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CHAPTER 2: CARBON COMPOUNDS
A: CARBON COMPOUNDS
-are compounds that contain Carbon as one of their constituent elements
Carbon Compound
Organic Compound-Carbon containing compounds
except oxides of carbon, carbonates, syanides and metallic carbides
Hydrocarbon-contain Carbon and
Hydrogen only
Alkanes(saturated
hydrocarbons)-contain only single
bond
Alkenes(unsaturated
hydrocarbons)-contain at least one
multiple bond
Non-hydrocarbon-contain C,H and O,N,P,S,F,Cl,Br,I
Alcohols
Carboxylic acids
Esters
Inorganic Compound-non-carbon containing
compounds
Organic compound Inorganic Carbon compound
Similarity
Both contain carbon atoms
Diffenrences
Examples
Origin
Effect of heat
Solubility
Protein, fats, cellulose, natural rubber, petroleum
Formed from living thing
Have low boiling points and low melting point
Dissolve in organic solvents such as ether, petrol, alcohol
and chloroform
Carbon dioxide, carbon monoxide
Formed from minerals
Have high boiling points and high melting point
Dissolve in inorganic solvents such as ether, water, acids and
alkalis
Hydrocarbons
Hydrocarbons are organic compound that contain only Carbon and Hydrogen
Natural sources of hydrocarbons:• Petroleum• Coal• Natural gas• Rubber trees
B: ALKANES
General Formula : CnH2n+2 , n=1,2,3… Naming alkanes:
Number of Carbon atoms
1 2 3 4 5 6 7 8 9 10
Root name
Meth- Eth- Prop- But- Pent- Hex- Hept- Oct- Non- Dec-
Final name
Methane Ethane Propane Butane Pentane Hexane Heptane Octane Nonane Decane
Structural Formula shows how the atoms in a molecule are bonded together and by what types of bonds
Example :
Ethane
C2H6 molecular formula structural formula
Physical properties of alkanes
Cannot conduct
electricity
Insoluble in water
Low melting and boiling
points-dissolve in
organic solvents
Less dense than water
because the molecules are held together by weak intermolecular forces which can be overcome by
small amount of energy
Chemical properties of alkanes
a) Combustion 1. Complete combustion Alkanes burn in air to form carbon dioxide and water CH4 (g) + 2O2(g) CO2 (g) + 2H2O(l)
More soot is given off when a higher alkane is burnt. For example, the burning of heptane produce more soot than the burning of ethane
2. Incomplete combustion If insufficient oxygen available, carbon monoxide or even carbon
may be formed 2CH4 (g) + 3O2(g) 2CO (g) + 4H2O(l) CH4 (g) + O2(g) C (s) + 2H2O(l)
b) Halogenation
-Reaction of alkanes with halogens.
-readily takes place in sunlight (not occur in the dark)
-carbon-hydrogen bonds are broken and new carbon-halogens bonds are formed
-is a substitution reaction occurs when one atom or a group of atoms in a molecule
is replaced by another atom or group of atoms
-Example: when a mixture of CH4 and chlorine is exposed to
ultraviolet light, 4 different products are formed• CH4 (g) + Cl2(g) CH3Cl (g) + HCl(l) Chloromethane hydrogen chloride
C: ALKENES
is a hydrocarbons containing at least one carbon-carbon double bond
General Formula : CnH2n , n=2,3,4… Naming alkenes:
Number of Carbon atoms
2 3 4 5 6 7 8 9 10
Root name
Eth- Prop- But- Pent- Hex- Hept- Oct- Non- Dec-
Final name
Ethene Propene But-1-ene Pent-1-ene Hex-1-ene Hept-1-ene Oct-1-ene Non-1-ene Dec-1-ene
Structural formula of alkenes
Ethene: C2H4
Propene : C3H6
Physical properties of alkenes
Low melting
and boiling point
Soluble in organic solvents
Insoluble in water
Less dense than
water
Cannot conduct
electricity at any state
Chemical properties of
alkenes
(a)Combustion
reaction
(b)Addition reaction
(c) Polymeriza
tion reaction
(i)Addition of hydrogen(ii)Addition of halogens(halogenation)(iii) Addition of hydrogen halides (HCl, HBr, HI)(iv) Addition of water (hydration)(v) Addition of hydroxyl groups
Chemical properties of alkenes
a) Combustion reaction
Alkenes burn in excess oxygen to form carbon dioxide and water
C2H4 (g) + 3O2(g) 2CO2 (g) + 2H2O(l)
Alkenes burn with sootier flames as compared to alkanes because alkenes have a higher percentage of carbon in their molecules than alkanes
b) Addition reaction
(i) Addition of hydrogen
This process is called catalytic hydrogenation
(ii) Addition of halogens (halogenation)
Observation: reddish-brown bomine is decolourised and colourless liquid is formed
This reaction is used as a test for the presence of a carbon-carbon double bond in organic molecules
(iii) Addition of hydrogen halides(HCl, HBr, HI)
• (iv) Addition of water (hydration)
(v) Addition of hydroxyl groups
Observation: purple solution of potassium manganate (VII) is decolourized
c) Poymerization reaction
Homologous Series
A group or family of organic compounds that has the followingcharacteristics:
a) Members of the series can be represented by a general formulab) Successive members differ from each other by –CH2c) Members can be prepared by similar methodsd) Physical properties change regularly with increasing number of carbon
atomse) Members have similar chemical properties because they have the same
functional group
functional group : -a special group of atoms attached to an organic mlecule -determines the chemical properties of the molecule -chemical reactions occur at the functional group
5 homologous series learnt in this chapter:
Homologous series
General formula Functional Group
Alkane CnH2n+2 , n=1,2,3… Carbon-carbon single bond, C-C
Alkene CnH2n , n=2,3,4… Carbon-carbon double bond, C=C
Alcohol CnH2n+1OH ,n=1,2,3… Hydroxyl group, -OH
Carboxylic Acid CnH2n+1 COOH ,n=0,1,2,… Carboxyl group, -COOH
Ester CnH2n+1 COOCmH2m+1, n=0,1,2,…m=1,2,3…
Carboxylate group, -COO-
First memberSecond memberThird member
…..…..…..
As the number of carbon atoms per molecule increases:•Melting point increases•Boiling point increases•Volatility decreases•Density increases
Descending homologous series
D: ISOMERISM
Isomerism is a phenomenon whereby 2 or moremolecules are found to have same molecular formula but different structural formula
Isomers: molecules with the same molecular formula but with different structural
formula
• Example: C4H10
Steps to draw structural formula of isomers of alkanes
Draw all the possible straight- chain and branched-chain carbon skeletons
Place single bonds around every carbon atom. Ensure that each carbon atom has 4 bonds
Place a hydrogen atom at each of the single bonds
Steps to draw structural formula of isomers of alkenes
Draw all the possible carbon skeletons
For each carbon skeleton, place a double bond at different locations
Place single bonds around each carbon atom. Ensure that each carbon atom has 4 bonds
Place a hydrogen atom at each of the single bonds
How to name isomers?Prefix
Denotes the number and identity of attached branches
RootDenotes the
longest carbon chain
EndingDenotes rhe family of the
organic compound
Steps to name an alkane:
1 : Find the longest continuous carbon chain in the molecule
2 : Give the name for this longest chain
3 : Number the carbon atoms in this longest chain beginning at the end nearest to the first branch (alkyl group)
4 : Locate and name the attached alkyl group
5 : Complete the name for the molecule by combining the three component parts together. Write the name as a single word. Use hyphens to separate numbers numbers and words, and commas to separate numbers
E: ALCOHOLS
General Formula : CnH2n+1OH ,n=1,2,3…
Functional Group : -OH (hydroxyl group)
Naming alcohols
(a) straight-chain alcohol
Step 1Obtain the name of the alkane with the same number of carbon atoms as the
alcohol
Step 2 Replace the ending –e from the name of the alkane with -ol
Step 3A number is placed to in front of the –ol to indicate which carbon atom the hydroxyl
group is attached to
(b) branched-chain alcohol
Step 1Find the longest continuous carbon chain containing the
hydroxyl group
Step 2
Name the longest chain by substituting the ending –ol
for the –e of the corresponding alkane
Step 3
Number of the carbon atoms in the longest chain
beginning at the end nearer to the hydroxyl group
Step 4
Step 5
Step 6
Identify the position of the hydroxul group by writing the number of the carbon atom to which it is attached
in front of the ending -ol
Locate and name all attached alkyl group
Complete the name for the alcohol molecule by combining the 3 component parts together. Write
the name as a single word
Industrial production of ethanol
a) Making ethanol by fermentation
C6H12O6 (aq) 2CH3CH2OH (aq) + 2CO2 (g) Glucose Ethanol
Temperature : 18-20 °CCatalyst : zymase from yeastOther condition : absence of oxygen
b) Making ethanol by hydration
CH2=CH2 (g) + H2O (g) CH3CH2OH (g) Ethene Steam Ethanol (From the cracking of petroleum fractions)
Temperature : 300 °CPressure : 60 atmCatalyst : phosphoric acid
Physical properties of ethanol
Completely
miscible with
water
Liquid at room
conditionsHighly
volatile (easily change into a gas)
Low boiling point
colourless
Sharp smell
Chemical properties of
ethanol
Oxidation
Dehydration
Combustion
Chemical properties of ethanol
a) Combustion
Ethanol burns with a non-smoky blue flame
C2H5OH (l) + 3O2 (g) 2CO2 (g) + 3H2O (l)
Combustion of ethanol releases large amountOf heat. Ethanol suitable as a fuel
b) Oxidation
CH3CH2OH (l) + 2[O] CH3COOH (l) + H2O (l) ethanoic acid
oxidising agent: acidified potassium dichromate (VI) solution ( colour change from orange to green)
acidified potassium manganate (VII) solution
( colour change from purple to colourless)
c) Dehydration
txt bk pg 64
module pg 72
2 methods to carry out a dehydration of ethanol
(a) Ethanol vapour is passed over a heated catalyst such as unglazed porcelain chips, porous pot, pumice stone or aluminium oxide
(b) Ethanol is heated under reflux at 170 °C with excess concentrated sulphuric acid
Uses of alcohols(a) As a solvent -perfumes, cosmetics -thinners for lacquers, varnishers
(b) as a fuel - a mixture of petrolwith 10-20 % ethanol (gasohol) - methanol (as a fuel for racing cars)
(c) As a source of chemicals - as a raw material in the manufacture of
polymers, fibres, explosives and plastics - ethanol ethanoic acid (vinegar)
(d) As a source of medicinal products - ethanol- as a solvent in the preparation of
cough syrups - propan-2-ol –as a rubbing alcohol (bring down high fever)
E: CARBOXYLIC ACIDS
General Formula : CnH2n+1COOH ,n=0,1,2…Functional Group : -COOH (carboxyl group)
Naming carboxylic acidsFind the longest continuous carbon chain containing the carboxyl
group
Name this longest chain by replacing the ending –e of the corresponding alkane with –oic acid
Number the carbon atoms in this longest chain beginning at the carboxyl group
Locate and name the attached alkyl group
Complete the name for the carboxylic acid molecule by combining the 2 component parts together
Making ethanoic acid
- oxidation of ethanol by refluxing ethanol with an oxidising agent such as acidified potassiun dichromate (VI) solution or acidified potassium manganate (VII) solution
Refluxing : prevent the loss of a volatile liquid by vaporisation Ethanoic acid formed is removed by fractional distillation
Physical properties of ethanoic acid
Very soluble in water
Colourless liquid at room
conditions
Sour smell like vinegar
Chemical properties of ethanoic acid
(a) Acid properties- ethanoic acid is a weak monoprotic acid
CH3COOH (aq) ↔ CH3COO⁻ (aq) + H⁺ (aq)
Ethanoic acid Ethanoate ion
(b) Reactions with metals
2CH3COOH (aq) + Zn(s) ↔ Zn(CH3COO)2 (aq) + H2 (g) (c) Reactions with base
2CH3COOH (aq) + CuO(s) ↔ Cu(CH3COO)2 (aq) + H2O (l)
(d) Reactions with carbonate
2CH3COOH (aq) + CaCO3(s) ↔ Ca(CH3COO)2 (aq) + CO2(g)+ H2O (l)
(e) Reactions with alcohols (esterification)
Chemical reactions of other carboxylic acid
• Carboxylic acid + reactive metal carboxylate salt + hydrogen• Carboxylic acid + basecarboxylate salt + water• Carboxylic acid + metal carbonate carboxylate salt + CO2 + H2O• Carboxylic acid +alcohol ester + water
Uses of carboxylic acids
•As food flavouring•As preservative
Ethanoic acid(acetic acid)
•Coagulate latexMethanoic acid(formic acid)
•As preservative in foodsBenzoic acid
G: ESTERS
General Formula : CnH2n+1COOCmH2m+1 ,n=0,1,2…
m=1,2,3…
Functional Group : -COO (carboxylate group)
Naming esters
• pg 77
• The name of an ester consists of 2 separate words. The alcohol part is named fist followed by the acid part
Identify and name the alcohol part of the ester (alkyl group)
Identify and name the acid part of the ester (change –oic acid to –oate)
Combine the both parts to obtain the name of the ester
Formation of esters
Esters are produced by an esterification reaction(carboxylic acid reacts with alcohol in the presenceof concentrated sulphuric acid as a catalyst)
Example :HCOOH + CH3OH HCOOCH3 + H2O
methanoic acid methyl methanoate
H2SO4
Physical properties of esters
Low density, less dense than water
Very volatile
Insoluble in water
Sweet smell
Colourless liquid at room temperature
Use of estersUsed in the preparation of cosmetics and perfumes
As artificial flavour in processed food and drinks
Used in the production of polyester (synthetic fibers for makng textiles)
Most are found naturally in fruits and flowers(Their fragrance are due to the presence of esters)
H: FATS
• Fats found in animals are solids at room temperature. Eg: butter
• Fats from plants are liquids. oils
• Fats and oils are esters (fatty acids + glycerol)
• Fatty acids containing 12-18 Carbon atoms per molecule
The importance of oils and fats
Source of energy
Source of nutrients
protection
Thermal insulation
Saturated and unsaturated fats
• Fats which contain esters of glycerols and saturated fatty acids
• saturated fatty acids : has all carbon atoms joined together by
carbon-carbon single bond
Saturated fats
• Fats which contain esters of glycerols and unsaturated fatty acids
• Unsaturated fatty acids: carbon chain has one or more carbon-
carbon double bond
Unsaturated fats
Converting unsaturated fats into saturated fats
• By a process called catalytic hydrogenation ( by bubbling hydrogen gas through hot liquid oil)
catalyst : nickeltemperature : 200oCpressure : 4atm
Module 88
Effects of fats on health
obesity
Plant or vegetable oil do not contain cholesterol: not cause cardiovascular
problems
Saturated fats raise the level of cholesterol: the flow of the blood in the arteries might be blocked and lead to heart attack and stroke
Extraction process of palm oil
Advantages of
palm oil
Rich in Vitamin
E(powerful antioxidant)
Rich in beta-carotene which
contains Vitamin E
Cholesterol free
I : NATURAL RUBBER
• Natural polymers are polymers that exist in nature and not man-made
Natural polymer Monomer
Protein Amino acid
Carbohydrate Glucose
Natural rubber Isoprene
Natural rubber• Monomer: isoprene (2-methylbut-1,3-diene)
• Nota pg 38
Coagulation process of latex
Each rubber particle is made up of rubber polymers covered by a layer of protein membrane
Negative charges are found on the surface of the membrane, making each rubber particle negatively charged. The negatively charged rubber particles repel each other, preventing themselves from combining and coagulating
When acid is added to latex:Hydrogen ion from the acid nautralise the negative charges on the surface of the membrane. A neutral rubber particle is formed.
When these neutral particles collide with each other, their outer membrane layers break up. The rubber polymers are set free.
The rubber polymers start to coagulate by combining together
•Bacteria from the air attack the protein on the membrane to produce lactic acid
•Alkalis such as ammonia solution are added to latex to prevent coagulation
•The hydroxide ions from alkali neutralise hydrogen ions produced by lactic acid as aresult of bacterial attack on protein
•Bcause there are no hydrogen ions to neutralise the negative charges on the rubber particles, they remain negatively charged and hence cannot combine and coagulate
Properties of natural
rubber
Insoluble in water
Unstable to heatelastic
Unstable to oxidation
Vulcanization• Is a process whereby rubber is reacted wth sulphur
to improved the properties of natural rubber Sulphur is heated together with natural
rubber Rubber stripe is soaked in sulphur
monochloride solution in methylbenzene for a few hours, then dried
Txt bk 95