organic chemistry Flashcards
what is crude oil?
Crude oil a fossil fuel formed mostly from dead sea creatures (eg. plankton). It is the source of many fuels and other chemicals such as plastic.
what is crude oil a mixture of
hydrocarbons
what are hydrocarbons?
compounds made up of only hydrogen and carbon atoms
what are alkanes made up of?
a chain of hydrocarbons
fill in a table for the first 4 alkanes. include the number of carbons in the chain, displayed formula, the molecular formula and the name.
google it
what’s the general formula for alkanes?
CnH2n+2
take the number of C atoms, x2 and +2 to get H atoms
how do the properties of alkanes change?
the properties of alkanes change with the number of carbons in the molecule
what happens as the number of C atoms increases in an alkane
- boiling point increases
- viscosity increases
- flammability decreases
- amount of soot/ smoke released when burned increases
why does fractional distillation take place?
crude oil is not useful as a mixture of hydrocarbons. it needs to be seperated into different fractions of alkanes and different chain lengths.
describe the method of fractional distillation in 6 steps.
- the crude oil is heated to 350°c
- most of the alkanes evaporate
- the different alkane vapours rise up the distillation column (the longest chains flow down the bottom)
- the column gets colder further up
5.when the alkane/ fraction cools down below its boiling point, it condenses back into a liquid and flows through a pipe - the smallest alkanes (eg methane) stay as gases and leave the column at the very top.
what happens when alkanes are burned in a plentiful supply of oxygen?
the carbon oxidises into carbon dioxide and the hydrogen oxidises into water. this is called complete combustion.
what does the complete combustion of an alkane produce?
carbon dioxide + water
what happens when alkanes are burned without enough oxygen?
incomplete combustion takes place and carbon monoxide or soot is made.
long alkanes can be split into a _______ _____________ reaction called cracking
thermal decomposition
long alkanes, which are in ____ demand but _____ supply, are cracked to make shorter alkanes, which are ____ in demand but _____ supply.
long alkanes, which are low in demand but high supply are cracked to make shorter alkanes which are high in demand but low in supply
catalytic cracking
high temperature & the long alkane vapours passed over a catalyst.
steam cracking
long alkane mixed with very high temp & high pressure steam
what are the 2 products of cracking an alkane?
1 alkane and 1 alkene
draw the cracking of C9H20
makes C6H14 and C3H6
alkanes are [saturated / unsaturated]
alkenes are [saturated / unsaturated]
alkanes are saturated, alkenes are unsaturated
what can the smaller alkanes be used for after cracking?
better fuels. eg. gasoline, kerosene jet fuel, diesel heating oil
draw a table of alkenes 2-5 including the number of C atoms, displayed formula, molecular formula and the name.
google it
what’s the general formula for an alkene
CnH2n
take the number of C atoms, x2 to get number of H atoms
what happens in addition reactions?
the double bond breaks open and atoms are added to the 2 carbon atoms that were part of the double bond
what are polymers?
long chain molecules formed by many monomers bonded together
how are addition polymers made?
when many alkenes join together.
the c=c bond opens up and each c atom makes a new bond to the next molecule
name the polymers based off the monomers:
ethene=
propene=
styrene=
polyethene
polypropene
polystyrene
draw the formula for the 3 polymers:
polyethene
polychloroethene
polypropene
knowunity
what’s the step by step tutorial for drawing a polymer?
draw the monomer, but:
- make the c=c a c-c
- add large brackets
- bring the lines out past the brackets
- add ‘n’
what are alcohols?
a series of organic compounds with the functional group -O-H and names ending in -ol
draw a table for the first 4 alcohols including the number of carbons in the chain, the displayed formula, the molecular formula and the name
knowunity
what are alcohols used as
- fuels
- solvents
- disinfectants
- alcohol (ethanol)
how do alcohols have a neutral pH
they dissolve well in water
what are the products of alcohols combusting with oxygen?
CO2 and water
what happens when sodium and alcohol react?
sodium reacts with alcohol like it does with water, just less violently. creates a salt and hydrogen gas
what do alcohols turn into when reacting with oxidising agents?
compounds called carboxylic acids
how can ethanol be made?
by fermentation (yeast, no oxygen, 25°c). once complete, filter out the yeast and distill the water-ethanol mixture
what are carboxylic acids?
a series of acidic compounds with the functional group (-COOH)
draw a table of the first 4 carboxylic acids including the number of C atoms, displayed formula, molecular formula and name.
knowunity
why don’t carboxylic acids release as many H+ ions as other acids?
it’s a weak acid, meaning it doesn’t fully dissociate in water
what’s the produce of carboxylic acid + a carbonate?
water, a salt, CO2
what’s the products of carboxylic acid + a metal?
hydrogen and a salt
what is an ester
a molecule formed by reacting an alcohol with a carboxylic acid.
how can you help esters react with alcohol?
the mixture is warmed and concentrated sulfuric acid is added as a catalyst.
how can esters be recognised? (name, formula, functional group)
name: ……yl and …..oate
formula: ….COO….
functional group: C bonded with =O and -O
turn ethanol and ethanoic acid into an ester
knowunity
what are esters used for and why?
they’re used in flavourings and perfumes as they have a strong smell and taste, and are volatile meaning they evaporate easily so they’re easier to smell
how do condesation polymers form?
when monomers react and join together end to end.
what is made each time 2 monomers join in a condensation monomer?
a small molecule like H2O
what’s the only way a condensation polymer can work?
if the monomers have 2 functional groups
shorten the condensation polymer chain shown on knowunity
knowunity
4 examples of condensation polymers in nature
- DNA
- starch
- cellulose
- protein
what are the 4 nucleotides in DNA
A, T, C, G
what is a nucleotide
a monomer that makes up DNA
what are dna molecules made of
2 polymer chains made from 4 different monomers called nucleotides
