organic 2

• What is a chiral centre?

  A chiral centre is a carbon atom with four different groups bonded around it.
• Why does a molecule with a chiral centre have no line of symmetry?

  Because the arrangement of the four different groups around the carbon atom prevents any symmetrical division.
• How is a chiral centre commonly indicated in chemical structures?

  It is indicated using an asterisk (*) next to the asymmetric carbon.

  
• What is optical isomerism?

  Optical isomerism is a type of stereoisomerism where molecules have the same molecular formula but different spatial arrangements of atoms.
• What are the two possible isomers produced by the presence of a chiral centre called?

  They are called optical isomers.
• What are enantiomers?

  Enantiomers are the two different isomers that are mirror images of each other due to the presence of a chiral centre.
• How do enantiomers affect plane polarised light?

  Each enantiomer causes the rotation of plane polarised light in opposite directions.
• What is a racemate?

  A racemate is formed when optical isomers are produced as a pair of enantiomers in a 1:1 ratio.
• Why is a racemic mixture optically inactive?

  Because the opposite directions of rotation caused by each enantiomer cancel out, resulting in an overall effect of zero.
• How can two isomers be produced in equal quantities?

  They can be produced by a nucleophilic addition reaction.
• What characterizes S​N​1 reactions?

  S​N​1 reactions proceed via a planar carbocation intermediate, allowing the nucleophile to attack from either face.

  
• What is the result of S​N​1 reactions in terms of product formation?

  S​N​1 reactions produce a racemic mixture.
• How do S​N​2 reactions differ from S​N​1 reactions?

  S​N​2 reactions occur in a single step, with the nucleophile attacking while the leaving group is removed.

  
• What is the outcome of S​N​2 reactions in terms of product formation?

  S​N​2 reactions produce a single enantiomer.
• How do nucleophiles attack in nucleophilic addition reactions involving carbonyl groups?

  Nucleophiles can attack from above or below the planar carbon-oxygen double bond.
• What do the products of nucleophilic addition reactions involving carbonyl groups represent?

  The products are mirror images and therefore optical isomers.
• What defines carbonyl compounds?

  Carbonyl compounds are organic compounds containing a carbonyl group, C=O.
• What are the most common types of carbonyl compounds?

  The most common carbonyl compounds are aldehydes and ketones.
• How do carbonyl compounds interact with water?

  They can form hydrogen bonds with water due to their carbonyl group.
• Why are aldehydes and ketones soluble in water?

  Because they can form hydrogen bonds with water molecules.
• What type of intermolecular forces exist between aldehyde and ketone molecules?

  Only van der Waals forces exist between their molecules.
• How are aldehydes produced?

  Aldehydes are produced from the initial oxidation and distillation of primary alcohols.
• Where is the carbonyl group located in aldehydes?

  The carbonyl group is located at the end of the carbon chain.
• What functional group do aldehydes have?

  Aldehydes have the functional group -CHO.

  
• How can aldehydes be further oxidised?

  Aldehydes can be oxidised further in the presence of acidified potassium dichromate(VI) to produce carboxylic acids.

  
• How are ketones produced?

  Ketones are produced from the oxidation of secondary alcohols with acidified potassium dichromate(VI).
• Where is the carbonyl group located in ketones?

  The carbonyl group is on a carbon atom that is attached to two other carbon atoms.
• What happens to primary alcohols when heated in the presence of acidified potassium dichromate(VI)?

  They can be oxidised to produce aldehydes.
• What occurs when primary alcohols are heated under reflux?

  They will be oxidised further to carboxylic acids.
• What can secondary alcohols be oxidised to?

  Secondary alcohols can be oxidised to ketones when heated in the presence of acidified potassium dichromate(VI).
• What is potassium dichromate(VI) used for?

  Potassium dichromate(VI) is used as an oxidising agent in the oxidation of alcohols.
• What indicates that potassium dichromate(VI) has been reduced during the oxidation of alcohols?

  The colour change from orange to green indicates the alcohol has undergone oxidation.
• How can aldehydes be tested for presence?

  Aldehydes can be tested using Tollen’s reagent or Fehling’s solution, which produce a positive result if present.
• What happens when Fehling’s solution is added to an aldehyde?

  A red precipitate will form if an aldehyde is present.
• What happens when Tollen’s reagent is added to an aldehyde?

  A layer of silver will form on the walls of the test tube if an aldehyde is present.
• How can the oxidation reactions of carbonyl compounds be reversed?

  They can be reversed via reduction reactions.
• What is the reducing agent used in the reduction of carbonyl compounds?

  The reducing agent used is lithium tetrahydridoaluminate(III) (LiAlH4).
• What is the reaction environment for the reduction of carbonyl compounds?

  The reaction is carried out in a solvent of dry ether due to the reactivity of LiAlH4.
• What does the reducing agent LiAlH4 provide in the reduction reaction?

  LiAlH4 provides the H:​- nucleophile.
• What happens during the reduction reaction involving LiAlH4?

  First a salt is formed, and then a dilute acid is added to release the alcohol from the salt.