Higher Unit 2

• An ester can be identified from the ester group and by the name containing the –‘yl’ ‘oate’ endings.
• An ester can be named given the names of the parent carboxylic acid and alcohol or from structural formulae.
• Structural formulae for esters can be drawn given the names of the parent alcohol and carboxylic acid or the names of esters.
• Esters have characteristic smells and are used as flavourings, fragrances and industrial solvents.
• Esters are formed by the condensation reaction between carboxylic acid and an alcohol.
• The ester link is formed by the reaction of a hydroxyl group and the carboxyl group.
• In condensation reactions, the molecules join together with the elimination of a small molecule, which is usually water.
• Esters can be hydrolysed to produce a carboxylic acid and alcohol.
• The parent carboxylic acid and the parent alcohol can be obtained by hydrolysis of an ester.
• In a hydrolysis reaction, a molecule reacts with water breaking down into smaller molecules.
• Fats and oils are a concentrated source of energy and are essential for the transport and storage of fat-soluble vitamins in the body.
• Fats and oils are esters formed from the condensation of glycerol (propane-1,2,3-triol) and three carboxylic acids.
• The carboxylic acids in fats and oils are known as ‘fatty acids’ and are saturated or unsaturated straight-chain carboxylic acids, usually with long chains of carbon atoms.
• Oils can be converted to fats by hydrogenation, an addition reaction with hydrogen which reduces the degree of unsaturation, increasing the melting point.
• The lower melting points of oils compared to those of fats are related to the higher degree of unsaturation of oil molecules.
• The low melting points of oils are a result of the effect that the shapes of the molecules have on close packing, hence on the strength of van der Waals’ forces of attraction.
• Proteins are the major structural materials of animal tissue and are also involved in the maintenance and regulation of life processes.
• Enzymes are proteins.
• Amino acids, the building blocks from which proteins are formed, are relatively small molecules which all contain an amino group (NH2), and a carboxyl group (COOH).
• The body cannot make all the amino acids required for body proteins and is dependent on dietary protein for supply of certain amino acids known as essential amino acids.
• Proteins are made of many amino acid molecules linked together by condensation reactions.
• In condensation reactions to form proteins, the amino group on one amino acid and the carboxyl group on a neighbouring amino acid join together, with the elimination of water.
• The link which forms between amino acids can be recognised as an amide link (CONH) also known as the peptide link.
• Proteins which fulfil different roles in the body are formed by linking differing sequences of amino acids together.
• During digestion, enzyme hydrolysis of dietary proteins can produce amino acids.
• The structural formulae of amino acids obtained from the hydrolysis of proteins can be identified from the structure of a section of the protein.
• Many flavour and aroma molecules are aldehydes.
• Aldehydes and ketones both contain the carbonyl functional group.
• Aldehydes and ketones can be identified from the ‘-al’ and ‘-one’ name endings respectively.
• Aldehydes, but not ketones, can be oxidised to carboxylic acids.
• Fehling’s solution (blue to brick red precipitate), Tollen’s reagent (formation of silver mirror) and acidified dichromate solution(orange to green) can be used to differentiate between an aldehyde and a ketone.
• Within proteins, the long-chain molecules may be twisted to form spirals, folded into sheets, or wound around to form other complex shapes.
• Protein chains are held in these forms by intermolecular bonding between the side chains of the constituent amino acids.
• When proteins are heated, during cooking, these intermolecular bonds are broken allowing the proteins to change shape (denature).
• Denaturing of proteins alters the texture of foods.
• Hydrogen bonding can be used to explain the properties of alcohols including, boiling points, melting points, viscosity and solubility/miscibility in water.
• Primary, secondary and tertiary alcohols can be drawn and classified.
• Diols have two hydroxyl groups in the molecule.
• Triols have three hydroxyl groups in the molecule.
• Primary alcohols are oxidised, first to aldehydes and then to carboxylic acids.