Introductory Organic Chemistry

• A hazard is something with a definitive potential to cause harm. 
• This is absolute- something either is or isn't hazardous.
• Types of hazard are: flammable, corrosive, toxic and oxidising.
• These hazards are all represented by different hazard symbols.

• Risk is the probability of a hazard causing active harm.
• This is variable- the chance of something happening depends on the conditions.
• A risk assesment identifies the hazards involved in an activity (does not reduce risk).
• Once hazards are identified, steps are taken to reduce the risk of the hazards happening.
• Risk can be reduced by using less reactive material, using lower concentrations, using electrical heating instead of a bunsen flame, wearing correct clothing. 

• Carbon is unique in its ability to form 4 covalent bonds with either other carbon atoms or non-metals.
• This is the main property that allows carbon to form so many organic covalent compounds.
• Organic compounds are part of different homologous series, where all compounds have similar physical properties, but gradually change as number of carbon atoms increases.
• They all also have the same general formula, and the same functional group(s). 

• The systematic name of an organic compound gives: the number of carbon atoms, the structure (straight, branched or ring), its homologous series, and the name of any non-carbon atoms.
• The prefix (fisrt part) of the name gives the number of carbon atoms in the longest chain.
• The suffix (second part) of the name gives the homologous series which it belongs to.
• -Ane = alkane, -oic = carboxylic acid, -al = aldehyde.

• We also have to include branches, funtional groups, and carbon=carbon double bonds in the name. 
• These are numbered in respect to the longest carbon chain, starting from the side that gives the smallest numbers.
• Multiple side chains or funtional groups are listed in alphabetical order.
• Commas separate numbers, hyphans separate words from numbers. 

Name this compound:

Answer: 1-bromo-1,2-dichlorobutane

• Alkanes are saturated hydrocarbons (contain maximum number of hydrogens), which means they only have single bonds.
• Alkanes with the same molecular formula but different structures are called structural isomers. 

• Alkanes are used as fuels. They burn in excess oxygen to produce carbon dioxide and water.
• Alkanes are produced by the fractional distillation of crude oil. Fractions are mixtures of hydrocarbons.
• Long alkanes can be cracked to yield smaller, more useful molecules (alkane forms shorter alkane and a very short alkene).
• Reforming is when long chain molecules are broken into smaller, branched or aromatic compounds (lower boiling point). 
• Reforming and cracking are thermal decompositon.

• Crude oil is a non-sustainable resource- it will eventually run out.
• Moreover, the increased use of fossil fuels is increasing CO2 emission, causing global warming.
• Alternative fuels try to reduce greenhouse gas emissions and increase sustainability.
• Hydrogen burns to make water only. It can also be combined with oxygen in a fuel cell to produce electricity.  Water is, however, a greenhouse gas.
• Also, the energy used to produce the hydrogen is from burning hydrocarbons in power plants. 

• Biofuels are made from plants, which absorb carbon dioxide from the atmosphere as they grow, and then release it when the biofuel is burned.
• Omitting the energy requirements for the manufacturing process, biofuels are more carbon neutral than coal, oil and gas.  

• Alkenes are unsaturated hydrocarbons, they contain C=C double bonds.
• The C=C consists of a sigma and a pi bond.
• In sigma bonds the electron cloud is concentrated between 2 nuclei (all single bonds).
• In pi bonds, the electron cloud is above and below the plane of the molecule.
• The pi bond does not allow rotation. 

• Geometric isomers occur due to the lack of rotation around a C=C double bond.
• Different groups can therefore be arranged on different sides of the molecule.
• E-Z system is used to name geometric isomers.
• Each group is ranked by atomic number (higher atomic number, higher rank).
• An 'E' isomer has the two highest ranked groups on opposite sides.
• A 'Z' isomer has the two highest ranked groups on the same side. 

• When burned in a limited supply of oxygen, alkanes undergo incomplete combustion and form carbon monoxide and water (oxygen is still O2).
• Carbon monoxide is odourless, invisible and toxic- it can be fatal. 

• In a substitution reaction, one atom/group is replaced with another atom/group.
• Chlorine will replace hydrogen in methane to form chloromethane.
• This is free-radical substitution.
• A free-radical is a species with an unpaired electron, such as Cl.
• This is formed from the dissociation of chlorine at about 300'C or in UV light. 
• The free-radical subsitution by chlorine is a 3 step mechanism.

• Initiation- UV light provides energy to break Cl-Cl bond, generating 2 free-radicals. The electron pair in the covalent bond is split so each Cl takes an electron with it. This is called homolytic fission.
• Propagation- a Cl reacts with a hydrogen in methane to form HCl and leaves a CH3 free-radical. The CH3 reacts with chlorine to produce chloromethane, leaving a Cl free radical.
• Termination- the combination of any of the free-radicals with eachother or with themselves produces stable molecules, eliminating the free radicals. 

• The C=C double bond in alkenes makes them very reactive, because they can react across the double bond- an addition reaction.
• This forms a single, saturated product.
• In catalytic hydrogenation, hydrogen is added to an alkene to produce an alkane at 200'C in the presence of a high surface area nickel catalyst.
• When an alkene is reacted with acidified potassium manganate, the alkene is oxidised as as addition takes place, forming a diol.
• potassium manganate changes purple to colourless.

• When bromine approaches the C=C double bond, its electron cloud shifts due to the repulsion from the dense C=C; producing an instantaneous dipole.
• The +ve part of the bromine acts as an electrophile and attracts an electron pair from the double bond, forming a C-Br bond on a carbocation, and leaving a bromide ion with an electron pair.
• The bromide ion (nucleophile) attacks the carbocation, forming another C-Br bond.
• The whole process is called electrophilic addition, because the first step is electrophilic. 

• The electrophilic addition mechanism for the addition of HBr is the same as Br2, except no initial repulsion is needed, because H-Br already has a periminant dipole. 

• In the addition of bromine to propene, a primary or a seconday carbocation can be formed, producing either 1-bromopropane or 2-bromopropane. 
• The seconday carbocation contains more methyl groups on either side, which donate electron density and stabilise the carbocation more than in a primary carbocation.
• The more stable carbocation is more likely to form, so the major product is 2-bromopropane and the minor product is 1-bromopropane. 

• If a compound contains a C=C double bond, it will decolourise bromine water.
• This mechanism is the same as the addition of bromine, however an OH- from the water can attack the carbocation instead of the bromide ion. 

• A monomer is a small molecule.
• A polymer is formed when a large number of monomers join together to form a chain.
• Alkenes undergo addition polymerisation- addition occurs across the double bond.
• A repeat unit is the monomer with the double bond replaced by a single bond and 2 side links drawn.

• Polymers are derived from crude oil, so they have high-energy production costs. They also use up non-renewable resources.
• Polymers are non-biodegradable so they forever occupy landfill space, and they burn to produce toxic gas.
• Using renewable energy reduces the use of fossil fuels, and recycling solves the issue of disposal of polymers.