Colour By Design Flashcards
Explain 3 pieces of evidence that suggest that the Kekule structure of benzene is not appropriate
• If benzene had C=C then it would decolorise bromine water, but it does not
• The bond lengths in Kekule’s benzene would be different as double bonds are shorter than single bonds, but this is not the case
• The enthalpy of hydrogenation of benzene would be expected to be triple that of cyclohexene but it is less than triple
Name the following compounds:
• C6H5NH2
• C6H5Cl
• C6H5(NO2)
• C6H5CHO
• Phenylamine
• Chlorobenzene
• Nitrobenzene
• Benzaldehyde
Draw the following compounds with skeletal formula:
• Phenylethene
• Phenylpropanoate
• Benzoic Acid
• C6H5CHCH3
• Benzene coming off of the O, 3 carbon chain coming off of
Give the reagents and conditions for the chlorination/bromination of benzene
• Cl2/Br2
• AlCl3/AlBr3 OR Fe/FeCl3 catalyst
• Anhydrous
• RTP
Give the reagents and conditions for the nitration of benzene
• Conc. HNO3 + Conc H2SO4
• Temp below 55°c
Give the overall equation for the formation of a positive electrophile required for the nitration of benzene
• H2SO4 + HNO3 ⇌HSO4- + H2O + NO2+
Give the reagents and conditions for the sulphonation of benzene, naming the product
• Conc H2SO4
• Boil under reflux
• Benzenesulphonic acid
Benzene reacts with molecule X to produce C6H5CH2CH3. Give the reagents and conditions for this reaction and the identity of molecule X
• Molecule X is chloroethane/bromoethane
• AlCl3/AlBr3 catalyst
• Anhydrous
• Boil under reflux
Give the reagents and conditions for the acylation of benzene with ethanoyl chloride
• AlCl3 catalyst
• Anhydrous
• Boil under reflux
Explain what the circle in the middle of a benzene molecule symbolises, giving the origin and arrangement of the electrons involved
• The circle represents delocalised electrons in benzene
• One electron is donated (to the delocalised system) from each carbon atom
• This creates two rings (π system) above and below the carbon ring
Give the reagents and conditions for diazotisation (formation of a diazonium ion)
• An aromatic amine (eg phenylamine)
• Dilute HCl
• Sodium Nitrate (III) (NaNO2)
• Temperature below 5°c
Give the equation of the reaction between HCl and NaNO2 to create a reactant involved in diazotising phenylamine
HCl + NaNO2 > HNO2 + NaCl
Give the equation of the reaction that forms a diazonium ion from an aromatic amine
Phenylamine + HNO2 + HCl > Diazonium ion and 2H2O
Give the name of C6H5NN+ Cl-
Benzene diazonium chloride
Give the reagents and conditions for a coupling reaction
• Diazonium ion
• Phenol OR Phenylamine
• Alkaline solution
• Temperature < 5°c
Describe what a chromophore is
The part of a molecule that is responsible for its colour
Explain the effect of increasing the delocalised system of a molecule on the colour it produces
• The ΔE/energy gap becomes smaller
• Meaning a lower frequency of the EM spectrum is absorbed (in the range of visible light)
• That frequency of light is absorbed and the complementary colours are reflected/transmitted
What are the mobile and stationary phases in gas-liquid chromatography?
• Mobile > Inert gas (eg Nitrogen)
• Stationary > High BP liquid
Name and describe the 2 tests to distinguish between aldehydes and ketones
Fehling’s:
• Contains Cu2+ and alkali (Fehling A and Fehling B)
• In presence of aldehydes, goes from blue to brick red [Cu2+ to Copper (II) oxide]
• No reaction with ketones
Tollen’s:
• Contains Ag+ and ammonia solution
• In presence of aldehydes, forms a silver
Draw the mechanism for the nucleophilic addition of hydrogen cyanide and propanone
First Step:
• C=O with two CH3 coming off the C, δ- on O and δ+ on C
• CN- ion with lone pair on the carbon
• Full headed arrow from lone pair on C to δ+ C, full headed arrow from C=O bond to the δ- O
Second Step:
• CN joins onto the central carbon, O- now present
• Full headed arrow from
