Page 337 - 9780077418427.pdf

/Users/user-f465/Desktop
tiL12214_ch12_299-322.indd Page 314 9/3/10 6:13 PM user-f465
tiL12214_ch12_299-322.indd Page 314 9/3/10 6:13 PM user-f465 /Users/user-f465/Desktop

H oil to the single bonds of a saturated one. As a result, the liquid
oils are converted to solids at room temperature. For example,
H C O C R 1
one brand of margarine lists ingredients as “liquid soybean oil
O (nonhydrogenated) and partially hydrogenated cottonseed oil
H C O C R 2
with water, salt, preservatives, and coloring.” Complete hydro-
O genation would result in a hard solid, so the cottonseed oil is
H C O C R 3 partially hydrogenated and then mixed with liquid soybean oil.
Coloring is added because oleo is white, not the color of butter.
H O
Vegetable shortening is the very same product without added
FIGURE 12.23 The triglyceride structure of fats and oils. Note coloring. Reaction of a triglyceride with a strong base such as
the glycerol structure on the left and the ester structure on the KOH or NaOH yields a fatty acid of salt and glycerol. A sodium
right. Also notice that R 1 , R 2 , and R 3 are long-chained molecules of or potassium fatty acid is commonly known as soap.
12, 14, 16, 18, 20, 22, or 24 carbons that might be saturated or
Excess food from carbohydrate, protein, or fat and oil sources
unsaturated.
is converted to fat for long-term energy storage in adipose tissue,
which also serves to insulate and form a protective padding. In
terms of energy storage, fats yield more than twice the energy
muscles and liver. Beyond this storage for short-term needs,
per gram oxidized as carbohydrates or proteins.
the body begins to store energy in a different chemical form
for longer-term storage. This chemical form is called fat in
animals and oil in plants. Fats and oils are esters formed from
glycerol (trihydroxypropane) and three long-chain carboxylic CONCEPTS Applied
acids (fatty acids). This ester is called a triglyceride, and its
structural formula is shown in Figure 12.23. Fats are solids and Brand News
oils are liquids at room temperature, but they both have this Pick two competing brands of a product you use (example:
same general structure. Tylenol and a store-brand acetaminophen) and write the
Fats and oils usually have two or three different fatty acids, follow ing information: all ingredients, amount of each
and several are listed in Table 12.7. Animal fats can be either ingredient (if this is not given, remember that by law,
ingredients have to be listed in order of their percent by
saturated or unsaturated, but most are saturated. Oils are liquids
weight), and the cost per serving or dose. Comment on
at room temperature because they contain a higher number of
whether each of the listed ingredients is a single substance
unsaturated units. These unsaturated oils (called “polyunsatu-
and thus something with the same properties wherever it is
rated” in news and advertisements), such as safflower and corn
found (example: salt, as a label ingredient, means sodium
oils, are used as liquid cooking oils because unsaturated oils are chloride no matter in what product it appears) or a mixture
believed to lead to lower cholesterol levels in the bloodstream. and thus possibly different in different products (example:
Saturated fats, along with cholesterol, are believed to contribute tomatoes, as a ketchup ingredient, might be of better
to hardening of the arteries over time. quality in one brand of ketchup than another). Then draw a
Cooking oils from plants, such as corn and soybean oil, are reasonably informed conclusion as to whether there is any
hydrogenated to convert the double bonds of the unsaturated significant difference between the two brands or whether
the more expensive one is worth the difference in price.
Finally, do your own consumer test to check your prediction.

TABLE 12.7
Some fatty acids occurring in fats
SYNTHETIC POLYMERS
Common
Name Condensed Structure Source Polymers are huge, chainlike molecules made of hundreds or
thousands of smaller, repeating molecular units called mono-
Lauric CH 3 (CH 2 ) 10 COOH Coconuts mers. Polymers occur naturally in plants and animals. Cellulose,
acid
for example, is a natural plant polymer made of glucose mono-
Palmitic CH 3 (CH 2 ) 14 COOH Palm oil
acid mers. Wool and silk are natural animal polymers made of amino
acid monomers. Synthetic polymers are manufactured from a
Stearic CH 3 (CH 2 ) 16 COOH Animal fats
acid wide variety of substances, and you are familiar with these poly-
mers as synthetic fibers such as nylon and the inexpensive light
Oleic CH 3 (CH 2 ) 7 CH==CH(CH 2 ) 7 COOH Corn oil
acid plastic used for wrappings and containers (Figure 12.24).
The first synthetic polymer was a modification of the natu-
Linoleic CH 3 (CH 2 ) 4 CH==CHCH 2 ==CH(CH 2 ) 7 COOH Soybean oil
acid rally existing cellulose polymer. Cellulose was chemically modi-
Linolenic CH 3 CH 2 (CH==CHCH 2 ) 3 (CH 2 ) 6 COOH Fish oils fied in 1862 to produce celluloid, the first plastic. The term plastic
acid means that celluloid could be molded to any desired shape.
Celluloid was produced by first reacting cotton with a mixture

314 CHAPTER 12 Organic Chemistry 12-16