Soap Chemistry involves all substances that are used in the manufacturing process of this product.
In general, we call solid soaps the special soaps used for body hygiene. They have specific chemical components for this purpose.
As they are soaps, solid soaps foam and remove body dirt (composed of oils, fats, microorganisms, etc.). To produce a solid soap, the following basic components are used:
Fats or Oils;
Barrilha (sodium carbonate) or hydroxides (sodium or potassium);
Essence.
- a) Chemical process of forming a solid soap
The solid soap is obtained from a reaction process called the saponification reaction . In this reaction, the oil or fat reacts with the basic component, forming a salt, as we can see in the saponification equation shown below:
Equation representing a saponification process
Equation representing a saponification process
We can see in the equation above that the triglyceride (which may be an oil or fat) reacts with the basic substance, being disintegrated into three structures. The three structures formed at the break receive a metal atom (sodium or potassium) from the basic compound, being classified as salts. In addition to salt, we also have the formation of the substance glycerin.
The salt formed in the saponification has a polar region (red) and an apolar region (blue), as shown in the structure below:
Polar and nonpolar regions in a soap
Polar and nonpolar regions in a soap
By presenting a polar and a non-polar region, the soap is able to perform the cleaning function, since it interacts with the most varied substances.
- b) Chemical characteristics of each component used in the production of solid soap
Fats
They are chemical compounds ( lipids ) originated from the reaction between glycerol (alcohol) and saturated or unsaturated fatty acids, which have long chains, containing a carboxyl group at one end.
Equation that represents the formation of a fat
Equation that represents the formation of a fat
A lipid is only considered a fat when at least two of the three groups (branches) present in the structure are saturated (they have only simple type bonds). Below is an example of a fat chain:
Don’t stop now … There’s more after the publicity;)
Structural formula of a fat
Structural formula of a fat
Because they have a greater amount of saturated branches, fats have a high melting point and, therefore, are always found in the solid state at room temperature.
Oils
They are chemical compounds (lipids) originated from the reaction between glycerol (alcohol) and saturated or unsaturated fatty acids, which have long chains, containing a carboxyl group at one end.
Equation that represents the formation of an oil
Equation that represents the formation of an oil
A lipid is only considered an oil when at least two of the three groups (branches) present in the structure are unsaturated (have one or more unsaturations). Below is an example of an oil chain:
Structural formula of an oil
Structural formula of an oil
Because they have a greater amount of saturated branches, oils have a lower melting point and, therefore, are always found in a liquid state at room temperature.
Alkalis
Alkalis are the basic substances used in the production of soap. The most used are:
– Sodium hydroxide (NaOH)
Ionic substance (formed by ionic bonding ), called the Arrhenius base , which is white (milky) and has a solid physical state, being extremely reactive and corrosive, in addition to being hygroscopic (absorbs moisture from the air).
– Potassium hydroxide (KOH)
Ionic substance (formed by ionic bonding), called the Arrhenius base, which presents a white color (opaque or transparent) and a solid physical state, being extremely toxic and corrosive.
– Sodium carbonate (Na 2 CO 3 )
Ionic substance (formed by ionic bonding), called Arrhenius salt , which is white (translucent) and has a solid physical state.
Essences
Essences, in general, are the products used to provide a pleasant odor to the solid soap. Chemically speaking, they are groups of substances that have functional groups of alcohols, esters and ketones, in addition to terpenes (organic compounds that have long chains of ten to fifteen carbons).
