Nomenclature and Isomerism (basic concepts)

What are saturated and unsaturated hydrocarbons

• Saturated: single C-C bond (alkane)

• Unsaturated: double C=C bond (alkene)

What is an aliphatic hydrocarbon

• A hydrocarbon which has a straight chain, branched chain, or a non aromatic cyclical rings

What is an alicyclic hydrocarbon

• A hydrocarbon with one more more cyclical structure (non aromatic ring) with or without side chains

What is an alkyl group

• A side chain in the hydrocarbon

• When a hydrogen is taken off a carbon

  • e.g ethane: C2H6 → ethyl: C2H5

What is a functional group

• A group of atoms that are responsible for the characteristics in chemical reactions of a compound

What is a homologous series

• A series of compounds of similar structure in which each successive member differs from the next by a common repeating unit, CH3

• Series members are called homologues where all share the same general formula and functional group and similar properties

What are alkanes

• Saturated straight-chained hydrocarbons

• functional group: C-C

• CnH2n +2

• suffix: -ane

• Each carbon atom has a tetrahedral shape: 109.5°

What are the molecular formulas and structural formulas for the first five alkanes

• methane: CH4

• ethane: C2H6 → CH3,CH3

• propane: C3H8 → CH3,CH2,CH3

• butane: C4H10 → CH3,CH2,CH2,CH3

How do you name organic compounds

• Stem: indicates number of carbon atoms in longest chain

• Prefix: added before stem (alkyl)

• Suffix: added after stem (end), based off functional group; -ane, -ene

What are the rules of naming an organic compound

• Number the principal chain from one end to give the largest number (stem)

• Alkyl groups are placed before stem

• Side-chain names appear in alphabetical order: butyl, ethyl, methyl, propyl

• If side-chain appears more than once, add prefix: di, tri, tetra, penta, hexa

• Numbers are separated from names by a hydrogen eg. 2-methylheptane

• Numbed are separated from other numbers by a comma eg. 2,3-dimethylbutane

• Functional groups have priority in order over alkyl groups

• Each covalent from carbon must connect to carbon of the alkyl group

What are alkenes

• unsaturated hydrocarbon

• functional group: C=C

• CnH2n

• suffix: -ene

• position of the double bond must be stated (using smallest number)

What are all the necessary functional groups

What are alcohols

• suffix: -ol

• functional group: OH

• position of OH must be stated in name (using smallest number)

What are aldehydes

• suffix: -al

• functional group: CHO

• functional group always at the end

What are ketones

• suffix: -one

• functional group: CRO

• functional group never at the end

What are carboxylic acids

• suffix: -anoic acid

• functional group: COOH

• functional group always at the end

What are haloalkanes

• prefix: bromo-, chloro-, fluoro-, iodo-

• prefix always alphabetical

• priority goes to alkyl group then halogens

What is the priority of functional groups when there are multiple in one molecule

• carboxylic acid → -oic acid

• aldehyde → -al

• ketone → -oxo (prefix)

• alcohol → -hydroxy (prefix)

• alkenes → -ene

• halogens

• alkyl groups

What is meant by structural formula

• The minimal detail using conventional groups, for an unambiguous structure

• (Alkyl groups go in brackets)

What is meant by displayed formula

Shows the relative placing of the atoms and the number of bonds between them

What is meant by skeletal formula

• The most simplified organic formula with hydrogens removed from the carbon chain

• This levels the carbon skeleton with its functional group

What is the C-H bond called and what is the definition

• sigma bond

• orbitals directly overlap between two bonding orbitals

• any single bond

Explain the trend in BP of alkanes as chain length increases

• molecular mass increases

• more surface area points of contact between the molecules

• leading to more LDFs

• more energy required to overcome the forces

Explain the trend of BP of alkanes as they become more branched

• fewer surface area points of contact between molecules as they are less closely packed

• so less LDFs

• less energy required to separate

What is the risk of incomplete combustion

• produces CO

• CO binds to haemoglobin, is toxic

• odourless and colourless

What is homolytic fission

• the process where a covalent bond breaks and each atom takes 1 electron from the bonded pair

What is the free radical substitution mechanism for methane and chlorine

• overall equation: CH4 + Cl2 → CH3Cl + HCl

• initiation: Cl2 → 2Cl• UV LIGHT required

• propagation 1: Cl• + CH4 → CH3• + HCl

• propagation 2: CH3• + Cl2 → CH3Cl + Cl•

• termination:

  • Cl• + Cl• → Cl2

  • CH3• + CH3• → CH4

  • Cl• + CH3• → CH3Cl

What are the limitations of free radical substitution

• further substitution can take place

• substitution can occur at different positions on the chain

  • creates a mixture of products

What is an aromatic compound

• a compound containing a benzene ring (3 opposite double bonds)

What is a structural isomer and what are the 3 types

• molecules with same molecular formula but different structural formula

  • chain (branching)

  • positional (of functional group)

  • functional (the functional group)

What is a stereoisomer

• molecules with the same structural formula but different arrangement of atoms in space

How does stereoisomerism take place

• C=C bond has restricted rotation

• two different groups must be attached to each carbon atom in the C=C bond

How does Z-Isomerism arise

• high priority groups are e.g CH3 and C2H5 and are on the same side of each carbon atom of the C=C bond

How does E-Isomerism arise

• high priority groups are e.g CH3 and C2H5 and are on different sides of each carbon atom of the C=C bond

How do cis/trans isomers arise

• When the C=C bond has an identical 2nd group attached, which CAN be hydrogens

• Cis: Z

• Trans: E

What is the CIP priority rule

• atoms with the highest mr take priority of the stereoisomer

• only applies to the first atom if it’s an alkyl group, if they are identical then include 2nd atom etc..

What are the functional group structural isomers

• alcohols + ethers

• aldehydes + ketones

• carboxlyic acids + esters