QCEChemistry

Structure of organic compounds

recognise that organic molecules have a hydrocarbon skeleton and can contain functional groups, including alkenes, alcohols, aldehydes, ketones, carboxylic acids, haloalkanes, esters, nitriles, amines, amides and that structural formulas (condensed and extended) can be used to show the arrangement of atoms and bonding in organic molecules

- Hydrocarbons are an organic compound consisting of only carbon and hydrogen atoms

- Functional groups are an atom or a group of atoms in a organic compound that determines the reactivity of that compound.

Order of priority functional groups in polyfunctional compounds

- Homologous series is a class of molecules in which each member differs by -CH2- from the previous member

• Compounds from the same homologous series have:

▪ A similar structure

▪ A pattern to physical properties

▪ Similar chemical properties

▪ Same general formula

- Comparing methods of notating a chemical

deduce the structural formulas and apply IUPAC rules in the nomenclature of organic compounds (parent chain up to 10 carbon atoms) with simple branching for alkanes, alkenes, alkynes, alcohols, aldehydes, ketones, carboxylic acids, haloalkanes, esters, nitriles, amines and amides

- Conventions when naming hydrocarbons

• No spaces in names
• Longest carbon chain is used to derive the parent name

▪ Longest chain must include the double or triple bond for alkenes and alkynes

• Suffixes are used in the parent name to indicate whether the hydrocarbon is an alkane, alkene or alkyne
• Number are used in parent name to identify carbon atoms that contain double or triple bonds.

▪ Stem must contain functional group and function group takes priority numbering

• Names and locations of substituents are added to the parent name
• If there is more than one type of substituent to be listed at the beginning of a name, they must be listed in alphabetical order
• If there is more than one of the same type of substituent, prefixes 'di' or 'tri' or 'tetra' are used
• Numbers and letters are separated by dashes
• Numbers are separated from other numbers by commas

- Cyclic compounds

• A prefix 'cyclo-' is added to the name
• Formula will have two less hydrogens than straight chain molecule

- Resonance structures

• Benzene is a cyclic compound (C6H6)

• Electrons in double bond are not fixed in position. They are delocalised and can move around - forming resonance

▪ Benzene is more stable (and less reactive) than most unsaturated molecules because its delocalised electrons are not as available to take part in reactions

identify structural isomers as compounds with the same molecular formula but different arrangement of atoms; deduce the structural formulas and apply IUPAC rules in the nomenclature for isomers of the non-cyclic alkanes up to Св

- Structural isomers are two or more organic compounds that have the same atoms but a different arrangement and bonding

• Chain isomers are consequence of the branching possible in carbon chains

• Positional isomers are molecules with the same carbon chain and functional group, but with the functional group attached at different locations in the molecule

identify stereoisomers as compounds with the same structural formula but with different arrangement of atoms in space; describe and explain geometrical (cis and trans) isomerism in non-cyclic alkenes.

- Stereoisomers are two or more organic compounds that have the same atoms and bonding but a different spatial arrangement

○ Geometrical isomers are two organic compounds that have different arrangements of atoms around a rigid double bond

• Due to lack of rotational ability in the double bond, causing fixed arrangements of the substituents attached to those carbon atoms
• Cis geometrical isomers have similar substituents on the same side
• Trans geometrical isomers have similar substituents on the opposite sides of the double bond
• The substituents do not need to be identical, but they need to have at least two substituents other than hydrogen attached to the double bond. They cannot generally form on the end of the main chain, because carbon atoms will have hydrogen atoms rather than substituents
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