Alcohols

Define primary secondary and tertiary alcohol

primary - the OH carbon is attached to 1xC and 2xH

Secondary - the OH carbon is attached to 2xC and 1xH

tertiaru - the OH carbon is attached to 3xC and 0xH

Q: Draw the displayed formula of 2 functional group isomers of butan-1-ol

pg 5 (ethers)

methoxypropane

ethoxyethane

3 physical properties of alcohols

reactivity - more electronegative oxygen produces polar bond

Boiling point is high - form hydrogen bonds

Soluble in water - form hydrogen bonds in water

tasks pg6-7

s

Use of alcohols

a solvent

alcoholic drinks

How are alcohols produced industrially?

Hydration of alkenes in presence of acid catalyst

Fermentation of glucose

Describe fermentation

carbohydrates broken down into sugars

sugars converted to ethanol by anaerobic respiration

ethanol is removed from reaction mixture by fractional distillation

Reagent and condition for fermentation

glucose and yeast

30-40 degrees
aqueous
anaerobic

Why must fermentation be carried out in absence of air?

prevent oxidation of alcohol

Why must fermentation use a compromise of 35degrees?

a reasonable rate of reaction is achieved without denaturing the enzyme

Why does the fermentation stop when the mixture contains 15% ethanol?

too much ethanol will poison yeast so it is seperated from mixture by fractional distillation

Compare hydration of ethene and fermentation to prdocue alcohols (6)

Reagents: steam - glucose
Conditions: 300,60atm,concH3PO4 catalyst - yeast,30-40,anaerobic
Raw material: Crude oil is non renewable - sugar is renewabel
Quality: Pure - impure
Rate of reaction: fast - slow
Energy: High - low energy use
Type of process: continous - batch
Atom economy: 100% - 52.1%
Costs: expensive set up low labour - low set up high labour

equation of fermentation

C₆H₁₆O₆ → 2C₂H₅OH + 2CO₂

What is a biofuel?

A fuel derived or produced from renewable biological sources

What is carbon neutral?

has no net carbon emissions into the atmosphere

Show biofuels are carbon neutral

pg12

photosynthesis of glucose

6CO₂ + 6H2O → C₆H₁₂O₆ + 6O₂

= -6CO₂

Fermentation fo glucose

C₆H₁₂O₆ → CO₂ + 2C₂H₅OH

= + 2CO₂

Combustion of ethanol

2C₂H₅OH + 6O₂ → 4CO₂ + 6H₂O

= +4CO₂

-6CO₂ + 2CO₂+4CO₂ = 0

Why is biofuel not actually carbon neutral?

fossil fuels are needed to burn to power machinery used to make fertilisers for the crops, to transport and refine them. Burning fuel produces carbon dioxide so it is therefore not carbon neutral

Disadvantages of bioethanal

land used to grow crops fro fuel cannot grow food

eutrophication

fertilisers added

deforestation to create land for biofuel

Three types of reaction of alcohols

combustion

elimination

oxidation

Q: Draw a diagram of apparatus needed to convert butan1ol to butanal

pg18

Why does water go in from the bottom in leibig condenser?

to go against gravity so more efficient cooling of the vapour

Describe the oxidation of alcohols and state the half equation

by oxidising agent like acidified potassium dichromate (H2SO4 and K2Cr2O7)

an orange to green solution

Cr₂O₇^2- +14H+ + 6e- → 2Cr³⁺ + 7H₂O

Possible oxidation product of a primary alcohol e.g ethanol

ethanal - aldehyde

then

ethanoic acid - carboxylic acid

Possible oxidation product of a secondary alcohol e.g propan2ol

propanone - ketone

Possible oxidation product of a tertiary alcohol

not oxidised when heated with potassium dichromate

Q: Write an equation illustrating the oxidation of ethanol to ethanal and state the reagents and conditions

CH₃CH₂OH + [O] → CH₃CHO + H₂O

potassium dichromate solution

acidified

immediate distillalation

Why does ethanal have a lower boiling point than ethanol?

There are hydrogen bonds between molecules of ethanol.

there are permanent dipole dipole forces between molecules of ethanal.

hydrogen bonds are stronger

Equation for oxidation from ethanol to ethanal

[Cr₂O₇^2- +14H+ + 6e- → 2Cr³⁺ + 7H₂O
CH₃CH₂OH → CH₃CHO + 2H+ + 2e-]

8H+ + Cr₂O₇^2- + 3CH₃CH₂OH → 3CH₃CHO + 2Cr³⁺ + 7H₂O

equation of propan1ol to propanal

CH₃CH₂CH₂OH + [O] → CH₃CH₂CHO + H₂O

Condition for primary alcohol too form carboxylic acid

excess oxidising agent and reflux conditions

Equation for ethanol to ethanoic acid

CH₃CH₂OH + 2[O] → CH₃COOH + H₂O

Q: Draw a diagram to convert ethanol to ethanoic acid

pg 22 reflux

Equation for oxidation of ethanol to ethanioic acid

2CH₃CH₂OH + 16H+ + 2Cr₂O₇^2- → 4Cr³⁺ + 11H₂O + 3CH₃COOH

Oxidation of the secondary alcohol propan2ol equation

CH₃CH(OH)CH₃ + [O] → CH₃COCH₃ + H₂O

Technique for

primary alcohol to aldehyde

primary alcohol to carboxylic acid

distillation

reflux

Q: How would you modify the apparatus to produce aldehyde rather than carboxylic acid?

Distillation using a Liebig condenser

(aldehyde needs distillation and c-acid needs reflux)

Q: Give the name and skeletal structure of the isomer of pentan1ol that is not oxidised explain why?

2methylbutan2ol

tertiary alcohol so no H atom on C bonded to OH

Q: Equation for the reduction of tollen’s reagent

[Ag(NH₃)₂]⁺ + e- → Ag + 2NH₃

What is tollen’s reagent?

ammoniacal silver nitrate [Ag(NH₃)₂]⁺

Equation of ethanal and tollens

2[Ag(NH₃)₂]⁺ + 2e- → 2Ag + 4NH₃

H₂O + CH₃CHO → CH₃COOH + 2H+ + 2e-

2[Ag(NH₃)₂]⁺ + H₂O + CH₃CHO → 2Ag + CH₃COOH + 4NH₃ + 2H+

Equation for reduction of fehlings solution

2e- + H₂O + 2Cu²⁺ → Cu₂O + 2H+

Equation of propanal with feelings solution

2e- + H₂O + 2Cu²⁺ → Cu₂O + 2H+

H₂O + CH₃CH₂CHO → CH₃CH₂COOH + 2H+ + 2e-

2H₂O + 2Cu²⁺ + CH₃CH₂CHO → CH₃CH₂COOH + Cu₂O + 4H+

Equation to test for carboxylic acid (2)

2CH₃COOH + Na₂CO₃ → CO₂ + H₂O + 2NaCH₃COO

2CH₃COOH +Mg → Mg(CH₃COO)₂ + H₂

what ion is formed from ethnic acid

ethanoate ion

CH₃COO^-