1

Topic 8 – National 5 Chemistry Summary Notes

Everyday Consumer Products

In this topic you will learn about two new homologous series of compounds called

alcohols and carboxylic acids and how they can be used to make an important group of

compounds called esters.

Alcohols from Carbohydrates

When we talk about alcoholic drinks we really mean drinks containing a particular

member of the alcohol family called ethanol.

Glucose is part of a large family of compounds called carbohydrates. Carbohydrates

contain the elements carbon, hydrogen and oxygen with a ratio of 2:1,

hydrogen:oxygen. As you have learnt about in earlier science topics, plants are a source

of carbohydrates and the main carbohydrate found in plants is starch. Starch is the

ideal way for plants to store energy. It is insoluble so cannot be washed away but this

large, insoluble and complex carbohydrate, is broken down easily by enzymes to form

glucose a small, simple sugar molecule which dissolves easily. This type of reaction uses

the addition of water to break down large molecules and is called hydrolysis.

This same hydrolysis reaction breaks down many compounds in our digestive

systems using acid and enzymes so that small soluble molecules can be made and

easily passed through the gut wall and on into our cells.

Remember!!- Enzymes are biological catalysts used by living things to make reactions

go faster. A good example of an enzyme is the catalyst amylase, used to break starch

down into simple sugars.

Summary of Properties of Starch and Glucose

Type of

Carbohydrate

Formula Solubility Reaction with

Iodine

Reaction with

Benedict’s

Starch

Glucose

LI 1-4

Ethanol is generally made by a process called fermentation. Fermentation is brought

about by enzymes in yeast which convert the simple sugar called glucose into ethanol.

2

Fermentation

Fermentation is big business in Scotland! There are nearly 20,000,000 barrels of

whisky sitting maturing in warehouses at any one time all made by fermenting barley.

Many different alcoholic drinks are made from different plant sources. They all contain

the alcohol called ethanol but have many other flavour molecules to give distinctive

drinks:

Type of

alcoholic drink

Plant source

of carbohydrate

Alcohol Content

(%)

Whisky Barley

Beer

Wine

Cider

We can make ethanol by fermentation in the school laboratory:

C6H12O6 2C2H5OH + 2CO2

glucose ethanol + carbon dioxide

We can prove we made carbon dioxide by bubbling it through limewater because it will

_________________________.

How can we prove we have made ethanol?

Answer- Ethanol has a lower boiling point than water ( 78⁰C) so we can separate it out

by distillation and show that it burns. Ethanol burns very well. (it also smells!!)

The maximum % of alcohol we can produce by fermentation is around 14% because the

ethanol is a poison and yeast, a living organism, is killed by high levels of ethanol.

Distillation has to be used to produce drinks of a higher alcohol content.

LI 5&6

http://www.google.co.uk/imgres?q=fermentation+laboratory+equipment+diagram&biw=1192&bih=598&tbm=isch&tbnid=6WMH-LJmjzTSyM:&imgrefurl=http://www.nuffieldfoundation.org/practical-chemistry/fermentation-glucose-using-yeast&docid=bTh7F30YYn8ISM&imgurl=http://www.nuffieldfoundation.org/sites/default/files/images/fermentation1-97.jpg&w=350&h=158&ei=rI0DUuKuMbST0QWDvYDYCQ&zoom=1&ved=1t:3588,r:87,s:0,i:349&iact=rc&page=6&tbnh=126&tbnw=280&start=76&ndsp=19&tx=146&ty=76

3

Enzyme Optimal Conditions

Not only do high levels of ethanol stop yeast working, the activity of the enzymes in

yeast ( and all enzymes) are easily affected by the conditions they are working in. They

are sensitive to changes in temperature and pH and work best within a narrow range of

pH and temperature. Each individual enzyme has its own set of ideal conditions called

“optimal conditions”.

Units of Alcohol

As mentioned ethanol is a poison and it is important not to take too much. You will

research as a homework how many units of alcohol we should be drinking and what

volume of each drink contains one unit of alcohol:

Alcoholic Drink Alcohol Content

%

What volume equals

ONE unit (cm3)

whisky

gin

beer

vodka

wine

http://www.google.co.uk/url?sa=i&rct=j&q=enzyme optimum graphs&source=images&cd=&cad=rja&docid=vD7ee27O2EXVzM&tbnid=TH9CD9N-gtRe2M:&ved=0CAUQjRw&url=http://revisionworld.co.uk/gcse-revision/biology/cell-activity/proteins-and-amino-acids/enzymes&ei=lpMDUun1Fo2r0gXrv4DADA&psig=AFQjCNGQZwxRM1ZC6TtgbbMgzzNrZmw9dw&ust=1376052276664180

4

Structure and Functional Group of Alcohols

Ethanol is the second member of a homologous series of alcohols known as alkanols

because they are based on the alkane structure.

As well as by fermentation ethanol can be made by an addition reaction called

“hydration” when a molecule of water is added to the unsaturated ethene molecule.

This sort of reaction requires high temperatures and pressure and a phosphoric acid

catalyst:

Names and structures of alkanols can easily be worked out because they are closely

related to the corresponding alkane. A hydrogen has been replaced by a new functional

group ( –OH) called the hydroxyl group and the name of the alkane has the ―e‖ removed

and an ― ol‖ substituted.

Name of

alcohol

Molecular formula

of alcohol

Structure formula of

alcohol

methanol

CH3OH

ethanol

C2H5OH

propanol

C3H7OH

From this table you can work out the general formula of the alkanols:

LI 7

CnH2n+1OH

http://www.google.co.uk/url?sa=i&rct=j&q=hydration of ethene equation&source=images&cd=&cad=rja&docid=DyybRlCANnfznM&tbnid=aHnH7wJOps0KFM:&ved=0CAUQjRw&url=http://www.chemhume.co.uk/ASCHEM/Unit 2/Ch9 Alkanes/Alkanesc.htm&ei=XpgDUrq2GoKm0wW73oGABQ&psig=AFQjCNFV3QtdtV6dsDxp6wKwBe18m7wG8A&ust=1376053602141331

5

Drawing and Naming Alkanols

All alkanols with more than 2 carbons have isomers and therefore have different names

due to the position of the hydroxyl group:

propan-1-ol propan-2-ol

Shortened structural formulae also show the different positions of the hydroxyl

groups:

Propan-1-ol - CH3CH2CH2OH

Propan-2-ol - CH3CH(OH)CH3

Systematic naming rules:

1. Count the number of carbons to give the correct basic name ie

4 carbons = butanol

5 carbons = pentanol etc…

2. Count from the end which gives the lowest number to show the position of the

hydroxyl group.

NOTE- You will only be asked to name straight chained alkanols.

Activity: Complete the following table

Name of alkanol Full structural formula Shortened structural

formula

Butan-2-ol

Pentan-3-ol

LI 8

6

Properties of Alkanols

Alkanols are a homologous series therefore they have similar chemical properties and

gradually changing physical properties. We will look at physical properties first:

Boiling Points

Using the data booklet, page 6, fill in the following table:

Name of Alkanol Boiling Point (ºC)

Methanol

Ethanol

Propan-1-ol

Butan-1-ol

There is a clear trend. The larger the molecule the higher the boiling point. This is

similar to what we discovered with the fractions of crude oil. The larger the molecule

the more energy is needed to separate the molecules from each other because larger

forces of attraction have to be overcome.

Boiling Points of Isomers

Using the data booklet, page 6, fill in the following table:

Name of Alkanol Boiling Point (ºC)

Propan-1-ol

Propan-2-ol

Butan-1-ol

Butan-2-ol

Isomers have different boiling points. The position of the hydroxyl group has an

effect. If the hydroxyl group is at the end of a chain the boiling point is higher so the

force of attraction must be higher. The effect of the hydroxyl group can be seen even

more if you compare two molecules with similar formula mass:

Propane (formula mass 44) has a boiling point of (minus) - 44 ºC

Ethanol ( formula mass 46) has a boiling point of +78ºC due to the attractive force of

the hydroxyl group.

LI 9

7

Solubility in water

Methanol and ethanol dissolve well in water, they mix completely and are described as

totally miscible.

As the hydrocarbon chain length increases, the solubility decreases so the bigger

alkanol molecules are less soluble in water.

Alkanol Formula Solubility in water in g/l

Butan-1-ol C4H9OH 63

Pentan-1-ol C5H11OH 22

Hexan-1-ol C6H13OH 5.9

Heptan-1-ol C7H15OH 1.7

Octan-1-ol C8H17OH 0.5

Draw a spike bar graph of the number of carbon atoms in the molecule versus the

solubility in water and staple it to your booklet here.

pH of Alkanols

Alkanols have no effect on the balance between hydroxide ions and hydrogen ions in

water therefore the pH is neutral.

Uses of Alkanols

Ethanol is often used as an ingredient in industry to make other compounds. It is also

an important solvent in perfumes and food flavourings. Look in your kitchen cupboards

and see if you can find ethanol in the ingredient lists.

Propan-2-ol is also used as a solvent and you have probably used it to clean your

computer screen or in a gel to sanitise your hands. Remember alkanols are poisonous to

bacteria as well as us!

Chemical Properties of Alkanols

All alkanols burn, ethanol and methanol in particular burn very cleanly, we will be

investigating the uses of alkanols as fuels at the end of this topic.

Alkanols also take part in many other reactions. One very important reaction is

oxidation. This oxidation reaction increases the ratio of oxygen to hydrogen in the

molecule and converts an alkanol, with a hydroxyl group on an end carbon, into a new

homologous series of compounds called the carboxylic acids. This reaction naturally

occurs in wine when the ethanol reacts with oxygen in the air to form ethanoic acid

(vinegar). This is what turns wine sour.

http://www.google.co.uk/imgres?q=burning+symbol&um=1&hl=en&biw=975&bih=528&tbm=isch&tbnid=hRUslc-JOL5ftM:&imgrefurl=http://sweetclipart.com/red-and-yellow-fire-logo-408&docid=zUL8NJ1kyJtliM&imgurl=http://sweetclipart.com/multisite/sweetclipart/files/red_yellow_fire_logo.png&w=5084&h=7399&ei=lWQwUuGFK8yp7AatjYHIAQ&zoom=1&iact=hc&dur=158&page=1&tbnh=145&tbnw=100&start=0&ndsp=19&ved=1t:429,r:2,s:0,i:88&tx=82&ty=183&vpx=183&vpy=118&hovh=271&hovw=186

8

Carboxylic Acids

Carboxylic acids are a homologous series that all contain the functional group called the

carboxyl group:

If the carboxyl group is on an alkane chain then the name will be similar to the alkane it

comes from but with an ―oic‖ ending. This family of carboxylic acids are known as the

―alkanoic acids”.To work out the name just count the carbons:

Number of carbons

Name of

carboxylic acid

1

Methanoic acid

2

Ethanoic acid

3

Propanoic acid

4

5

Shown below is the full structural formula of the most well known carboxylic acid called

ethanoic acid (vinegar):

Ethanoic acid

LI 10

http://www.google.co.uk/imgres?imgurl=http://1.bp.blogspot.com/-0S1obHMc-oY/UIZEha7UDtI/AAAAAAAAABU/9VLUOTUd2MU/s320/carboxyl.jpg&imgrefurl=http://scienceineverydayterms.blogspot.com/2012/10/facts-on-functional-groups.html&h=344&w=514&sz=40&tbnid=RTUUOe528RBPaM:&tbnh=86&tbnw=129&prev=/search?q=carboxyl+group&tbm=isch&tbo=u&zoom=1&q=carboxyl+group&usg=__0QRwPB2dCFOqDFqSvxta_j5ifiQ=&docid=j_qgNo1JBpulHM&sa=X&ei=luYDUvPaIsW40QWS-oGgAQ&sqi=2&ved=0CE8Q9QEwBA&dur=687http://www.google.co.uk/imgres?imgurl=http://0.tqn.com/d/chemistry/1/0/f/m/aceticacid.jpg&imgrefurl=http://chemistry.about.com/od/factsstructures/ig/Chemical-Structures---E/Ethanoic-Acid---Acetic-Acid.htm&h=550&w=800&sz=15&tbnid=iuK6p2TzFQVAsM:&tbnh=93&tbnw=135&prev=/search?q=ethanoic+acid+formula&tbm=isch&tbo=u&zoom=1&q=ethanoic+acid+formula&usg=__1f1a-vB5-l_67BFT_ULuzxx9bJU=&docid=3feLzEuMeP9kSM&sa=X&ei=9eUDUofeBczu0gXm34GYAw&ved=0CFQQ9QEwBA&dur=930

9

Structures of Carboxylic Acids

All alkanoic acids are an alkane chain with the last carbon converted to a –COOH.

To draw the structure of an alkanoic acid from its name work out the number of

carbons, fill them completely with hydrogen except for the last carbon which needs to

be double bonded to an oxygen and single bonded to an –OH group to form the carboxyl

group. Try these:

Name of

carboxylic acid

Shortened Structural

Formula

Full Structural formula

Propanoic acid

CH3CH2COOH

Butanoic acid

CH3CH2CH2COOH

CH3CH2CH2CH2COOH

Carboxylic Acids in the Natural World

You will all have met carboxylic acids in everyday life. They are hard to miss because

they are a very smelly, stingy group of compounds. The best known are:

1. Methanoic acid (old name formic acid‖) is in ant and bee stings.

2. Lactic acid is what causes milk to go sour.

3. Citric acid is in fruit.

4. Vinegar, a dilute and smelly solution of ethanoic acid.

5. Vomit!!

Part of the reason vomit is so smelly is that some of the digestion products of fats are

brought back up. When fats are digested a special group of carboxylic acids called

fatty acids are made.

LI 11

10

Uses of Vinegar

Read the extract below then answer the questions:

Vinegar’s role in history is well documented. This versatile product was used by

everyone—from kings and conquerors to explorers and everyday people.

The Babylonians used vinegar to preserve and pickle food.

Hippocrates prescribed vinegar as a remedy for a variety of ailments.

Caesar’s armies used vinegar as a beverage.

Hannibal drenched huge boulders in hot vinegar which cracked them into small

pieces, enabling his army to continue its journey across the Alps.

Helen of Troy bathed in vinegar to relax.

Jesus was offered vinegar before he was crucified.

Early Europeans used vinegar as a deodorizer.

During the Bubonic Plague people poured vinegar on their skin to protect

themselves from germs.

Cleopatra dissolved pearls in vinegar to prove that she could consume a fortune

in a single meal.

Sailors used vinegar as a food preservative during long voyages.

World War I medics used vinegar to treat soldiers’ wounds.

Today, people are still using white distilled vinegar in hundreds of different ways—from

cooking and cleaning to gardening and the laundry.

Q1. Vinegar is often used to remove lime scale. Lime scale is made of the same

substance that pearls are. Suggest why vinegar is able to dissolve lime scale.

Q2. Can you give two examples of foods we still preserve using vinegar.

Q3. Can you suggest why vinegar was used to treat wounds and why this might be linked

to its preservative effect.

11

Making Esters

One of the main industrial uses of carboxylic acids is to make compounds called esters.

Esters are an important group of carbon based compounds formed by reacting a

carboxylic acid molecule and an alcohol molecule together. The reaction requires a

catalyst such as concentrated sulphuric acid.

Word equation:

The characteristic link between the molecules is called the ester link

This type of reaction is called a condensation reaction

Condensation reactions are reactions which join two molecules together

by releasing a small molecule, often water

A condensation reaction that makes an ester is also called esterification

Condensation reactions are reversible

The name of the ester comes from the alcohol and carboxylic acid that

made it with the alcohol part coming first

LI 12

The "ester link"

methanol + butanoic acid ⇄ methyl butanoate (ester) + water

CH3OH + C3H7COOH ⇄ C3H7COOCH3 (ester) + H2O

http://www.google.co.uk/url?sa=i&rct=j&q=esterification+general+equation&source=images&cd=&cad=rja&docid=hBeUqWlnKLJQaM&tbnid=1eQKqrgtJEdCJM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway_pre_2011/carbon_chem/3_smells1.shtml&ei=jxYEUuvgDoH40gXS24GYCw&bvm=bv.50500085,d.d2k&psig=AFQjCNEQ5f-SzAh-FIlqD9xtwXQ0GADdkA&ust=1376085986258140

12

Names of Esters

Identify the names of the alcohol and the carboxylic acid used to make the

ester, change the endings and add them together:

Alcohol

Name

Ester

Name

Carboxylic Acid

Name

Ester Name

methanol methyl…… methanoic acid ……methanoate

ethanol ethyl….. ethanoic acid …..ethanoate

propanol propyl…. propanoic acid …..propanoate

butanol butyl….. butanoic acid …..butanoate

Properties and Uses of Esters

Esters can be made easily in the lab.

Once they are made they are identified due to their characteristic fruity smells and

the fact that they do not mix with water and form an oily, immiscible layer.

Esters are often used as food flavourings

Esters are often used as perfumes

Many nail varnishes contain ester solvents because they easily evaporate

LI 13