Flashcards in F335 - Colour By Design Deck (21):
Conditions and reagents for Hydrolysis of Esters
Heating under reflux with moderately concentrated sodium hydroxide solution.
What is a conjugated system?
A system with alternate C=C and C-C bonds. The delocalised electrons in this system require less energy to get excited so will absorb UV/Visible frequencies.
If a substance ABSORBS blue and green light, what colour will it appear in white light?
How is the colour of substance found from an absorption/wavelength graph?
The wavelength for which absorption is greatest is found. The colour of the substance is the complementary colour of this wavelength.
How does gas liquid chromatography work?
- Stationary phase: a non volatile liquid coated on the surface of finely divided solid particles.
- This material is packed inside a long thin column, which is coiled in an oven.
- Mobile phase: An unreactive carrier gas (Often nitrogen) carries the mixture through the column.
- Components emerge from the column, peak is recorded on the chromatogram.
- The area under the peak is proportional to the amount of component in the mixture. The time that a component takes to emerge is called the retention time.
Does benzene react with bromine water?
No. Benzene does not contain any carbon carbon double bonds, the bonds are delocalised therefore they do not react with bromine water. The bromine water does not turn from brown to colourless.
What type of reactions do a arenes normally undergo? And why?
Benzene will normally undergo substitution reactions and rarely addition reactions. Substitution reactions keep the delocalised electrons structure where as addition would destroy this structure. This means the vast majority of benzene reactions are electrophilic substitutions.
Reagents and conditions for nitration of benzene.
Benzene and concentrated nitric acid mixed with concentrated sulphuric acid. Temperature kept below 55°C.
Reagents and conditions for sulphonation of benzene.
Benzene and concentrated sulphuric acid. Heat under reflux for several hours.
Reagents and conditions for chlorination of benzene.
Benzene and chlorine and anhydrous aluminium chloride. At room temperature.
Reagents and conditions for bromination of benzene.
Benzene and bromine and anhydrous iron (III) bromide. Room temperature.
Reagents and conditions for Alkylation of benzene.
Benzene and chloroalkane and anhydrous aluminium chloride. Heat under reflux.
Reagents and conditions for acylation of benzene.
Benzene and acyl chloride and anhydrous aluminium chloride. Heat under reflux.
Characteristics and examples of Friedel-Crafts reactions.
- add carbon sidechains to a benzene ring, which can then be modified further.
- involve a halogen carrier.
- Alkylation and acylation are examples of this.
Reagents and conditions for formation of diazonium ions. (Diazotisation)
Phenylamine dilute hydrochloric acid, sodium nitrate (III). Temperature kept below 5°.
Formation of azo compounds (coupling reaction).
diazonium Ion and Phenylamine (coupling agent).
Affect of adding SO3 Na to chromophore.
The solubility of the dye in water is improved, due to the ionic group-it can form ionic bonds with a protein fibre such as wool.
Affect of adding NH2 or NR2 to a chromophore.
The colour of the dye is modified or enhanced.
Why are transition metal ions coloured?
Electrons in the D orbitals can be excited. When a transition metal ion is surrounded by ligands the D orbitals are split into two different energy levels. Electrons in the lower energy level can be excited to the higher energy level. The excitation energy required corresponds the absorption of visible light.
Factors that affect the excitation energy and therefore the colour of the complex.
-The type of ligand
- The shape of the complex-octahedral or tetrahedral.
- The coordination number of the complex.
- The charge on the central transition metal ion.