Waxes.. in details

Waxes.. in details

1. Mansoura university
Faculty of pharmacy


Research in

Waxes


Prepared by:





Wax
** Introduction

2. there is no satisfactory definition of the word
"wax" in chemical terms. It is derived from the
Anglo-Saxon word "weax" for beeswax, so a
practical definition of a wax may therefore be "a
substance similar in composition and physical
properties to beeswax". Technologists use the
term for a variety of commercial products of
mineral, marine, plant and insect origin that
contain fatty materials of various kinds.
Biochemists link waxes with the thin layer of fatty
constituents that cover the leaves of plants or
provide a surface coating for insects or the skin of
animals. All of these tend to contain wax esters as
major components, i.e. esters of long-chain fatty
alcohols with long-chain fatty acids.

** difinitions:

a class of chemical compounds that are plastic
(malleable) near ambient temperatures. They
are also a type of lipid. Characteristically, they
melt above 45 °C (113 °F) to give a low

3. viscosity liquid. Waxes are insoluble in water
but soluble in organic, nonpolar solvents. All
waxes are organic compounds, both synthetic
and naturally occurring.


** composition:
- Plant and animal waxes
Waxes are synthesized by many plants and animals. Those of
animal origin typically consist of wax esters derived from a
variety of carboxylic acids and fatty alcohols. In waxes of plant
origin characteristic mixtures of unesterified hydrocarbons may
predominate over esters. The composition depends not only on
species, but also on geographic location of the organism.
Because they are mixtures, naturally produced waxes are softer
and melt at lower temperatures than the pure components.

- Animal waxes
The most commonly known animal wax is beeswax, but other
insects secrete waxes. A major component of the beeswax used
in constructing honeycomb is the ester myricyl palmitate which
is an ester of triacontanl and palmitic acid. Its melting point is
62-65 °C. Spermaceti occurs in large amounts in the head oil of
the sperm whale. One of its main constituents is cetyl palmitate,
another ester of a fatty acid and a fatty alcohol. Lanolin is a wax
obtained from wool, consisting of esters of sterols.

4. - Plant waxes
Plants secrete waxes into and on the surface of their cuticles as a
way to control evaporation, wettability and hydration. The
epicuticular waxes of plants are mixtures of substituted long-
chain aliphatic hydrocarbons, containing alkanes, alkyl esters,
fatty acids, primary and secondary alcohols, diols, ketones,
aldehydes. From the commercial perspective, the most
important plant wax is Carnauba wax, a hard wax obtained from
the Brazilian palm Copernicia prunifera. Containing the ester
myricyl cerotate, it has many applications, such as confectionery
and other food coatings, car and furniture polish, floss coating,
surfboard wax, and other uses. Other more specialized vegetable
waxes include candelilla wax and ouricury wax.

- Petroleum derived waxes
Known as parrafin wax
Although many natural waxes contain esters, paraffin waxes are
hydrocarbons, mixtures of alkanes usually in a homologous
series of chain lengths. These materials represent a significant
fraction of petroleum. They are refined by vacuum distillation.
Paraffin waxes are mixtures of saturated n- and iso- alkanes,
naphthenes, and alkyl- and naphthene-substituted aromatic
compounds. The degree of branching has an important influence
on the properties. Millions of tons of paraffin waxes are
produced annually. They are used in foods (such as chewing
gum and cheese wrapping), in candles and cosmetics, as non-
stick and waterproofing coatings and in polishes.

5. - Montan wax
Montan wax is a fossilized wax extracted from coal and lignite.
It is very hard, reflecting the high concentration of saturated
fatty acids and alcohols. Although dark brown and smelly, they
can be purified and bleached to give commercially useful
products.

- Polyethylene and related derivatives
Some waxes are obtained by cracking polyethylene at 400 °C.
The products have the formula (CH2)nH2, where n ranges
between about 50 and 100. As of 1995, about 200 million
kilograms/y were consumed.


** Type of waxes:

Commercial Waxes
A number of waxes are produced commercially in large amounts for
use in cosmetics, lubricants, polishes, surface coatings, inks and
many other applications. Some of these are of mineral origin (e.g.
montan wax from brown coal/peat deposits), and only those from
living organisms are discussed here. Amongst them are
Beeswax
- Glands under the abdomen of bees secrete a wax, which they use to
construct the honeycomb. The wax is recovered as a by-product when
the honey is harvested and refined. It contains a high proportion of wax

6. esters (35 to 80%). The hydrocarbon content is highly variable, and
much may be "unnatural" as beekeepers may feed some to bees to
improve the yield of honey. The wax esters consist of C40 to C46
molecular species, based on 16:0 and 18:0 fatty acids some with
hydroxyl groups in the ω-2 and ω-3 positions. In addition, some diesters
with up to 64 carbons may be present, together with triesters, hydroxy-
polyesters and free acids (which are different in composition and nature
from the esterified acids).
Jojoba
- The jojoba plant (Simmondsia chinensis), which grows in the semi-arid
regions of Mexico and the U.S.A., is unique in producing wax esters
rather than triacylglycerols in its seeds, and it has become a significant
crop. It consists mainly of 18:1 (6%), 20:1 (35%) and 22:1 (7%) fatty
acids linked to 20:1 (22%), 22:1 (21%) and 24:1 (4%) fatty alcohols.
Therefore, it contains C38 to C44 esters with one double bond in each
alkyl moiety. As methylene-interrupted double bonds are absent, the
wax is relatively resistant to oxidation.
Carnauba
- The leaves of the carnauba palm, Copernicia cerifera that grows in
Brazil, have a thick coating of wax, which can be harvested from the
dried leaves. It contains mainly wax esters (85%), accompanied by
small amounts of free acids and alcohols, hydrocarbons and resins. The
wax esters constitute C16 to C20 fatty acids linked to C30 to C34 alcohols,
giving C46 to C54 molecular species.
Other vegetable "waxes" such as bayberry or Japan wax are better
described as "tallows" as they consist mainly of high melting
triacylglycerols.
Wool wax (lanolin)
- The grease obtained from the wool of sheep during the cleaning or
refining process is rich in wax esters (of 1- and 2-alkanols, and 1,2-
diols), sterol esters, triterpene alcohols, and free acids and sterols. The
nature of the product varies with the degree and type of processing
involved, but can contain up to 50% wax esters and 33% sterol esters.

7. A high proportion of the sterol component is lanosterol. The fatty acid
components are mainly saturated and iso- and anteiso-methyl-
branched-chain.

Plant Surface Waxes
Plant leaf surfaces are coated with a thin layer of waxy material that has
a myriad of functions. This layer is microcrystalline in structure and
forms the outer boundary of the cuticular membrane, i.e. it is the
interface between the plant and the atmosphere. It serves many
purposes, for example to limit the diffusion of water and solutes, while
permitting a controlled release of volatiles that may deter pests or
attract pollinating insects. The wax provides protection from disease
and insects, and helps the plants resist drought. As plants cover much
of the earth's surface, it seems likely that plant waxes are among the
most abundant of all natural lipids.
The range of lipid types in plant waxes is highly variable, both in nature
and in composition.
In addition, there may be hydroxy-β-diketones, oxo-β-diketones,
alkenes, branched alkanes, acids, esters, acetates and benzoates of
aliphatic alcohols, methyl, phenylethyl and triterpenoid esters, and many
more.
The amount of each lipid class and the nature and proportions of the
various molecular species within each class vary greatly according to
the plant species and the site of wax deposition

Skin Lipids
In most animals, the main wax production is associated with the
sebaceous glands of the skin. Most of these glands are associated with
hair follicles, but there are also related structures on the eyelids termed
Meibomian glands. Sebaceous glands secrete mainly non-polar lipids in

8. the form of sebum onto the skin surface, where they are easily
recovered for analysis. Although relatively few species have been
studied in real detail, it is evident that a wide range of lipid classes are
present and that these vary greatly in amount and nature between
species (there may also be variation with age). The composition of
human sebum differs appreciably from that of other species, especially
in the high content of triacylglycerols and in fatty acid composition.
Sebaceous glands appear to be the only source of wax esters in
mammalian tissues and the only tissue where squalene accumulates in
significant amounts. A high proportion of the fatty acid constituents of
sebum lipids can be branched chain, which are not common in other
organs. Human sebum is unique in containing cis-6-hexadecenoic acid
(6-16:1 or ‘sapienic’ acid), which is the single most abundant
component indeed, and is accompanied by an elongation and
desaturation product 5,8-octadecadienoic acid (‘sebaleic’ acid), also
unique to human skin. Sapienic acid is formed in the sebaceous glands
by a distinctive Δ6 desaturase and has powerful antibacterial properties.
Skin also contains a wide range of more polar lipids based on the
ceramide backbone. They have been most studied in the skin of the pig,
where a range of unusual ceramides have been identified, some of
which contain linoleic acid esterified to a hydroxy acid that is in turn
linked to a long-chain base. In addition, several molecular forms of
glucosylceramide, based on similar structures, have been characterized
(see our web pages on ceramides) for further information

Other Waxes
Insect waxes.
The surface of insects is covered by a layer of wax that, amongst other
functions, serves to restrict movement of water across the cuticle and
prevent desiccation. The nature of this lipid is dependent on species,
but in general a high proportion tends to be saturated alkanes (C23 to
C31) often with one or two methyl branches. In addition, wax esters,

9. sterol esters, and free fatty alcohols and acids may be present. Some
species of insect secrete triacylglycerols in their waxes together with
free sterols and other terpenoid components. The composition of
beeswax is discussed above.
Marine waxes.
Many marine animals from invertebrates to whales contain appreciable
amounts of waxes in the form mainly of hydrocarbons and wax esters.
In addition, glycerol ethers and sterols could be classified as wax
components in some species. They are found in a variety of tissues
from fish roe, to liver and muscle tissues. The wax esters consist of the
normal range of saturated, monoenoic and polyunsaturated fatty acids
typical of fish, esterified to mainly saturated and monoenoic alcohols
often with the 18:1 fatty alcohol as the main component. Squalene and
other terpenoid hydrocarbons are frequently major components of the
hydrocarbon fraction, and can be accompanied by saturated (straight-
chain and methyl-branched), monoenoic and polyenoic components.
Waxes appear to have a variety of functions in fish, from serving as an
energy source to insulation, buoyancy and even echo location.
Spermaceti or sperm whale oil (wax esters, 76%; triacylglycerols, 23%)
was once in great demand as a lubricant but now is proscribed.
Bird waxes.
The uropygial or preen glands of birds secrete waxes that consist
largely of wax esters. The fatty alcohol components of these are usually
relatively simple in nature, consisting largely of normal C16 and C18
saturated compounds, although those with branched-chains can make
up an appreciable proportion in some species. However, the fatty acids
can be highly complex and are often shorter chain than usual with up to
four methyl branches. The main purpose of the waxes is presumed to
be to give a water-proof layer to the feathers, but other functions have
been suggested.
Microbial waxes.
Waxes are not common in prokaryotes, but the mycobacteria produce
waxes, termed 'mycoserosates', based on branched-chain alcohols or

10. 'phthiocerols'. These are C34 or C36 branched-chain compounds with
hydroxyl groups in positions 9 and 11, or 11 and 13. These are
esterified with long-chain fatty acids varying in chain length from C18 to
C26 and with two to four methyl branches that may occur at the 2, 4, 6,
and 8 positions. The dimycocerosate esters are major virulence factors
of pathogenic mycobacteria including Mycobacterium tuberculosis and
M. leprae.


** Uses :
Waxes are mainly consumed industrially as components of
complex formulations, often for coatings. The main use of
polyethylene and polypropylene waxes is in the formulation of
colourants for plastics. Waxes confer matting effects and wear
resistance to paints. Polyethylene waxes are incorporated into
inks in the form of dispersions to decrease friction. They are
employed as release agents. They are also used as slip agents,
e.g. in furniture, and corrosion resistance.
Candles
Waxes and hard fats such as tallow are used to make candles,
used for lighting and decoration.
Wood products
Waxes are used as finishes and coatings for wood products.
Beeswax is frequently used as a lubricant on drawer slides
where wood to wood contact occurs.
Other uses
Sealing wax was used to close important documents in the
Middle Ages. Wax tablets were used as writing surfaces. There

11. were different types of wax in the Middle Ages, namely four
kinds of wax (Ragusan, Montenegro, Byzantine, and Bulgarian),
"ordinary" waxes from Spain, Poland, and Riga, unrefined
waxes and colored waxes (red, white, and green). Waxes are
used to make wax paper, impregnating and coating paper and
card to waterproof it or make it resistant to staining, or to
modify its surface properties. Waxes are also used in shoe
polishes, wood polishes, and automotive polishes, as mold
release agents in mold making, as a coating for many cheeses,
and to waterproof leather and fabric. Wax has been used since
antiquity as a temporary, removable model in lost-wax casting
of gold, silver and other materials.
Wax with colorful pigments added has been used as a medium
in encaustic painting, and is used today in the manufacture of
crayons and colored pencils. Carbon paper, used for making
duplicate typewritten documents was coated with carbon black
suspended in wax, typically montan wax, but has largely been
superseded by photocopiers and computer printers. In another
context, lipstick and mascara are blends of various fats and
waxes colored with pigments, and both beeswax and lanolin are
used in other cosmetics. Ski wax is used in skiing and
snowboarding. Also, the sports of surfing and skateboarding
often use wax to enhance the performance.


** Specific examples
Animal waxes :
Beeswax - produced by honey bees
 Chinese wax - produced by the scale insect Ceroplastes
ceriferus
 Lanolin (wool wax) - from the sebaceous glands of sheep

12.  Shellac wax - from the lac insect Kerria lacca
 Spermaceti - from the head cavities and blubber of the sperm
whale
Vegetable waxes :
Bayberry wax - from the surface wax of the fruits of the
bayberry shrub, Myric faya
 Candelilla wax - from the Mexican shrubs
 Carnauba wax - from the leaves of the Carnauba palm,
Copernica cerifera
 Castor wax - catalytically hydrogenated castor oil
 Esparto wax - a byproduct of making paper from esparto
grass, (Macrochloa tenacissima)
 Japan wax - a vegetable triglyceride (not a true wax), from the
berries of Rhus and Toxicodendron species
 Jojoba oil - a replacement for spermaceti, jojoba is pressed
from the seeds of the jojoba bush, Simmondsia chinensis
 Ouricury wax - from the Brazilian feather palm, Syagrus
coronata.
 Rice bran wax - obtained from rice bran (Oryza sativa)
 Soy wax - from soybean oil
 Tallow Tree wax - from the seeds of the tallow tree Triadica
sebifera.
Mineral waxes :
Ceresin waxes
 Montan wax - extracted from lignite and brown coal
 Ozocerite - found in lignite beds
 Peat waxes
Petroleum waxes
 Paraffin wax - made of long-chain alkane hydrocarbons
 Microcrystalline wax - with very fine crystalline structure
 Petroleum jelly

13. Synthetic waxes :
Polyethylene waxes - based on polyethylene
 Fischer-Tropsch waxes
 Chemically modified waxes - usually esterified or saponified
 substituted amide waxes
 polymerized α-olefins







References :
1- http://en.wikipedia.org/wiki/Wax
2-http://www.britannica.com/EBchecke
d/topic/342808/lipid/257726/Waxes
3-http://www.vocabulary.com/dictiona
ry/wax

14. 4-http://www.merriam-
webster.com/dictionary/wax
5-http://www.igiwax.com/
6-http://www.cyberlipid.org/wax/wax0
001.htm








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