3.2.10 All Alcohols Notes with Reactions and Organic Spot Tests

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  • Created on: 09-03-15 20:03
Preview of 3.2.10 All Alcohols Notes with Reactions and Organic Spot Tests

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Reaction Reagents Conditions Observations
Combustion Alcohol Excess oxygen Complete combustion burns with a
Oxygen Flame or spark blue flame leaving no soot
Incomplete combustion burns with a
yellow flame leaving soot
(Partial) Primary alcohol Immediate distillation Colour change from orange
Oxidation of Acidified(by dilutesulphuric acid) otherwise the aldehyde (dichromate(VI) to blue-green
Primary sodium/potassium dichromate(VI) can be oxidised to a chromium(III))
Alcohol to solution ketone
(Complete) Primary Alcohol Heating under reflux Colour change from orange
Oxidation of Excess (i.e. 2[O]) acidified(by (unreacted aldehyde will (dichromate(VI) to blue-green
Primary concentrated sulphuric acid) drip back down to be chromium(III))
Alcohol to sodium/potassium dichromate(VI) oxidised )
Carboxylic Acid
Oxidation of an Aldehyde Heating under reflux for ~ Colour change from orange
Aldehyde to a Excess (i.e. 2[O]) acidified(by 20 mins (unreacted (dichromate(VI) to blue-green
Carboxylic concentrated sulphuric acid) aldehyde will drip back chromium(III))
Acid/Salt of sodium/potassium dichromate(VI) down to be oxidised ).
the carboxylic
Gentle heating with
ethanal as it has a low
Aldehyde Heating under reflux for ~ Colour change from orange
Excess (i.e. 2[O])alkaline 20 mins (unreacted (dichromate(VI) to blue-green
sodium/potassium dichromate(VI) aldehyde will drip back chromium(III))
down to be oxidised ).
Gentle heating with

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Oxidation of Secondary Alcohol Heating under reflux Colour change from orange
Secondary Acidified (by dilute sulphuric acid) (dichromate(VI) to blue-green
Alcohol to sodium/potassium dichromate(VI) chromium(III))
Ketone solution
Oxidation of Not possible with most oxidising agents N/A If acidified sodium/potassium
Tertiary (including acidified sodium/potassium dichromate(VI) solution was used, no
Alcohols dichromate(VI) solution) as requires C-C colour change would be seen,
bond to break rather than C-H bond. solution remains orange.…read more

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Alcohol Alcohol Moist If then tested with nitric acid and
reacting with Red allotrope of phosphorous (makes Heat under reflux silver nitrate, halide ions will be able
phosphorous phosphorous tribromide, tri-iodide and to be seen.
halide. trichloride in situ
. Other product is This shows an ­OH group is present
phosphoric(III) acid)
substitution.…read more

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Add acidified potassium manganate(VII) Solution turns from dark pink to Unsaturated compound
Shake at standard conditions colourless/pale pink Could be an alkene
Manganate (II) ions formed
Add alkaline potassium manganate (VII) Solution turns from dark pink to: Unsaturated compound
o Green if manganate(VI) ions are Could be an alkene
o Brown if solid manganese(IV)
oxide is formed.…read more

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Add sodium carbonate to neutralise Copper(II) complex ions reduced to
anything copper(I) ions.
Warm gently Benedict's solution does the same
Sodium/potassium Effervescence Carboxylic acid
carbonate/hydrogencarbonate CO2 ­ bubbled through limewater turns
-COOH group present
Standard conditions milky.…read more

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Production of ethanol
Biofuel ­ A fuel derived from renewable biological sources
Carbon neutral ­ An activity that has no net annual carbon (greenhouse gas) emissions to the atmosphere
- Solvent (cosmetics)
- Intermediate in chemical processes
Method 1 ­ Hydration of ethene
Crude oil fractions are cracked to make ethene. From naphtha or mostly natural gas.…read more

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2+ <=> C
2H 5OH
Method 2 (No longer used industrially)­ Electrophilic addition using sulphuric acid (Mechanism in 3.2.9)
Concentrated sulphuric acid is added to ethene.
Method 2 ­ Fermentation of sugars
Carbohydrates from plants are broken down into sugars and then metabolised by yeast during anaerobic respiration to alcohol.
12O 6(aq)
-> 2C
+ 2CO2(g)
Temperature too low slow rate of reaction, too high zymase enzymes denatured. 35°C used.…read more

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Plants with high starch content ­ Starch is polymer of glucose so must first be broken down (by other bacteria). Used to make motor fuel in USA.
Plant waste ­ Lots of cellulose, a polymer of glucose, in wood shavings, wheat straw and corn husks. Need bacteria to break down cellulose. Can use
enzymes with the enzyme cellulase which can also ferment glucose to alcohol.…read more

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Methanol usually used as chemical feedstock (starting place for making other chemicals). Made using copper catalyst. CO(g) + 2H CH
2(g) 3OH(g)
starting mixture of CO and H2is called synthesis gas and is made from propane or methane with steam. Favours high pressure and low temperature.
Compromise of 500K and 10 atmospheres.
Burn with a clean flame as they contain oxygen and release lots of energy per gram but not as much as petrol.…read more

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CO2released per mol of glucose Total = -4
3. Combustion of ethanol
+ 6O2->4CO2+ 6H2O
(Carry the 2 mols of ethanol made across)
4 mols of CO2 released per mol of glucose (from the start of the ethanol equation) Total = 0
In theory ethanol is carbon neutral but practically it is not.
Doesn't take into account energy used in:
Planting, harvesting and milling plants.…read more


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