Zusammenfassung der Ressource
Unit 2 - The
World of Carbon
- Fuels
- Petrol
- made from
reforming the
naptha fraction
(fractional
distillation of
crude oil)
- hydrocarbon
- 5 to 10
carbons in a
chain
- summer - less
volatile
hydrocarbons
to stop it
evaporating
too quickly
- winter - more volatile
hydrocarbons to
make it evaporate
more quickly
- small
molecules
are more
volatile
- Petrol
Engine
- combustion of petrol
produces hot gases that
expand against parts of
the engine - causing
them to move
- waste gases -
carbon dioxide,
carbon monoxide,
nitrogen oxides &
water vapour
- Knocking
- combustion
of petrol-air
mixture is
triggered by
a spark
- fuel can
auto-ignite out of
sequence
(pre-ignition)
- reduces engine
performance
- octane number
- measure of a
fuel's ability to
resist knocking
- high octane
number less
likely to
cause
knocking
- using branched alkanes, aromatic
hydrocarbon or cycloalkanes prevents
knocking (in the past lead was used but
it was damaging to the environment)
- Reforming
- alters the arrangement of atoms in a molecule without
necessarily changing the no. of carbon atoms per mollecule
- can change straight chain alkanes into
branched-chain alkanes, cycloalkanes,
cycloalkanes & aromatic hydrocarbons
- e.g. heptane to methylbenzene
- Alternative
Fuels
- Biofuels
- fuels made from
plant or animal matter
- Ethanol
- made from the fermentation of sugars
- pros: high octane number, very clean burning, liquid
- cons: expensive, lots of land needed to grow sugar cane which some climates are unsuitable for
- Methane
- produced by the anaerobic respiration of plant & animal waste
- pros: more harmful than carbon dioxide for greenhouse effect but
when burnt converts to less harmful substances, renewable
- cons: must be stored in high pressure cylinders - dangerous in a crash
- Methanol
- produced from the reaction of methane and steam
- pros: clean burning, liquid, high octane number
- cons: very corrosive, very toxic
- Hydrogen
- made from the
electrolysis of
water
- pros: renewable, when
environmentally friendly
ways of providing
energy for electrolysis it
is completely green,
product of combustion is
water which can be
reused to make more
hydrogen
- cons: stored
under high
pressure which
is expensive
and dangerous,
is highly
flammable
- Carbon
Compounds
- Alkanes
- Cn H2n+2
- straight
chain but can
be branched
or bent
- Alkenes
- Cn H2n
- C=C bond
- when naming
count from the
side with the
C=C
- Alkynes
- Cn H2n-2
- C to C
triple
bond
- Alkanols
- alcohol, functional group OH (hydroxyl group)
- Primary Alcohols
- OH at end of the molecule
- oxidises (acidified
potassium dichromate)
into an aldehyde
- then oxidised to a carboxylic acid
- e.g. propan-1-ol to propanal to propanoic acid
- Secondary Alcohol
- OH in the middle
of the molecule
- oxidised into a ketone
- NO FURTHER REACTION
- e.g. propan-2-ol to propanone
- Tertiary Alcohol
- DOES NOT OXIDISE
- oxidising agent take the hydrogen from the OH group and the
hydrogen from the carbon attached to the OH group - tertiary
alcohols do not have a hydrogen attached to that carbon
- Aldehydes &
Ketones
- functional
group: the
carbonyl
group C=O
- Aldehydes
- known as alkanals & have the C=O group
at the end of the molecule
- Ketones
- known as alkanones & have a C=O bond in the middle of a molecule
- Carboxylic
Acids
- carboxyl
group:
COOH
- carboxyl group
always at the
end of the
molecule
- Esters
- condensation reaction or esterification: ALCOHOL = ALKANOIC ACID =/= ESTER = WATER
- alcohol is first part of name, acid is second e.g methanol = ethanoic acid = methyl ethanoate
- ester
link
- used as flavourings, chemicals & solvents
- Aromatic
Hydrocarbons
- benzene, C6H6
- delocalised electrons
make it very stable -
resistant to addition
reactions
- does not decolourise bromine solution as it has no C=C
- a benzene ring in which one of
the hydrogen atoms has been
substituted by another group is
known as the phenyl group
- Reactions
of Carbon
Compounds
- Addition
- alkenes
undergo
addition
reactions to
form
saturated
compounds
- addition of
hydrogen is
known as
hydrogenation
- addition of halogens
forms
halogenoalkanes
- addition of water is
called hydration
- Dehydration
- removal of water
- alcohols can be
converted into
alkenes by
dehydration
- Oxidation
- loss of
oxygen
- oxidising
agents
- acidified potassium
dichromate solution:
orange to green
- Tollens Reagent:
colourless to
silver mirror
- Fehlings solution:
blue to orange
- Copper (II)
oxide (solid)
- complete
oxidation is
combustion
- burning a
hydrogen
compound
in a poor
supply of
oxygen will
make a
poisonous
gas CO
- Reduction
- gain of
oxygen
- aldehydes & ketones
can be reduced back
to their corresponding
alcohol
- Polymers
- Plastics & Fibres
- addition polymers - when small
unsaturated molecules like ethene
form polymers like poly(ethane) by
addition polymerisation
- ethene is an
important
feedstock in
the
petrochemical
industry -
especially the
manufacture
of plastics
- ethene is made
from cracking of
the naptha fraction
- condensation
polymers - made
from monomers
with 2 functional
groups per
molecule
- polyesters
- contain
the ester
link
- polyester
fibre is a
thermoplastic
linear
polymer, the
polymer
chains have
weak van der
Waals forces
between
them which
can be easily
broken
- polyester resin has strong covalent cross links between
polymer chains, this forms a rigid 3D structure which is not
easily broken on heating - thermosetting plastic
- Polyamides
- formed be the
condensation of a
di-amide & a di-acid
- amines contain the amino
function group NH2
- repeating
units of
polyamides
are held
together by
amide links
- nylon is a polyamide
- it is so strong because of hydrogen bonding between the chains
- Thermosetting & Thermoplastic Plastics
- Thermoplastic
- can be melted/shaped many times
- when a thermoplastic polymer is heated the
chains are free to move away from each other
- Thermosetting
- thermosetting
polymers don't
melt due to
cross-links
between chains
so they can't
move away from
each other
- Methanal
- feedstock in the manufacture of thermosetting plastics
- steam reforms methane or coal to make synthesis gas (CO & H)
which is converted to methanol which is oxidised to methanal
- Bakelite & melamine are made from methanal
& have a 3D cross-link network structure
- Urea-methanal has many
cross-links which are
almost impossible to
separate & does not melt
on heating
- Recent Developments
- Kevlar: aromatic
polyamide, v. strong
due to rigid linear
polymer chains
joined with hydrogen
bonds, light,
waterproof, fireproof
- Poly(ethanol):
soluble in water,
used for laundry
bags in hospitals
to prevent contact
with infected
material, ester
exchange allows
for H's to be
replaced with OH's
which makes it
soluble
- Poly(ethyne):
addition
polymerisation of
ethyne molecules,
conducts
electricity when a
dopant'
- Poly(vinyl carbazole): addition polymer made from vinyl carbozole, conducts
electricity when light shines on it (photoconductivity), used for photocopiers
- Biopol: natural polyester, biodegradable
- Photodegradable low-density
poly(ethene): low-density poly(ethene) is
modified to produce a photodegradable
polymer - will degrade on exposure to
ultra-violet light
- Natural
Products
- Fats
&
Oils
- animal(lard),
vegetable(olive
oil), marine(fish
oil)
- esters made
through the
condensation
between
propane- 1, 2,
3-triol
(glycerol) &
fatty acids
- fatty acids
are saturated
or unsaturated
straight chain
carboxylic
acid e.g.
stearic acid &
oleic acid
- glycerol is a
trihydric
alcohol which
means it has
3 hydroxyl
groups & will
form 3 ester
links with 3
fatty acid
molecules
- the ester formed
from glycerol is
known as
glyceride - fats &
oils are called
triglycerides
- fats have a higher
melting point than
oils because they
are made up of
saturated fatty acid
chains which allow
for closer packing
and van der Waals
forces
- oils are made up
of unsaturated fatty
acid chains which
are bent due to the
double bonds
which prevents the
chains from
packing cloely
together
- oils can be
converted into fats
by the addition of
hydrogen across the
C=C, this is called
hardening, the
reaction uses a
nickel catalyst & is
an example of
hydrogenation
- when fats &
oils are
hydrolysed 1
mole of glycerol
& 3 moles of
fatty acids will
be produced
- Proteins
- condensation polymers of
many amino acid molecules
joined together
- amino acids have
functional groups:
carboxyl & amino
- 2 amino acids make a
dipeptide, 3 make a
tripeptide & many make
a polypeptide or a protein
- tripeptide
formation: the
peptide
(amide) link is
formed in a
reaction
between
carboxylic
acids & the
amino group
- the body can
produce most of the
amino acids needed
to make the proteins
required by the body
but some can't be
made by the body &
must be acquired
through diet -
essential amino acids
- Digestion
- during
digestion
proteins are
hydrolysed
into their
original amino
acids
- the proteins by the
body are built up
from the amino acids
in the bloodstream
- Types of
protein
- fibrous
proteins are
long & thin &
are the
major
structural
materials of
animal
tissue e.g.
keratin in
hair &
collagen in
tendons
- globular proteins have spiral chains folded in a compact shape & are involved in
maintenance & regulation of life processes e.g. hormones (insulin) & haemoglobin
- enzymes
- biological
catalysts
- specific to
substrates -
shape of
active sites
- they work
best within
narrow
temperature
& pH ranges
& outwith
these ranges
become
denatured
- Soaps
- soaps made from fat/oil by alkaline hydrolysis
- reacted with NaOH
- hydrocarbon tail dissolves other liquids
with hydrocarbon chains e.g. oil
- ionic head dissolves in the water
- negative charged
surfaces of
grease globules
repel each other