Ch 8 - Organic Chemistry 1 Flashcards
What does organic mean?
‘from living things’
What is organic chemistry?
the study of carbon compounds - living or once living
What is a hydrocarbon?
a molecule made up of hydrogen and carbon atoms only
Where are hydorcarbons found?
in crude oil
What are alkanes?
they are the simplest hydrocarbons
they have a central chain of carbon atoms, joined by carbon-carbon signle bonds, surronded by hydrogen atoms
Different alkanes have chains of … lengths
Different alkanes have chains of different lengths
What are the first five alkanes?
methane: CH4
ethane: C2H6
propane: C3H8
butane: C4H10
What is the displayed formula for methane?
What is the displayed formula for ethane?
What is the displayed formula for propane?
What is the displayed formula for butane?
What is the displayed formula for pentane?
How do you remember the names of alkanes and alkenes after butane/ene?
they take on the names of their mathematical shapes
5C = pentene/ane
6C = hexene/ane
7C = heptene/ane
8C = octene/ane
Are alkanes saturated or unsaturated hydrocarbons?
saturates
they contain the maximum possible number of hydrogen atoms for a given number of carbons
What is methane a major component of?
natural gas
Alkanes are the simplest …
homologous series
What is a homologous series?
a group of compounds with similar properties because they have similar bonding
they can all be represented by the same general formula
they have the same functional group
they have the same number of electrons on the outer shell
they have similar chemical reactivity
they are differentiated by CH2 group
What is the general formula of alkanes?
CnH2n+2
e.g. butane = C4H10 because it has four carbons so it has to have (2 x 4) + 2 hydrogens
What bonds do carbon and hydrogen form? How many can these atoms form?
carbon and hydrogen form covalent bonds
carbon can form four covalent bonds
hydrogen can form one covalent bond
The first four alkanes are … at room temperature. All the other ones you are likely to come across at GCSE are …. Alkanes are … around C17H36
The first four alkanes are gas at room temperature. All the other ones you are likely to come across at GCSE are liquids. Alkanes are solids around C17H36
As alkanes get bigger, what increases between them? What does this mean?
the intermolecular forces
this means that more energy has to be put in to break the attractions between one molecule and its neighbours
Are alkanes reactive?
they are very unreactive because they have strong covalent bonds
Where do you find alkanes?
in crude oil
What is the written equation for the complete combustion of any alkane? When does complete combustion occur?
alkane + oxygen → carbon dioxide + water (+ energy)
this occurs when there is enough oxygen
Complete combustion releases … and only produces two …. When there’s … and combustion is complete, the gas burns with a … flame.
Complete combustion releases lots of energy and only produces two harmless waste products (carbon dioxide and water). When there’s plenty of oxygen and combustion is complete, the gas burns with a clear blue flame.
Explain why the combustion of hydrocarbon fuels is believed to by some scientists to be responsible for global warming
Include one effect of global warming in your answer
carbon dioxide and water vapour are one of the main greenhouse gases
it rises into the atmosphere but traps all the air so it is re-emmited back out again
one effect of global warming is the melting of ice caps which causes flooding
What is the balanced equation for the complete combustion of methane?
methane + oxygen → carbon dioxide + water
CH4 + 2O2 → CO2 + 2H2O
When does incomplete combustion of an alkane occur?
when there isn’ enough oxygen
Is incomplete combustion of an alkane safe? Why?
no
carbon monoxide or carbon (soot) is produced instead of carbon dioxide
State three things that carbon monoxide is
colourless
odourless
very poisonous
Why is carbon monoxode poisonous?
it combines with haemoglobin (the molecule that carries oxygen in the blood stream), preventing it from carrying oxygen
you are made ill, or even die, because not enough oxygen gets to the cells in your body
What type of reaction is making haloalkanes by reacting chlorine or bromine with alkanes? Expalin this
a substitution reaction
a hydrogen atom from the alkane is substituted (replaced) by chlorine or bromine
A mixture of bromine and methane is the colour … because …. If exposed to U.V. light, such as sunlight, what is formed and what happens to the colour?
A mixture of bromine and methane is the colour brown because of the presence of the bromine. If exposed to U.V. light, such as sunlight, bromomethane and hydrogen bromide gas is formed and the colour is lost
Alkenes are … but are different to alkanes because they have … bonds
Alkanes are hydrocarbons but are different to alkanes because they have C=C carbon double bonds
What colour is the flame in incomplete combustion?
smoky yellow
What is the balanced equation for the incomplete combustion of methane?
methane + oxygen → carbon monoxide + water
2CH4(g) + 3O2(g) → 2CO(g) + 4H2O(l)
What is made when halogens react with alkanes?
haloalkanes
Halogens, such as chlorine and bromine react with alkanes in the presence of … (e.g. …). This is called …
Halogens, such as chlorine and bromine, react with alkanes in the presence of ultra-violet light (e.g.sunlight). This is called photolysis
What is the displayed formula for ethene?
What is the displayed formula for propene?
What is the displayed formula for butene?
Halogens have … bonds that are … to break by U.V. light
Halogens have weak bonds that are easy to break by U.V. light
Do alkenes undergo photolysis?
No, only alkanes
Alkenes undergo … reactions. What does this entail?
Alkenes undergo addition reactions
part of the double bond breaks and the electrons are used to join other atoms onto the two carbon atoms
What is often used to test for carbon-cabon double bonds? Explain how this test works
the reaction between bromine and alkenes is often used
when you shake an alkene with orange bromine solution (‘bromine water’), the solution becomes colourless
this is because the bromine molecules, which are orange, are reacting with the alkened to make dibromoalkane, which is colourless
Are alkenes saturated or unsaturated?
unsaturated
this is because they contian a double carbon bond
How do you obtain alkenes?
from cracking alkanes
What is cracking?
the process where a long chain alkane is broken down from larger molecules into smaller molecules; more useful alkanes and alkenes
What are the first three alkenes?
ethene: C2H4
propene: C3H6
butene: C4H8
What is the general formula for alkenes?
C2H2n
The first four alkenes are … at room temperature. All the other ones you are likely to come across at GCSE are …. Alkenes are … around C17H34
The first four alkenes are gas at room temperature. All the other ones you are likely to come across at GCSE are liquids. Alkenes are solid around C17H34
In the complete combustion of alkenes, what is formed?
carbon dioxide and water
What is made when halogens react with alkenes?
haloalkenes
For bromine to add to alkenes, heat or a catalyst is/isn’t needed
For bromine to add to alkenes, heat or a catalyst isn’t needed
What do alcohols belong to?
a homologous series
What group do alcoholes all contain?
an -OH group
e.g. ethanol is C2H5OH
How are alcohols bonded?
they are covalently bonded onto a carbon chain
What is the familiar alcohol in drinks? What is its chemical formula?
ethanol - C2H5OH
What is the general formula for alcohols?
CnH2n+1OH
The best way to make ethanol often depends on …
The best way to make ethanol often depends on what resource is most easily available - oil or sugar
What is the equation for the hydration of ethene?
What are the two different methods of producing ethanol?
fermentation
hydration of ethene
Is yeast a chemical?
yeast is not a chemical but a microorganism
N.B. do not write it as a molecule in a formula but instead out it over the arrow
How is ethanol produced by fermentation?
yeast is added to a sugar or starch solution and left for several days in the warm (30-40oC) with the absence of air (anaerobic conditions)
enzymes (biological catalysts) in the yeast convert the sugar into ethanol and carbon dioxide
Explain the biochemistry of how ethanol is made by fermentation
ordinary sugar (sucrose) is split into two smaller sugars: glucose and fructose
glucose and fructose have the same molecular fomulae, but are differet structures (they are isomers)
enzymes in the yeast convert these sugars into ethanol and water
- C12H22O11 (aq) (sucrose) + H2O (l) (water) → C6H12O6 (aq) (glucose) + C6H12O6 (aq) (fructose)
- C6H12O6 (aq) (glucose) → 2C2H5OH (aq) (zymase) + 2CO2 (g) (carbon dioxide)
Is it possible to make pure ethanol by fermentation? Why?
no, it is impossible
yeast is killed by +15% of alcohol in the mixture
instead, the alcohol is purified by fractional distillation - this takes advantage of the difference in boiling point between ethanol (78oC) and water (100oC)
the liquid distilling over 78oC is 96% pure ethanol and the rest is water - it is impossible to remove this last 4& of water by simple distillation
Which resources are used in the production of ethanol by fermentation?
renewable resources
sugar beet or sugar cane, corn and other starchy materials
Which type of process is used in the production of ethanol by fermentation?
a batch process
everything is mixed together in a reaction vessel, then left for a several days
that batch is removed and a new reaction is set up
this is inefficient
What is the rate of reaction of the production of ethanol by fermentation?
very slow, taking several days for each batch
What is the quality of ethanol produced by fermentation?
very impure - needs further processing
not very concentrated - needs to be distilled to increase its strength (as in whiskey distilleries)
What are the reaction conditions used in the production of ethanol by fermentation?
gentle temperatures (about 30oC)
simple, cheap equipment
ordinary pressures
Is sugarand yeast easily grown?
yes
sugar (sugar cane) is grown as a major crops in several parts of the world, including poorer countries