Topic 6 Flashcards
What are the different ways to represent C_2H_6
What is a homologous series?
A group of organic compounds which have the same functional group and general formula
*Consecutive members differ by CH_2
What is are functional groups?
An atom or group of atoms in an organic molecule that determines its characteristic chemical and physical properties
How do you name organic compounds using IUPAC?
IUPAC Process
- Identify the longest chain (stem name)
- Name any groups that are not part of the main chain
If more than one then put in alphabetical order - Numbering of carbon atoms is done from the end that gives the lowest numbers to the the side groups
- If there are 2 identical side groups on the same carbon atom then we use the prefix di, tri, tetra, etc.
- If there are 2 identical groups on a different carbon atoms then use the prefix di, tri, tetra, etc.
What are the different reaction types?
Addition - Joining two or molecules together to form a larger molecule
Polymerisation - Joining together lots of simple molecules to form a Giant molecule
Elimination - when a small group of atoms breaks away from a larger molecule
Substitution - when one species is replaced by another
Hydrolysis - splitting a molecule into two new molecules by adding $H^+$ and $OH^-$ dervies from water
Oxidation - any reaction in which species loses electrons
Reduction - any reactions in which species gains electrons
What are isomers?
Isomers have the same formula but different structural formula
What are the three types if isomers
- Positional Isomers
- Chain Isomers
- Functional Group Isomers
What are positional isomers
Positional Isomers
- Isomers where the functional group moves
- Different physical and chemical properties
What are chain isomers?
Chain Isomers
- Carbon skeleton changes (unbranched ⇒ branched)
- Similar chemical properties
- Physical properties change (change in molecule shape)
What are functional group isomers
Functional Group Isomers
- Same atoms rearranged into different functional groups
- Very different Chemical and Physical Properties
What changes and stays the same in stereoisomerism?
The ONLY thing that changes is SPACIAL ARRANGEMENT
Carbon chain, position of functional group and type of functional group stay the same
This is only possible due to the restricted rotation from the C=C bond
What is cis-trans isomerism?
Cis-Trans Isomerism
Requires at least one common group attached to the carbon atom
- Cis = the same groups are on the same side of the double bond
- Trans = the groups in common are on different sides of the double bond
Trans-1-bromopropene
What is E/Z Isomerism?
E/Z Isomerism
- Looks at group priority rather than group type
- Priority of a group is determined by the atomic mass
- If the higher priority groups are on different sides of the double carbon bond then its a E Isomer
- If the higher priority groups are on the same side of the carbon bond its a Z Isomer
What is a hydrocarbon?
A hydrocarbon is a molecule compound which consists of solely carbon and hydrogen molecules.
What is the general formula for alkanes?
Are alkanes saturated or unsaturated?
Alkanes and cycloalkanes are saturated because of all the carbons have 4 saturated bonds.
What is the purpose of fractional distillation?
What is cracking?
What are the different types of cracking
What is reforming?
What are the different types of reforming?
How is nitrogen oxide produced?
High pressure and temperature in the car engine cause the oxygen and sulphur / nitrogen to react
How is sulphur oxide produced?
Sulphur impurities in fossil fuels would be burned and react with oxygen when used as fuel in cars.
Why are nitrogen oxide and sulphur oxide bad?
The pollutants would rise up into the air and hen react with the water in the atmosphere created nitrogen / sulphuric acid which then damages the environment by lowering ph.
What is complete and incomplete combustion?
Why is soot and carbon monoxide dangerous?
What problem does catalytic convertors solve?
How do catalytic converters work?
What are the advantages and disadvantages of fossil fuels?
What are the advantages and disadvantages of biofuel?
What is the combustion reaction involving alkanes?
What is the reactions for free radical substitution?
What is the limitations of free radical substitution?
- Propagation step step can continue many times resulting in multiple substitution
- The conditions can be altered to favour the termination step limiting the number of substitutions
- But the termination step may produce more than one product including the desired and undesired product
What is the general formula for alkenes?
What is the difference between unsaturated and saturated hydrocarbons?
- Saturated means that there is only single carbon bonds
- Unsaturated means there is double bonds present
- Cycloalkenes
- Alkenes
What is the sigma and pi bonds and how is it related to alkenes?
- Double bond is an area of high electron density
- Susceptible to attacking from electrophiles
- Consists of a pi bond and a sigma bond
What is the addition reaction for hydrogen with alkene?
What is the addition reaction for forming di-halogenoalkanes?
What is the addition reaction for forming halogenoalkanes?
What is the addition reaction for forming alcohols?
What is the addition reaction for forming diols?
What is an electrophile?
- A species that is attracted to a negative charge.
What is homolytic fission?
What is heterolytic fission?
What is the mechanism for the electrophilic addition of hydrogen halides?
What are the mechanisms for the electrophilic addition of halogens?
- Requires 150 Temp
- Nickel Catalyst
Why do primary and secondary carbocations form?
- In an unsymmetrical double bond, the major product will always be the product which has the group (like Cl) bonded to the most stabilised carbon cation
- Primary carbocation = carbocation attached to one carbon (less stable than secondary)
- Secondary carbocation = carbocation attached to two carbons (less stable than tertiary)
- Markvnikoff’s rule
- The carbon that already had the most hydrogen atoms attached to it
- would be more likely to get more hydrogen atoms attached to it
What can polymers can be separated into?
Waste Plastics can be processed by:
- Buried and dumped in a landfill
- Reused and remolded (Recycling)
- Used for cracking
- Incinerated to release energy
How can plastics be processed (REUSE)?
Reusing Polymers
- Plastics ⇒ non-renewable oil-fractions so reusing makes sense
- Polymers (like polypropene) can be melted and remolded
- Some polymers can be cracked into monomers and used for cracking feedstock for other reactions
How can plastics be processed (BURN)?
- Plastics can be burned and used to generate electricity
- Needs to be controlled to limit toxic gas created PVC ⇒ HCl gas
- Waste gas can go through scrubber to neutralise gas and allow for base reaction
What should a polymer design take into account?
- Is the manufacturing process safe?
- What is the impact on the environment?
What are the principles of a sustainable manufacturing process?
- Reactants should be safe and eco friendly
- Minimise use of other materials (preferably ones that wont harm the environment)
- Minimise energy cost ( use a catalyst)
- Limit waste products ( danger to human life and environment)
- Make sure lifespan of polymer is appropriate for use (NO invincible plastic spoon)
What are Biodegradable polymers?
- Biodegradable polymers - polymers decompose naturally from organisms breaking down polymer
- Made from renewable raw materials like starch or oil fractions like isoprene
- However need to collect and separate normal and biodegradable plastics making them expensive
How do you classify haloalkanes?
- Depending on the number of alkyl groups joined to the C atom
- Bonded to the halogen atom
What makes haloalkanes reactive?
- Haloalkanes have a halogen with a higher electronegativity than carbon
- C-X bond is polar
- Slightly positive carbon
- Slightly negative halogen
- The polarity of the C-X bond increases as you use halogens down the group
- The carbon attracts nucleophiles
What is a nucleophile?
A species that donates a lone pair of electrons to form covalent bond with an electron-deficient atom
What is the reaction involving silver nitrate and ethanol?
- The water molecule’s polar bonds
- Is attracted to the positive carbon on the haloalkane
- C-X bond breaks forming a -OH
What is the reaction to forming alcohols?
- Haloalkane heated under reflux with potassium hydroxide
- OH- ion from -hydroxide is the nucleophile
- Which attacks the carbon
What is the reaction to produce nitriles?
- Cyanide dissolved in ethanol under reflux
- CN- ion from potassium cyanide is the nucleophile
- Extends the carbon chain
- Important to manufacture more complex compounds
What is the reaction to produce amines?
- Heated with ammonia in a sealed tube
- To trap and react with ammonia gas
- Produces primary amines
What is the reaction to produce alkenes?
- Dehalogenatioon of haloalkanes
- Using potassium hydroxide acting as base
- Donating OH- to remove the hydrogen
- Potassium forming a potassium halide
What makes haloalkanes reactive?
- Carbon-hydrogen bonds have similar electronegativities
- Bonds are non-polar
- Bond between halogen and carbon has difference in electronegativity
- Electronegativities increase down the group
- Meaning the polarity increases too
- Increasing in reactivity
What happens when haloalkanes are hydrolysed?
- Polar bonds in water is attracted to carbon atom in the haloalkane
- Haloalkane → alcohol
- RX + H2O → ROH + HX
Whats the practical for hydrolysing a haloalkane?
Hydrolysis Practical
- Ethanol used as a solvent Allowing haloalkanes and silver nitrate to mix
- Silver nitrate to react with the halide ions to form a precipitate
- Time how long it takes for a precipitate to form
- Controlling for temperatures
What are the different rates of hydrolysis for different haloalkanes?
- Iodo = Fastest, Chloro = Slowest
- Delta + charge on carbon atom is greatest
- Meaning attacking nucleophile I attracted more strongly
- BUT bond breaking requires energy
- With weaker bonds break more easily than stronger bonds
What is the different rates of hydrolysis for primary, secondary and tertiary haloalkanes?
- Tertiary = Fastest, Primary = Slowest
What is a nucleophilic substitution reaction?
- The attacking species is the nucleophile
What is the reaction between bromoethane and aqueous KOH?
- Donation of lone pair electron from O (in OH-) to C
- Forming a C-O bond
- Electrons from C-Br bond move to Br atom
- C-Br bond breaks through heterolytic fission
What is the reaction between Chloroethane and ammonia?
How do you name alcohols?
- Use the -ol suffix
- Depending on the carbon the -OH group is on you would do 2-ol or 4-ol
How do you classify alcohols?
- Depending on the number of alkyl groups joined to the carbon joined to the -OH
- Alcohols can be primary, secondary, tertiary
What is the reaction involving the combustion of alcohols?
- Alcohols are a biofuel
- Complete combustion results in carbon dioxide and water being made
- This is an Oxidisation Reaction
What are Halogenating Agents?
- Involved in the halogenation reactions
- Generally acidic
- Can react violently with bases
- Help with replacing the hydroxyl group in an alcohol molecule
How does chlorination of alcohols work?
- Phosphorus(V) chloride is a White Solid
- Vigorous reaction at room temp
- So no heat is required
-
Two additional products made
- Phosphorous Oxychloride
- Hydrogen Chloride
How does the chlorination of tertiary alcohols work?
- Due to tertiary alcohols being the least reactive out of primary and secondary
- Alcohol needs to be mixed through shaking with HCl at room temp
How do you produce bromoalkanes from alcohol?
- Two step rection
- Hydrogen Bromide formed in the first Reaction
- Which is then reacted with alcohol to form bromoalkene
- Reaction mixture warmed in alcohol
How do you produce iodoalkanes?
How do you get alkenes from alcohols?
- Heating the alcohol with concentrated phosphoric acid
- -OH group and H atom from the adjacent carbon being removed
- Forming a C=C in the carbon chain
- As well as water which reacts with the phosphoric acid used diluting the acid
What happens generally when you oxidise and alcohol?
- Loss of hydrogen from the -OH group
- Forming a C=O bond which is a carboxyl group
- Done using potassium dichromate and sulfuric acid
What happens when you oxidise a primary alcohol?
- Done using potassium dichromate and sulfuric acid
- Alcohol to aldehyde
- Oxidised further from aldehyde to carboxylic acid
- Gains an oxygen atom rather than loosing hydrogen
What happens when you oxidise a secondary ketone
- Done using potassium dichromate and sulfuric acid
- Alcohol to ketone
What is the purpose of heating under reflux?
Refluxing prevents the evaporation or catching fire of organic reactants when heating as organic reactions are slow and need time.
We use reflux for oxidation for ketones and carboxylic acid formation
How does Refluxing work?
Products of oxidation are able to still react even if they evaporate as they condense in the Liebig condenser returning to the heating flask
The heating is done electrically to avoid using flames
What is the point of distillation?
Intended to allow for incomplete oxidation, distillation to obtain aldehydes instead of carboxylic acids (distillation with addition is used)
How does distillation work?
- Only the oxidising agent is heated (reaction mixture on this diagram)
- The alcohol is slowly added and slowly oxidising
- This is so that the aldehyde immediately moves the the conical flask when it forms and condenses
Why do you need to purify organic liquids?
Organic products are far from pure and are contaminated by:
- unreacted starting materials
- other organic products
- the organic reagents used
- water
What is Solvent Extraction?
Solvent Extraction
Use a solvent to remove desired product from other substances in a reaction mixture
The solvent needs to be:
- Immiscible (not mix) with the solvent containing the desired organic product
- less soluble than the desired organic product
How does solvent extraction work?
- Reaction mixture under solvent in separating funnel
- Add chosen solvent (Forming a separate layer)
- Stopper at neck of funnel and gently shake the contents of the funnel
- Contents should settle to 2 layers
- Remove stopper and open tap (allowing lower layer to drain into flask)
- Then transfer the upper layer into another flask
