Transcript Chapter 17

Chemistry for Changing Times
11th Edition
Hill and Kolb
Chapter 17
Household
Chemicals
John Singer
Jackson Community College, Jackson, MI
© 2007 Prentice Hall
History of Cleaning
Many years ago and even today in the
third world, clothes are cleaned by beating
on rocks in a river or stream. Some plants
such as soapworts or soapberries contain
saponins, which produce a soapy lather.
Wood ashes contain potassium and
sodium carbonate, which form alkaline
solutions in water with some detergent
properties. Sodium carbonate is still sold
today as washing soda.
Fat + Lye → Soap
Soap is made by reacting animal fat or
vegetable oil with lye (NaOH).
Fat + Lye → Soap
Soap works because one end of the molecule is
hydrophilic (water-attracting) and the other end is
hydrophobic (water-repelling).
Fat + Lye → Soap
The hydrophobic “tail”
dissolves into oil, leaving
the hydrophilic “head” on
the outside. This
spherical structure is
called a micelle.
Fat + Lye → Soap
Oil and water form an emulsion with the
soap acting as the emulsifying agent.
Any substance, such as soap, that
stabilizes the suspension of nonpolar
substances in water is called a surfactant
(surface-active) agent.
Fat + Lye → Soap
Disadvantage of Soap
Water that contains calcium, magnesium, and iron ions is
called hard water. These ions will react with and
precipitate soap, reducing its effectiveness.
Fat + Lye → Soap
Water Softeners
Additives such as washing soda (Na2CO3 . 10
H2O) and trisodium phosphate (TSP = Na3PO4)
will raise the pH of water and precipitate calcium
and magnesium ions.
Fat + Lye → Soap
Water Softeners
Water softening tanks are
also used in homes and
businesses. They
contain a polymeric
material that holds the
calcium, magnesium, and
iron ions and exchanges
them with sodium ions.
Synthetic Detergents
During World War II, the raw materials for
soap production became scarce.
Synthetic detergents were developed
with cleansing action similar to soap but
without the negative effects of hard water.
Synthetic Detergents
ABS Detergents: Nonbiodegradable
The first synthetic detergents were
alkylbenzenesulfonates (ABS) detergents.
Unfortunately they are nonbiodegradable
and produced a foam that appeared on
natural lakes and rivers as well as in wells
and sewage treatment plants. ABS
detergents were banned and replaced by
biodegradable detergents.
Synthetic Detergents
ABS Detergents: Nonbiodegradable
Synthetic Detergents
LAS Detergents: Biodegradable
Linear alkylsufonates (LAS) detergents have
linear chains of carbon atoms that can be
broken down by microorganisms.
Laundry Detergent Formulations
Laundry detergents contain a variety of
compounds designed for specific
functions. These compounds are
classified as surfactants, builders, and
brighteners.
Laundry Detergent Formulations
Surfactants emulsify the soil and oils. They can
be either anionic, cationic, nonionic, or
amphoteric.
Amphoteric surfactants carry both a positive
and negative charge on the same molecule. A
betaine is an example of an amphoteric
surfactant.
CH3(CH2)nCH2NH2+CH2COO-
Laundry Detergent Formulations
Builders are added to detergent formulas
to increase the detergency of the
surfactant. Examples include sodium
citrate (Na3C6H5O7), sodium
tripolyphosphate (Na5P3O10) , and sodium
hexametaphosphate. These compounds
act by causing the sequestration of the
calcium and magnesium ions.
Laundry Detergent Formulations
Phosphate builders increase the eutrophication
of lakes. Some states have banned their use.
Zeolites trap calcium and magnesium ions in a
cage-like structure.
Laundry Detergent Formulations
Brighteners are added to detergent
formulations to make clothing appear bright and
new.
Laundry Detergent Formulations
Liquid laundry detergents have captured
much of the market in recent years. Liquid
laundry detergents can either be built
formulations with sodium citrate, sodium
carbonate, or zeolites, or they can be
unbuilt formulations high in surfactants
and no builders.
Dishwashing Detergents
Liquid dishwashing detergents, for hand washing,
usually contain one or more surfactants such as
LAS or cocamido DEA
[CH3(CH2)nCON(CH2CH2OH)2].
Dishwashing detergents for automatic
dishwashers are usually strongly alkaline. They can
contain sodium tripolyphosphate, sodium carbonate,
sodium metasilicate, and a bleach, along with a
small amount of surfactant. Sodium hydroxide may
also be present.
Fabric Softeners: Quaternary
Ammonium Salts
Quaternary ammonium salts with two long alkyl
chains are used as fabric softeners. They attach
to clothing fibers, forming a layer one molecule
thick, giving the clothing a smooth flexible
softness.
Laundry Bleaches: Whiter Whites
Bleaches are oxidizing agents that react with
colored stains on fabrics. The more common
bleaches are chlorine bleaches containing
sodium hypochlorite (NaOCl). Oxygenreleasing bleaches contain either sodium
percarbonate (2 Na2CO3 . 3 H2O2) or sodium
perborate (NaBO2 . H2O2). These bleaches
liberate the oxidizing agent hydrogen peroxide in
hot water.
All-Purpose Cleaning Products
A number of all-purpose cleaning products
are commonly found in the home. These
include household ammonia solutions,
baking soda, and common vinegar.
Special-Purpose Cleaners
Toilet bowl cleaners are usually acidic materials to
remove calcium carbonate deposits.
Scouring powders contain abrasive materials like silica
(SiO2). They may also contain a surfactant and bleach.
Glass cleaners contain isopropyl alcohol, ammonia, and
sometimes vinegar.
Drain cleaners usually contain sodium hydroxide to
saponify grease. Some contain bits of aluminum that
react with the NaOH to release hydrogen gas to agitate
the clog. Many contain bleach to degrade hair.
Oven cleaners contain NaOH to cut the greasy material
on oven walls.
Organic Solvents in the Home
Organic solvents are
available for removing
paint, adhesives,
waxes, and other
materials. Most are
volatile and
flammable.
Paints
Paints include lacquers, enamels,
varnishes, oil-based coatings, and waterbased finishes. They are composed of
three basic ingredients: a pigment, binder,
and solvent.
Waxes
Waxes are esters of long-chained fatty acids and long
chained alcohols. Paraffin wax is a mixture of longchained hydrocarbons. Waxes serve both plants and
animals as protective coatings. Many natural waxes are
being replaced by silicones.
Cosmetics
The U.S. Food, Drug, and Cosmetic Act of 1938
defined cosmetics as “articles intended to be
rubbed, poured, sprinkled, or sprayed on,
introduced into, or otherwise applied to the
human body or any part thereof, for cleansing ,
beautifying, promoting attractiveness, or altering
the appearance….” The main difference
between drugs and cosmetics is that drugs must
be proven “safe and effective” before they can
be marketed.
Cosmetics
Skin Creams and
Lotions
Cosmetics are
applied to the dead
cells of the corneal
layer of the skin.
Cosmetics
Skin Creams and Lotions
A lotion is an emulsion of oil
droplets dispersed in water.
A cream is an emulsion of
water droplets dispersed in
oil.
Cosmetics
Skin Creams and Lotions
The oily substance of the cream or lotion forms a
protective film over the skin that retains
moisture.
Emollients protect the skin by coating and
softening it.
Moisturizers hold moisture to the skin.
Humectants such as glycerol or lactic
acid actually attract water to the skin.
Cosmetics
Sunscreen Lotions
Sunscreen lotions work by blocking shortwavelength (UV-B) radiation but allow the less
harmful long wavelength (UV-A) radiation to pass.
Older formulations contained paraminobenzoic acid
(PABA), which is water-soluble. Newer formulations
contain octyl methoxycinnamate (OMC) which is
insoluble in water. Skin protection factor (SPF)
tells how long you can stay in the sun compared to
no protection, i.e., an SPF = 15 means that you can
stay in the sunlight 15 times longer than with no
protection. Sunblocks contain opaque powders like
zinc or titanium oxide that block all UV radiation.
Cosmetics
Lipsticks and lip balm are similar to skin
creams or lotions in make-up and function.
They contain oil and a wax and work by
holding moisture against the skin.
Eye makeup is used to accentuate and
decorate the eyes. It typically contains
waxes, soaps, fats, oils, and pigments.
Cosmetics
Deodorants and Antiperspirants
Deodorants contain perfume to mask body odor
and a germicide to kill odor-causing bacteria.
Antiperspirants may contain perfumes and
germicides but also contain compounds, such as
aluminum chlorohydrate
[Al2(OH)5Cl . 2 H2O], which are astringents that
constrict the pores of sweat glands to prevent
perspiration.
Toothpaste
Toothpaste is perhaps the most important
cosmetic product. Toothpastes are
typically composed of a detergent and an
abrasive. In addition, there are flavoring
agents, coloring agents, sweeteners, and
thickeners.
Perfumes, Colognes, and
Aftershaves
Perfumes may contain many ingredients. Their
components are divided into three “notes.”
Notes are categories of volatility. The first note
is the most volatile fraction and the third or end
note the least volatile fraction. The end notes
often have musky odors.
Colognes are perfumes that have been diluted
with alcohol or alcohol/water mixtures.
Aftershave lotions are similar to colognes but
with a higher percentage of alcohol. Some
contain menthol or an emollient.
Hair Chemistry
Shampoos contain a detergent such as
sodium dodecyl sulfate. They can also contain
coloring agents, fragrances, and proteins for
repairing split ends.
Conditioners are mainly long-chained
alcohols or quaternary ammonium salts that
coat the surface of the hair and allow the
strands to slide past each other.
Hair Chemistry
Hair color is due to two pigments, melanin
(brownish-black) and phaeomelanin (redbrown). Hair color can be lightened by oxidizing
with hydrogen peroxide or changed by dying.
Hair treatment like Grecian Formula ® contains
lead acetate [Pb(CH3COO)2]. The lead ions
penetrate the hair shaft and react with the sulfur
to form black lead sulfide.
Hair Chemistry
Perms are accomplished by
breaking the disulfide bonds
in the proteins with reducing
agents such as thioglycolic
acid and curling the hair on
rollers and treating with
hydrogen peroxide to
reestablish the disulfide
linkages.
Hair Chemistry
Hair sprays are resins that form a sticky film to hold the
hair in place. A mousse is simply a foam that contains
such a resin.
Hair removers are called depilatories. Most contain a
strongly basic soluble sulfur compound that attacks the
peptide bonds in the hair so that it can be washed off.
Hair restorers such as Rogaine contain Minoxidil.
Minoxidil was first used as a treatment for high blood
pressure. It has the ability to grow fine hair when it is
applied to the skin anywhere that hair follicles are
located.
The Well-Informed Consumer
Many companies spend a lot of money on
advertising their products, and the most
expensive product is not always the best.
It is worth the effort to be informed about
the products that you buy and use.