Section 3 IGCSE Chemistry: Organic chemistry
Terms in this set (32)
What is a "Homologous series"?
A series of *organic compounds* that have the *same general formula, similar chemical reactions* and where each member *differs* from the next by a *-CH₂-* group
What is a Hydrocarbon?
A compound containing only the elements hydrogen and carbon
An organic compound in which all the bonds are single bonds
An organic compound that contains a carbon-carbon double bond
What is the general formula for Alkanes?
What is "Combustion"?
When oxygen combines with another compound to form *water and carbon dioxide*.
These reactions are exothermic.
What is "Incomplete combustion"?
When a lack of oxygen combines with another compound to form *water and carbon monoxide*. Carbon monoxide is poisonous - it reduces the capacity of the blood to carry oxygen.
What is a "Substitution reaction"?
When one atom is replaced by another atom in a reaction.
Methane and bromine react together in the presence of ultraviolet light. This is a substitution reaction.
Give the formula and name the compounds formed.
CH₄ + Br₂ → CH₃Br + HBr
bromomethane and hydrogen bromide.
What is the general formula for Alkenes?
What is an "Addition reaction"?
When an *unsaturated compound becomes saturated*. The double bond breaks and two new atoms/groups are added to each of the previously double bonded carbon.
How would you test for the presence of unsaturation in a molecule?
Shake with bromine water.
Unsaturated: orange → colourless (NOT clear!)
Saturated: no change.
Ethene gas is bubbled through bromine water:
a) what happens to the bromine water?
b) give the chemical equation.
a) bromine water changes from orange to colourless.
b) C₂H₄ + Br₂ → C₂H₄Br₂
Alkanes react with bromine in the presence of UV light.
a) explain what happens in simple terms
b) what name is given to this type of reaction?
a) a bromine atom pushes out a hydrogen atom.
b) *substitution* reaction.
Methane is reacted with bromine (with UV light). Give the chemical equation.
CH₄ + Br₂ → CH₃Br + HBr
What does "biodegradable" mean?
*decay* through the action of *living organisms* such as *bacteria* and *microbes*.
What feature of addition polymers makes it difficult for them to biodegrade?
addition polymers are *unreactive/inert*.
Fermentation #1: from sugar
When sugar (glucose) is dissolved in water and *yeast* is added.
*Fermented* for several days in the absence of oxygen *(anaerobic)* at room temperature.
C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ (ethanol + carbon dioxide)
Fermentation #2: catalytic hydration of ethene
When a mixture of ethene and steam is passed over a *phosphoric acid catalyst* at a temperature of *300°C and 60-70 atm* of pressure.
C₂H₄ + H₂O → C₂H₅OH
Give 1 advantage and 2 disadvantages of fermentation from sugar
1. renewable resources
3. ethanol produced is impure (further processing).
Give 2 advantages and 2 disadvantages of catalytic hydration of ethene
2. pure ethanol.
3. non-renewable resources
4. high temperatures and pressures → high cost.
How would you convert ethanol to ethene?
Dehydrate by passing ethanol vapour over *hot aluminum oxide catalyst*.
Why would you bother to convert ethanol to ethene?
Ethene is used for the production of poly(ethene) - the most common plastic.