnH2n+1, n = 0, 1, 2, 3, ………

-R’ : Derived from alcohol, name ending with ‘yl’.

R’ is alkyl group with general formula CnH2n+1 ; n = 1, 2, 3, ………

4 Formation of esters :

Esters are produced when …………………….reacts with ……………in the presence of concentrated sulphuric acid as a catalyst (Esterification reaction) :

O O || || R - C – O-H + H-O-R’ R - C - O - R’ + H-O-H

carboxylic acid alcohol ester water

Example:

CH3COOH + C3H7OH → CH3 COOC3H7 + H2O

ethanoic acid propanol prophyl ethanoate

5 Naming of esters :

Name for esters are :first : read from the alcohol componentfollowed by : the carboxylic acid component.

Example:

CH3COOH + C2H5OH → CH3 COOC3H7 + H2O

ethanoic acid ethanol ethyl ethanoate

or

ethanoic acid ethanol ethyl ethanoate


(i) H2SO4

HCOOH + C2H5OH → + H2O


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(ii) H2SO4

C3H7OH + C4H9COOH → C4H9COOC3H7 + H2O

Propanol pentanoic acid water

(iii) H2SO4

C3H7COOH + C2H5OH → + H2O

(iv) H H H O H H H H H | | | || | | | | | H – C – C - C - C - OH + HO - C - C - C - C - C - H → | | | | | | | | H H H H H H H H Butanoic acid pentanol

6 Physical properties of esters :

Ester is a neutral compound with a …………….smell .

Esters have…………………; less dense than water.

Simple esters are ………………… at room temperature.

Simple esters are very volatile.

………………..in water.

7 Uses of esters :


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Most simple esters are found naturally in fruits and……………... The fragrance of flowers and fruits is due to the presence of esters.

Example:

Ester Name Naturel source

CH3COOC5H11 Pentyl ethanoate Pineapple

C2H5COOCH3 Methyl propanoate Apple

C3H7COOC5H11 Pentyl butanoate Banana

Used in the preparation of ………………….and perfumes.

As artificial ……………………in processed of food and drinks

Used in the production of ……………………..( synthetic fibers for making textiles)

11.8 FATS

1

Fats


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Fats :

A natural ester found in ………..and ……………tissue

…………….at room temperature

Oils :

A natural ester found in ………………….

……………………at room temperature


2

3

+ → Fats + water

R1, R2 and R3 represent hydrocarbon chains (alkyl groups) that are the same or different.

4 Saturated and unsaturated fat :

Saturated fats molecules are esters of saturated fatty acids. Saturated fatty acids

contain …………..carbon- carbon (-C-C- ) covalent bonds.

Example :


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fatty acid (organic acid with long carbon chain).

Glycerol

The importance of oils and fats :

1 Fats and oil provide ………………………… bodies

2 Build …………cell and certain ………………

3 Dissolve ………………………………………..


Unsaturated fats molecules are esters of unsaturated fatty acids .that contain

………………..and ……………..covalent bonds between ………………their hydrocarbon chain.

Example :

5 Converting unsaturated fats to saturated fats

The double covalent bonds between carbon atoms in ………………fats are easily oxidized. When this happen, the fat has turn…………………...

Unsaturated fats can be converted to saturated fats by ………………………process

for example in the manufacture of………………... Catalyst used is ………..at ……oC :

H H H H | | Ni | | C = C + H2 C - C 180 oC | | H H

Unsaturated fat (liquid) Saturated fat (solid)

6 The effect of fats on health


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Double bondSingle bond

Causes : .


Animals fats (saturated fats) contain higher …….cholesterol whereas vegetable oils (unsaturated fats) contain higher HDL cholesterol.

7 Advantages of palm oil in food production.

(a) …………………………………………………………………………………..

(b) …………………………………………………………………………………..

(c) ……………………………………………………………………………………

2.12 NATURAL RUBBER

1 Natural polymers are polymers that exist in nature and are not man made.

Example :

Natural polymer Monomer

Protein

2 The Structure of Rubber

Rubber is formed from the monomer……………………. Molecular formula of ……………………….is C5H8

Isopropane molecules are joined together by addition …………………process to

form the polymer of natural rubber, ………………………..:


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Cholesterol

…….cholesterol

………cholesterolCauses :

…………..deposit on the artery walls


Isopropane (2-methylbut-1,3-diene) Poly isopropane

3 Coagulation of latex

Latex is milk like liquid obtained from tapped rubber tree. Latex is a ……………which contains suspension of rubber particles in water.

The rubber particles are made up of ………………………rubber polymers [(C5H8)n]

surrounded by a………………….. The protein membrane is ………………..charged.

The forces of repulsion between negatively charged particles prevent them from combining or coagulate.

4 Latex coagulates when : …………………………………………………………………………..

Left aside for 1 - 2 days due to bacterial action on latex. Bacteria

produces …………….that contains ……………………..( H + ) which causes coagulation of latex. Coagulate latex is semi solid

The repulsion between the negatively charged particles prevents

…………………………………………………………………………………………………Latex could not coagulation


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When an acid is added, the …………………ion ………………..the negative charges on the protein membrane.

The rubber particles can now come …………………together………………………with

one another ………………………..of the protein membranes

The rubber molecules ……………………….with one another and entangle Causing the latex to ………………………

5 Presence of an alkali can prevent the coagulation process of latex :

Hydroxide ions, OH- from …………neutralised the hydrogen ions, H+

produced by ………………..as a result of bacterial attack on protein.

The protein membrane remain ……………..charge because there are no

more ………………………ions.

The rubber particles ………………….each other

The rubber polymers cannot ………………………….and ……………………….

.


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6 Properties and Uses of Natural Rubber


Property Description Uses

ElasticWhen it is stretched, it straighten out.It return back to its ……………….shape once the stretching force is released.

.

Resistance to oxidation

The natural rubber polymers are easily ……………..due to presence of double bonds.

Effect of heat

When it is heated, it is soften and become……………..When it is cooled, it becomes ………and………………….

Effect of solvent

Natural rubber is soluble in organic, ……………and …………….solution.

The properties of natural rubber can be improved through the ………………process.

7 Vulcanisation of rubber :

Natural rubber is………………...(return to its original shape after stretching force released).

When the rubber is over stretched, the rubber molecules do not return to its original position. The rubber has lost…………………….

Natural rubber becomes more ……………………and elastic after vulcanisation.

In vulcanised rubber :


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Rubber stripe is soaked in …………………………

solution in methylbenzene for a few hours and then dried.

Natural rubber Vulcanised rubber


The sulphur atoms form ………………………..between the long rubber molecule.

This reduces the ability of the polymers to ……………….over each other.

The rubber molecules ……………………to its original positions after being stretched.

Properties Natural rubber Vulcanised rubber

Elasticity Less elastic

Hardness Harder

Tensile strength

END OF CHAPTER 11


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C11 TAHAP 3 RUSLI

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