SOAP AND DETERGENT

WHAT SOAP IS????

# Soap is a chemical used as a cleansing agent to

remove grease and dirt. 

# Soaps are sodium or potassium salts of long chain fatty acids with 12 to 18 carbon atoms per molecule. 

The general formula of soaps is RCOO-Na+ or RCOO-K+

             

PREPARATION OF SOAP

# Soap is produced by the reaction between sodium hydroxide or 

potassium hydroxide with animal fats or vegetable oils. This reaction is known as saponification.

# Fats and vegetable oils are large, naturally occuring ester 

molecules. when fats or oils are boiled with concentrated 
alkalis such as sodium hydroxide or potassium hydroxide, saponification occurs and the ester molecules are broken down into soap and glycerol.

Fats an oils    +     NaOH or KOH  ---->    Glycerol   +   Soap

# Saponification is the alkaline hydrolysis of enters using alkali solution from a chemical aspect, soaps are sodium salts or potassium salts of long chain fatty acids (with 12 to 18 carbon atoms per molecule)

# Glyceryl tristearates are naturally occurring esters commonly found in animal fats and vegetable oils. When ester is boiled with concentrated  sodium hydroxide solution, saponification (alkaline hydrolysis) occurs and mixture of sodium stearate (soap) and glycerol is obtained.

        

# The soaps produced can be precipitated by adding common salt(sodium chloride) to the reaction mixture. Sodium chloride reduces the solubility of soap in aqueous solution and causes the soap to be precipitate out.

WHAT DETERGENT IS???

1. Detergent are synthetic cleasing agent made from hydrocarbons obtained from petroleum                                                                                                                                fractions.Thus, detergents are petrochemicals.

2. Type of detergent:

              > Anionic detergents (head of the detergent particle contains a negatively-charged ion)

         e.g:  R – O – SO₃^-Na⁺ (sodium alkyl sulphate)

             > Cationic detergents (head of the detergent particle contains a positively-charged ion)

                                e.g: R – N(CH₃)₃⁺Br^-

         > Non-ionic detergents

         eg: R – O – CH₂CH₂OH

PREPARATION OF DETERGENT

1. The detergent, sodium alkyl sulphate can be prepared from alcohols with chain lengths of 12 to 18 carbon atoms in two steps.

        Step 1 : Reaction with concentrated sulphuric acid.

        Step 2 : Neutralisation with sodium hydroxide solution.

2.  An example of long chain alcohol is lauryl alcohol (dodecan-1-ol), CH₃(CH₂)₁₀CH₂OH. The detergent prepared from dodecan- 1-ol is calledsodium dodecyl sulphate (IUPAC name) or sodium lauryl sulphate (common name), CH₃(CH₂)₁₀CH₂O-SO₃^-Na⁺

3.  The equation for the preparation of sodium lauryl sulphate is shown below:

Step 1 : Preparation of lauryl hydrogen sulphate

CH₃(CH₂)₁₀CH₂OH+ H₂SO₄ → CH₃(CH₂)₁₀CH₂OSO₃H + H₂O(HOSO₃H)

Step 2 : Preparation of sodium lauryl sulphate

CH₃(CH₂)₁₀CH₂OSO₃H + NaOH  → CH₃(CH₂)₁₀CH₂OSO₃^-Na⁺ + H₂O

CLEANSING ACTION OF SOAP AND DETERGENT

The cleansing action of soap and detergent depends on their chemical bonding and structures.

~The ionic head’ (negatively-charged) is soluble in water (hydrophilic ) but insoluble in oil.

~The long hydrocarbon ‘tail’ (neutral) is insoluble in water (hydrophobic) but soluble in oil.

Step 1: Action of soap/detergent  on dirt

~when soap or detergent is mixed with water, it lowers the surface tension of water and wets the   dirty surface.

~The negatively-charged ‘head’ of soap or detergent ions dissolves in water (hydrophilic).

~The hydrocarbon ‘tails’ of soap or detergent ions dissolves in the layer of grease (hydrophobic)

Step 2 : Dirt being surrounded by soap/detergent ions

~If the water is agitated slightly, the grease begins to lift off the surface.

Step 3 : Lifting dirt from cloth.

~On further agitation during washing, the greasy dirt is lifted from the surface since the density of grease is less than water.

Step 4 : Emulsifying dirt in water.

~When the water is shaken ,the grease will be emulsified when it breaks into smaller droplets.

~These greasy droplets repel one another because they carry the same charge. As a result, the grease is suspended in the solution.

~When the cloth is rinsed with water, the droplets will be carried away.

EFFECTIVENESS OF THE CLEANSING ACTION OF SOAP AND DETERGENT

Properties	Soap	Detergent
Cleaning power	Less powerfull	More powerfull
Ease of rinsing	It  is difficult  to wash away all  soap on  clothes. The  soap  that  remains leave  and  odour  and  spoils  the fabrics	Rinse out well from clothes
pH	Slightly alkaline	Can be controlled  to suit  the cleaning task
Molecular structure	Determined by  the fatty acids found in the oil or fat used to produce soap	Can  be modified  to  suit  the cleaning  task.  For  example, a  detergent  can  be  made specially  for  cleaning  toilet bowls
Formation of scum	Form scum with hard water	Does  not  form  scum  with hard water