Organic chemistry Flashcards
What are the chemical properties of Carbon?
Carbon can form rings and very long chains, which may be branched
Carbon atom has four electrons in its outer shell, so it forms four covalent bonds
The carbon-hydrogen bond is also strong (413 kJ mo1-1)
Relatively non-polar. Hydrocarbon chains form the skeleton of most organic compounds
What does molecular formula show?
Shows the actual number of atoms of each element in the molecule
How are free radicals formed?
When a covalent bond (which consists of a pair of electrons shared between two atoms) may break in such a way that one electron goes to each atom that originally formed the bond. These fragments of the original molecule - then have free radicals
What are the types of functional groups? What are the prefixes?
Alkanes (-ane)
Alkenes (-ene)
Halogenalkanes
Alcohols (-ol)
Aldehydes (-al)
Ketones (-one)
Carboxylic Acid (-ioc acid)
What is a functional group?
A reactive group
What is the function of the IUPAC?
This is an international organisation of chemists that draws up standards so char chemists throughout the world use the same conventions- like a universal language of chemistry
What does the systematic name tell us?
Systemaric names tell us abour the structures of the compounds
What does IUPAC stand for?
International Union of Pure and Applied Chemistry
What is the root name for (each numb. of carbon)?
1 Carbon - Meth
2 Carbon - Eth
3 Carbon - Prop
4 Carbon - But
5 Carbon - Pent
6 Carbon - Hex
What is a homologous series?
is a family or organic compounds with the same functional group, but different carbon chain length.
What are isomers?
are molecules that have the same molecular formula but whose atoms are arranged differently
What are the types of isomerism?
structural isomerism
stereo-isomeris
What are structural isomers?
having the same molecular formula but different structural formulae
What are the three types of structural isomers? What are they like?
Positional Isomers - the same functional groups attached to the main chain at different points.
Functional group isomerism -functional groups that are different
Chain isomerism - a different arrangement of the hydrocarbon chain.
What are stereoisomerism?
is where two (or more) compounds have the same structural formula. They differ in the arrangement of the bonds in space
What are the types of stereoisomerism?
E-Z isomerism
Optical Isomerism
What does E-Z isomerism tell you?
E-Z isomerism tells us about the positions of substituents at either side of a carbon-carbon double bond.
Same side of the bond - Z (cis)
Opposite side - E (trans)
What can’t you convert E - isomers to Z - isomers or vice versa?
This is because substituted groups joined by a single bond can rotate around the single bond, so there are no isomers. But there is no rotation around a double bond
What are the physical properties of an alkane?
[Polarity]
Have weak inter-molecular forces between their molecules and are van der walls ( The larger the molecule the larger the van der walls)
They are non-polar because of their electronegativies are similar
[Boiling Point]
Boiling points of alkanes increase as the chain length increases
Short chains tend to be gases at room temperature but at chain length they tend to be solid
Alkanes with branched chains have lower melting points than straight chain alkanes with the same number of carbon atoms - because they cannot pack together as closely as unbranched chains and so the van der Waals forces are not so effective
[Solubility]
Alkanes are insoluble in water - This is because water molecules are held together by hydrogen bonds which are much stronger than the van der Waal’s forces that act between alkane molecules
How reactive is alkanes?
They are relatively unreactive
They do not react with with acids, bases, oxidising agents or reducing agents
They burn and react with halogens when in plenty of oxygen
How is fractional distillation of crude oil done?
The crude oil is first heated in a furnace
A mixture of liquid and vapour passes into a tower that is cooler at the top than at the bottom
The vapours pass up the tower via a series of trays containing bubble caps until they arrive at a tray that is sulficiently cool (at a lower temperature than their boiling point). Then they condense to liquid
The mixture of liquids that condenses on each tray is piped off.
The shorter chain hydrocarbons condense in the trays nearer to the top of the tower, where it is cooler, because they have lower boiling points
The thick residue that collects at the base of the tower is called tar or bitumen. This fraction is often further processed to give more valuable products
How was crude oil formed?
it was formed Millions of years ago by the breakdown of plant and animal remains at the high pressures and temperatures deep below the Earth’s surface
What causes sulfer dioxide when crude oil is burnt?
small amounts of other compounds dissolved in it.These come from other elements in the original plants and animals the oil was formed from (e.g. sulfer)
What causes the formation of acid rain?
Sulphur dioxide reacts with oxygen high in the atmosphere to form Sulfur trioxide. This reacts with water in the atmosphere to form sulfuric acid.
How is thermal cracking carried out?
First heating alkanes to a high temperature,
700-1200K under high pressure, up to 7000 kPa
The carbon-carbon bonds break in such a way that one electron from the pair in the covalent bond goes to each carbon atom
Initially two shorter chains are produced, each ending in a carbon atom with an unpaired electron. These fragments are called free radicals.
Free radicals are highly reactive intermediates and react in a number of ways to form a variety of shorter chain molecules.
As there are not enough hydrogen atoms to produce two alkanes, one
of the new chains must have a C= C
What products are commonly formed by a result of Catalytic Cracking?
Products tend to be:
> Alkanes
> Cycloalkanes
> Aromatic Compounds
Commonly used to produce motor fuels
What is the physical structure of zeolites and what are there chemical properties?
They consist of silicon dioxside and aluminium oxide
They have a honeycomb structure with enormous surface area
They are acidic
Give examples of alkane fuels and there uses?
Methane
Propane - used as camping gas
Butane - Calor gas
Petrol and paraffin
What are the components of a chain reaction? When does this happen?
1) Initiation
2) Propagation
3) Termination
reaction between an alkane and halogen
Why are chlorine bad for ozone?
They act as a catalyst in the breakdown of ozone to oxygen
How does CFCs contribute the the breakdown of the ozone layer?
Chlorine free radicals are formed from CFCs because the C-Cl bond breaks homolytically in the presence of UV radiation to produce chlorine free radicals.
Ozone molecules are then attacked by
these:
Cl• + 03—>• CIO• + 02
The resulting free radicals also attack ozone and regenerate Cl•:
CIO• + 0(3) —> 20(2) + Cl•
Why is ozone important?
> Protects the Earth from the harmful exposure to too many ultraviolet (UV) rays
> Too much UV radiation causes skin cancer in people by damaging DNA
What is ozone?
a molecule made from three oxygen atoms, O(3)
Why is ozone bad for you on the ground level?
Too much ozone at ground level causes lung irritation
> degradation of paints and plastics
What is the general formula of haloalkanes?
C(n)H(2n+1)X where X is the halogen
What is the structure of a haloalkane?
alkane skelecon with one or more halogen (fluorine, chlorine, bromine, or iodine) atoms in place of hydrogen atom
What is polarity like in halogenoalkanes? Why?
They have polar bonds between carbon and halogen - because halogens are more electronegative than carbon
What are the main forces of attraction in halogenoalkanes?
Are dipole-dipole attractions and van der Waal forces
Why are halogenalkanes used in dry-cleaning fluids?
Halogenoalkanes can mix with hydrocarbons
What is the solubility of halogenalkanes like?
soluble in water
How does carbon and halogens bond enthalpies change as you go down group 7?
The bond enthalpies goes down - down the group
What factors effect how halogen-carbon bonds react?
There bond polarity
There bond enthalpy
How does bond polarity effect how haloalkanes?
Due to bonding polarity - This means that the carbon bonded to the halogen has a partial positive charge
This means that it can be attacked by reagents that are electron rich or have electron-rich areas. These are called nucleophiles
What are nucleophiles?
are reagents that attack and form bonds with positively or partially positively charged carbon atoms
Give examples of commo nucleophiles?
Hydroxide ion, -:OH
Ammonia, :NH3
the cyanide ion, -:CN.
What are the chemical properties of a nucleophile?
They are negatively charged ion or have an atom with a S- charge
Lone pair is situated on the electronegative atom
Lone pair is situated on an electronegative atom
How do nucleophiles behave when reactinng with an organic compound?
The nucleophile’s has a lone pair of electrons with which it forms a bond by donating its electrons to an electron deficient carbon atom
What happens during nucleophlic substitution?
The halogen is replaced by a nucleophile
Why is nucleophlic substitution useful?
Nucleophilic substitution reactions are useful because they are a way of introducing new functional groups into organic compounds.
Can be used to convert Halogenoalkanes: alcohols, amines, and nitriles
What happens to the halogenalkane during elimination?
hydrogen halide is eliminated from the molecule, leaving a double bond in its place so that an alkene is formed.
What condition does elimination occur between halogenalkane and hydroxide ions?
When there is high temperature and the halogenalkane is dissolved in ethanol
What condition does substitution occur between halogenalkane and hydroxide ions?
At room tempreture
When the halogenalkane is dissolved in water
What are the 3 types of haloalkanes
Primary Halogenoalkanes
Secondary Halogenoalkane
Tertiary Halogenoalkane
What types reactions does Primary Halogenoalkanes?
Substitution Reaction
What types reactions does Secondary Halogenoalkanes through?
Elimination and Nucleophlic Substitution Reaction
What types of reactions does Tertiary Halogenoalkane go through?
Elimination reaction
What elements make Chloroflurorocatbons?
Chlorine and Fluorine
What are the chemical properties of CFCs?
Very unreactive under normal conditions
What are the uses of CFCs?
The short chain ones are gases and were used as aerosol propellants
Longer chain ones are were used for dry cleaning
What is the general formula for alkenes?
C(n)H(2n)
What are the chemical properties of a alkene?
They are unsaturated hydrocarbons
Made up of carbon and hydrogen. Carbon forms a double bonds
They are more reactive than alkanes due to their double bond - therefore high concentration of electrons (high electron density) between the two carbon atoms
What can ethene be used for?
can be used as a starting material for a large range of products. including polymers such as polythene, PVC, polystyrene, and terylene fabric, as well as product.s like antifreeze and paints
What is the general formula of a alkene?
C(n)H(2n)
Why can’t double bond between alkenes rotate?
This is because the have a pi bond so they have restricted rotation
What is a pi bond?
When a p-orbital (which contains a single electron) on each carbon to overlap to form an orbital with a cloud of electron density above and below
the single bond - so the bond can no longer rotate
What are the 2 ways that ethanol can be produced? What are the difference between the 2 methods?
[Crude oil non-renewable]
Done by cracking and hydration
This reaction happens very fast
This process is continuous
[Carbohydrates renewable]
Done by fermentation and distillation
Slow rate of reaction
This process is batch
Process produces aqueous solution of ethanol is produced
Why are alcohols very important in industry?
Used as intermediates
Can be easily converted to other compounds
What can alcohols be used for?
Solvents in cosmetic
Used to manufacture drugs
How do you carry out infrared spectrometry?
1) A beam of infrared radiation containing a spread of frequencies is passed through a sample.
2) A beam of infrared radiation containing a spread of frequencies is passed through a sample.
3) The instrument plots a graph of the intensity of the radiation emerging from the sample, called the transmittance, against the frequency of radiation
4) The frequency is expressed as a wavenumber, measured in cm-1•
How do you carry out a test for an alkene?
Shake with bromine water
Orange colour disappears
How do you carry out a test for a halogenoalkane?
- add NaOH and warm
- Acidify with NHO(3)
- Add AgNO(3)
Precipitate of AgX
How do you test for alcohols?
Add acidified K(2)Cr(2)O(2)
Orange colour turns green with primary or secondary alcohols (also with aldehydes)
With tertiary alcohol nothing happens
How do you test for aldehydes?
Warm with Tollens solution or Fehlings solution
Blue colour turns to red precipitate silver mirror forms
How do you test for carboxylic acid?
Add NaHCO(3)
CO(2) given off
How does an infrared spectrometry work?
Stronger bonds vibrate faster (at higher frequency) and heavier atoms make the bond vibrate more slowly (at lower frequency). Every bond has its own unique natural frequency that is in the infrared region of the electromagnetic spectrum
When a beam of infrared is shined at through a sample. The bonds in the sample absorb energy from radiation that has the same frequency as the natural frequency of the bond. Therefore radiation that emerges from the sample will be missing the frequencies that correspond to the bonds in the sample
What is a fingerprint region?
The region between 500 cm-1 and 1500 cm-1
What are high resolution mass spectrometers?
Spectrometers that measure the atomic/molecular masses extremely accurately
Can be used to identify compounds with similar Mr
How do you test for alcohols?
(1) Add 10 drops of the alcohol to 2cm(3) of acidified potassium dichromate solution in the test tube
(2) Warm the mixture gently in the hot water bath
(3) Watch colour change:
Primary - the orange solution slowly turns green as aldehyde is formed
Secondary - the orange solution slowly turns green as a ketone is formed
Tertiary - nothing happens
What further test can you carry out to to test for alcohol?
(1) Add an excess alcohol to 2 cm(3) of acidified potassium dichromte in a round bottomed flask
(2) Set up the flask as part of the distillation apertures
(3) Gently heat the flask. The alcohol is the oxidised and the product is distilled off immediately to collect
What 2 ways can you test for aldehydes or ketone?
Fehlings and tollens
How do you carry out a test for Aldehydes and Ketones? (Fehlings) & (Tollens)
{Fehlings}
(1) Add 2 cm(3) of Fehlings or Benedicts solution to test tube
(2) Add 5 drops of the aldehyde or ketone to the test tube
(3) Put the test tube in hot water bath
Aldehyde - blue solution to give brick red perciptate
{Tollens}
(1) Put 2 cm(3) of 0.10 mol dm silver nitrate solution in a test tube
2) Add a few drops of dilute sodium hydroxide solution. A light brown precipitate should form.
3) Add drops of dilute ammonia solution untill the brown precipitate dissolves completely
4) Place the test tube in a hot water bath and add 10 drops of aldehyde or ketone
Ketone - nothing happens
Aldehydes - silver mirror forms on the walls of the test tube
How do you test for alkenes?
1) Add 2 cm(3) of solution that you want to test the test tube
2) Add 2 cm(3) of bromine water to the test tube
3) shake the test tube
If alkene is present it is orange to colourless
What is the structure of addition polymers like?
> Made up of monomers with carbon - carbon double bond
> Made from monomers
What are addition polymers made from alkanes called?
polyalkanes
