Chemistry Basic Concepts and Hydrocarbons

A series of organic compounds with the same functional group but with each successive member differing by CH₂

The part of the organic molecule responsible for its chemical reactions

A compound of hydrogen and carbon only

• Saturated: Has single bonds only
• Unsaturated: contains a carbon-carbon double bond

• 1. Methane
• 2. Ethane
• 3. Propane
• 4. Butane
• 5. Pentane
• 6. Hexane
• 7. Heptane
• 8. Octane
• 9. Nonane
• 10. Decane

• Alkane C-C
• Alkene C=C
• Halogenoalkane F, Cl, Br, I
• Alcohol -OH
• Aldehyde -CHO
• Ketone C-CO-C
• Carboxylic Acid -COOH

• Empirical formula: simplest whole number ratio
• Molecular formula: actual number of atoms of each element in a molecule
• General formula: simplest algebraic formula e.g. C_nH_2n+2
• Displayed formula: shows relative positioning of all the atoms
• Structural formula: shows minimal detail for the arrangement e.g. CH₃CH₂CH₂Br
• Skeletal formula: simplified organic formula

Molecules with the same molecular formula but with different structural arrangements of atoms

Compounds with the same structural formula but with a different arrangement of the atoms in space

A type of stereoisomerism in which different groups attached to each carbon of a C=C bond may be arranged differently in space because of restricted rotation of the C=C bond

A special type of E/Z isomerism in which there is a non-hydrogen group and hydrogen on each C of a C=C bond. Cis, H on same side

• Homolytic: the breaking of a covalent bond, with one of the bonded electrons going to each atom, forming two radicals. X-Y -> X. + Y.
• Heterolytic: the breaking of a covalent bond with both of the bonded electrons going to one of the atoms. X-Y -> X⁺ + Y-

• Nucleophile: electron pair donor
• Electrophile: electron pair acceptor

A species with an unpaired electron

• A reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule
• E.g. Ethene + Bromine -> 1,2-dibromoethane

• A reaction in which an atom or group of atoms is replaced with a different atom or group of atoms
• E.g. Bromoethane + OH- -> Ethanol + Br-

• Mixture of over 150 different hydrocarbons
• Fractional distillation: the separation of the components in a liquid mixture into fractions which differ in boiling points

• Chain length: increasing chain length, increases boiling point, more van der Waals' forces between the molecules in longer chains, takes more energy to separate them
• Branching: same molecular mass, unbranched molecules have a higher boiling point, more points of contact for van der Waals' forces

• burning in a plentiful supply of oxygen
• carbon dioxide and water is formed

• burning in a limited supply of oxygen
• such as in an internal combustion engine
• carbon monoxide is formed

• the breaking down of long-chained saturated hydrocarbons to form a mixture of shorter-chained alkanes and alkenes
• catalytic cracking: uses a zeolite catalyst at about 450 degrees
• many different possible equations for cracking
• Branched alkanes: unbranched alkanes can be converted into branched alkanes using isomerisation
• Cyclic hydrocarbons: reforming, alphatic hydrocarbons being converted into cyclic or aromatic hydrocarbons

• a type of substitution reaction in which a radical replaces a different atom or group of atoms
• UV radiation needs to be present
• covalent bonds are broken by homolytc fission to form radicals with an unpaired electron
• Mechanism: initiation, propagation, termination
• Limitations: mixture of products are formed

• alkenes and cycloalkenes are unsaturated hydrocarbons (have atleast one C=C double bond)
• General formula: C_nH_2n

• made up from a sigma bond and a pi bond
• Formation of the double bond: sigma bond is formed between two carbon atoms by the overlap of orbitals, a pi bond is formed above and below the plane of the carbon atoms by sideways overlap off p-orbitals, the pi bond fixes the carbon atoms in place
• pi-bond prevents rotation of the bond

• 3 regions of electron density around each carbon atom in the double bond
• the pairs of electrons repel each other as far apart as possible to minimise repulsions
• trigonal planar shape: bond angles 120 degrees
• ethane is a flat planar molecule

• Hydrogenation: addition of hydrogen gas, catalyst of nickel, temperature 150^oC
• Halogenation: addition of halogens, room temperature
• Test for unsaturation: adding bromine to a sample, if it contains an alkene the colour changes from orange to colourless

• produing a halogenoalkane
• Unsymetrical alkenes:

• hydration of an alkene
• high temperature and pressure
• phosphoric acid catalyst

• Electrophile: electron pair acceptor
• Curly arror: movement of an electron pair