ALCOHOLS Flashcards
Outline the general formula for alcohols
CnH2n+1OH
Outline the rules for naming alcohols
-ol suffix (remove the e)
Hydroxy- prefix when other functional group is a suffix
More than on OH group leades to di/ tri etc with the addition of e to the stem name
Outline the bond angles in an alcohol
H-C-H/C-C-O 109.5 Tetrahedral shape (4 bond pairs repelling to position of minimum repulsion)
H-O-C 104.5
Bent line shape (2 bond pairs, 2 lone pairs which repel more than bond pairs)
Outline the boiling points of alcohols
Low volatility
High BP
Due to ability to form hydrogen bonds
Outline the different types of alchol
Primary (1 carbon attached to C-OH)
Secondary (2 carbon attached to C-OH)
Tertiary (3 carbon attached to C-OH)
Outline the oxidation of a primary alcohol
Reagent: Potassium dichromate (VI) solution and dilute sulphuric acid (H+/Cr2O7^2-)
Conditions: Limited dichromate, warm gently, distil out aldehyde as it forms
Primary alcohol to aldehyde
How is an oxidising agent represented?
[O]
The equation for propan-1-ol to propanal
CH3CH2CH2OH + [O] > CH3CH2CH2CHO + H2O
Outline the rules for drawing distillation
Round/Pear Bottomed flask, Condenser (to right pointing downward), Thermometer, large condenser
Don’t draw lines between flask, adaptor and condenser
Thermometer at junction of adaptor
Water in at bottom out at top
Condenser must have outer tube for water sealed from the inner tube
Why is distillation used?
Separation technique
Of organic product from its reacting mixture
Collect distillate at approximate boiling point range of desired liquid
Outline the FULL oxidation of a primary alcohol
Reagent: Potassium dichromate (VI) solution and dilute sulphuric acid (H+/Cr2O7^2-)
Conditions: Limited dichromate, heat under reflux (distil off product after the reaction has finished)
Primary alcohol to carboxylic acid
The equation for propan-1-ol to propanoic acid
CH3CH2CH2OH +2[O] > CH3CH2COOH + H2O
Outline the rules for drawing reflux
Round/Pear Bottomed flask, Condenser (directly above flask)
Don’t draw lines between flask and condenser
Water in at bottom out at top
Condenser must have outer tube for water sealed from the inner tube
No seal at top of condenser
Why is reflux used?
Heating organic reaction mixtures for long periods
Prevents organic vapours from escaping by condensing back to liquid
What are anti-bumping granules?
Added to distillation and reflux reactions to prevent vigorous, uneven boiling
and reduce the formation of large bubbles
by making small bubbles
Outline the oxidation of a secondary alcohol
Reagent: Potassium dichromate (VI) solution and dilute sulphuric acid (H+/Cr2O7^2-)
Conditions: heat under reflux
Secondary alcohol to ketone
Why can’t tertiary alcohols be oxidised by potassium dichromate?
There are no hydrogen atoms bonded to the carbon with the OH group
Outline the test for alcohols
Add H+/Cr2O7^2- (potassium dichromate solution)
Orange to green (CwO7^2- > Cr^3+)
Outline the test for aldehydes
Tollens’ Reagent (heat gently 60C)
Produces silver mirror inside the test tube
Fehling’s Solution/Benedict’s Reagent (heat gently)
Blue to Red precipitate
Outline the test for a carboxylic acid
Add sodium carbonate/sodium hydrogen carbonate
Bubbles of CO2
Outline the reaction of alcohols with dehydrating agents
Reagents: Concentrated sulphuric/phosphoric acid
Dehydrating agent/catalyst
Conditions: Warm under reflux
Mechanism: acid catalysed elimination
Alcohol to alkene
The reaction of propan-1-ol to propene
CH3CH2CH2OH > CH2=CHCH3 + H2O
Outline an acid catalysed elimination mechanism
Lone pair on O-H bonds to H+ ion Forms a O+ O+ breaks from alkane Forms carbocation (C+) Hydrogen beside carbocation (not bound) breaks Forms double bond and H+
Outline fermentation to form ethanol
Conditions: Yeast, No Air, Temp (30-40C)
C6H12O6 > 2 CH3CH2OH + 2 CO2
Batch process
Outline hydration/addition to form ethanol
Conditions: High temp (300-600C), High pressure (70atm) strong acid catalystic (eg conc H3PO4)
CH2=CH2 + H2O > CH3CH2OH
Continuous process
Outline the strengths of fermentation forming ethanol
Sugar is renewable
Production uses lower level technology/equipment
Low temp and pressures needed
Carbon neutral
Outline the strengths of hydration forming ethanol
Faster
Purer product
Continuous process
Atom economy 100%
Outline the weaknesses of fermentation forming ethanol
Batch process is slow (high production cost)
Non-pure product (requires fractional distillation)
Depletes land used for growing crops
CO2 product reduces atom economy
Outline the weaknesses of hydration forming ethanol
High technology equipment used (expensive)
Ethene is from crude oil (non-renewable)
High energy cost for pumping (high pressure and temp)
Not carbon neutral
Define biofuel
Fuel produced by plants
Define carbon neutral
No net annual carbon emissions to the atmosphere
Outline the equations to show ethanol as a biofuel is carbon neutral
6 CO2 + 6 H2O > C6H12O6 + 6O2
C6H12O6 > 2 CH3CH2OH + CO2
2 CH3CH2OH + 6 O2 > 3 CO2 + 6 H2O
