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
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