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AS CHEMISTRY > ALCOHOLS > Flashcards

ALCOHOLS Flashcards

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1
Q

Outline the general formula for alcohols

A

CnH2n+1OH

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2
Q

Outline the rules for naming alcohols

A

-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

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3
Q

Outline the bond angles in an alcohol

A 
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)

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4
Q

Outline the boiling points of alcohols

A

Low volatility
High BP
Due to ability to form hydrogen bonds

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5
Q

Outline the different types of alchol

A

Primary (1 carbon attached to C-OH)
Secondary (2 carbon attached to C-OH)
Tertiary (3 carbon attached to C-OH)

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6
Q

Outline the oxidation of a primary alcohol

A

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

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7
Q

How is an oxidising agent represented?

A

[O]

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8
Q

The equation for propan-1-ol to propanal

A

CH3CH2CH2OH + [O] > CH3CH2CH2CHO + H2O

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9
Q

Outline the rules for drawing distillation

A

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

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10
Q

Why is distillation used?

A

Separation technique
Of organic product from its reacting mixture

Collect distillate at approximate boiling point range of desired liquid

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11
Q

Outline the FULL oxidation of a primary alcohol

A

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

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12
Q

The equation for propan-1-ol to propanoic acid

A

CH3CH2CH2OH +2[O] > CH3CH2COOH + H2O

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13
Q

Outline the rules for drawing reflux

A

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

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14
Q

Why is reflux used?

A

Heating organic reaction mixtures for long periods

Prevents organic vapours from escaping by condensing back to liquid

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15
Q

What are anti-bumping granules?

A

Added to distillation and reflux reactions to prevent vigorous, uneven boiling
and reduce the formation of large bubbles
by making small bubbles

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16
Q

Outline the oxidation of a secondary alcohol

A

Reagent: Potassium dichromate (VI) solution and dilute sulphuric acid (H+/Cr2O7^2-)
Conditions: heat under reflux

Secondary alcohol to ketone

17
Q

Why can’t tertiary alcohols be oxidised by potassium dichromate?

A

There are no hydrogen atoms bonded to the carbon with the OH group

18
Q

Outline the test for alcohols

A

Add H+/Cr2O7^2- (potassium dichromate solution)

Orange to green (CwO7^2- > Cr^3+)

19
Q

Outline the test for aldehydes

A

Tollens’ Reagent (heat gently 60C)
Produces silver mirror inside the test tube

Fehling’s Solution/Benedict’s Reagent (heat gently)
Blue to Red precipitate

20
Q

Outline the test for a carboxylic acid

A

Add sodium carbonate/sodium hydrogen carbonate

Bubbles of CO2

21
Q

Outline the reaction of alcohols with dehydrating agents

A

Reagents: Concentrated sulphuric/phosphoric acid
Dehydrating agent/catalyst
Conditions: Warm under reflux
Mechanism: acid catalysed elimination

Alcohol to alkene

22
Q

The reaction of propan-1-ol to propene

A

CH3CH2CH2OH > CH2=CHCH3 + H2O

23
Q

Outline an acid catalysed elimination mechanism

A 
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+
24
Q

Outline fermentation to form ethanol

A

Conditions: Yeast, No Air, Temp (30-40C)

C6H12O6 > 2 CH3CH2OH + 2 CO2

Batch process

25
Q

Outline hydration/addition to form ethanol

A

Conditions: High temp (300-600C), High pressure (70atm) strong acid catalystic (eg conc H3PO4)

CH2=CH2 + H2O > CH3CH2OH

Continuous process

26
Q

Outline the strengths of fermentation forming ethanol

A

Sugar is renewable
Production uses lower level technology/equipment
Low temp and pressures needed
Carbon neutral

27
Q

Outline the strengths of hydration forming ethanol

A

Faster
Purer product
Continuous process
Atom economy 100%

28
Q

Outline the weaknesses of fermentation forming ethanol

A

Batch process is slow (high production cost)
Non-pure product (requires fractional distillation)
Depletes land used for growing crops
CO2 product reduces atom economy

29
Q

Outline the weaknesses of hydration forming ethanol

A

High technology equipment used (expensive)
Ethene is from crude oil (non-renewable)
High energy cost for pumping (high pressure and temp)
Not carbon neutral

30
Q

Define biofuel

A

Fuel produced by plants

31
Q

Define carbon neutral

A

No net annual carbon emissions to the atmosphere

32
Q

Outline the equations to show ethanol as a biofuel is carbon neutral

A

6 CO2 + 6 H2O > C6H12O6 + 6O2

C6H12O6 > 2 CH3CH2OH + CO2

2 CH3CH2OH + 6 O2 > 3 CO2 + 6 H2O

AS CHEMISTRY (17 decks)

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