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

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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

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