Chem 2.1

Rules of NomenclatureAlkanes1. Identify the longest unbranched chain - parent chain 2. Name the stem3. Identify any side chains -  alkyl groups 4. Add name to stem as a prefix5. Put a number before the group to show which carbon the branch is on6. If there are more than one ,  name them alphabetically-e.g 4-ethyl-3-methylheptane

AlkenesPosition of double bond must be stated.e.g but-2-enedouble bond is between carbon 2 and 3. Use the smallest number

Molecules with Functional Groups1. Identify parent chain2. Name the stem3. Identify any alkyl or functional groups4. Identify the name of the prefix or suffix5. Number any alkyl groups or functional groups

Curly Arrow mechanisms 

Percentage Yield  Actual Yield     x 100Theoretical Yield

Atom EconomyMr of desired products   x 100sum of Mr of all products

Fractional DistillationAlkanes in crude oil can be separated as they have different  boiling points.Alkanes and cycloalkanes are saturated - have no double bondsAs chain length increases there are more points of contact between molecules so there are more intermolecular forces. Therefore the boiling point increases as more energy is needed to break them.In a branched alkane there are fewer points of contact and therefore fewer Van der Waals forces. Boiling points of branched alkanes are lower than unbranched alkanes.CrackingLong-chain hydrocarbons broken down into smaller ones as they have a higher demandUses zeolite catalyst and 450oC Unbranched can be made into branched (isomerisation)Cyclic hydrocarbons can be formed from alkanes (reforming) produces H2

Combustion                                       Incomplete combustion CH4 + O2  -> CO2 + 2H2O                C8H18 + 8.5O2 -> 8CO + 9H2O

Radical Substitution

Alkenes and cycloalkenes are unsaturated

Double bond made of a sigma bond and a pi bond.Single bond made of just sigma bond. sigma bond formed by the overlap of s-orbitals, pi bond formed by the sideways overlap of p-orbitalspi bond is weaker than a sigma bondAlkene moleculeelectron pairs repel each other Trigonal planar shape with bond angle of 120o . Ethene is a flat planar molecule HydrogenationHydrogen added across double bondH2 gas, gaseous alkene, nickel catalyst, 150oC

HalogenationHalogen added across the double bond -  addition

Addition of hydrogen halidesH and Cl, gas is bubbled into liquid alkaneAdded across the double bondHydrationHigh Pressure and Temperature, phosphoric acid catalyst ( H2SO4 )

Basic Concepts

Alkanes

Alkenes