✅6 - Organic Chemistry I Flashcards
What is a functional group?
The group of atoms which gives an organic compound its characteristic properties and reactions
What is a hydrocarbon?
A compound of hydrogen and carbon only
What is a homologous series?
Family of compounds which all contain the same functional group and each member of there series contains one CH2 unit more than the previous member
What is a general formula?
Represents all the members of a homologous series
Why can carbon form so many compounds?
- the atoms have an exceptional ability to form chain, branches chains and rings of various sizes
- Carbon is relatively inert and unreactive when in C-C or C-H bonds
What is empirical formula?
The simplest whole number ratio of atoms in a compound
What is molecular formula?
The actual number of atoms in each molecule
What is structural formula?
Shows the arrangement of atoms carbon by carbon with the attached hydrogens and functional groups
What is skeletal formula?
Shows the bonds of the carbon skeleton only, with any functional groups
What is displayed formula?
Shows how all the atoms are arranged, and the bonds between them, drawn out
What is addition?
Joining two or more molecules together to form a larger molecule
What is polymerisation?
Joining together lots of simple molecules to form a large one
What is elimination?
When a small group of atoms breaks away from a larger molecule
What is substitution?
When one species is replaced by another
What is hydrolysis?
Splitting a molecule into two molecules by adding H+ and OH- derived from water
What is a species?
An atom, an ion, a radical or a molecule
What is a nucleophile?
An electron pair donor, often negatively charged ions or species with a lone pair
What are nucleophiles attracted to?
A delta positive Carbon
What is an electrophile?
Electron pair acceptors, positively charged ions attracted to electron rich areas
What is a radical?
A species with an unpaired electron
What are structural isomers?
The molecular formula is the same but the structural formula is different
What are chain isomers?
The carbon chain is arranaged differently
What are positional isomers?
Where the functional group is attached to a different carbon
What are functional group isomers?
The isomers have different functional groups
Can atoms rotate around a C-C bond?
Yes
What type of hydrocarbons are alkanes?
Saturated
What are the two types of fission?
Homolytic and heterolytic
What is heterolytic fission?
The bond breaks unevenly with one of the bonded atoms recieving both electons from the bonded pair
What is homolytic fission?
The bond breaks evenly and each bonding atom receives one electron from the pair
What does heterolytic fission produce?
Two ions, one + and one -
What does homolytic fission produce?
Two radicals
In what reactions do alkanes react with halogens?
Free radical substitution
What are the steps of free radical substitution?
Initiation
Propagation
Termination
What is photodissociation?
When radicals are produced by sunlight in Cl-Cl bonds
What happens in propagation reactions?
Radicals are created and used up
What can happen in propagation between methan and a chlorine radical?
Cl. + CH4 ——> CH3. + HCl
.CH3 + Cl2 ——> CH3Cl + Cl.
What happens in termination reactions?
Radicals are used up as they react with each other
What is the main problem with free radical substitution?
A mixture of products is created
What is crude oil mainly made up of?
Alkanes
What temperature is used to vaporise crude oil?
350 degrees C
Why don’t the largest hydrocarbons vaporise?
Their boiling points are too high
What happens to the vapour as it moves up the fractionating column?
It cools, and each fraction condenses at a different temperature
What happens to the hydrocarbons with the lowest boiling points?
The don’t condense, they’re drawn out as gases at the top of the column
How can the heaviest fractions be used?
They can be ‘cracked’ to form smaller molecules
What are the two types of cracking?
Thermal and catalytic
What are the conditions of thermal cracking?
1000 degrees C and high pressure (70 atm)
What does thermal cracking produce?
Alkenes and short chain alkanes.
What is the catalyst in catalytic cracking?
Zeolite (hydrated aluminosilicate)
What does catalytic cracking produce?
Aromatic hydrocarbons and motor fuels
Why is catalytic cracking more beneficial?
It cuts costs, because lower pressure and temperature can be used and the reaction is sped up by the catalyst
What can alkanes be reformed into?
Cycloalkanes and aromatic hydrocarbons
What is knocking?
Where alkanes explode of their own accord when the fuel/air mixture in the engine is compressed
What are the most likely hydrocarbons to cause knocking?
Straight chain ones
What catalysts are used for reforming?
Platinum on aluminium oxide
What state do fuels have to be in to undergo combustion reactions?
Gaseous
Why do larger alkanes produce more energy per mole?
They have more bonds to break
What are the issues with carbon monoxide?
Carbon monoxide is better at bonding with haemoglobin so less oxygen is carried around the blood stream, leading to oxygen deprivation, and this can be fatal
What are the issues with SO2 and NOx?
Acid rain can be caused by the burning of fuels that contain sulfur, as the sulfur dioxide can be converted to sulfuric acid.
Oxides of Nitrogen can also cause acid rain as they are converted into nitric acid
What is the main issue with fossil fuels?
They are non-renewable
What biofuels are available?
Bioethanol
Biodiesel
Biogas
How is bioethanol made?
By the fermentation of sugar from crops sch as maize
How is diodiesel made?
By refining renewable fats and oils such as vegetable oils
How is biogas made?
Produced by the breakdown of organic waste matter
Why are biofuels classed as carbon neutral?
Because although they release CO2 when burnt, the plants took in CO2 as they grew.
What are the problems with biofuels?
Petrol car engines have to be modified to use the fuel and land used to grow the crops then can’t be used to grow food, an issue in developing countries
What are sigma bonds?
Single covalent bonds
When is a sigma bond formed?
When two orbitals overlap in a straight line, giving the highest possible electron density between two positive nuclei
What does the high electron density between the nuclei mean for sigma bonds?
That there is strong electrostatic attraction and so sigma bonds are the strongest
What is a pi bond?
The second part of a double bond, along with a sigma bond
How are pi bonds formed?
When two lobes of two orbitals overlap sideways - one above and one below the molecular axis
What is the electron density in a pi bond like?
Spread out, above and below the nuclei so the electrostatic attraction is weaker and they are more easily broken
How do strengths of double and single bonds compare?
A double bond is less than twice as strong as a single bond
Can double bonds rotate?
No
Why can double bonds rotate?
Because the p-orbitals overlap in pi bonds
What are Z-isomers?
When the same groups are either both above or both below the bond
What are E-isomers?
When the same groups are on opposite sides, one above and one below the double bond
How does E/Z isomerism work when all the groups are different?
The atoms with the larger atomic numbers are given priority
What are cis isomers?
When the groups are on the same side of the double bond, eg both above or both below
What are trans isomers?
When the groups are on different sides of the double bond, eg one above and one below
When is E/Z isomerism used?
When there are two high-priority groups
When is cis/trans isomerism used?
When there are two groups the same, no matter of their priority
How are dihalogenoalkanes made?
By reacting halogens with alkenes
How are alcohols made from alkenes?
Through steam hydration
How are diols made from alkenes?
Oxidation by acidified potassium dichromate
How many products are formed when hydrogen halides are added to unsymmetrical alkenes?
Two
What is Markownikoff’s rule?
The major product from addition of hydrogen halides to unsymmetrical alkenes is the one where the hydrogen adds to the carbon with the most hydrogens already attached (ie ones with alkyl groups)
What do alkenes join up to form?
Addition polymers
What are the different methods for disposing of polymers?
Waste plastics can be buried, reused or burned
When is landfill used to dispose of plastics?
When they are difficult to separate from other waste
Not are not in sufficient quantities to make separation worthwhile
Too difficult to technically recycle
How can waste plastics be reused?
They can be melted and remoulded
They can be cracked into monomers and resued again
What can the burning of waste plastics be used for?
Generating electricity
How can making polymers be made sustainable?
Use reactant molecules that are as safe and environmentally friendly as possible
Use as few other materials, eg solvents, as possible
Use renewable raw materials
Keep energy use to a minimum
What is a primary halogenoalkane?
One alkyl group attached to Carbon with X bonded
What is a tertiary halogenoalkane?
Three alkyl groups attached to Carbon with X bonded
What can halogenoalkanes be hydrolysed to form?
Alcohols
Why are iodoalkanes hydrolysed the fastest?
Iodoalkanes have the longest, weakest bonds, which are easiest to break
How can the rate of hydrolysis of halogenoalkanes be compared?
Mix halogenoalkane with ethanol
Add silver nitrate
Time how long it take for precipitate to form
Halogenoalkane + Aqueous KOH —->
Alcohol + KX
Hlaogenoalkane + CN- —->
Nitrile + X-
Halogenoalkane + NH3 —->
Amine + NH4+
Halogenoalkane + KOH + Ethanol + reflux —->
Alkene + H2O + KBr
Alcohol + PCl5 —->
Chloroalkane + HCl + POCl3
Alcohol + HBr —->
Bromoalkane + H2O
Alcohol + PI3 —->
Iodoalkane + H3PO3
Alcohol + acid catalyst + heat —->
Alkene + water
What is the simplest way to oxidise alcohols?
Burn them
What can primary alcohols be oxidised to?
Aldehydes, then carboxylic acids
What can secondary alcohols be oxidised to?
Ketones
What can tertiary alcohols be oxidised to?
Nothing - they can’t be oxidised
What is used to oxidise alcohols?
Acidified potassium dichromate
