Organic Chemistry

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  • Created by: Jessinoch
  • Created on: 26-04-18 17:48
What is a structural isomer?
Same molecular formula, but different structures
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What is a chain isomer?
A type of structural isomer - Compounds with the same molecular formula but different structures of the carbon skeleton
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What is a position isomer?
A type of structural isomer - Compounds with the same molecular formula but different structures due to different positions of the same functional group on the same carbon skeleton
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What is a functional group isomer?
A type of structural isomer - Compounds with the same molecular formula, but with atoms arranged to give different functional groups
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What is stereoisomerism?
Stereoisomers have the same structural formulae but have different spacial arrangements of atoms
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What is E-Z Isomerism and how does it arise?
In alkenes - there is restricted rotation around the C=C bond and there are two different groups attached to both ends of the double bond with varying priorities
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How do you undergo fractional distillation in the lab?
1. Heat flask with hydrocarbons in 2. Vapours will be produced 3. Vapour passes up fractionating column (lower bp reaches top first) 4. Thermometer at most volatile 5. Vapours with high bp condense back into flask 6. Most volatile is collected
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What are the 3 economic reasons for cracking?
1. Hydrocarbons with shorter chains more in demand 2. Uses up large hydrocarbons to make smaller ones 3. Products of cracking are more valuable than the starting materials
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What are the conditions of thermal cracking & what does it produce?
Conditions - High pressure (7000kPa), high temperature (400-900 degrees celsius) - produces mostly alkenes & sometimes hydrogen
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What are the conditions of catalytic cracking & what does it produce?
Conditions - Low pressure, high temperature (450 degrees celsius), zeolite catalyst - Produces branched and cyclic alkanes & aromatic hydrocarbons
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What is the process of neutralising sulphur oxide compounds?
Flue Gas Desulphurisation - SO2 + CaO -> CaSO3 (used to make plasterboard)
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How are nitrogen oxides formed in the engine of a car and what causes them?
N2 + O2 -> 2NO or N2 + 2O2 -> 2NO2 - high temperatures & sparks
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What are the 5 pollutants and environmental consequences with them?
1. Nitrogen oxides (toxic/acidic gas formed/acid rain) 2. Carbon monoxide (toxic) 3. Carbon dioxide (global warming) 4. Unburnt hydrocarbons (formation of smog) 5. Soot (global dimming & respiratory problems)
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How is carbon and nitrogen oxides used up in catalytic converters?
2CO + 2NO -> 2CO2 + N2
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What are catalytic converts made from & what do they look like?
Metals like platinum, palladium and rhodium - the metals coat the catalyst in a ceramic honeycomb to provide a large surface area
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Free Radical Substitution
Initiation: X2 -> 2X· Propagation: (1) CH3 + X· -> HX + ·CH3 (2) ·CH3 + X2 -> CH3X + X· Termination: Two free radicals added together (always written in structural formulae)
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Nucleophilic Substitution
(Halogenoalkanes) Nucleophiles: :OH- (KOH/NaOH, aqueous solution, heat under reflux), :CN- (KCN in aqueous ethanol, heat under reflux), :NH3 (in ethanol, heat under pressure)
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Which is the strongest C-X bond from C-F to C-I?
C-F is the strongest (most electronegative difference)
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Elimination 1
(Halogenoalkane -> Alkene) Reagents: potassium/sodium hydroxide (acts as a base) Conditions: In ethanol, heat
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Ozone Chemistry
(1) Cl· + O3 -> ClO· + O2 (2) ClO· + O3 -> 2O2 + Cl· Overall Equation: 2O3 -> 3O2
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Why are HFCs now used instead of ClFCs?
Does not contain the C-Cl bonds & the C-F bond is stronger than the C-Cl bond, therefore not affected by UV
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What is the general formula of an alkane?
CnH2n+2
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What is the general formula of an alkene?
CnH2n
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Electrophilic Addition
(Alkenes) Br2 (room temperature), HCl/HBr (room temperature), H2SO4 (room temperature) (& then reacts again in a warm mixture of water to reform H2SO4 and make an alcohol)
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Test for Alkenes
1. Add compound to bromine water 2. If decolourises then a double bond is present
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Describe poly(chloroethene)
Waterproof, electrical insulator, rigid in pure form due to strong intermolecular bonding btwn polymer chains prevents from moving over eachother, used to make guttering/window frame coverings - imf weakened when plasticiser added giving flexibility
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Oxidation of Primary Alcohols
[PARTIAL] Primary Alchohol -> Aldehyde (limited amount potassium dichromate sol & dilute sulphuric acid, warm gently, distil) [FULL] Primary Alcohol -> Carboxylic Acid (Excess Potassium dichromate sol & dilute sulphuric acid, heat under reflux)
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Oxidation of Secondary Alcohols
Secondary Alcohol -> Ketone (potassium dichromate sol & dilute sulphuric acid, heat under reflux)
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Oxidation of Tertiary Alcohols
Cannot be oxidised as there is no hydrogen atom bonded to the carbon with OH group
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How can you distinguish between aldehydes & ketones?
(1) Tollen's Reagent (Ag(NH3))2+), heat gently, silver mirror formed with aldehydes (2) Fehling's Solution with blue Cu2+ ions heat gently, aldehydes only turn from blue sol -> red ppt
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How would you test for the presence of a carboxylic acid?
1. Add sodium carbonate 2. It will fizz & produce CO2
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What reaction forms alcohol -> alkene
Acid Catalysed Elimination - concentrated sulphuric or phosphoric acid to act as a dehydrating agent/catalyst, warm under reflux
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Fermentation to form ethanol
C6H12O6 -> 2CH3CH2OH + 2CO2 Conditions: Yeast, anaerobic, 30-40 degrees temp Advantages: Sugar is renewable, low level tech production, cheap equipment Disadvantages: Batch process, not a pure product, depletes land used for growing food crops
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Hydration of ethene to form ethanol
CH2=CH2(g) + H2O(g) -> CH3CH2OH(l) C: High temp (300 degrees), high pressure (70atm), strong acidic catalyst (H3PO4) Pros: faster reaction, purer product, continuous process Cons: high tech equipment, ethene non-renewable, high energy costs
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What is optical isomerism?
Occurs in carbon compounds with 4 different groups of atoms attached to a central carbon
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What are enantiomers?
Two compounds that are optical isomers of each other, they have similar physical and chemical properties but they rotate plane polarised light in different directions
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What is a racemic mixture?
A mixture of equal amounts of the two optical isomers - will not rotate plane polarised light
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Reduction of Carbonyls
Nucleophilic Addition: Carbonyls -> Alcohols (NaBH4/LiAlH4, room temperature & pressure)
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Catalytic Hydrogenation
Carbonyls -> Alcohols (Hydrogen and nickel catalyst, high pressure)
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Formation of Hydroxynitriles
Nucleophilic Addition: Carbonyl -> Hydroxynitrile (NaCN and dilute sulphuric acid, room temperature & pressure)
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Acid + Metal
Salt + Hydrogen
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Acid + Alkali
Salt + Water
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Acid + Carbonate
Salt + Carbon Dioxide + Water
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How is an ester formed?
Carboxylic Acid + Alcohol -> Ester and Water (reversible, heat under reflux, acid catalyst of H2SO4)
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What are the uses of esters?
1. Perfumes & flavourings 2. Solvents for polar organic substances 3. Plasticisers for polymers
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Hydrolysis of Esters
With Acid: dilute acid, heat under reflux, reverse reaction of ester formation With Sodium Hydroxide: dilute sodium hydroxide, heat under reflux, forms a salt and an alcohol
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Acyl Chloride/Acid Anhydride + Water
Nucleophilic Addition Elimination: Forms carboxylic acid (steamy white fumes of HCl given off with acyl chloride)
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Acyl Chloride/Acid Anhydride + Alcohol
Nucleophilic Addition Elimination: Forms ester (steamy white fumes of HCl given off with acyl chloride)
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Acyl Chloride/Acid Anhydride + Ammonia
Nucleophilic Addition Elimination: Forms primary amide (white smoke of NH4Cl given off with acyl chloride)
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Acyl Chloride/Acid Anhydride + Primary Amine
Nucleophilic Addition Elimination: Forms secondary amide
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How do enthalpies of hydrogenation show thermodynamic stabilitity?
ΔH of 1 double bond is -120, therefore theoretically -120 x 3 = -360 should be the ΔH for benzene, however it is actually less due to the pi electrons being delocalised in the ring, therefore benzene is more thermodynamically stable by -152kJ/mol
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Nitration of Benzene
Electrophilic Substitution: Benzene -> Nitrobenzene (conc nitric acid & conc sulphuric acid as catalyst)
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How is the electrophile formed in the nitration of benzene?
HNO3 + 2H2SO4 -> NO2+ + 2HSO4- + H3O+
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Friedel Crafts Acylation
Electrophilic Substitution: (Acyl chloride in presence of aluminium chloride catalyst, heat under reflux)
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How is the electrophile formed in Friedel Crafts Acylation?
AlCl3 + RCOCl -> RCO+ + AlCl4-
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Reducing a nitroarene
When the group on a benzene goes from NO2 -> NH2 (Equation is compound + 6[H+] -> compound + 2H2O) (Sn and HCl or Fe and HCl, heating, reduction reaction) - can also be done with catalytic hydrogenation
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What is the overall order of base strengths?
From strong to weak: Secondary Amine -> Tertiary Amines -> Primary Amines -> Ammonia -> Aromatic Amines
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Why are amine groups strong bases?
Alkyl groups are electron releasing and push electrons/their electron density towards the nitrogen atom
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Why are aromatic amines weak bases?
Lone pair of electrons on the nitrogen delocalise with the ring of electrons in the benzene ring, meaning the N is less able to accept protons
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What is the one step reaction to form amines?
Nucleophilic substitution between halogenoalkanes and ammonia - it will keep reacting
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What is the two step reaction to form amines?
1. Convert halogenalkane to nitrile with KCN in ethanol & heat under reflux (nucleophilic sub) 2. Reduce nitrile to amine using LiAlH4 in ether (nucleophilic addition) or H2 and a nickel catalyst
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What can quaternary ammonium salts be used as?
Cationic Surfactants (reduces the surface tension of liquids) used in fabric softeners, hair conditioners, etc.
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Why are poly(alkenes) non-biodegradable?
They are chemically inert due to the strong C-C and C-H bonds and their non-polar nature of the bonds.
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Why are condensation polymers biodegradable?
They can be broken down by hydrolysis due to the presence of polar bonds which attract attacking species such as nucleophiles and acids.
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What are the three ways that polymers can be disposed of?
1. Landfill 2. Incineration 3. Recycling
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What is added to an NMR spectrum to calibrate it & why?
TMS (tetramethylsilane) 1. Signal is away from others 2. Only gives one signal 3. Non-toxic 4. Inert 5. Low boiling point so can be removed from sample easily
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What solvent is added to a compound before obtaining their NMR spectrum?
CDCl3
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Card 2

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What is a chain isomer?

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A type of structural isomer - Compounds with the same molecular formula but different structures of the carbon skeleton

Card 3

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What is a position isomer?

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Preview of the front of card 3

Card 4

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What is a functional group isomer?

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Card 5

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What is stereoisomerism?

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