DRAFT GCSE Chemistry- Organic Chemistry (Y11)

Topic 4 (alcohols, fermentation, carboxylic acids, condensation polymerisation)

What does a functional group tell you?

Chemical properties

What is an alcohol’s functional group?

OH

What do all alcohols end in?

-ol

What is the general formula for an alcohol?

C_nH_2n+1OH

What is the OH part of an alcohol called (other than functional group)?

Hydroxyl

Properties of alcohols

• Soluble in water

• Solutions have a neutral pH

• Flammable

Word equation for alcohol combustion

alcohol + oxygen → carbon dioxide + water

Symbol equation for combustion, using methanol as an example.

CH₃OH_(l) + 1.5O_2(g) → CO_2(g) + 2H₂O_(g)

Why is water a gas in alcohol combustion?

Because it is being given off as steam

Word equation for alcohol’s reaction with sodium

alcohol + sodium → sodium alkoxide + hydrogen

Symbol equation for alcohol’s reaction with sodium

2CH₃OH + 2Na → 2CH₃ONa + H₂

What do you do to form an alkoxide in a symbol equation?

• Remove the hydrogen from the functional group (OH)

• Replace with a sodium atom (OH → ONa)

Word equation for oxidation of alcohols

alcohol + oxygen → carboxylic acid

Uses of alcohols in industry

• Methanol and Ethanol are used as solvents

  • dissolve most substances insoluble in water

• The first four alcohols are used as fuels

  • they burn cleanly and without smell

Formula for Methanol

CH₃OH

Formula for Ethanol

C₂H₅OH

Formula for Propanol

C₃H₇OH

Formula for Butanol

C₄H₉OH

Describe how you could compare the reactivity of different alcohols with sodium metal. [3]

• Reacting the different alcohols (e.g. methanol, ethanol) with the same mass of sodium metal

• In a test tube with a rubber bung and a tube leading from that connecting to a gas syringe

• The more hydrogen gas given off, the more reactive the alcohol

Which of the four alcohols has the lowest boiling point?

Methanol

Which of the four alcohols has the highest boiling point?

Butanol

Why is this?

There are more strong covalent bonds to break, thus requiring more energy.

Give three reasons why ethanol, propanol and butanol are part of the same homologous series. [3]

• Same functional group (OH)

• Same general formula (C_nH_2n+1OH)

• Similar physical properties

How can ethanol be made?

Fermentation

Word equation for fermentation

glucose →ethanol + carbon dioxide

Symbol equation for fermentation

C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂

Fermentation

Using yeast to convert sugar into alcohol

Fermentation: Step 1

Yeast and a carbohydrate solution are mixed in a clean container

• sealed and kept in a warm place

Fermentation: Step 2

Temperature is kept between 30-40 degrees Celsius for fastest fermentation

Fermentation: Step 3

Glucose is broken down anaerobically

Fermentation: Step 4

When concentration of ethanol reaches 10-20%, fermentation stops

• yeast cells are killed by the alcohol

Fermentation: Step 5

Once yeast falls to the bottom of the container, ethanol can be collected from the top

What happens if oxygen is allowed into the container?

Ethanoic acid (vinegar) is created

What is ethanol produced via fermentation like?

Very dilute

How would you make ethanol more concentrated?

By distilling it

What is ethanol’s boiling point like in comparison to water’s?

Low

What does this mean for distillation?

Ethanol can be collected after water

Describe how the solution of sugar in water is used to produce the mix of ethanol & water. [2]

• add yeast

• ferment it with absence of air

Explain why fermentation is carried out in the absence of air and with a temperature below 40 degrees Celsius. [4]

• Carried out in absence of air to prevent formation of ethanoic acid instead of ethanol

• Carried out < 40 degrees because yeast is an enzyme, which denatures above optimum temperature, causing fermentation to slow down.

What is the functional group of a carboxylic acid?

COOH

What is the functional group of a carboxylic acid called?

Carboxyl

What is the functional group of an alcohol called?

Hydroxyl

What is a C=O bond called?

Carbonyl

What is the general formula for carboxylic acids?

C_n-1H_2n-1COOH

What happens when something is oxidised?

It gains oxygen

What happens when alcohols are oxidised?

They form carboxylic acids

What can carboxylic acids do in solution?

Neutralise (alkali) metals

Example of carboxylic acid neutralisation

methanoic acid + sodium → sodium methanoate + hydrogen

Formula for methanoic acid

HCOOH

Displayed formula for methanoic acid

Formula for ethanoic acid

CH₃COOH

Displayed formula for ethanoic acid

Formula for propanoic acid

C₂H₅COOH

Displayed formula for propanoic acid

Formula for butanoic acid

C₃H₇COOH

Displayed formula for butanoic acid

acid + metal →

salt + hydrogen

acid + metal oxide →

salt + water

acid + metal hydroxide →

salt + water

acid + metal carbonate →

acid + water + carbon dioxide

How are esters formed?

When a carboxylic acid and an alcohol react

Word equation for reaction between ethanoic acid and ethanol

ethanoic acid + ethanol → ethyl + ethanoate + water

Displayed formula for reaction between ethanoic acid and ethanol

What is an ester’s functional group?

-COO-

What do the names of esters end in?

-oate (e.g. methyl methanoate)

What is also used in an ester reaction?

An acid catalyst, e.g. sulfuric acid

Describe what you would see when a piece of magnesium ribbon is added to dilute ethanoic acid. [2]

• Effervescence

• Solid (Mg) disappears

What is different about condensation polymerisation?

Involves two different types of monomer

What happens in condensation polymerisation?

The monomers reacts together and bonds form between them, making polymer chains.

How many functional groups does each monomer contain?

At least two, one on each end of the molecule

What happens when the functional groups of two adjacent molecules react?

A water molecule is lost

Diol

An alcohol with two hydroxyl (OH) functional groups

Diocarboxylic acid

A carboxylic acid with two carboxyl (COOH) functional groups