Fat and Oil as higher Esters, sources, properties and Uses. Detergents and Soaps-  Structure, their mode and action.

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TOPIC: Fats and Oils as Higher Esters.

 

CONTENT

Sources, properties and uses detergents and soaps

Structure, their mode and action.

Fats and oils belong to a general group of compounds known as lipids.

SOURCES:

Fats are solids that usually come from animals e.g. Tallow (mutton fat).  Oils are liquids that come from plants e.g. vegetable oil, coconut oil etc.  Both fat and oil are esters of the trihydricalkanol (propane -1, 2, 3- triol).

 

PHYSICAL PROPERTIES:

1. Fats have higher melting points due to the presence of higher proportion of esters of saturated fatty acid.
2. Oils have lower melting points because of the presence of esters of unsaturated fatty acid.

 

CHEMICAL PROPERTIES:

1. Hydrogenation of oils.

This is carried out in the presence of nickel as catalyst at 180⁰C to yield margarine.

 

2. Saponification:

Hydrolysis of fats and oils with canotic alkali yields propane-1,2,3-triol and fatty acid of sodium or potassium.

 

USES OF FATS AND OILS

1. Fats are consumed as food.
2. Oils are used to make margarine.
3. Tallow (a fat) is used for making soaps.
4. Ground nut oil and cotton seed oil are used for cooking.
5. Coconut oil and palm oil are used for making soap and for cooking.

 

EVALUATION

1. Identify two (2) uses of fats and oils.
2. Write two (2) chemical properties and two (2) physical properties of fats and oils.

 

DETERGENTS:

Detergents are any substance which have ability to clean an object e.g. soaps, soap powders, washing liquids and water.

 

TYPES OF DETERGENT

1. SOAPY DETERGENTS: This is soap of sodium salt of fatty acid.

 

PREPARATION

Animal fat or vegetable bits are steam-heated with sodium or potassium hydroxide in a large container.  A concentrated Nuel solution is added to decrease the soluble of the soap – so that it comes out as hard

cake on cooling known as salting out

 

STRUCTURE:-

CH₃(CH₂)₁₆ COOCH₂

CH₃(CH)₂)₁₆ COOCH     +       3NaOH

(Sodium Hydroxide)

CH₃(CH₂)₁₆ COOCH

Propane1,2,3-triyltrioctadecanoate

 

NATURE OF SOAP

Each molecule of soap has long hydrocarbon chain (alkyl) which is attached to ionic head of either COO^– Na⁺ or COO^–K⁺.  The alkyl tail hydrophobic) dissolves oil or organic solvent while the ionic soluble in water (hydrophilic).

 

ACTION OF SOAP (CLEANSING ACTION)

When soap solution is applied to a grease-coated piece of fabric, the soap molecule moves to the grease spot.  The hydrophobic tails dissolve in grease while the hydrophilic dissolves in the water.

The grease spot is lifted up and more soap particles dissolve the grease.

 

2.  SOAPLESS DETERGENTS

Soapless detergents are the more favoured all-purpose cleansing agents nowadays. They are available as liquids or solids. The example of soapless detergent is alkyl benzenesulphates (ABS).  These are sodium salt of an     acid e.g. sulphonic acid.

 

STRUCTURE:

The molecule of detergent has hydrophobic tail and hydrophilic head.

The hydrophobic tail is a long chain hydrocarbon or benzene ring with long alkyl group.

 

The hydrophilic unlike soap can be positively or negative change or neutral.  The high solubility of soapless detergent in water is due to the presence of –SO₃^– Na⁺ in the molecules.

 

The soapless detergents are called synthetic detergents.  The raw materials are petrochemicals from refining crude oil.

 

Hydrophilic

 

 

R    –    SO₃^– Na⁺

Hydrophobic tail

R is a long hydrophobic chain.

 

ACTION OF SOAPLESS DETERGENT

• They do not form scum or react with hydrogen ions.

 

EVALUATION

1. Draw the structure of soapless detergent.
2. State one advantage of soapless detergent over soapy detergent.

 

READING ASSIGNMENT

New School Chemistry by Osei Yaw Ababio pages.509-514

 

WEEKEND ASSIGNMENT

1. The structure of soap according to saponification process is
2. CH₃(CH₂)₁₆COONa B.  CH₃CH₂COOCa    C.  CH₃CH₂CH₂COONa
3. C₂H₅COONa

2          . The example of soapless detergent is

1. alkyl     B.  ethylethanoate    C.  alkanol   D.  alkylbenzenesulphonates
2. Hydrophobic tail of soap dissolves in grease while hydrophilic dissolves in
3. benzene B.  water    C.  propanol    D.  kerosene
4. Fats and oils belong to a general group of compounds known as ………..
5. glycerol   B.  soap              C.  margarine     D.  lipids
6. Hydrolysis of fat and oil to yield alkanol and soap is called …………
7. esterification     B.  hydrogenation     C.  hydrolysis     D.  saponification

 

THEORY

1. Explain the structure of soapless detergent and its mode of action.
2. Explain the following;

(a) saponification                   (b) hydrogenation

 

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