Soaps, Detergents, and Detergent Builders

Question 1

What is a Soap?

Answer 1

• Cleaning agents which are derivatives of natural products

- K or Na salts of fatty acids

Question 2

What is a ‘fatty acid’?

Answer 2

Long-chain carboxylic acid found in many living organism
- eg. Stearic C17H35COOH (zigzag chain ending in COOH)
(Sodium Stearate a soap (same as above except ending in COO- and Na+))

Question 3

Saponification

Answer 3

Soapmaking process
Fats (triglycerides - tri-esters of glycerol (Glycerin))
1 Tristearin (some kind of stearic group with glycerin group) + Lye (NaOH) or KOH, water, and heat
= 1 Glycerol + Soap (3 C17H35COO-Na+)

Question 4

Biodiesel production

Answer 4

Similar to saponification

1 Tristearin + NaOH (Lye) and CH3OH (Transesterfication) = 3 CH3O-C(=O)C17H35 (biodiesel) + Glycerol group

Question 5

What are the most important features of a soap molecule?

Answer 5

It is Amphiphilic

• Has hydrophilic and hydrophobic parts
  eg. Sodium Stearate the tail (chain) is non-polar hydrophobic and lipophilic and the COO-Na+ head is hydrophilic

Question 6

Surfactant

Answer 6

Surface Active Agent

- lowers surface tension of water which improves wetting action

Question 7

How do soaps work?

Answer 7

• washing action is associated w/ ability to suspend or emulsify dirt particles (oil, grease, etc.)
• Congregates around grease particles in large units called Micelles
• non-polar lipophilic tails attach to the fat (missing the rest from notes?)

Question 8

What is one major problem with soaps?

Answer 8

They are ineffective in hardwater (ie. Ca2+/Mg2+)

• Form insoluble salts with hardwater ions
  eg. Ca2+(aq) + 2NaOOCC17H35(aq) = Ca(OOCC17H35)(a grey-white scummy solid) + 2Na+(aq)
• Therefore detergents were developed

Question 9

What is a Detergent?

Answer 9

Modern, man-made surfactant used in laundry detergents that don’t precipitate scum with Ca2+/Mg2+ ions

• Mainly derivative salts of sulphonic acids (RSO3H where R is an organic group)
• eg. Alkyl Benzene Sulphonate (ABS) with polar Na+O- head - S(=O)(=O) - Benzene - and nonpolar tail of alternating C(-H)(-CH3) or C(-H)(-H) ending with CH3

Question 10

What are detergent mainly derived from?

Answer 10

Petrochemicals

Question 11

What are detergent advantages over soaps?

Answer 11

• Very good cleaning action
• Don’t form insoluble salt w/ hardwater ions
  (strong acids?)

Question 12

What is a problem with ABS?

Answer 12

Alkyl Benzene Sulphonates do not biodegrade readily and were building up in water supply
- 1960s research showed presence of many Tertiary Carbons that made biodegradation difficult

Question 13

What is a Tertiary Carbon?

Answer 13

A carbon atom bonded to 3 other C atoms

Question 14

What was the solution to the ABS problem?

Answer 14

LAS (Linear Alkyl Benzene Sulphonates)

• more biodegradable b/c of fewer tertiary carbons
• CH3(CH2 x 7)CH(-benzene with SO3-Na+)CH2CH2CH3

Question 15

Problems from detergent builders?

Answer 15

• Bind hardwater ions to stop them interfering with surfactants
• Basic properties: raise pH (improves cleaning action)

Question 16

Detergent Builder

Answer 16

Substances added to enhance the action of the surfactant

• Originally Polyphosphates (chain-like derivatives of Orthophosphate)
  eg. Sodium TriPolyphosphate (NA5P3O10)

Question 17

How does Sodium TriPolyphosphate (detergent builder) work and what is the issue with it?

Answer 17

Contains P3O10^5-

• lone pairs on O atoms form covalent bonds w/ metal ions (Ca2+/Mg2+)
• complexes the metal ions and sequesters them so it cannot interfere w/ surfactant
• in water body the PO4^3- acts as a source of P in the water causing eutrophication

Question 18

Eutrophication

Answer 18

Cultural eutrophication: caused by human activity

• P is a limiting nutrient in fresh water
• addition of P from detergent builders adds P to water
• results in huge biomass increase from algae blooms
• when the biomass dies it sinks and is oxidized under anaerobic conditions, decreases DO and chokes aquatic life

Question 19

Eutrophication issue in NA

Answer 19

Lake Erie prior to 1970

• 1972 Canada + US created Great Lakes Water Quality Agreement
• Building of sewage treatment plants (8 billion $)

Question 20

Chelating Agent

Answer 20

A molecule or ion that can form 2 or more bonds to a metal center
- eg. Ethylenediamine
H2N-CH2-CH2-NH2 where the lone pair on each N combines to Metal cation of some charge (n+) forming a ring

Question 21

Sodium Citrate

Answer 21

Anion of Citric Acid

- Naturally occurring

Question 22

Alternative Chelating Agents

Answer 22

• Eg. Sodium NitriloTriAcetate (used in Canada/Europe, banned in US) N bonded to 3 CH2 (which are each bonded to CO2-), the 3 negative ends can bond to a Metal ion
• Washing Soda Na2CO3 10H2O
• Borax Na2B4O7 10H2O
• Sodium Silicate Na2SiO3
  Problem: CaCO3 and CaSiO3 are insoluble