Soaps and detergents
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Soaps are metal salts of long chain fatty acids prepared from oils and fats, while detergents are sodium salts of long chain hydrocarbons made from petroleum. Soaps cannot be used in hard water as they form insoluble precipitates, but detergents do not form precipitates and can be used in soft, hard, or salt water. The document discusses the production, structures, cleansing actions and advantages/disadvantages of soaps and detergents.
Soaps and detergents
- 2. SOAP • Introduction • Saponification • Soap molecule(Micelles) • Cleansing action of soaps • Advantagesand disadvantages DETERGENT • Introduction • Classification of detergents • Cleansing action of detergents • Advantagesand disadvantagesof detergents DIFFERENCES BETWEEN SOAPSAND DETERGENTS
- 3. Soapsarethesodium and potassium saltsof thelong chain carboxylic acid. A soap moleculeconsistsof along hydrocarbon chain (composed of carbonsand hydrogen's) with acarboxylic acid on oneend which is ionic bonded to metal ion usually asodium or potassium.
- 4. A soap hasalargenon-ionic hydrocarbon group and an ionic group COO-Na+. It isasalt of astrong base(NaOH) and aweak acid (carboxylic acid), so asolution of soap in water isbasic in nature.
- 5. Sodiumstearic (Chemical formula: C17H35COO-Na+) Sodium stearic soap isthesodium salt of along chain saturated fatty acid called stearic acid. Sodium stearic soap hasalong alkyl group (C17H35) and an ionic carboxylategroup (COO- Na+ ).
- 6. Sodiumpalmitate (Chemical formula: C15H31COO-Na+) Sodium Palmitate‘soap’ isthesodium salt of long chain saturated fatty acid called stearic acid (C15H31COOH).
- 7. A soap moleculeismadeup of two parts: along hydrocarbon part and ashort ionic part containing COO- Na+ group. Thesoap moleculeissaid to haveatadpole structure.
- 8. A soap moleculehastwo ends with different properties- 1. A long hydrocarbon part which ishydrophobic (i.e. it dissolves in hydrocarbon). 2. A short ionic part containing COO-Na+ which ishydrophilic (i.e. it dissolvesin water). micelle
- 10. Theprocessof making soap by the hydrolysisof fatsand oilswith alkaliesis called saponification. Soap ismadeby heating animal fatsor vegetableoil with concentrated sodium hydroxide(NAOH). Fat or Oil + NaOH → Soap + Glycerol
- 11. When a dirty cloth is put is put in water containing soap than the hydrocarbon ends of the soap molecule in the micelle attach to the oil or grease particles present on the surface of dirty cloth. In this way the soap micelles entraps the oily particles by using the hydrocarbon ends. The ionic ends of the soap molecules remain attached to the water when the dirty cloth is agitated in soap solution. The oily particles presents on its surface gets dispersed in the water due to which the cloth gets clean.
- 12. Weusesoapson daily basis. Following aresomeuses of soaps:- Washing hands Washing clothes Cleaning utensils
- 13. ADVANTAGES Soaps are eco-friendly and bio degradable DISADVANTAGES Soaps are not suitable in the hard water. They have weak cleansing properties than detergents.
- 14. LIMITATIONS OF SOAPS :- Hard water contains calcium and magnesium salts. Soap is not suitable for washing clothes with hard water because of two reasons :- When soap is used for washing clothes with hard water, a large amount of soap is wasted in reacting with the calcium and magnesium ions of hard water to form an insoluble precipitate called scum, before it can be used for the real purpose of washing . So a larger amount of soap is needed for washing clothes when the water is hard. The scum (or the curdy precipitate) formed by the action of hard water on soap, sticks to the clothes being washed and interferes with the cleaning ability of the additional soap. This makes the cleaning of clothes difficult.
- 15. Detergents are defined as ammonium, sulphonate or sulphate salts of long chain hydrocarbon containing 12-18 carbon atoms. Detergents are soap less soaps because they have all the properties of soaps but actually they do not contain any soap. More common detergents are the sodium salt of long chain sulphonic acid.
- 16. Detergentsareprimarily surfactants, which could beproduced easily from petrochemicals. Surfactantslower thesurfacetension of water, essentially making it 'wetter' so that it isless likely to stick to itself and morelikely to interact with oil and grease. Theionic group in adetergent isSO3¯Na⁺ They can beused in hard water asthey do not form curdy whiteprecipitates(scum) with hard water.
- 18. These are so called because a large part of their molecule are anions and it is the anionic part of the molecule which is involved in cleansing action. Anionic detergents are of two types: 1. Sodium alkyl sulphate 2. Sodium alkyl benzene sulphonate These are used in toothpaste.
- 19. They are obtained from long straight chain alcohols containing 12-18 carbon atoms. Example: Sodium lauryl sulphate and sodium stearyl sulphate
- 20. They are 100% biodegradable These detergents are also effective in slightly acidic medium since they form alkyl hydrogen sulphated which are soluble material whereas soaps react with acidic solution to form insoluble fatty acid.
- 21. These detergents are sodium salt of long chain alkyl benzene sulphonic acids. Most widely used domestic detergent is sodium 4-(1-dodecyl) benzene sulphonate (SDS).
- 22. These are so named because the major part of their molecule is cation and it is the cationic part which is involved in cleansing. They are also called as invert soaps. These are quaternary ammonium salts (bromide, chloride, acetate) containing one or more long chain alkyl group.
- 23. They are more expensive than anionic detergents. They possess germicidal properties thus used in hospitals. Example: cetyl trimethyl ammonium bromide They are used in hair shampoos and hair conditioner.
- 24. They do not contain any ions. They are esters of high molecular mass alcohol obtained by reaction between polyethylene glycol and stearic acid. Example: Polyethylene glycol stearate Liquid dishwashing detergents are of non ionic type.
- 25. Synthetic detergentshavethesametypeof molecular structureassoaps i.e., onelargenon-polar hydrocarbon group that iswater repelling (hydrophobic) and oneshort ionic group usually containing the group that iswater attracting (hydrophilic). Thusthecleansing action isexactly similar to that of soapswhereby theformation of micelles. However, synthetic detergentscan lather well even in hard water. Thisisbecausethey aresolublesodium or potassium saltsof sulphonic acid or alkyl hydrogen sulphate. Detergentsform solublecalcium or magnesium saltson reacting with thecalcium ionsor magnesium ionspresent in water. Thisisamajor advantageof thecleansing property of detergentsover soap.
- 26. • Detergentscan beused even with hard water whereas soapsarenot suitablefor usewith hard water. • Detergentshaveastronger cleansing action than soaps. • Detergentsaremoresolublein water than soaps. • Detergentscan beused in acidic medium whilesoaps get precipitated in acidic medium.
- 27. Many detergentsareresistant to theaction of biological agentsand thusarenot biodegradable. Their elimination from municipal wastewatersby theusual treatmentsisaproblem. They haveatendency to producestablefoamsin riversthat extend over several hundred metersof the river water. Thisisdueto theeffectsof surfactants used in their preparation. Thusthey poseadanger to aquatic life. Detergentsconsist of sidechainswhich stop bacteria from attacking and breaking thechain . Thisresults in slow degradation of detergent moleculeleading to their accumulation.
- 28. SOAPS They aremetal saltsof long chain higher fatty acids. Theseareprepared from vegetableoilsand animal fats. They cannot beused effectively in hard water asthey producescum i.e., insoluble precipitatesof Ca2+, Mg2+, Fe2+ etc. DETERGENTS Thesearesodium saltsof long chain hydrocarbonslike alkyl sulphatesor alkyl benzenesulphonates. They areprepared from hydrocarbonsof petroleum or coal. Thesedo not produce insolubleprecipitatesin hard water. They areeffectivein soft, hard or salt water.