(e) Alcohols

4:30 (Triple only) understand how to draw structural and displayed formulae for methanol, ethanol, propanol (propan-1-ol only) and butanol (butan-1-ol only), and name each compound, the names propanol and butanol are acceptable

Structural formula and displayed formula for methanol:

CH₃-OH

 

Structural formula and displayed formula for ethanol:

CH₃-CH₂-OH                    (or simply C₂H₅OH)

Image result for ethanol

 

Structural formula and displayed formula for propan-1-ol:

CH₃-CH₂-CH₂-OH

 

Structural formula and displayed formula for butan-1-ol:

CH₃-CH₂-CH₂-CH₂-OH

 

4:31 (Triple only) know that ethanol can be oxidised by: burning in air or oxygen (complete combustion), reaction with oxygen in the air to form ethanoic acid (microbial oxidation), heating with potassium dichromate(VI) in dilute sulfuric acid to form ethanoic acid

1) Ethanol can be oxidised by complete combustion. With excess oxygen the complete combustion of ethanol (C₂H₅OH) in air produces carbon dioxide and water:

C₂H₅OH (l)         +         3O₂ (g)         →         2CO₂ (g)         +         3H₂O (l)

 

2) Ethanol can be oxidised in air in the presence of microorganisms (‘microbial oxidation’) to form ethanoic acid (CH₃COOH).

 

3) Ethanol can be oxidised by heating with the oxidising agent potassium dichromate(VI) (K₂Cr₂O₇) in dilute sulfuric acid (H₂SO₄).

In the equation below, [O] means oxygen from an oxidising agent.

CH₃CH₂OH         +         2[O]         →         CH₃COOH         +         H₂O

This mixture starts orange but when the reaction happens turns green which indicates the presence of Cr³⁺ ions which are formed when the potassium dichromate(VI) is reduced.

4:32 (Triple only) know that ethanol can be manufactured by: 1) reacting ethene with steam in the presence of a phosphoric acid catalyst at a temperature of about 300⁰C and a pressure of about 60–70atm; and 2) the fermentation of glucose, in the absence of air, at an optimum temperature of about 30⁰C and using the enzymes in yeast

In the hydration of ethene, ethanol is made by passing ethene and steam over a catalyst.

Water is added to ethene, this is known as hydration.

Conditions

Catalyst: Phosphoric acid (H3PO4)

Temperature: 300°C

Pressure: 60 atm

 

 

Fermentation is the conversion of sugar, e.g. glucose into ethanol by enzymes from yeast.

 

Conditions

Catalyst: Zymase (enzyme found in yeast)

Temperature: 30°C  –  The process is carried out at low temperatures as not to denature the enzymes.

Other: Anaerobic (no oxygen present) – if oxygen were present, the yeast produce carbon dioxide and water instead of ethanol.

 

4:33 (Triple only) understand the reasons for fermentation, in the absence of air, and at an optimum temperature

In the production of ethanol the process of fermentation is carried out at a low temperature (30⁰-40⁰).

Above 40⁰ the enzymes would permanently lose their structure (denature).

At a temperature lower than 30⁰ the process would be too slow.

 

Fermentation is conducted in the absence of air. In the presence of air (aerobic conditions), enzymes in the yeast produce carbon dioxide and water instead of ethanol.

 

 

Select a set of flashcards to study:

     Terminology

     Skills and equipment

     Remove Flashcards

Section 1: Principles of chemistry

      a) States of matter

      b) Atoms

      c) Atomic structure

     d) Relative formula masses and molar volumes of gases

     e) Chemical formulae and chemical equations

     f) Ionic compounds

     g) Covalent substances

     h) Metallic crystals

     i) Electrolysis

 Section 2: Chemistry of the elements

     a) The Periodic Table

     b) Group 1 elements: lithium, sodium and potassium

     c) Group 7 elements: chlorine, bromine and iodine

     d) Oxygen and oxides

     e) Hydrogen and water

     f) Reactivity series

     g) Tests for ions and gases

Section 3: Organic chemistry

     a) Introduction

     b) Alkanes

     c) Alkenes

     d) Ethanol

Section 4: Physical chemistry

     a) Acids, alkalis and salts

     b) Energetics

     c) Rates of reaction

     d) Equilibria

Section 5: Chemistry in industry

     a) Extraction and uses of metals

     b) Crude oil

     c) Synthetic polymers

     d) The industrial manufacture of chemicals