paper 2 past exam questions

    Cards (30)

    • explain why one of the organic products forms in much greater quantity than the other organic product
      • carbocation bonded to more carbon atoms
      • more stable carbocation
    • stereoisomerism
      • same structural formula but a different arrangement of atoms
    • structural isomerism
      • they have the same molecular formula but different structural formula
    • what is meant by heterolytic fission
      • one atom receives both electrons
      • breaking of a covalent bond
    • which statement is correct for the different rates of hydrolysis of RCl and RBr
      RBr is hydrolysed faster because the C-Cl bond enthalpy is greater than the C-Br
    • atom economy equation
      mr of desired product/ mr of all products
    • describe a chemical test to confirm the presence of a carbonyl group
      • 2,4-DNPH/ brady's reagent - if a carbonyl group is present, an orange precipitate will form
      • take the melting point of crystals
      • compare to known values/ database
    • reaction of propanoic acid with aqueous potassium hydroxide
      • C2H5COOH + KOH \rightarrow C2H5COOK
    • reaction of aqueous methanoic acid with magnesium
      • 2HCOOH + Mg \rightarrow (HCOO)2Mg + H2
    • chemical test used to confirm the presence of phenol groups
      • indicator and observation of acidity - no reaction with carbonate
    • compounds K and L react with chlorine much more readily than compound J, explain why
      • electron density increases
      • phenols more susceptible to electrophilic attack
      • lone pair of electrons on O is delocalised into the ring
    • explain the term optical isomerism
      Non-superimposable mirror images
    • pi bond
      sideways overlap of p orbitals
    • sigma bond
      overlap of orbitals between atoms
    • Explain why phenol is nitrated more readily than benzene
      • electron density is higher than benzene
      • phenol attracts electrophile more
      • phenol is more susceptible to electrophilic attack
    • State and explain how the halogen in the haloalkane affects the rate of hydrolysis
      • links rate of reaction to strength of bond
      • C-F is hydrolysed slowest
      • C-I bond hydrolysed faster than C-Br
    • Methylcinnamaldehyde is an E stereoisomer. Explain this statement in terms of the Cahn-Ingold-Prelog (CIP) rules
      • priority groups are on opposite sides
      • state the highest priority groups e.g highest priority group is CHO
    • Describe a chemical test to confirm that cinnamaldehyde and methylcinnamaldehyde contain a carbonyl group. How could the products of this test be used to distinguish between the two compounds?
      • 2,4-dinitrophenylhydrazine AND orange/yellow/red precipitate
      • Take melting point (of crystals)
      • Compare to known values/database
    • Explain the difference in the boiling points of the fuels
      • hydrogen bond e.g in an alcohol (OH) are stronger than induced dipole- dipole interactions
      • longer chains have higher melting points
    • Describe, in terms of orbital overlap, the similarities and differences between the bonding in the Kekulé model and the delocalised model of benzene.
      similarities:
      • overlap of p orbitals
      • ring above and below carbon atoms
      difference
      • kekule has alternating pi bonds
      • delocalised has a pi ring system
    • regeneration of a catalyst
      H+ + AlCl4- \rightarrow AlCl3 + HCl
    • explain what is meant by heterolytic fission
      heterolytic = one atom receives both electrons
      fission = breaking of a covalent bond
    • What chemical test(s) could be used to confirm the presence of the phenol group in compounds K and L?
      Indicator AND observation of acidity AND No reaction with carbonate
    • What is the reason for heating under reflux?
      to prevent any substances escaping
    • The boiling point of butan-1-ol is 118 °C. The boiling point of 2-methylpropan-2-ol is 82 °C. Why is the boiling point of butan-1-ol higher than that of 2-methylpropan-2-ol?
      butan-1-ol has stronger induced dipole–dipole interactions because it has a straight-chain structure
    • The student is told by a friend that the FeCl3 catalyst is not needed because quinol is more reactive than benzene. Explain why the student’s friend is correct
      • the lone pair of electrons on the oxygen atom
      • is donated into the π system
      • making quinol more susceptible to electrophilic attack
    • Describe 2 limitations of the synthesis of 2-bromo-2-methylpropane from an alkane and bromine
      • Further substitution can occur
      • Substitution could occur on different carbon atoms
    • what is meant by homologous series
      • same chemical properties
      • each subsequent member differing by CH2
    • regeneration of catalyst H2SO4
      H+ + H2SO3- \rightarrow H2SO4
    • density = mass/volume