I came across glycerol as I am browsing through a CET guide on chemistry in the section on oils and fats. I went back to organic chemistry text to locate glycerol. There is a need to think of various concepts repeatedly to recollect them when needed.
Glycerol is a triol.
The alcohols with three –OH groups are named as triols.
It is also termed as trihydroxy alcohol.
Glycerol is formed when 3 Hs of Propane (C3H8) are replaced by 3 OH groups.
Glycerol is C3H5(OH)3 = OHCH2-OHCH-OHCH2
Triglycerides (glyceride or triacyl glycerol or oils or fats)
When glycerol (glycerine) is heated with fatty acid, triglycerides are produced. Tyiglycerides have wide application in preparation of soap, paints, varnishes, ink, ointments and cream.
Fatty acid is represented is a monocarboxylic acid and is represented as HOOCR
CH-OH + 3HOOCR
Formation of soap
Soap is a sodium or potassium salt of fatty acid. Alkaline hydrolysis of triglycerides to form soap and glycerol is known as saponification.
Fatty acid + NaOH (Acqueous) → soap + glycerol
On completion of saponification precipitate of soap is completed by common ion effect. For this saturated solution of NaCl (brine) is used.
Sodium soaps are hard and hence used as washing soap. (ex. Sodium stearate)
Potassium soaps are soft and hence used as bathing soap.(Ex. Potassium oleate (remember Oil of Olay), Potassium stearate)