study smart chapter 2 f5
Post on 05-Apr-2018
223 Views
Preview:
TRANSCRIPT
-
8/2/2019 Study Smart Chapter 2 f5
1/21
1
Study Smart
www.studysmart.page.tl
STUDYSMART
CHEMISTRY FORM 5
CHAPTER 2 : CARBON COMPOUND
2.1 Understanding carbon compounds
2.2 Analysing Alkanes
2.3 Analysing Alkenes
2.4 Synthesising ideas on isomerism
2.5 Analysing Alcohols
2.6 Analysing carboxylic acids
2.7 Analysing esters
2.8 Evaluating fats
2.9 Analysing natural Rubber
2.10 Creating awareness of order in homologous series
2.11 Expressing gratefulness for the variety of organic materials in nature
2.1 UNDERSTANDING CARBON COMPOUNDS
Carbon compound are compound that containing carbonCarbon compound can be classified into inorganic and organic carbon compound.
Examples of inorganic carbon compound (usually non-living things)
- Carbon Monoxide, CO
- Carbon Dioxide, CO2
- Calcium Carbide, CaC2
- Carbonate salts for example Na2CO3, CaCO3, CuCO3
Examples of organic carbon compound (usually living things)
- Urea - Natural rubber
- Glucose - Protein
- Cellulose - Ethanol- Starch - Glucose
Hydrocarbon are organic compound containing hydrogen and carbon only
Organic compound in which some or all of the hydrocarbon atoms have been replaced
other atoms are called non-hydrocarbons.
Hydrocarbon molecules that are made entirely of carbon-carbon single bonds are said
to be saturated hydrocarbon. Hydrocarbon containing at least one carbon-carbon
double or triple bonds is referred as unsaturated hydrocarbon.
Combustion product of organic compounds
- When an organic compound is burnt in excess oxygen, the main product are CO2, and ,
H2O.Example : Combustion of glucose, C6H12O6
C6H12O6 + 6O2 6CO2 + 6H2O
-
8/2/2019 Study Smart Chapter 2 f5
2/21
2
Study Smart
www.studysmart.page.tl
2.2 ANALYSING ALKANES
Usually in fuels, examples: natural gas, petrol, diesel
Are homologous series
Have a formula of CnH2n+2, where n is a positive integers.
Example : propane has three carbon atom, thus n=3. Then the formula of propane is C3H8
Ends with suffixaneNext alkane formula differ byCH2 atoms. Eg: methane: CH4, ethane: C2H6
Structure of Alkanes
Shows how all atoms in a molecule joined together by drawing lines between atoms to
represent the bonds
Example: butane has a formula of C4H10, therefore the structural formula is:
It has 4 carbon atoms bonded together with 10 hydrogen atoms.
All alkanes are saturated. All alkenes are unsaturated
Name of carbon atoms are shown in table below
Complete the table on left and below
n Name Molecular
Formula
Structural Formula
1 Methane CH4
2 Ethane
Name of carbon atom Root name
1 Meth-
2 Eth-
3 Prop-
4 But-
5 Pent-
6 Hex-
7 Hept-
8 Oct-
9 Non-
10 Dec-
-
8/2/2019 Study Smart Chapter 2 f5
3/21
3
Study Smart
www.studysmart.page.tl
3 Propane
4 Butane
5 Pentane
6 Hexane
7 Heptane
8 Octane
-
8/2/2019 Study Smart Chapter 2 f5
4/21
4
Study Smart
www.studysmart.page.tl
9 Nonane
10 Decane
Physical properties of alkanes are :-
- Melting points and boiling points increase as the bonds become larger and heavier which
increases the forces of attraction between molecules so more energy (from heat) is needed to
separate them with the increase of strength of forces of attraction
- Alkanes are insoluble in water but soluble in organic solvents such as tetrachloromethane as a
alkanes are organic compounds
- Alkane density increases down the series; all alkenes are less than 1g/cm3
- Alkanes become more viscous (uneasily flow) going down the series as the longer molecules
tangles together when it flows
- Alkanes become less flammable down the series as B.P. becomes larger
- Alkanes are unreactive with either metals, water, acids or bases because the C C and C H
covalent bonds are harder to break
Alkane Formula Boiling point [C] Melting point [C] Density [gcm3] (at 20C)
Methane CH4 -162 -183 gas
Ethane C2H6 -89 -172 gas
Propane C3H8 -42 -188 gas
Butane C4H10 0 -138 gas
Pentane C5H12 36 -130 0.626(liquid)
Hexane C6H14 69 -95 0.659(liquid)
Heptane C7H16 98 -91 0.684(liquid)
Octane C8H18 126 -57 0.703(liquid)
Nonane C9H20 151 -54 0.718(liquid)Decane C10H22 174 -30 0.730(liquid)
http://en.wikipedia.org/wiki/Methanehttp://en.wikipedia.org/wiki/Ethanehttp://en.wikipedia.org/wiki/Propanehttp://en.wikipedia.org/wiki/Butanehttp://en.wikipedia.org/wiki/Pentanehttp://en.wikipedia.org/wiki/Hexanehttp://en.wikipedia.org/wiki/Heptanehttp://en.wikipedia.org/wiki/Octanehttp://en.wikipedia.org/wiki/Nonanehttp://en.wikipedia.org/wiki/Decanehttp://en.wikipedia.org/wiki/Decanehttp://en.wikipedia.org/wiki/Nonanehttp://en.wikipedia.org/wiki/Octanehttp://en.wikipedia.org/wiki/Heptanehttp://en.wikipedia.org/wiki/Hexanehttp://en.wikipedia.org/wiki/Pentanehttp://en.wikipedia.org/wiki/Butanehttp://en.wikipedia.org/wiki/Propanehttp://en.wikipedia.org/wiki/Ethanehttp://en.wikipedia.org/wiki/Methane -
8/2/2019 Study Smart Chapter 2 f5
5/21
5
Study Smart
www.studysmart.page.tl
Chemical properties of alkanes
Alkanes are unreactive compound
Chemical properties of alkanes
COMBUSTION
Alkanes burn in air to ALWAYS form carbon dioxide and water.
2C4H10(g) + 13O2(g)
8CO2(g) + 10 H2O (l)
When there is insufficient oxygen, the product is ALWAYS carbon monoxide and unburnt
carbon.
2CH4 (g) + 3O2 (g) 2CO(g) + 4H2O
CH4 (g) + O2 (g) C(g) + 4H2O
Example: Butane is commonly used camping gas.
High alkanes burn less completely and gives soot (unburnt carbon) and CO
HALOGINATION / SUBSTITUTION REACTION
Reaction of alkanes with halogens (Cl2, Br2, and I2)
Light is needed to break covalent bond between halogens molecule atoms
Substitution reaction the reaction in which one or more atoms replace other atoms in a
moleculeExample : Mixture of methane, CH4 and chlorine is exposed to UV light
CH4 + Cl2 CH3Cl + HCl
monochloromethane
CH3Cl + Cl2 CH2Cl2 + HCl
dichloromethane
CH2Cl2 + Cl2 CHCl3 + HCl
trichloromethane
CHCl3 + Cl2 CCl4 + HCl
tetrachloromethane
2.3 ANALYSING ALKENES
Have general formula CnH2n.
All alkene names end withene.
The formula of one alkene differs from the next byCH2.
Have similar properties like alkane going down the series.
Example : butene has a formula of C4H8, therefore the structural formula is:
It has 4 carbon atoms with a double bond bonded together with 8 hydrogen atoms.
All alkenes are unsaturatedThe Importance of Ethene
- Ethanol solvent & fuel
- poly(ethene) PE plastic variations
- Ethanoic acid vinegar
Complete the table below
-
8/2/2019 Study Smart Chapter 2 f5
6/21
6
Study Smart
www.studysmart.page.tl
n Name Molecular
Formula
Structural Formula
1 Methane
METHENE IS NOT IN ALKENES GROUP SINCE ITS CONTAIN SINGLE
CARBON ATOM THUS, NO DOUBLE BOND.
2 Ethane
C2H4
3 Propane
4 Butane
5 Pentane
6 Hexane
-
8/2/2019 Study Smart Chapter 2 f5
7/21
7
Study Smart
www.studysmart.page.tl
7 Heptane
8 Octane
9 Nonane
10 Decane
Physical properties of alkenes are
- cannot conduct electricity
- Less dense than water
- Obeys like dissolve like rule where it dissolve in organic solvent but insoluble in water
- Alkenes have low melting and boiling points
Chemical Reaction of Alkenes
Alkenes are chemically more reactive than alkanes due to the presence of the C = C doublebond.
COMBUSTION
Burns in air to form carbon dioxide and water
Example: Ethene burns in air.
C2H4(g ) + 3O2(g) 2CO2(g) + 2H2O (l)
Incomplete combustion forms soot and CO. Its produced more than alkane
-
8/2/2019 Study Smart Chapter 2 f5
8/21
8
Study Smart
www.studysmart.page.tl
To differentiate the percentage of carbon in alkene and alkane
C2H4(g ) + 3O2(g) 2CO2(g) + 2H2O (l)
Alkenes burn with sootier flame as compared to alkanes. This is because alkenes have a higher
percentage of carbon in their molecules.
For ethane, C2H4
% of carbon = 2 x 12 . x 100%
2(12) + 4(1)
= 24 x 100%
28
= 85.71 %
For ethane, C2H6
% of carbon = 2 x 12 . x 100%
2(12) + 6(1)
= 24 x 100%
30
= 80 %
ADDITION REACTION
I) Addition of hydrogen, H2 / Hydrogenation [ethane ethane]
C2H4 + H2 -----------> C2H6Ethene ------------------------------------> Ethane
II) Addition of halogens (Bromine, Br2)
Ethene + Br2 -----------> 1,2-dibromoethane
III) Addition of hydrogen halides
Ethene + HCl -----------> Chloroethane
-
8/2/2019 Study Smart Chapter 2 f5
9/21
9
Study Smart
www.studysmart.page.tl
IV) Addition of water, H2O / Hydration [ alkene alcohol ]
V) Addition of hydroxyl groups, -OH
- Acidified potassium manganite (VII), KMnO4
Ethene + H2O + [O] -----------> Ethane-1,2-diol
POLYMERIZATION
The joining of several identical alkene molecules to form a big molecule.
-
8/2/2019 Study Smart Chapter 2 f5
10/21
10
Study Smart
www.studysmart.page.tl
2.4 SYNTHESISING IDEAS ON ISOMERISM
Isomers are compound with the same molecular formula but different structural formula
Examples :
1. Isomers of pentane
2. Isomers of butane
Naming of each isomer is based on IUPAC. There are several steps before naming an isomers
STEP 1 : Specify the number of carbon atom in the largest continuous carbon chain
STEP 2 : Numbering carbon atoms with 1,2,3,. Starting near functional group / and branch.
STEP 3 : Branch names, -CH3, methyl
-CH2CH3, ethyl
Examples :
Isomer of Pentene
Isomer of Hexane
Isomer of Butane
Isomer of Butene
-
8/2/2019 Study Smart Chapter 2 f5
11/21
11
Study Smart
www.studysmart.page.tl
2.5 ANALYSING ALCOHOLS
The general formula of alcohol is CnH2n+1OH (n = 1,2,3)
Alcohol contain the hydroxyl group (-OH) as the functional group that covalently bonded to a
carbon atom
Naming of alcohol
- Root denotes the number of carbon atom (meth-, eth-, prop-)- Ending replacee from the name of the alkane withol
NUMBER OF
CARBON
ATOM
MOLECULAR
FORMULA
STRUCTURAL FORMULA NAME
1 CH2OH Methanol
2
3
4
5
6
-
8/2/2019 Study Smart Chapter 2 f5
12/21
12
Study Smart
www.studysmart.page.tl
Naming alcohol based on IUPAC
STEP 1 : Identify the longest carbon chain containing the hydroxyl group
Root obtain from the number of carbon atom in the longest carbon chain
STEP 2 : Identify the position pf hydroxyl group by numbering the carbon atom in the longest
chain
Beginning at the end nearer to the hydroxyl group
STEP 3 : identify and name that attracted alkyl group (branch)prefix
STEP 4 : Complete the name by combining the three component
Examples :
1. 2
Name : _____________________ Name : _____________________
3. 4.
Name : __________________________________ Name : ____________________________
Isomerism in alcohol exists in the alcohol with three or more carbon atoms
Examples :
1. Propanol (C3H7OH)
2. Butanol
-
8/2/2019 Study Smart Chapter 2 f5
13/21
13
Study Smart
www.studysmart.page.tl
Preparation of Ethanol
Industrial production of ethanol
i) from sugar and starch by fermentation
ii) from petroleum fractions by hydration
H3PO4
CH2 = CH2 + H2O CH3CH2OH
300oC / 60 atm
Laboratory preparation of ethanol
In the fermentation process, the zymase enzyme decompose the glucose to form ethanol and
carbon dioxide
Equation of the fermentation process :
zymase
C6H12O6 2C2H5OH + 2CO2
30oC -4
oC
Reacting ethane with steam to produce alcohol (fractional distillation)
Ethene and steam are passed over phosphoric acid H3PO4(as a catalyst) under high temperature
of 300oC and pressure of 65 atm.
C2H4(g) + H2O(g) C2H5OH(aq)
Since this is reversible reaction, both ethene and water are produced aside from ethanol.The ethanol is separated by fractional distillation.
Physical properties of alcohol :
A simple alcohol are liquids and very soluble in water
As the number of carbon atoms in their molecules increases, the molecules get bigger, the
forces of attraction between molecules becomes stronger, more energy needed to overcome
the forces of attraction. Thus, melting and boiling points increase gradually.
Physical properties of ethanol are :-
- colourless liquid - sharp smell
- complete miscible with water - boiling point : 78oC at 1atm
Chemical properties of ethanol
COMBUSTION
* Complete combustion of alcohol produces carbon dioxide and water
C2H5OH + 3O2 2CO2 + 3H2O
* Ethanol burns with a non-smoky blue flame
-
8/2/2019 Study Smart Chapter 2 f5
14/21
14
Study Smart
www.studysmart.page.tl
* Release lots of heat, use as a fuel
C4H9OH + 6O2 4CO2 + 3H2O
OXIDATION
* Alcohol can be easily oxidized to carboxylic acid by using oxidizing agent
* Oxidising agent : acidified potassium manganat(VII) colour turns from purple to green
acidified potassium dichromate(VI) colour turns from orange to green
* Ethanol undergo oxidation reaction to form ethanoic acid
[ -CH2OH group has removed 2 hydrogen atoms and gained an oxygen atom]
C2H5OH + 2[O] CH3COOH + 3H2O
Ethanol carboxylic acid
Draw the structural formula :
DEHYDRATION
* Involves the removal of water by using catalyst such as heated porcelain chips, porous pot,
aluminium oxide, concentrated sulphuric acid
* The dehydration of ethanol produces ethane and water
heated
C2H5OH C2H4 + H2O
Porcelain chips
-
8/2/2019 Study Smart Chapter 2 f5
15/21
15
Study Smart
www.studysmart.page.tl
Uses of alcohol
As a fuel Volatile, highly flammable and high content
As a solvent and thinner colourless, volatile, miscible with water and good organic solvent
As a raw material to make pharmaceutical products volatile, good solvent, and antiseptic
2.6 ANALYSING CARBOXYLIC ACIDSCommon carboxylic acid in nature are acetic acid in vinegar, lactic acid in sour milk, citric acid in
citrus fruits.
Contain the element carbon, hydrogen and oxygen.
When comparing to alcohols, carboxylic acids contain 2 oxygen atoms
Functional group for carboxylic acid is carboxyl group, -COOH or
General formula of carboxylic acid is CnH2n+1COOH, where n = 0,1,2,3,.
Straight chain carboxylic acids are named with endingoic acid
n Number of C atom (s) Molecular Formula Structural Formula Name
0 1
HCOOH Methanoic Acid
1 2
2 3
3 4
4 5
-
8/2/2019 Study Smart Chapter 2 f5
16/21
16
Study Smart
www.studysmart.page.tl
5 6
6 7
Naming the branches carboxylic acid
- Identify the longest carbon chain containing the carboxyl group
- Number the carbon atom beginning at the carboxyl groupExamples
___________________ ___________________ ___________________
Making ethanoic acid
Laboratory preparation by the oxidation of ethanol by using oxidizing agent (Acidified KMnO4
or K2Cr2O7 solution)
Physical properties of ethanoic acid
- a colourless liquid at room temperature
- a sour smell
- very soluble in water
Chemical Properties of Carboxylic acids
Ethanoic acid is a weak monoprotic acid. Hydrogen atoms from carboxyl group, -COOH can be
ionize in water to form hydrogen ions
Reaction with reactive metals, bases and carbonates (Act as acid)
CH3COOH + Mg
CH3COOH + NaOH
CH3COOH + Na2CO3
-
8/2/2019 Study Smart Chapter 2 f5
17/21
17
Study Smart
www.studysmart.page.tl
Reaction with alcohols to form ester and water (Esterification)
A mixture of carboxylic acid and alcohol with a few drops of concentrated sulphuric acid is
heated, an ester is formed.
Example
2.7 ANALYSING ESTERS
General formula of ester is CnH2n+1COOCmH2m+1
Functional group in ester is called carboxylate group, -COO or
Naming ester
Formation of ester
i)
___________________
ii)
_______________ _________________ _____________________
Physical properties of ester
- has sweet pleasant smell (fruity smell)
- a colourless liquid
- low melting and boiling points
- slightly soluble in water but readily dissolve in organic solvent
Carboxylic acid + Alcohol Ester + Water
H2SO4
Ending -yl Ending -oate
-
8/2/2019 Study Smart Chapter 2 f5
18/21
18
Study Smart
www.studysmart.page.tl
GENERAL CONCLUSION FOR ALKANE, ALKENE, ALCOHOL, CARBOXYLIC ACID AND ESTER
2.8 EVALUATING FATSFats are found in animals which is solid at room temperature. Example : butter, tallow
Oils are found in plants which is liquid at room temperature. Example : palm oil, sunflower oil
Fats and oils are ester formed from glycerol (alcohol with 3 hydroxyl group) and fatty acids
(long-chain carboxylic acids)
Chemical equation :
Saturated and Unsaturated fats
Saturated fats
- saturated alkyl group ( contains single covalent bond only)
- Glycerol and saturated fatty acids, only contain carbon carbon single bond
- Animal fats contain large proportion of saturated esters, have high melting points and solid in
room temperature
- Example : Tristearin, tripalmitin
Unsaturated fats
- unsaturated alkyl group ( contains one or more carbon carbon
double bonds.
- Glycerol and unsaturated fatty acids contain one or more carbon carbon double bonds.
- Plant / vegetable oils contain a large proportion of unsaturated ester, have lower melting
Fermentation
Esterification
Oxidation
dehydration
HydrationHydrogenation
Alkane
CnH2n+2
Alkene
CnH2n
Alcohol
CnH2n+1OH
Glucose
C6H12O6
Carboxylic Acid
CnH2n+1COOH
Ester
CnH2n+1COOCmH2m+1
R1 , R2 , and R3 :
same or different
alkyl group
-
8/2/2019 Study Smart Chapter 2 f5
19/21
19
Study Smart
www.studysmart.page.tl
points, and liquids at room temperature.
- Example : Triolein
Converting unsaturated fats to saturated fats
- by hydrogenation process
- Margarine is made by hydrogenating some of the carbon carbon double bonds in
polyunsaturated vegetable oil so that the physical state changes from liquid to soft.
Industrial extraction of palm oil
[Refer Textbook]
-
8/2/2019 Study Smart Chapter 2 f5
20/21
20
Study Smart
www.studysmart.page.tl
2.9 ANALYSING NATURAL RUBBER
A polymer is a large molecules consisting of a long chain. It is made by joining together many
small molecules called monomers
Natural polymers exist naturally. Below are the examples of natural polymers and their
monomers.
Natural rubber is actually poly(isoprene)
Its monomer is 2-methyl-1,3-diene or isoprene with molecular formula C5H8
The isoprene molecules undergo addition polymerization to produce a long chain molecules
called poly(isoprene)
Latex is a white milk-like fluid
Rubber particles is made up of many long-chain rubber molecules enclosed by a protein-like
membrane which is negatively charged
The repulsion between the negatively-charged particles prevents the rubber particles from
coming close to each other. Hence, latex could not coagulate
Latex will coagulate when
- An acid is added. (Methanoic acid or ethanoic acid)
- Exposed to air
Coagulation process of latexa) When an acid is added, the hydrogen ions neutralize the negative charges on the protein
membrane.
b) The rubber particles can now come closer together and collide with one another resulting in
the breakage of the protein membrane
c) The rubber molecules combine with one another and entangle thus causing the latex to
coagulate.
Latex will coagulate when it is exposed to air because the growth and spread of bacteria
produce lactic acid.
Natural Polymer MonomerNatural Rubber Isoprene
Starch Glucose
Cellulose Glucose
Protein Amino Acid
-
8/2/2019 Study Smart Chapter 2 f5
21/21
21
Study Smart
Latex can be preserved in the liquid by adding ammonia solution. Ammonia solution contain
hydroxide ions that neutralize the acid produced by bacteria
Vulcanization of rubber
Properties of natural rubber :
- Soft
- Elasticity decrease over time
- Sensitive to heat
- Easily oxidized by air
The properties can be improved through vulcanization process.
Vulcanization process can occur when
a) latex is heated with sulphur (industry)
b) rubber products are exposed to disulphur dichloride, S2Cl2 gas (industry)
c) by soaking natural rubber in the solution of disulphur dichloride in methylbenzene.
(Laboratory preparation)
The presence of cross-linkage of sulphur atoms between the rubber molecules improves the
properties of rubber.
Uses of natural rubber
a) making tyres, footwear, rubber threads, rubberized bitumen roads
b) Gloves, tubes and hoses
c) insulator of electrical appliance and cables
Vulcanized rubber Difference Unvulcanized rubber
More elastic Elasticity Less elastic
Harder Hardness Softer
Stronger Tensile strength Weaker
Can withstand highertemperature
Resistance on heat Cannot withstand highertemperature
Hard to be oxidized Resistance to oxidation Easily oxidized
Does not become soft
and sticky easily
Effect of organic solvent Becomes soft and sticky
easily
Limit its uses
top related