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Alkanes1. General Formula : CnH2n+2 (number of atoms, n = 1,2,3......)2. They are saturated hydrocarbons; each carbon atom is bonded to four other atoms by single covalent bonds. 3. The members of the family, ending with name “ane”.
Number of carbon atoms
(n)Name Molecular formula
CnH2n+2
Molar mass
(g mol-1)
Physical state at room
temperature
1 Methane C1H2x1+2 = CH4 16 Gas
2 Ethane C2H2x2+2 = C2H6 30 Gas
3 Propane C3H2x3+2 = C3H8 44 Gas
4 Butane C4H2x4+2 = C4H10 58 Gas
5 Pentane C5H2x5+2 = C5H12 72 Liquid
6 Hexane C6H2x6+2 = C6H14 86 Liquid
7 Heptane C7H2x7+2 = C7H16 100 Liquid
8 Octane C8H2x8+2 = C8H18 114 Liquid
9 Nonane C9H2x9+2 = C9H20 128 Liquid
10 Decane C10H2x10+2 = C10H22 142 Liquid
Consecutive members different in molar mass is 14 g mol-1
4. Structural formulae of alkanes
Name No. of isomers Structural formulae and Name
Methane
CH4
0
Ethane, C2H6
0
Propane, C3H8
0
Butane,C4H10
2
H │ H ─ C ─ H │ H
H H │ │ H ─ C ─ C ─ H │ │ H H
H H H │ │ │H ─ C ─ C ─ C ─ H │ │ │ H H H
H H H H │ │ │ │H ─ C ─ C ─ C ─ C ─ H │ │ │ │ H H H H
n-butane
Pentane,C5H12
3
2 - methyl propane
H H H │ │ │H ─ C ─── C ─── C ─ H │ │ │ H H─C─H H │ H
H H H H H │ │ │ │ │H ─ C ─ C ─ C ─ C ─ C ─ H │ │ │ │ │ H H H H H
n-pentane
H H H H │ │ │ │H ─ C ─── C ─── C ─ C ─ H │ │ │ │ H H─C─H H H │ H
2-methyl butane
1 2 3 4
Hexane, C6H14
5
H │ H H ─ C ─ H H │ │ │H ─ C ─── C ─── C ─ H │ │ │ H H─C─H H │ H
2,2-dimetyl propane
H H H H H H │ │ │ │ │ │H ─ C ─ C ─ C ─ C ─ C ─ C ─ H │ │ │ │ │ │ H H H H H H
n-hexane H H H H H │ │ │ │ │H ─ C ─── C ─── C ─ C ─ C ─ H │ │ │ │ │ H H─C─H H H H │ H
2 - methyl pentane
H │ H H ─ C ─ H H H │ │ │ │ H ─ C ─── C ─── C ─ C ─ H │ │ │ │ H H─C─H H H │ H
2,2 - dimethyl butane
2,3 - dimethyl butane
H H H H H │ │ │ │ │H ─ C ─ C ─── C ─── C ─ C ─ H │ │ │ │ │ H H H─C─H H H │ H
3 - methyl pentane
H │ H H H ─C─H H │ │ │ │ H ─ C ─── C ─── C ─── C ─ H │ │ │ │ H H─C─H H H │ H
Physical PropertiesPhysical properties of alkanes
i. cannot conduct electrityii. less dense than wateriii. dissolve in organic solvents, insoluble in wateriv. low melting and boiling points
Conclusion: - molecule held together by weak intermolecular forces- properties of covalent compound
- gradually steady increase as the number of carbon in alkane increases
6. Steps to name branched alkanes;i. determined and named the long chains ii. determined and named the branch chain
CH3 : methylC2H5 OR CH2CH3 : ethylC3H7 OR CH2CH2CH3 : prophyl
iii. give number to the carbon atoms in long chain, which started from the nearest branchediv. The number for carbon atom which branched emerged from, must put before/infront the alkylv. Named the branched first, followed by the named of long chains
The word “ di, tri” is used if the branched chains is more than one
Chemical PropertiesPg 38
Reactivity of alkanes1. Not reactive/unreactive because saturated hydrocarbon2. Did not decolourized purple solution of acidified potassium manganate(VII)3. Did not decolourized reddish brown solution of bromin water 4. Neutral.
Combustion of alkanes1. In the presence of sufficient oxygen, alkanes burns to form carbon dioxide and water. – complete combustion
Chemical equation:
i. CH4 + O2 CO2 + H2O CH4 + 2O2 CO2 + 2H2O
ii. C2H6 + 7/2 O2 2CO2 + 3H2O
iii. C4H10 + 13/2 O2 4CO2 + 5H2O
iv. C6H14 + 19/2 O2 6CO2 + 7H2O
Answers i. CH4 + 2O2 → CO2 + 2H2O
ii. C2H6 + 7 O2 2CO2 + 3H2O 2
2 x C2H6 + 2 x 7 O2 2x 2CO2 + 2x 3H2O 2
2C2H6 + 7 O2 4CO2 + 6H2O
iii. C4H10 + 13/2 O2 4CO2 + 5H2O
iv. C6H14 + 19/2 O2 6CO2 + 7H2O
C3H8
C5H12
C7H16
C8H18
C9H20
C10H22
2. If there is insufficient oxygen, carbon monoxide or carbon may be formed – incomplete combustion
i. CH4 + 3/2 O2 CO + 2H2O 2CH4 + 3 O2 2CO + 4H2O
ii. CH4 + O2 C + 2H2O
Halogenation1. The reaction is between alkane dan chlorine. 2. Takes place under sunlight/ultra violet light. 3. Carbon-hydrogen bonds broken and new carbon-halogen bonds
are formed. One or more hydrogen atoms in alkanes molecule may be subtituted by halogen. 4. Halogenation is substitution reaction.
Chlorination of methaneFirst stage;
Second stage;
Third stage ;
Fourth stage;
Overall equation/chemical equation CH4 + 4Cl2 CCl4 + 4HCl
H H │ | H ─ C ─ H +Cl-Cl → H — C — Cl + HCl │ | H H monochloromethane H Cl │ | H ─ C ─ Cl + Cl2 → H — C — Cl + HCl │ | H H dichloromethane Cl Cl │ | H ─ C ─ Cl + Cl2 → H — C — Cl + HCl │ | H Cl trichloromethane Cl Cl │ | H ─ C ─ Cl + Cl2 → Cl — C — Cl + HCl │ | Cl Cl tetrachloromethane
HW: PG41 EP B no. 1-3
Prepared;Kamal Ariffin Bin SaaimSMKDBL
Alkenes1. General formulae : CnH2n
[ no alkene corresponding to n = 1 as CH2 is not exist]
2. Alkenes is unsaturated hydrocarbon because the presence of the double bond.3. Name of each members end with “ene”.
No. of carbon atom Name Molecular formulae Molar mass /
g mol-1Physical state at room
condition
1 None
2 Ethene C2H4 28 Gas
3 Propene C3H6 42 Gas
4 Butene C4H8 56 Gas
5 Pentene C5H10 70 Liquid
6 Liquid
7 Liquid
8 Liquid
ethenes
Alkenes containing at least one carbon-carbon double bond
9 Liquid
10 Liquid
WHEN THE NUMBER OF CARBON IN HYDROCARBON INCREASES/GREATER/HIGHER, THE SIZE OF HC MOLECULE IS BIGGER.
THUS, THE INTERMOLECULAR FORCES/Van der Waals FORCES IS STRONGER.
THUS, MORE ENERGY IS NEEDED TO OVERCOME THE FORCES.
4. Structure formula for few members of alkenesName Number of isomer Structure formula and name
EtheneC2H4
0
Propene C3H6
0
H H │ │ C ═ C │ │ H H
H H │ │ C ═ C ─ C ─ H │ │ │ H H H
Butene,C4H8
3
H H H │ │ │ C ═ C ─ C ─ C ─ H │ │ │ │ H H H H
but -1- ene
H H │ │H ─ C ─ C ═ C ─ C ─ H │ │ │ │ H H H H
H H │ │ C ═══ C ─── C ─ H │ │ │ H H─C─H H │ H
but -2- ene
2-methyl propene
Pentene,C5H10
5
H H H │ │ │ C ═══ C ─── C ─ C ─ H │ │ │ │ H H─C─H H H │ H
2-methylbut -1- ene
H H H │ │ │H ─ C ─ C ─ C ═ C ─ C ─ H │ │ │ │ │ H H H H H
H H H H │ │ │ │ C ═ C ─ C ─ C ─ C ─ H │ │ │ │ │ H H H H H
pent -1- ene
pent -2- ene
H H H H │ │ │ │ C ═ C ─── C ─── C ─ H │ │ │ H H─C─H H │ H
3-methyl but -1- ene
Hexene, C6H12
12
H H H │ │ │H─ C ─── C ═══ C ─C ─ H │ │ │ H H─C─H H │ H
2-methyl but -2- ene
H H H H H │ │ │ │ │ C ═ C ─ C ─ C ─ C ─ C ─ H │ │ │ │ │ │ H H H H H H
H H H H │ │ │ │H ─ C ─ C ═ C ─ C ─ C ─ C ─ H │ │ │ │ │ │ H H H H H H
H H H H │ │ │ │H ─ C ─ C ─ C ═ C ─ C ─ C ─ H │ │ │ │ │ │ H H H H H H
H H H H │ │ │ │ C ═══ C ─── C ─ C ─ C ─ H │ │ │ │ │ H H─C─H H H H │ H
H H H H │ │ │ │ C ═ C ─── C ─── C ─ C ─ H │ │ │ │ │ H H H─C─H H H │ H
H H H H │ │ │ │ C ═ C ─ C ─── C ─── C ─ H │ │ │ │ │ H H H H─C─H H │ H
H H H H │ │ │ │H ─ C ─── C ═══ C ─ C ─ C ─ H │ │ │ │ H H─C─H H H │ H
H H H │ │ │ H ─ C ─ C ═══ C ─── C ─ C ─ H │ │ │ │ │ H H H─C─H H H │ H
H H H │ │ │ H─C ─ C ═ C ─── C ─── C ─ H │ │ │ │ │ H H H H─C─H H │ H
H H H H H │ │ │ │ │ C ═══ C ─── C ─ C ─ C ─ H │ │ │ │ │ H H─C─H H H H │ H
H │ H H─C─H H │ │ │ C ═══ C ─── C ─── C ─ H │ │ │ │ H H─C─H H H │ H
H │ H H─C─H H │ │ │ H─ C ─── C ═══ C ─── C ─ H │ │ │ H H─C─H H │ H
H │ H H─C─H H │ │ │ C ═══ C ─── C ─── C ─ H │ │ │ │ H H H─C─H H │ H
Can you named the molecules?
Steps to name branched alkenes ; i. determined and named the long chains that has double covalent bondii. numbered the carbon atom from the nearest end to double covalent bondiii. determined and named the branch chain
CH3 : methylC2H5 or CH2CH3 : ethylC3H7 or CH2CH2CH3 : prophyl
vi. give number to branched chain vii. The number for carbon atom which branched emerged from, must put before/infront the alkylviii. The word “ di, tri” is used if the branched chains is more than one
Physical PropertiesPhysical properties of alkenes (similar to alkanes)
i. cannot conduct electrityii. less dense than wateriii. obeys “ like dissolve like”;
• dissolve in organic solvents• insoluble in water
v. low melting and boiling points, gradually steady increase as the number of carbon in alkene increases
Chemical Properties
Reactivity of alkenes1. Alkenes is more reactive because the presence of double covalent bond, (unsaturated hydrocarbon) 2. Alkenes decolourized purple solution of acidified potassium manganate(VII)3. Alkenes decolourized reddish brown solution of bromin water 4. Neutral.
Combustion of alkenes.
Addition Reaction (5.2)
The carbon-carbon double bond is converted into
two single bonds
H H H H
C = C + X Y → X C − C Y H H H H
Alkenes Molecule Alkanes (Unsaturated) (Saturated)
1. Addition of hydrogen
Mixture of alkenes gas/vapour and hydrogen gas, is passed through platinum or nickel at 180 oC. The process is known as catalytic Hydrogenation.
Catalyst: platinum or nickel
H H H H Ni/Pt C = C + H2 → H C − C H 180oC H H H H
Ethene Hydrogen Ethane
Chemical equation: C2H4 + H2 C2H6
Example use of this process: Manufacture of margarine is through hydrogenation
2. Addition of halogens
The process is known as halogenation
H H H H C = C + Br Br → Br C − C Br
H H H H Ethenes Bromine 1,2-dibromoethanes
(unsaturated) (saturated)
Chemical equation: C2H4 + Br2 C2H4Br2
[HW-notes book]Q1: Write a chemical equation reaction between but-1-ene with bromine water. Show the structural formula as well.
[HW-exercises book]Q2: Halogenation process is best used to differentiate between alkanes and alkenes. Explain how it can be done?
[notes: refer to SAB]
3. Addition of hydrogen halides
i. Alkenes reacts with hydrogen halide in room condition. Hydrogen halide molecules is added to double bond in alkenes, to produce halogenoalkane.
ii. When
hydrogen chloride gas is passed through into ethenes, monochloroethanes is produced.
H H H H C = C + H Cl ─ → H C − C Cl H H H H
Ethenes Hydrogen chloride Monochloroethanes (Unsaturated) (Saturated)
Chemical equation: C2H4 + HCl → C2H5Cl
4. Addition of acidified potassium manganate(VII)
1. When alkenes is mixed with acidified potassium manganate(VII), its purple colour is decolourised.
2. This is because addition process occurred, a group of hydroxyl (--OH) is added to the molecules of alkenes to form a molecule of –diol (type of alcohol) which is saturated and
colourless.
C = C + H2O → C − C
OH OH
Alkenes alkanes-diol compound
(Unsaturated) (Saturated)
[O][from acidified KMnO4]
Example;
H H H H C = C + H2O + [O] → H C − C H H H OH OH
Ethene Ethane-1,2-diol (Unsaturated) (Saturated)
Q: Use propene as example.
H H H H H │H— C — C = C + H2O + [O] → H C−C − C H
│ │ H H H H OH OH
Propene, C3H6 Propane-1,2-diol
C3H6 + H2O + [O] C3H8O2
5. Steam (Hydration process)
1. Alkenes react with steam to produce equivalent alcohol at the temperature of 300 oC and in the pressure of 60 atmosphere.
2. Reactions catalyst by concentrated phosphoric acid, H 3PO4.
3. This method is one of the industrial preparation to produce alcohol.
H H H H C = C + H OH ─ → H C − C H H H H OH
Ethene Steam Ethanol C2H4 + H2O → C2H5OH @ C2H6O
Q: Use but-1-ene
C4H8 + H2O C4H9OH / C4H10O
300 oC, 60 atmH3PO4
300 oC, 60 atmH3PO4
Polymerization 5.3
Polymer : Large molecules made up from many identical repeating sub-units called monomers, which joined
together by covalent bond.
Polymerization is a process of repeated linking when a monomers are joined into chains
Reaction to form a polymer from alkene monomers is called an addition polymerisation
Homologous Series
Characteristic of Homologous Series
Kamal Ariffin Bin SaaimSMKDBLhttp://kemhawk.webs.com
Comparing properties of Alkanes and AlkenesSimilarities:
Properties Alkanes & Alkenes
Solubility in water NoSolubility in organic solvent YesConductivity NoBoiling and melting point Low
Molecular formula Each member of homologous differs from the next/successive member by a unit −CH2−
Molecular mass Each member of homologous differs from the next/successive member of 14 unit
Differences:
Properties Alkanes Alkenes
Reaction with oxygen, O2 gas It burned with less sooty yellow flame It burned with a more sooty yellow flame
Reaction with bromine, Br2 water The reddish-brown colour of bromine water remains unchanged
The reddish-brown colour of bromine water decolourised
Reaction with acidified potassium manganate(VII), KMnO4 solution
The purple colour of acidified potassium manganate(VII)solutions remained unchanged
The purple colour of acidified potassium manganate(VII)solutions was decolourised
ESSAY;
HOW TO DIFFERENTIATE THE ALKANE and ALKENE IN THE BOTTLES?Solutions: i. Procedure ii. Observations iii. Inference
[8marks]Sample answerAim: To investigate the liquid in bottle A and B
Procedure;1. The apparatus shown above is prepared.2. 2-5 cm3 bromine water is measured with measuring cylinder 5ml and poured into a test tube. 3. A few drops of liquid from bottle A is put/added with dropper into the test tube, and shake.4. Obsevation is recorded.5. The experiments is repeated by replace the liquid from bottle A with bottle B.
Observation:
Test Tube Observation Inference
BA
Test tube A Test tube B
Dropper
Test tube
Liquidin bottle A
The reddish-brown colour of bromine water remains unchanged Contains alkane
Liquidin bottle B
The reddish-brown colour of bromine water decolourised Contains alkene
Easylah!
Prepared by;Kamal Ariffin Bin SaaimSMKDBLhttp://kemhawk.webs.comALCOHOL
The Alcohol Family1. One of member of homologous series which contain carbon, hydrogen and oxygen.
2. General formula for alcohol is CnH2n+1OH. [n=1,2,3..]
3. Alcohol contains the hydroxyl group, -OH as their functional group. [notes: not hydroxide ion, OH- , alcohol not is alkaly ]
4. Alcohol is neutral compound.
5. Alcohol are named by replacing -e for alkane with –ol.
6. Structural formula and molecule for few alcohol.
n Name Mr Molekul Formula Structural formula
1 Methanol12+3+16+1= 32
CH3OH@
CH4O
H |H— C — OH | H
2 Ethanolvery important
12x2 + 5 +16 + 1 = 46
C2H5OH@
C2H6O
H H | |H— C — C — OH | | H H
3 Propan-1-ol 60 C3H7OH
H H H | | |H — C— C — C — OH | | | H H H
4 Butan-1-ol 74 C4H9OH
5 Pentan-1-ol 88 C5H11OH
6 Hexan-1-ol 102 C6H13OH
Q: Give names for this alcohol.
OH
CH3 CH2 CH CH2 CH2 CH3
Formula: C6H13OH
Name : HEXAN-3-OL
Naming Alcohol 1. Find the longest continous carbon chain containing –OH.- Number the carbon beginning at the end nearer to the – OH, write the number in front of the ending –ol. - Locate the alkyl group (branch chain), give number to the carbon and named the alkyl group. Put the number in front of the
group. CH3 : methyl
C2H5 atau CH2CH3 : ethyl C3H7 atau CH2CH2CH3 : propyl
- Complete the name for the alcohol
(ii)
OH
CH3 CH2 C CH2 CH2 CH3 | CH3
Formula: C7H15OHName : 3-methyl hexan-3-ol
(iii)
OH
CH3 CH2 CH CH CH2 CH3 | CH3
Formula : C7H15OHName : 4-methyl hexan-3-ol
(iii)
OH
CH3 CH CH CH CH2 CH2 | | | CH3 CH3 CH3
Formula : C9H19OHName : 2, 4 – dimethyl heptan-3-ol
(iv)
C2H5 OH
CH3 CH2 CH CH2 CH CH2 CH─ 3
Formula : C9H19OHName : 5-ethyl heptan-3-ol
Physical Properties1. Liquid at room temperature. (pg. 62) [ no gas]2. Simple alcohol are very soluble in water, infinite solubility. Methanol, ethanol dan propan-1-ol is miscible in all proportions (terlarut campur dengan air dalam semua kadaran). The rest of the alcohol less soluble or insoluble.
Isomerism Similar to alkenes, isomerism in alcohol results from the branching of the carbon chain and the different location of the hydroxyl
group.
You only have to know the isomerism in propanol dan butanol.
Q : Draw 2 isomers for propanol and 4 isomers for butanol, and dan named the isomers.
Propanol
Butanol
Propanol
Butanol
H H H │ │ │H ─ C ─ C ─ C ─ OH │ │ │ H H H
H H H │ │ │H ─ C ─ C ─ C ─ H │ │ │ H OH H
Molecular formula: C3H
7OH
Name: Propan-1-ol
Molecular formula: C3H
7OH
Name: Propan-2-ol
Molecular formula: C4H
9OH
Name: Butan-1-ol
Molecular formula: C4H
9OH
Name: Butan-2-ol
H H H H │ │ │ │H ─ C ─ C ─ C ─ C ─ OH │ │ │ │ H H H H
H H H H │ │ │ │H ─ C ─ C ─ C ─ C ─ H │ │ │ │ H H OH H
H H H │ │ │H ─ C ─── C ─── C ─ OH │ │ │ H H─C─H H │ H
Molecular formula: C4H
9OH
Name: 2-methylpropan-1-ol
H OH H │ │ │H ─ C ─── C ─── C ─ H │ │ │ H H─C─H H │ H
Molecular formula: C4H
9OH
Name: 2-methylpropan-2-ol
ETHANOL1. Preparation of ethanol.
i. Laboratory preparation (fermentation)ii. Industrial production (hydration process)
Making Ethanol Fermentation1. Two stages;
i. Fermentation ii. Purification
- through fractional distillation at 78 oC ( boiling point of ETHANOL)
Fermentation of Glucose1. Yeast is added to sugar or starch.
2. Anaerobic process ( takes place in the absence of oxygen).
3. Yeast releases enzymes. These enzymes break down the sugars/starch into glucose, C6H12O6.
4. Zymase slowly decomposes the glucose to form ethanol and carbon dioxide.
When the concentration of ethanol reach 15%, the yeast dies.
Q: How to produce pure alcohol?
A: Purified the ethanol through fractional distillation.
Delivery tube
Lime water
Beaker
Glucose + yeast
Conical flask
Zymase @ C2H5OH @ C2H6O C6H12O6 (aq) → 2CH3CH2OH (l) + 2CO2 (g)
30 oC
Purification of Ethanol1. Ethanol produced from the fermentation process is impure, because its mix with the glucose solution.
Q : Draw labeled diagram to carry out the purification of ethanol through fractional distillation process.
Q: Why the solution/filtrate in rounded conical must heated at 78oC.
A: The boiling point of ethanol is 78 oC.
Q: Ethanol produced may still contains of some water. What should be done to be sure that ethanol is 100% pure?
A: Anhydrous calcium oxide or anhydrous calcium chloride is add/put into the ethanol.
Q: What is the function of;- thermometer- porcelain chips- Liebig condenser
A: thermometer is used to ensure that temperature is always
●
○
XXXXXXXXXXXXXXX
Thermometer
Fractioning collum
Liebig condenser
Water in
Water out
Product from fermentation Porcelain
chips
Retort stand with clamp
Distillate (Ethanol)
Bunsen burner
Rounded conical
Water
Wire gauge
at 78 oC.
B: Porcelain chips is used to avoid the solution jumped/ effervesence (breaking bubbles)
C: To cooled the ethanol vapour to become liquid.
Q: Named the process in Liebig condenser.
A: Condensation
Q: What is the properties of ethanol
A: Properties;- colourless- volatile- good organic solvent- miscible with water- highly flammable- antiseptic- chemically reactive
Q: What is the uses of ethanol
A: Uses;- As a solvent in perfumes/cosmetics- As a thinner in varnish, ink- As a cleaner for compact disc.- As a fuel for transport- As a raw material for the manufacture of vinegar,- As a raw material to make industrial product such as
antiseptic and cough syrup.
Industrial production of ethanol
Ethene is mix with steam is passed through concentratedphosphoric acid (catalyst) at 300 oC (temperature) and 60 atmosphere (pressure).
H3PO
4
@ C2H
4 concentrsted C
2H
5OH
CH2 = CH
2 + H
2O —————→ CH
3CH
2OH
300 o C, 60 atm
Chemical Properties
1. Combustion
i. Alcohol are very flammable sustances. ii. Ethanol burns with non-smoky and blue flame and releases lot of heat. Suitable for use as fuel, described as clean fuel.
Q: Write combustion equation for hexanol
2. Oxidationi. Ethanol can be oxidised into ethanoic acid by an oxidising agent.
[Ethanoic acid is a family of carboxilic acids]
Q: Show the structural formula for the equation above.
Q: Named 2 solutions are commonly used as oxidising agent.
(i) Acidified potassium manganate(VII), KMnO4 (purple to colourless / decolourised)
(ii) Acidified potassium dichromate(VI), K2Cr2O7 (orange to green)
Q: Draw a labeled diagram for the process.
H H H O | | | ║ H — C — C — OH + 2[O] → H — C — C — OH + H
2O
| | | H H H
C2H5OH + 3O2 → 2CO2 + 3H2O Ethanol Oxygen Carbon Water dioxide
C6H13OH + 9O2 → 6CO2 + 7H2O hexanol Oxygen Carbon Water dioxide
CH3CH2OH + 2[O] → CH3COOH + H2O Etanol Ethanoic acid
Distillate (ethanoic acid)
- Colourless- Vinegar smell - Blue litmus paper turns red (acidic properties)
3. Dehydration
ALCOHOL → ALKENE
1. Converted ethanol into ethene and a molecule of water.
2. The elimination of water results the formation of a carbon-carbon double bond.
3. Dehydration occur when a. ethanol vapours is passed over a heated catalyst such as.
i- Porous pot / porcelain chipsii- Purnice stone / aluminium oxide, Al2O3 /alumina
b. Ethanol is heated under reflux at 170 oC with excess concentrated sulphuric acid.
Q : Draw the structural molecule for the process
Heat
Ethanol + potassium dikromat(VI) + dilute sulfuric acid
Cold water
Distillate (ethanoic acid)
H H H H | | | | H — C — C — H → H — C ═ C — H + H2O | | H OH
CH3CH2OH → CH2 = CH2 + H2O Ethanol Ethene
- H2O
Q : Draw labeled diagram.
Prepared by;Kamal Ariffin Bin SaaimSMKDBLhttp://kemhawk.webs.comCARBOXILIC ACID
General formula CnH2n+1COOH
One hydrogen atom is replaced with functional group – COOH
Heat
Glass wool soaked with ethanol
Heat
Ethene gas
Water
Porcelain chips
Retort stand with clamp
Test tube
Delivery tube
Why families known as carboxylic ‘acid’
Carboxyl group plays a vital role to gives acidic properties to carboxilic acid families.
H O | ║ H — C — C — OH | H
Formula: HCOOH
O ║ H — C — OH
Formula: CH3COOH
CARBOXYL GROUP
CH3COOH H+ + CH
3COO-
Ethanoic acid
Hydrogen ion
Ethanoate ion
Molecular and Structural Formula
n Name Molecular formula Mr Structural
formula
0 Methanoic acidC0H2(0)+1COOH
= HCOOH46
O ║ H — C — OH
1 Ethanoic acid
C1H2(1)+1COOH
= CH3COOH [C2H4O2]
60
H O | ║ H — C — C — OH | H
2 Propanoic acidC2H2(2)+1COOH
= C2H5COOH74
H H O | | ║H — C — C — C — OH | | H H
3 Butanoic acid
Naming carboxilic acids
Example 1:
Example 2:
C C C
O
O H
H
H
H
H
Carbon number 123
C C COOHH
H
H
H
C
Longest continuous chains: propanoic acid
HH
H
Attached alkyl group: 2-methyl
Carboxyl carbon: carbon number 1
Name: 2-methylpropanoic acid
C4H
8O
2 / C
3H
7COOH
Example 3:
CH3
C COOH
H
C2H
5
Longest continuous chains: butanoic acid
Carboxyl carbon: carbon number 1
Name: 2-methylbutanoic acid
Attached alkyl group: 2-methyl
Example 4:
Ethanoic AsidCan be prepared through oxidation of an ethanol.
Chemical equation:
C2H
5C COOH
H
C3H
7
Name: 2-ethyl pentanoic acid
C3H
7C COOH
H
C2H
5
Name: 2-ethyl pentanoic acid
CH3CH2OH + 2[O] → CH3COOH + H2O Etanol ethanoic acid
This is carried out by refluxing ethanol with an oxidising agent such as acidified potassium dichromate(VI) or potassium manganate(VII) solution.
Preparation of ethanoic acid through refluxing
Condenser is used to prevent the loss of a volatile liquid by vaporisation.
This method of retaining a volatile liquid during heating is called refluxing.
H H │ │H — C — C — OH │ │ H H
H O │ ║H — C — C — OH │ H
+ 2[O] + H2O
K2Cr
2O
7 solutions
+ dilute H
2SO
4
reflux
Tissel tube
Water out
xxxxxxxxxxxxxx
Label the diagram please
Water in
Liebig condenser
Rounded bottom flask
Retort stand
Absolute ethanol, C2H
5OH +
Acidified potassium dichromate(VI), K
2Cr
2O
7 solution
Heat
Wire gauge
How to carry out the activity?
Physical Properties- pH less than 7- sharp or unpleasant smell- turn moist blue litmus paper to red- colourless liquid
Chemical PropertiesAcid Properties- Only hydrogen atom in the carboxyl group, [-COOH] can ionize in water to produce hydrogen ions, H+.
Ethanoic acid is a weak acid. Why? - it dissociates in water partially, most of
the molecules remain unchanged.
Reactions with metals- Dilute ethanoic acid reacts with reactive metal (Zn, Mg, Al) to produce a salt and hydrogen gas.
CH3COOH CH
3COO- + H+
CH3COO-
Ethanoic acid
Hydrogen ion
Ethanoate ion
2CH3COOH + Mg → Mg(CH3COO)2 + H2 Ethanoic acid Magnesium ethanoate2CH3COOH + Zn → Zn(CH3COO)2 + H2 Ethanoic acid Zink ethanoate6CH3COOH + 2Al → 2Al(CH3COO)3 + 3H2 Ethanoic acid Aluminium ethanoate
Reactions with bases- Dilute ethanoic acid neutralizes alkalis such as sodium hydroxide solution to give an organic salt and water.
- Black copper(II) oxide powder dissolves in dilute ethanoic acid.
Reactions with carbonates- Dilute ethanoic acid reacts with metal carbonates to produce a salt, carbon dioxide and water.
Reactions with alcohols [Esterification]
Esterification:
Carboxilic acid reacts with alcohol to produce an ester and water.
CH3COOH + NaOH → CH3COONa + H2O Ethanoic acid Sodium ethanoate
2CH3COOH + CuO → Cu(CH3COO)2 + H2O Ethanoic acid Copper(II) ethanoate
2CH3COOH + CaCO3 → Ca(CH3COO)2 + CO2 + H2O Ethanoic acid Calcium ethanoate
2CH3COOH + Na2CO3 → 2CH3COONa + CO2 + H2O Ethanoic acid Sodium ethanoate
Concentrated H2SO4 Carboxilic acid + Alcohol ———→ Ester + Water
Concentrated H2SO4 : catalyst
[will discuss more in next chapter]
Uses of carboxilic acid:
i. Ethanoic acid is known as acetic acids use in;- Food flavoring- Food preservatives- To make drugs, dyes, paints insectisides, plastics - To make esters for use as slovents
ii. Methanoic acid is used to coagulate latex.iii. Benzoic acids is used as food preservatives iv. Fatty acids used in making soapsv. Carboxilic acids use in the manufactured of polyester and polyamids (fibres) in textile
Conclusion on chemical reaction;
Carboxilic acid + reactive metal carboxylate salt + hydrogen
Carboxilic acid + base carboxylate salt + water
Carboxylate acid + metal carbonate carboxylate salt + carbon dioxide +
Water
Carboxilic acid + alcohol ester + water
1. Learning task 2.9 Summarizing pg 75 [notes book]
2. Effective Practise pg 75 1, 2, 3 [exercise book]
ESTER
General formula CnH2n+1COOCmH2m+1
R : alkyl group in carboxilic acidR’ : alkyl group in alcohol
Esterification- Carboxilic acid reacts with alcohol to produce ester and water.- The functional group of ester is carboxilate group. - Concetrated sulphuric acid is catalyst. - Carboxilic acid losses ‘OH’ and - Alcohol losses ‘H’ - The bond that ‘break up’ will ‘rejoin’ again
O ║ CnH2n + 1C — OH + CmH2m+1OH (carboxilic acid) (alcohol)
O ║ CnH2n + 1C — O — CmH2m+1 + H2O (ESTER)
Naming Ester- Name of ester consists of two parts, the name of alcohol part is given first and followed by the acid part.
Example: i. Ethanoic acid + methanol methyl ethanoate + waterChemical equation:
CnH
2n + 1 — C
O
O CmH
2m+1
Break up and rejoin
Carboxilate group, -COO-
Derived from carboxilic acid
Derived from alcohol
CH3COOH + CH3OH → CH3COOCH3 + H2O
Example: ii. Ethanoic acid + ethanol ethyl ethanoate + waterChemical equation:
H O | ║ H — C — C — OH | H
CH3COOH
(Etanoic acid)
H |H— C — OH | H
CH3OH
(Methanol)
+
H O H | ║ | H — C — C — O — C — H + H
2O
| | H H
CH3COOCH
3
(Methyl ethanoat) Water
CH3COOH + CH3CH2OH → CH3COOCH2CH3 + H2O
Example: iii. Methanoic acid + Ethanol ethyl methanoate + waterChemical equation:
H O | ║ H — C — C — OH | H
Ethanoic acid
H H | |H— C — C — OH | | H H
Ethanol
+
H O H H | ║ | | H — C — C — O — C — C — H + H
2O
| | | H H H ethyl etanoat Water
HCOOH + CH3CH2OH → HCOOCH2CH3 + H2O
Q: Draw structural molecule of i. Methyl metanoateii. Pentyl propanoate iii. Propyl ethanoate
Solutions; i. Methyl metanoate
O ║ H — C — OH
Methanoic acid
H H | |H— C — C — OH | | H H
Ethanol
+
O H H ║ | | H — C — O — C — C — H + H
2O
| | H H
Ethyl metanoat Air
ii. Pentyl propanoate
Try now
Methyl methanoate
H |H— C — OH | H
O ║ H — C — OH
MethanolMethanoic acid
Break up and rejoin
From alcoholFrom carboxilic acid
O H ║ | H — C — O — C — H + H
2O
| H
methyl metanoate Air
Preparation of ester through reflux
Prophyl ethanoate
H H H | | |H— C — C —C — OH | | | H H H
H O | ║ H — C —C — OH | H
PropanolEthanoic acid
Break up and rejoin
From alcoholFrom carboxilic acid
H O H H H | ║ | | | H — C — C — O — C — C —C — H + H
2O
| | | | H H H H
propyl ethanoate Water
How to carry out this process?[Success pg 378]
After boiling, Liebig condenser is rearranged To carry out the fractional distillation at 74oC – 78oC to collect ethyl ethanoate.
Physical properties of ethyl ethanoate- colourless- fragrant smell- insoluble in water- lese dense in water
Natural Sources- Most simple esters are found in fruits and flowers.
ex: benzyl ethanoate in Jasmine ethyl butanoate in pineapple
XXXXXXXXXXXXXXX
Tissel tubeLiebig condenser
Ethanol +ethanoic acid + concentrated sulphuric acid
Porcelain chip
Water bath
Water in
Water out
To prevent bumping and ensure smooth boiling
To cold the ethanol and ethanoic acid
Uniform heating
- Palm oil are liquid ester.- The higher and complex ester does not produce pleasant smells
Uses of ester
- to make perfume, cosmetics- to make artificial food flavoring
[Text Book: Table 2.8 pg 81] - used as organic solvents eg. ethyl ethanoate used in sunburn lotion, polish removers, glues. - to make synthetic polymers/fabrics- to make aspirin (pain reliever)
Exercise: Effective Practise pg 84 no. 1-3[Ex. Books]
Prepared by;Kamal Ariffin Bin SaaimSMKDBLhttp://kemhawk.webs.com
FATSFats and oils are chemically similar, but differ in physical states.
ETHANOLC
2H
5OH
ETHANOIC ACIDCH
3COOH
Hydration process
Concentrated phosphoric acid, H
3PO
4 300 oC
, 60 atmosphere
Dehydration process
ii. Concentrated sulphuric acid, H
2SO
4 180 oC (reflux)
Oxidation process
Acidified potassium manganate(VII)/Acidified potassium dichromate(VI)
GLUCOSEC
6H
12O
6
Fermentation process
Yis (zymase)30 oC
ETIL ETHANOATECH
3COOC
2H
5Esterification process
Concentrated sulphuric acid,
H2SO
4
CARBON DIOXIDE + WATERC
2H
5OH
Combustion process
Oxygen, O
2
Oxygen, O
2
Combustion process
i. Heated porcelain chips/ porous pot
ETHENEC
2H
4
PETROLEUM( Hydrocarbon)
Catalytic hydrogenation process
Nickel/platinum180 oC
Alumina, Al2O
3
(heated)
Cracking process
HOT SPOT SPM’09
MEMORISED THE LABELED DIAGRAMS FOR EACH PROCESS. IT WILL HELP YOU A LOT.
Fats : - found in animals - solid in room temperature - butter and tallow (types of fat)
Oil : - fats from plants - liquid in room temperature
- palm oil, coconut oil, sunflower oil
- Fats and oil are mixtures of different esters. - Fats are formed from 3 molecules of long-
chain carboxylic acids called fatty acids with 1 molecules of alcohol called glycerol.
Formation of a fat molecule
H │H ― C ― OH │ H ― C ― OH │ H ― C ― OH │ H
Fatty acids- R
1 , R
2 , R
3 contains
12 to 18 carbon atoms per molecule- R
1 , R
2 , R
3 are three
alkyl groups which may be the same or different- group: carboxilic acid
O ║OH ― C ― R
1
O ║OH ― C ― R
2
O ║OH ― C ― R
3
Glycerol- propane-1,2,3-triol- group: alcohol
Importance of fats and oils- energy- nutrients- thermal insulation
H │H ― C ― OH │ H ― C ― OH │ H ― C ― OH │ H
O ║OH ― C ― R
1
O ║OH ― C ― R
2
O ║OH ― C ― R
3
H O │ ║H ― C ― O ― C ― R
1
│ │ O │ ║H ― C ― O ― C ― R
2
│ │ O │ ║H ― C ― O ― C ― R
3
│ H
+ 3H2O
+
Break up and rejoin
Break up and rejoin
Break up and rejoin
- protection to internal organ
[Text book: Figure 2.34 pg. 86]
Saturated and unsaturated fats- Fat or oil molecules is affected by parent fatty
acids.- Fatty acids can be differentiated in two ways;
i. the length of the carbon chains(12 to 18 carbon atoms)
ii. saturated or unsaturated
Saturated fatty acid- All carbon atoms joined together by carbon-carbon single covalent bond.- example:
Lauric acid (12 carbon atoms)Palmitic acid (16 carbon atoms)Stearic acid (18 carbon atoms)
Unsaturated fatty acid- The carbon chain has one or more carbon-carbon double covalent bond.
Example: i. Oleic acid: monounsaturated fatty acid (one carbon-carbon double bond)- [no of C = 18, DB = 9&10]
ii. Linoleic acid: polyunsaturated fatty acid (two carbon-carbon double bond)
[no. of C = 18, DB = 9&10, 12&13]
iii. Linolenic acid: polyunsaturated fatty acid (three carbon-carbon dauble bond) [no. of C = 18, DB = 9&10, 12&13, 15&16]
Saturated Fats- Fats contain esters of glycerol and saturated fatty acids.
- Example: i. Tristearin ( glycerol + stearic acid)
ii. Tripalmitin (glycerol + palmitic acid)
Tristearin
Tripalmitin
H O │ ║H ― C ― O ― C ― (CH
2)
16 — CH
3
│ │ O │ ║H ― C ― O ― C ― (CH
2)
16 — CH
3
│ │ O │ ║H ― C ― O ― C ― (CH
2)
16 — CH
3
│ H
- Animal fats have large proportions of saturated fats.
- They have high melting point and solids at room temperature.
Unsaturated Fats- Fats contain esters of glycerol and
unsaturated fatty acids.
Example:i. Triolein (glycerol + oleic acid)
H O │ ║H ― C ― O ― C ― (CH
2)
14 — CH
3
│ │ O │ ║H ― C ― O ― C ― (CH
2)
14 — CH
3
│ │ O │ ║H ― C ― O ― C ― (CH
2)
14 — CH
3
│ H
- Plant or vegetable oils contain a large proportions of unsaturated fats. - They have lower melting points and are liquids at room tempoerature.
Converted unsaturated fats to saturated fats- Unsaturated fats can be converted into saturated fats by process called catalytic hydrogenation.
The hydrogenation process is carried out by bubbling hydrogen gas through hot, liquid oil in the presence of fine particles of nickel catalyst.
H O │ ║H ― C ― O ― C ― (CH
2)
7 — CH ═ CH — (CH
2)
7 — CH
3
│ │ O │ ║H ― C ― O ― C ― (CH
2)
7 — CH ═ CH — (CH
2)
7 — CH
3
│ │ O │ ║H ― C ― O ― C ― (CH
2)
7 — CH ═ CH — (CH
2)
7 — CH
3
│ H
Effect of fats on health- Saturated fats (animal oil) will raise the level of cholesterol.- Cholesterol causes fatty deposites or the wall of veins or arteries.- Blood circulation is restricted and will raise the blood presure - Arteriosclerosis, can result in heart attack.- Unsaturated fats (plant oil) do not contain cholesterol. Do not cause cardiovascular problems.
Uses of palm oil- Has many advantages. - A cheaper, better and healthier oil.
[Text book: Figure 2.36 pg. 90]
Prepared by;Kamal Ariffin Bin SaaimSMKDBLhttp://kemhawk.webs.com
Natural Rubber
Natural rubber is a natural polymer.
Natural rubber is obtained from the latex secreted by rubber tree.
Latex is a colloid. It consists of rubber particles dispersed in water.
Natural rubber is poly(isopropene).
Its monomer is 2-metyhlbuta-1,3-diene or isopropene. Each isopropene molecule contains two pairs of double bonds.
The isopropene molecules undergo addition polymerization to produce a long-chain molecule called poly(isopropene)
Each rubber particles is made up of many long-chain rubber molecules, enclosed by a protein-like membrane which is negatively charged.
Polymerization of Isopropene
Negatively-charge protein membrane
Long chain rubber molecules
Rubber particle
─
─
─
─
─
─
─
─
─
─
─
─
── ─
─
──
─
──
─
─
─
─
─
──
Latex
Coagulation process of latex
H CH3 H H
│ │ │ │C ═ C ― C ═ C │ │H H
+ H CH3 H H
│ │ │ │C ═ C ― C ═ C │ │H H
H CH3 H H
│ │ │ │C ═ C ― C ═ C │ │H H
+
H CH3 H H
│ │ │ │― C − C ═ C − C ― │ │ H H
H CH3 H H
│ │ │ │― C − C ═ C − C ― │ │ H H
Isoprene
H CH3 H H
│ │ │ │― C − C ═ C − C ― │ │ H H
Repeated unit in polymer
polymerization
Isoprene Isoprene
Rubber particle has negatively-charged protein membrane.
The repulsion between the negatively-charged particles prevents the rubber particles from coming close to each other.
Latex could not coagulate.
Q: So what causes the latex to coagulate?
Rubber particle─
─
─
─
─
─
─
─
─
──
─
──
─
─
──
─
──
When an acid is added, the hydrogen ions, H+ neutralize the negative charges on the protein membrane.
Q: Can you named the acid that usually used to coagulated the latex in rubber industry?
A: Ethanoic acid also known as acetic acid. [notes: all acid solutions can make latex coagulate]
Q: What do you think will happen next?
─
─
─
─
─
─
─
─
─
──
─
──
─
─
──
─
──
+
+
+
++
+
+
+
+
+
+
+
+
+
++
+
+
+
+
+
The rubber particles now come close together.
This enable them to collide with one another resulting in the breakage of the protein membrane.
The rubber molecules/polymer combine with one another and entangle.
Thus, causing the latex to coagulate.
EASY lah
Q: The coagulation of latex will also occur if latex is exposed to air. Why?
A: Bacteria from air can enter latex. The growth and spread of bacteria produce lactic acid that causes the process above.
Q: Named the substance can be used to preserve latex in liquid state? Explain.
A: Ammonia, NH3. NH3 solutions contains hydroxide ions, OH- that neutralised the acid/hydrogen ions, H+ produced by the bacteria. The rubber particles remain negatively charged and the coagulation is prevented.
[notes: all alkaly solutions also can be used]
Properties of natural rubber- Soft- Elasticity decreases over time.- Easily oxidized by air. - Sensitive to heat. When heated, it becomes sticky. When cooled, it becomes hard and brittle.
Vulcanization of rubber
Properties of rubber can be improved through vulcanization.
Vulcanization is a process whereby rubber is reacted with sulphur to improved its properties.
Q: How the vulcanization process is carry out in industry?
A: 1st method: Latex is heated with sulphur, or
2nd method: Rubber products are exposed to disulphur dichloride, S2Cl2.
Q: Compare and contrast the properties of vulcanised and unvulcanised rubber.
Similarities Vulcanised and unvulcanised rubber is elastic, and heat and electrical insulator
Differences [notes: draw a table]
Properties Vulcanised rubber Unvulcanised rubberElasticity More elastic Less elastic
Hardness Harder Softer
Tensile strength Stronger Weaker
Resistance to heat Can withstand higher temperature Cannot withstand temperature
Resistance to oxidation Less easily oxidized Easily oxidized
Effect of organic solvent Does not become soft and sticky easily
Become soft and sticky easily
Q: Why?
vulcanisation
S
S
C
C
S
S
C
C
S
S
C
C
S
S
C
C
S
S
C
CS
S
C
C
C═C C═C
C═C
C═C C═C
C═CC═C C═C
C═C
C═C
Natural rubber Vulcanised rubber
S
S
C
C
S
S
C
C
S
S
C
C
S
S
C
C
S
S
C
CS
S
C
C
Rubber molecules
Cross-linkage of sulphur atoms
A: Improved properties of vulcanised rubber is due to the presence of cross-linkage of sulphur atoms between the rubber molecules.
Q: How the cross-linkage of sulphur atom improve elasticity and strength of the vulcanized rubber:
A: When vulcanised rubber is streched and released, the cross linkage pull the chains back to their original arrangement.
Q: Why vulcanized rubber more resistant to heat and organic solvent?
A: The presence of sulphur cross-linkage increases the size of rubber molecules.
Q: Why vulcanized rubber more resistant to oxidation?
A: Vulcanized rubber has much lesser carbon-carbon double bond.
Uses of natural rubber
Home WorkReview Questions pg 100 - 102
i. objective (no. 1-8)ii. subjective questions (1 and 2)iii. essay (no. 1c)
SPM Question (2006)
Diagram 2 shows the stretching phases of a vulcanised rubber and an unvulcanized rubber strands.
Stretching phases Length of vulcanized rubber Length of unvulcanized rubber
Before
During
45 mm 45 mm
59 mm 60 mm
After
Diagram 2Plan an experiment to compare one characteristic shown in Diagram 2 for both types of rubber.
Your planning should include the following aspects: (a) Aim of the experiment(b) All the variables(c) Statement of the hypothesis(d) List of substances and apparatus(e) Procedure of the experiment(f ) Tabulation of data [17 marks]
Answer(i) Problem statement: Does vulcanized rubber is more elastic than unvulcanized rubber?
(a) Aim: To compare the elastic properties between vulcanized rubber and unvulcanized rubber.
(b) List of variable:
Manipulated variable = Type of rubber
Responding variable = Elasticity // length of rubber strip during and after stretching phase.
Fixed variable = Original length of rubber strip // Length/size/mass of rubber
(before stretching phase)
(c) Hypothesis:
Vulcanized rubber is more elastic than unvulcanized rubber. // sk3
The more elastic of the rubber, the less length of the rubber during and after stretching phase. // sk2
45 mm 50 mm
Rubber that is more elastic shows less length when/after it has been stretched. sk3
(iv) List of materials and apparatus: Vulcanized rubber, unvulcanized rubber, Meter ruler, 50 g weight, retort stand and clamp, clip, thread.
(vi) Procedure :1. Clip is used to hung the strip of vulcanized rubber.2. The original length of the vulcanized rubber is
measured.3. A weight of 50 g is hung on the strip of vulcanized rubber. 4. The increased in length of the vulcanized rubber
strip is measured. 5. The weight is removed. 6. The final length of the vulcanized rubber strip is measured. 7. Step 1 to 6 are repeated using unvulcanized rubber.
(vii) Tabulation:
Type of rubber strip Original length /mm
Final Length when weight is hung /mm
Increase in length /mm
Final length when weight is removed /mm
Retort stand with clamp
Clip
Rubber strip
Thread
Weight 50 g
Vulcanized rubber 45 59 14 45
unvulcanized rubber 45 60 15 50
HOT SPOT SPM 2008
Prepared by;
Kamal Ariffin B SaaimSMKDBL
Manipulated variable: Action to be taken:
Responding variable: Action to be taken:
How the variable responds?:
Fixed variable: Action to be taken:
Alumina, Al2O3
C9H20 (ce) ————→ C2H6 (g) + C7H14 (g) PanasNonana Etana Heptena
Alumina, Al2O3
C9H20 (ce) ————→ C2H6 (g) + C7H14 (g) PanasNonana Etana Heptena
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