Chemistry - Aromatic compounds Flashcards

organic compounds where carbon aoms form open chains or closed rings but does not contain a benzene ring in their structure
eg. ethane

organic compounds contaning a benzene ring in their structure

six carbon-hydrogen bonds formed by sigma bonds - 12 fixed electrons
six carbon-carbon single bonds formed by sigma bonds - 12 fixed electrons

three carbon-carbon double bonds are formed by 6 pi electrons

the 6 pi electrons are delocalised-free to move around the benzene ring
the carbon carbon bonds are a identical intermediate between single and double bonds

freely moving electrons and are shared between More than two atoms

the number of
six carbon-hydrogen bonds formed by sigma bonds - 12 fixed electrons
six carbon-carbon single bonds formed by sigma bonds - 12 fixed electrons

three carbon-carbon ‘double’ bonds are formed by 6 pi electrons

12 electrons involved not involved in bonding

does not correctly describe the distribution of pi electrons
the kekule structure has the pi electrons localised to three double bonds but in reality the electrons are delocalised
all of benzenes carbon tp carbon bonds are an identical intermediate between double and single bonds

*Lack of reactivity - benzene is very stable/ unreactive
expeirmental evidence - benzene will not decolourise red bromine water or acidified potassium manganate vii
(not undergo an addition reaction)

*unusual bond lenght- all of benzenes bonds are the same lenght, smaller than a single bond, larger than an dounle

neither, benzene is neither saturated or unsaturated, also not an alkene

non polar molecule - doesnt dissolve in water
carcinogenic- causes cancer- health hazard

1. 2 electrons, only single bonds

2. 2 sigma always shared +2 delocalised electrons

result
1 when bubbled from water, each gas does not dissolve and forces itself into syringe B,syringe B opens to almost 100cm3

2 when bubbled through cyclohexane: each gas does dissolved and syringe B remains mostly closed
methane, thene, ethyne, methylbenzene are all non-polar molecules

pharmaceuticals - paraceramol, ibuprofen
acid base indicators- methyl orange and phenolphthalein
food preservatives - bezoic acid and its salts ( sodium benzoate)

safety tube
steam generator
hot plate/ bunsen burner
steam trap
cloves in water
liebig condenser
emulsion of clove oil and water

liquids that do not mix

the boiling point of two immiscible liquids is below the boiling point of both liquids seperately

clove oil has high boiling point, if it were distilled directly, the oil would decompose at the high tempertures

eugenol

1 - a safety tube is placed in the steam generator to prevent build up of pressure

2- gloves are worn when handleing the cloved, eugenol can burn the skin

below the water level to prevent steam from escaping

collect any steam that has condensed and avoid it condensing into and filling up flask full of cloved

water and clove oil as an emulsion

An emulsion is a dispersion of small droplets of ONE LIQUID (OIL) IN ANOTHER LIQUID in which it is not soluble

Milky coloured

whole cloves contain more oil

add emulsion into a seperating funnel, using a dropper add cyclohexane.

stopper and shake(funnel is inverted when shaken) tap is opened to release the pressure of the vapourised liquid

allow aqueous layer to drain into a beaker, organic to drain seperatly into a conical flask

the aqueous layer will still contain some oil, precedure is repeated at least two more time to obtain the max amount of clove oil

used to separate two immisible liquids. a slovent is added in whcih one of the liquids will dissolve but the other will not

clove oil is soluble in cytohexane , water is not, adding ctyohexane dissolces the clove oil from the emulsion, doesnt dissolve water

ethanol would not be a suitable solvent.

to remove the clove oil from the elmunsion a non polar solvent must be used.ethanol has a polar hydroxyl group and it would dissolve water from the elmusion

the eparating funnel is invertes when shaking, tap is gentaly opened to release the pressure, avoid pointing it at another person

the milkey colour is caused by the presence of deoplets of clove oil in the water as an emulaion, each wahing ectracts more oil

using a spatula, add anhydrous magnesium sulfate to the clove oil and ctyohexane mixture.

the anhydrous magnesium sulfate brinds with any water present in the mixture and forms clumps of hydrated magnesium sulfate.

filter clove oil/cytohexane mixture with flutef filter paper into a new preweighes conical flask to remove the clumps of hydrated magnesium sulfate/ excess anhydrous magnesium sulfate

rinse the orginal conical flask with cytohexane and filter again to ensure all clove oil is retrieved

magnesium sulfate is a drying agent, absorbs and clumps any remaining water

add until it settles at the bottom of the flask and no longer clumps, all the water has been absorbed

to remove any hydrated magnesium sulfate and excess magnesium sulfate from the mixture

fluted filter oaoer has a greater surface are- filtration will be quicker

place clove oil/ cytohexane in a water bath in a fume cuboard @81 C and boil the cytohexane off to leave the clove oil isolated.

leave the concial flask in the fume cuboard overnight, ensuring cyclohexane will be evaporated

cytohexane is a volatile organic solvent, boiing point in 81, the cytohexane is boiled off leaving the clove oil completely isolated behind

thr clove oil could boil off as well as the cytohexane

cyclohexane is a flammble solcent- it must never be heated with a bunsen burner

flavoring agent

perfumes, soaps