TOPIC 6: ORGANIC CHEMISTRY Flashcards
Name the Nomenclature stems?
Carbon number:
1: meth-
2: eth-
3: prop-
4: but-
5: pent-
6: hex-
7: hept-
8: oct-
9: non-
10: dec-
Define Homologous series?
A homologous series is a group of organic compounds that have the same functional group and general formula.
Consecutive groups of a homologous series differ by -CH2
Prefix or suffix of an alkane?
-ane eg propane
Prefix or suffix of a branched alkane?
alkyl (-yl) eg methyl
Prefix or suffix of an alkene?
-ene eg propene
Prefix or suffix of a halogenoalkane?
chloro/bromo/iodo eg chloroethane
Prefix or suffix of alcohols?
-ol eg ethanol
Prefix or suffix of aldehydes?
-al eg ethanal
Prefix or suffix of ketones?
-one eg propanone
Prefix or suffix of cycloalkanes?
cyclo-…-ane eg cyclohexane
Prefix or suffix of carboxylic acids?
-oic acid eg ethanoic acid
What is addition?
joining two or more molecules together to form a larger molecule
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 new molecules by adding H+ and OH- derived from water
What is Oxidation?
any reaction in which a species loses electrons
What is Reduction?
any reaction in which a species gains electrons
Example of radical substitution?
radical subsititution of halogens in alkanes to make halogenoalkanes
Example of electrophillic addition?
electrophillic addition of halogens and hydrogen halides to alkenes, to make halogenoalkanes
Example of nucleophilic substitution?
nucleophilic substitution of primary halogenoalkanes with aqueous potassium hydroxide to make alcohols and with ammonia to make amines
What is a nucleophile?
Nucleophiles are electron pair donors they are often negatively charged ions that contain a lone pair of electrons and are electron rich. Nucleophiles are attracted to electron poor areas so they attack positive ions eg the C+ atom in a polar carbon-halogen bond. (nucleophilic substitution)
What is an electrophile?
Electrophiles are electron pair acceptors they are often postitively charged ions.They ar eelctron poor so they are attracted to places that are electron rich. They like to react with negative ions, atoms with lone pairs and the electron rich area around the C=C bond
What is radical?
Radicals have an unpaired electron and are very reactive. They will react with anything positive, negative or neutral.
What are isomers?
Two molecules are isomers if they have the same molecular formula but different structural formula
Name the three types of structural isomers?
- Chain isomers
- Positional isomers
- Functional group isomers
What are chain isomers?
Chain isomers are when the carbon skeleton can be arranged differently for example a straight chain or branched. These isomers have similar chemical properties but their physical properties like boiling point will be different because of the change in the shape of the molecule
What are positional isomers?
The skeleton and the functional group could be the same only with the functional group attached to another carbon atom. These also have different physical properties and the chemical properties might be different too
What are Functional Group isomers?
The same atoms can be arranged into different functional groups. These have very different physical and chemical properties eg C4H8O2 into butanoic acid and methyl propanoate
When can atoms rotate as much as they want?
Around single C-C bonds
What is the general formula for am alkane?
CnH2n+2
What is an Alkane?
An alkane is a hydrocarbon it only contains carbon and hydrogen atoms. Alkanes are saturated-all the carbon-carbon double bonds are single bonds
What is the bond fission?
The breaking of a covalent bond
What is a single covalent bond?
A shared pair of electrons between two atoms
Define Heterolytic fission
Heterolytic fission is when the bond breaks unevenly with one of the bonded atoms receiving both electrons from the bonded pair. Two different substances can be formed -a positively charged cation and a negatively charged anion.
Define Homolytic fission
Homolytic fission is when the bond breaks evenly and each bonding atom receives one electron from the bonded pair. This produces two electrically uncharged radicals that have an unpaired electron
How are Halogenoalkanes formed?
Halogens react with alkanes in photo-chemical reactions. Photo-chemical reactions are started by ultraviolet light. A hydrogen atom is substituted by chlorine or bromine. This is radical substitution
Describe the reaction mechanism initiation stage to produce radicals in radical substitution
- Initiation: Radicals are produced sunlight provides enough energy to break the CL-CL bond- this is photodissociation. The bond splits equally and each atom gets to keep one electron- this is homolytic fission. The atom becomes a highly reactive radical cl. because of its unpaired electron.
Describe the reaction mechanism propagation stage to produce radicals in radical substitution
- Propagation: During propagation reactions, radicals are used up and created in a chain reaction.
eg
1) Cl. attacks a methane molecule
2) The new methyl radical CH3 can attack another Cl2 molecule and produces a Cl. radical again
3) The new Cl. can attack another CH4 molecule, and so on,until all the Cl2 or CH4 molecules are wiped out
Describe the reaction mechanism termination stage to produce radicals in radical substitution
- Termination: In termination reactions, radicals react together to form stable molecules
1) If two free radicals join together, they make a stable molecule
2) There are heaps of possible termination reactions
What is the issue with Radical Substitution?
- if you are trying to make a particular product then the issue is that you don’t only get the product your after but a mixture of products.
- Another problem with radical substitution is that it can take place at any point along the carbon chain you get a mixture of structural isomers
Describe the process of Fractional distillation
- The crude oil (petroleum) is vaporised at about 350 degrees.
- The vaporised crude oil goes into a fractionating column and rises up through the trays. The largest hydrocarbons dont vaporise and run to the bottom and form a gooey mixture.
- As the crude oil vapour goes up the fractionating column it gets cooler.
- The alkane molecules have different chain lengths and therefore different boiling points so each fraction condenses at a different temperature.
- The hydrocarbons with the lowest boiling points don’t condense they are drawn off at the top of the column.
Why is cracking used?
Heavy large hydrocarbon chains are often not in demand so cracking can be used to break the C-C binds to make them into lighter and smaller hydrocarbons like petrol as they are more in demand
What are the two types of cracking
- Thermal Cracking
2. Catalytic Cracking
What is Thermal Cracking?
- Thermal Cracking takes place at a high temperature of about 1000 degrees ad high pressure of around 70 atm.
- It produces a lot of alkenes.
- These alkenes are used to make valuable products such as polymers.