topic 9 - organic chem Flashcards
alkane
saturated hydrocarbon
general formula alkane
Cn H2n+2
what does saturated mean
the atoms have formed bonds with as many other atoms as they can
prefix for 1 carbon atom
meth
prefix for 2 carbon atom
eth
prefix for 3 carbon atom
prop
prefix for 4 carbon atom
but
formula methane
CH4
formula ethane
C2H6
formula propane
C3H8
formula butane
C4H10
alkene
unsaturated hydrocarbons with a double carbon bond
general formula alkene
Cn H2n
functional group alkenes
one double carbon bond C = C
formula ethene
C2H4
H H \ / C=C / \ H H
formula propene
C3H6
formula but-1-ene (structure)
C4H8
but-1-ene means that the unsaturated point is at position 1
H H H \ I I C=C - C - C - H / I I I H H H H
formula but-2-ene (structure)
C4H8
but-2-ene means that the unsaturated point is at position 2
H H H
I I I
H - C- C=C - C - H
I I I
H H H
how do you test for an alkene or alkane
shake substance with bromine water
- if bromine water is bleached an alkene is present
alkanes don’t react with bromine water because they don’t have double bonds
why does the bromine water test work
if the water bleaches it is because an addition reaction has occurred - bromine has been added to the double bond
eg. ethene + bromine water (structural diagram)
H H H Br
\ / I I
C=C + Br2 -> H - C - C - H
/ \ I I
H H Br H
what happens when an alkane or alkene is burnt
in complete combustion, alkenes and alkanes react with oxygen to produce CO2 and H2O
ethane + oxygen gives what
balanced equation too
ethane + oxygen -> carbon dioxide + water
2C2H6 + 7O2 -> 4CO2 + 6H2O
alcohol general formula
Cn H2n+1 OH
function group alcohols
OH (hydroxyl)
methanol formula
CH3OH
ethanol
C2H5OH
propanol
C3H7OH
butanol
C4H9OH
describe the dehydration of alcohols
heat and ALCOHOL with an ACID CATALYST to form an ALKENE and WATER
fermentation
the process of using yeast to convert a type of carbohydrate (sugars) into alcohol
for example symbol equation of glucose fermentation with yeast to produce ethanol and carbon dioxide (balanced)
C6H12O6 –(yeast)——> 2C2H5OH + 2CO2
how do you make ethanol in a lab (using fermentation) (5)
using FERMENTATION
1) mix yeast and carbohydrate solution in a clean container which is sealed and left in a warm place
2) keep the mixture between 30°C and 40°C (this is because fermentation happens fastest at this temperature)
3) mixture should be kept in anaerobic conditions - if oxygen were present it would convert the ethanol to ethanoic acid
4) when the concentration of alcohol reaches 10-20%, fermentation stops as the yeast is killed by the alcohol
5) yeast falls to the bottom and ethanol solution can be collected from the top
how to produce a more concentrated ethanol solution
fractional distillation
describe fractional distillation of ethanol solution
to make a concentration of above 20%, fractional distillation has to be used
ethanol’s boiling point is lower than water’s so when the fermentation mixture is heated ethanol evaporates first, leaving the water a liquid
a liebig condenser condenses the ethanol and the more concentrated ethanol can be collected in a separate flask
why can alcohols be used as fueld
when they burn, they release energy
how to test for the best alcohol (7)
1) place alcohol in spirit burner and measure the mass of the two using a mass balance
2) measure 100cm^3 distilled water into a copper calorimeter
3) insulate the calorimeter using a draught excluder and an insulating lid once the thermometer is inside
4) take initial temperature of the water, place burner underneath and light wick
5) stir water and once it reaches 20°C blow out the burner
6) immediately reweight burner and fuel
7) repeat with different alcohols as fuels
how do you compare the efficiency of fuels
more efficient fuels - less alcohol is needed to raise the temperature of the water by a given amount
general formula carboxylic acids
Cn-1 H 2n-1 COOH
functional group carboxylic acids
COOH (carboxyl)
properties of carboxylic acids
react like typical acids
- in solution they can ionise to release H+ ions
- they only partially dissociate so are classed as weak acids
how are carboxylic acids produced from alcohols
through oxidation, using an oxidising agent
for example: show the structural equation for ethanol into ethanoic acid
H H H O
I I I //
H - C - C - O - H ——–> H - C - C
I I oxidising I \
H H agent H O - H
how do the names change (eg methanol become what acid)
methanol - methanoic acid
ethanol - ethanoic acid
propanol - propanoic acid
butanol - butanoic acid
formula methanoic acid
HCOOH
formula ethanoic acid
CH3COOH
formula propanoic acid
C2H5COOH
formula butanoic acid
C3H7COOH
homologous series
all members of a homologous series have the same functional group which means they all have similar reactions
(if you know how one member of a homologous series reacts, you can predict how the others will react too)
