Organic chem Flashcards
What is petroleum made of
Mixture of hydrocarbons, mainly alkanes
How does fractional distillation work
Low bp at top, High bp at bottom
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Refinery gas, Petrol, Naphtha, Kerosine, Diesel, Lubricating Oil, Fuel Oil, Bitumen
Properties of Carbon
- Tetravalent
- Can bond to each other to form long chain like structures
- C-C bonds are very strong, leading to greater stability for compounds that contain it
Number of carbon atoms
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Meth
Eth
Prop
But
Pent
Hex
Hept
Oct
Non
Dec
Prefixes
Methyl
Ethyl
Propyl
Butyl
Functional group of carboxyl acids are always where?
On first carbon atom (so no need to state in naming)
What are isomers
2 or more compounds with the same molecular formula but exist in different forms due to a difference in arrangement of the atoms in the molecule
Types of isomers
Structural, Positional, Functional
When naming halogenoalkanes with substituents, write the halogen first
eg. 1-bromo 2-methylbutane
How to name the halogens
Bromo Fluoro Chloro
Types of organic reactions
- Addition
- 2 reactants become 1 product - Elimination
- 1 reactant + base –> 2 products
- number of products > number of reactants
(eg. 1-bromobutane take out the bromine and replace with H) - Substitution
- 2 reactants exchange parts to form two new products
Complete vs Incomplete combustion
Complete will produce CO2 but incomplete (limiting reactant is O2) produces CO
Saturated vs unsaturated
Saturated is C-C bonds
Unsaturated is C=C double bonds
Alkanes general formula
Cn H2n+2
Solubility of alkanes
Insoluble in water, Soluble in organic solvents
How many alkanes are gases
First 4
First few alkenes also gases
Alkanes boiling/melting point trend
Alkanes are simple covalent molecules held tgt by weak intermolecular forces
As number of carbon atoms increase, molecular size increases and electron cloud size increase
A greater amount of energy is needed to overcome the strong intermolecular forces of attraction
Hence increasing bp/mp
Branched-chain alkanes vs Straight-chain alkanes
Branched-chain alkanes are more spherical in shape and have less surface area of contact with neighbouring molecules, leading to weaker intermolecular forces
Less energy is required to overcome these forces, hence mp/bp lower than straight-chain alkanes
Alkanes viscosity
Increases as carbon increases
Greater molecular size, flows less easily
Flammability of alkanes
As molecular size increases, bp increases so flammability decreases
As carbon atoms increase, percentage of carbon in alkanes increase, produce smokier and sootier flames due to incomplete combustion
Density of alkanes
Increases as carbon atoms increase
Chemical property of alkanes
Generally unreactive because the C-C and C-H bonds are strong and hard to break
Combustion of alkanes
HIGHLY EXOTHERMIC MAKING THEM GOOD FUELS
Forms CO2 and H2O (gas)
Incomplete combustion will form CO and carbon as soot + H2O (gas)
eq. CxHy + (x + y/4)O2 —> xCO2 + (y/2)H2O
Cracking of alkanes (product + conditions)
Produces alkenes (ALWAYS)
Conditions:
600˚C + SiO2 or Al2O3 catalyst
Substitution of alkanes (products + conditions)
Produces halogenoalkanes
Conditions: UV light and halogen
Can become multi substituted when there is excess halogen and limited alkane
How to get alkanes
From petroleum or crude oil
used as a fuel for heating etc.
Alkenes general formula
Cn H2n
Alkenes mp/bp trends
Same as alkanes
Alkanes are simple covalent molecules held tgt by weak intermolecular forces
As number of carbon atoms increase, molecular size increases and electron cloud size increase
A greater amount of energy is needed to overcome the strong intermolecular forces of attraction
Hence increasing bp/mp
Branched-chain alkanes are more spherical in shape and have less surface area of contact with neighbouring molecules, leading to weaker intermolecular forces
Less energy is required to overcome these forces, hence mp/bp lower than straight-chain alkanes
Combustion equation for all (it hink)
CxHy + (x+y/4) O2 –> xCO2 + (y/2)H2O
Alkenes vs alkanes flame/soot
Alkenes are sootier because higher % of carbon (double bonds means less hydrogen so % is higher)
Alkane reactions
Combustion
Cracking
Substitution
Alkene reactions
Combustion
Addition reactions
1. Hydrogenation
2. Bromination
3. Hydration
4. Addition polymerisation
Explain the vegetable oil and margarine thing
Hydrogenation of vegetable oil increases its mp/bp so its still kind of solid at room temp (margarine)
Vegetable oil is the alkene and margarine is the alkane
Bromination of alkenes
Add halogen to the original C=C double bond
At room temp and pressure
Need liquid bromine or bromine in tetrachloromethan (CCl4)
Alkene will decolourise the reddish brown bromine in CCl4 rapidly
Hydration of alkene (product + conditions)
Addition of steam
Produces alcohol
Phosphoric (V) acid catalyst, 300˚C and 60 atm
Alkanes vs Alkenes (reactivity, bromination, polymerisation, flame, sub/add reactions)
Alkanes
- generally unreactive
- does not react with bromine under normal conditions (need UVlight)
- does not have addition polymerisation
- less sooty flame
- substitution reactions
Alkenes
- very reactive
- bromination occurs (rapidly decolourises reddish brown bromine)
- addition polymerisation
- sootier flame
- addition reactions
Test for alkene vs alkane
Add a few drops of liquid bromine at room temperature in the absence of UV light
Alkene will rapidly decolourise the reddish-brown liquid bromine
For gases, can bubble it into liquid bromine
Hydrogenation of alkenes (products and conditions)
Produces alkanes
Add hydrogen gas
200˚C and nickel catalyst
Alcohols formula
Cn H2n+1 OH
OH does not dissociate in water because it is covalently bonded to the C atom
Alcohol vs alkane combustion
Alcohols produce less energy per unit mass (less efficient) (less exo than w alkanes)
Alcohol oxidation
Forms carboxylic acid
Need acidified potassium manganate VII (as oxidising agent) and heat under reflux
Add oxygen and remove 2 hydrogen
since its oxidation, KMnO4 will go from purple to colourless
Alcohols state
Liquids at room temp
Alcohols solubility
Soluble in water
Decreases down the homologous series
Hydroxyl group can form hydrogen bonds with water molecules
Alcohols bp + comparison to alkanes alkenes
Increases as carbon increases as molecular size increases, strength of intermolecular forces increase too
Have both van der Waals forces and hydrogen bonds which is stronger than just van der Waals forces in alkanes/alkenes hence higher bp/mp
How to produce ethanol
Hydration of ethene
or
Fermentation of glucose w yeast (produces ethanol and co2)
- C6H12O6 –> 2C2H5OH + 2CO2
- the absence of O2 (if not will become ethanoic acid and water)
Carboxylic acid formula
Cn H2n+1 COOH
Carboxylic acid solubility +compare w alcohols
Very soluble as OH can form hydrogen bonds w water
More soluble than alcohols because COOH is more polar than OH and can form stronger hydrogen bonds
Carboxylic acid mp/bp + compare w alcohol
Same explanation as alcohol
carboxylic acid has stronger hydrogen bonds between molecules than alcohol (hence greater bp/mp than alcohol)
Electrical conductivity of carboxylic acids
can dissolve in water to produce mobile ions
Carboxylic acids reaction w metals, bases, carbonates
same as acid-base etc reactions
Solubility of esters
Insoluble
What are esters used for
Sweet smelling colourless liquids
used for perfumes, food flavourings, solvents
How to form esters
Reaction between alcohol and carboxylic acid to form ester + water
strong heat and strong concentrated base
Roles of conc sulfuric acid in forming esters
Acts as a catalyst that speeds up the reaction
It is a drying agent and removes H2O as it is formed, causing the equilibrium (drive equil position to the right) to favour the forward reaction to increase yield
what is a polymer
a long chain macromolecule that is bonded tgt by many small repeat units
Types of polymers
Addition (alkenes)
- eg. Poly(ethene)
Condensation
- polyamides
- polyesters
Addition polymerisation definition + conditions
successive linking tgt of unsaturated monomers without losing any molecules or atoms to form an addition polymer
High temp, high pressure, catalyst (to break C=C double bond)
Repeat units have how many inside
ONLY 2
Monomers of polyamides + linkage name
Dicarboxylic acid + diamine (NHH one)
forms amide linkage
eg. nylon
Uses of polyamides and polyesters
polyamides: fabrics and garments
polyesters: make audio and video tapes and soft plastic bottles + fabrics
Monomers of polyesters
Dicarboxylic acid + diol (alcohol)
forms ester linkage
eg. Terylene
