Chemistry Of Lipids Fats And Oils Soaps And Detergents Pdf

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Saponification value

The lipids are a large and diverse group of naturally occurring organic compounds that are related by their solubility in nonpolar organic solvents e. There is great structural variety among the lipids, as will be demonstrated in the following sections. You may click on a topic listed below, or proceed page by page.

The common feature of these lipids is that they are all esters of moderate to long chain fatty acids. Acid or base-catalyzed hydrolysis yields the component fatty acid, some examples of which are given in the following table, together with the alcohol component of the lipid. These long-chain carboxylic acids are generally referred to by their common names, which in most cases reflect their sources.

Natural fatty acids may be saturated or unsaturated, and as the following data indicate, the saturated acids have higher melting points than unsaturated acids of corresponding size. The double bonds in the unsaturated compounds listed on the right are all cis or Z. The higher melting points of the saturated fatty acids reflect the uniform rod-like shape of their molecules. The cis-double bond s in the unsaturated fatty acids introduce a kink in their shape, which makes it more difficult to pack their molecules together in a stable repeating array or crystalline lattice.

The shapes of stearic and oleic acids are displayed in the models below. You may examine models of these compounds by clicking on the desired model picture. Two polyunsaturated fatty acids, linoleic and linolenic, are designated "essential" because their absence in the human diet has been associated with health problems, such as scaley skin, stunted growth and increased dehydration.

These acids are also precursors to the prostaglandins, a family of physiologically potent lipids present in minute amounts in most body tissues. Because of their enhanced acidity, carboxylic acids react with bases to form ionic salts, as shown in the following equations. In the case of alkali metal hydroxides and simple amines or ammonia the resulting salts have pronounced ionic character and are usually soluble in water.

Heavy metals such as silver, mercury and lead form salts having more covalent character 3rd example , and the water solubility is reduced, especially for acids composed of four or more carbon atoms. Unusual Fatty Acids Nature has constructed a remarkable variety of fatty acid derivatives. To see some of these compounds Click Here.

Carboxylic acids and salts having alkyl chains longer than eight carbons exhibit unusual behavior in water due to the presence of both hydrophilic CO 2 and hydrophobic alkyl regions in the same molecule.

Such molecules are termed amphiphilic Gk. Fatty acids made up of ten or more carbon atoms are nearly insoluble in water, and because of their lower density, float on the surface when mixed with water. Unlike paraffin or other alkanes, which tend to puddle on the waters surface, these fatty acids spread evenly over an extended water surface, eventually forming a monomolecular layer in which the polar carboxyl groups are hydrogen bonded at the water interface, and the hydrocarbon chains are aligned together away from the water.

This behavior is illustrated in the diagram on the right. Substances that accumulate at water surfaces and change the surface properties are called surfactants. Alkali metal salts of fatty acids are more soluble in water than the acids themselves, and the amphiphilic character of these substances also make them strong surfactants. The most common examples of such compounds are soaps and detergents, four of which are shown below.

Note that each of these molecules has a nonpolar hydrocarbon chain, the "tail", and a polar often ionic "head group". The use of such compounds as cleaning agents is facilitated by their surfactant character, which lowers the surface tension of water, allowing it to penetrate and wet a variety of materials.

Very small amounts of these surfactants dissolve in water to give a random dispersion of solute molecules. However, when the concentration is increased an interesting change occurs. The surfactant molecules reversibly assemble into polymolecular aggregates called micelles.

By gathering the hydrophobic chains together in the center of the micelle, disruption of the hydrogen bonded structure of liquid water is minimized, and the polar head groups extend into the surrounding water where they participate in hydrogen bonding. These micelles are often spherical in shape, but may also assume cylindrical and branched forms, as illustrated on the right. Here the polar head group is designated by a blue circle, and the nonpolar tail is a zig-zag black line.

An animated display of micelle formation is presented below. Notice the brownish material in the center of the three-dimensional drawing on the left.

This illustrates a second important factor contributing to the use of these amphiphiles as cleaning agents. Micelles are able to encapsulate nonpolar substances such as grease within their hydrophobic center, and thus solubilize it so it is removed with the wash water.

Since the micelles of anionic amphiphiles have a negatively charged surface, they repel one another and the nonpolar dirt is effectively emulsified.

To summarize, the presence of a soap or a detergent in water facilitates the wetting of all parts of the object to be cleaned, and removes water-insoluble dirt by incorporation in micelles. If the animation has stopped, it may be restarted by clicking on it. The oldest amphiphilic cleaning agent known to humans is soap. Soap is manufactured by the base-catalyzed hydrolysis saponification of animal fat see below. Before sodium hydroxide was commercially available, a boiling solution of potassium carbonate leached from wood ashes was used.

Soft potassium soaps were then converted to the harder sodium soaps by washing with salt solution. The importance of soap to human civilization is documented by history, but some problems associated with its use have been recognized. One of these is caused by the weak acidity pK a ca. Solutions of alkali metal soaps are slightly alkaline pH 8 to 9 due to hydrolysis. If the pH of a soap solution is lowered by acidic contaminants, insoluble fatty acids precipitate and form a scum.

A second problem is caused by the presence of calcium and magnesium salts in the water supply hard water. These divalent cations cause aggregation of the micelles, which then deposit as a dirty scum. These problems have been alleviated by the development of synthetic amphiphiles called detergents or syndets. By using a much stronger acid for the polar head group, water solutions of the amphiphile are less sensitive to pH changes.

Also the sulfonate functions used for virtually all anionic detergents confer greater solubility on micelles incorporating the alkaline earth cations found in hard water. Variations on the amphiphile theme have led to the development of other classes, such as the cationic and nonionic detergents shown above. Cationic detergents often exhibit germicidal properties, and their ability to change surface pH has made them useful as fabric softeners and hair conditioners. These versatile chemical "tools" have dramatically transformed the household and personal care cleaning product markets over the past fifty years.

The triesters of fatty acids with glycerol 1,2,3-trihydroxypropane compose the class of lipids known as fats and oils. These triglycerides or triacylglycerols are found in both plants and animals, and compose one of the major food groups of our diet. Triglycerides that are solid or semisolid at room temperature are classified as fats, and occur predominantly in animals.

Those triglycerides that are liquid are called oils and originate chiefly in plants, although triglycerides from fish are also largely oils. Some examples of the composition of triglycerides from various sources are given in the following table. As might be expected from the properties of the fatty acids, fats have a predominance of saturated fatty acids, and oils are composed largely of unsaturated acids.

Thus, the melting points of triglycerides reflect their composition, as shown by the following examples. Since fats are valued over oils by some Northern European and North American populations, vegetable oils are extensively converted to solid triglycerides e. Crisco by partial hydrogenation of their unsaturated components. Some of the remaining double bonds are isomerized to trans in this operation. These saturated and trans-fatty acid glycerides in the diet have been linked to long-term health issues such as atherosclerosis.

Triglycerides having three identical acyl chains, such as tristearin and triolein above , are called "simple", while those composed of different acyl chains are called "mixed". The hydrogenation of vegetable oils to produce semisolid products has had unintended consequences. Although the hydrogenation imparts desirable features such as spreadability, texture, "mouth feel," and increased shelf life to naturally liquid vegetable oils, it introduces some serious health problems.

These occur when the cis-double bonds in the fatty acid chains are not completely saturated in the hydrogenation process. The catalysts used to effect the addition of hydrogen isomerize the remaining double bonds to their trans configuration.

These unnatural trans-fats appear to to be associated with increased heart disease, cancer, diabetes and obesity, as well as immune response and reproductive problems. Waxes are esters of fatty acids with long chain monohydric alcohols one hydroxyl group. Natural waxes are often mixtures of such esters, and may also contain hydrocarbons. The formulas for three well known waxes are given below, with the carboxylic acid moiety colored red and the alcohol colored blue.

Waxes are widely distributed in nature. The leaves and fruits of many plants have waxy coatings, which may protect them from dehydration and small predators. The feathers of birds and the fur of some animals have similar coatings which serve as a water repellent.

Carnuba wax is valued for its toughness and water resistance. Phospholipids are the main constituents of cell membranes. They resemble the triglycerides in being ester or amide derivatives of glycerol or sphingosine with fatty acids and phosphoric acid.

The phosphate moiety of the resulting phosphatidic acid is further esterified with ethanolamine, choline or serine in the phospholipid itself. The following diagram shows the structures of some of these components.

Clicking on the diagram will change it to display structures for two representative phospholipids. To see a model of a phospholipid Click Here. As ionic amphiphiles, phospholipids aggregate or self-assemble when mixed with water, but in a different manner than the soaps and detergents.

Because of the two pendant alkyl chains present in phospholipids and the unusual mixed charges in their head groups, micelle formation is unfavorable relative to a bilayer structure. If a phospholipid is smeared over a small hole in a thin piece of plastic immersed in water, a stable planar bilayer of phospholipid molecules is created at the hole. As shown in the following diagram, the polar head groups on the faces of the bilayer contact water, and the hydrophobic alkyl chains form a nonpolar interior.

The phospholipid molecules can move about in their half the bilayer, but there is a significant energy barrier preventing migration to the other side of the bilayer. To see an enlarged segment of a phospholipid bilayer Click Here. This bilayer membrane structure is also found in aggregate structures called liposomes.

Liposomes are microscopic vesicles consisting of an aqueous core enclosed in one or more phospholipid layers. They are formed when phospholipids are vigorously mixed with water. Unlike micelles, liposomes have both aqueous interiors and exteriors. A cell may be considered a very complex liposome.

Soap and detergent

Soap is a salt of a fatty acid [1] used in a variety of cleansing and lubricating products. In a domestic setting, soaps are surfactants usually used for washing , bathing , and other types of housekeeping. In industrial settings, soaps are used as thickeners , components of some lubricants , and precursors to catalysts. When used for cleaning, soap solubilizes particles and grime, which can then be separated from the article being cleaned. In hand washing , as a surfactant, when lathered with a little water, soap kills microorganisms by disorganizing their membrane lipid bilayer and denaturing their proteins. It also emulsifies oils, enabling them to be carried away by running water.


Fats and oils are naturally occurring lipids found in plants and animals and are Chemical formula. Characteristics and uses. Formic acid. Methanoic acid soaps. Common soaps are prepared from natural fatty acid but detergents are made.


25.3: Saponification of Fats and Oils; Soaps and Detergents

Carboxylic acids and salts having alkyl chains longer than eight carbons exhibit unusual behavior in water due to the presence of both hydrophilic CO 2 and hydrophobic alkyl regions in the same molecule. Such molecules are termed amphiphilic Gk. Fatty acids made up of ten or more carbon atoms are nearly insoluble in water, and because of their lower density, float on the surface when mixed with water. Unlike paraffin or other alkanes, which tend to puddle on the waters surface, these fatty acids spread evenly over an extended water surface, eventually forming a monomolecular layer in which the polar carboxyl groups are hydrogen bonded at the water interface, and the hydrocarbon chains are aligned together away from the water.

Healthy Cleaning This section is intended to be a valuable information resource about cleaning products for consumers, educators, students, media, government officials, businesses and others. Water, the liquid commonly used for cleaning, has a property called surface tension. In the body of the water, each molecule is surrounded and attracted by other water molecules. However, at the surface, those molecules are surrounded by other water molecules only on the water side.

The lipids are a large and diverse group of naturally occurring organic compounds that are related by their solubility in nonpolar organic solvents e. There is great structural variety among the lipids, as will be demonstrated in the following sections. You may click on a topic listed below, or proceed page by page.

Chemical Reactions of Fats and Oils

Saponification value or saponification number SV or SN represents the number of milligrams of potassium hydroxide KOH required to saponify one gram of fat under the conditions specified. The higher the saponification value, the lower the fatty acids average length, the lighter the mean molecular weight of triglycerides and vice-versa. Practically, fats or oils with high saponification value such as coconut and palm oil are more suitable for soap making. To determine saponification value, the sample is hot-saponified with an excess of alkali usually potassium hydroxide dissolved in ethanol , in standard conditions, generally for half an hour under reflux. Handmade soap makers who aim for bar soap use sodium hydroxide NaOH , commonly known as lye , rather than KOH caustic potash which produces soft paste, gel or liquid soaps. For instance, triolein , a triglyceride occurring in many fats and oils, has three oleic acid residues esterified to a molecule of glycerol with a total MW of

 Мы погибли, - прошептала Мидж. - Подождите, - сказала Сьюзан.  - Прочитайте еще. Соши прочитала снова: - …Искусственно произведенный, обогащенный нейтронами изотоп урана с атомным весом 238. - Двести тридцать восемь? - воскликнула Сьюзан.  - Разве мы не знаем, что в хиросимской бомбе был другой изотоп урана.

Зачем им переходить на Цифровую крепость.

Повернувшись, она увидела заместителя оперативного директора АНБ; он стоял возле ТРАНСТЕКСТА, не сводя с нее глаз. Вокруг него бушевала настоящая буря, но в его глазах она увидела смирение. Губы Стратмора приоткрылись, произнеся последнее в его жизни слово: Сьюзан. Воздух, ворвавшийся в ТРАНСТЕКСТ, воспламенился. В ослепительной вспышке света коммандер Тревор Стратмор из человека превратился сначала в едва различимый силуэт, а затем в легенду.

Шестнадцать часов. Но это не все, сэр. Я запустил антивирус, и он показывает нечто очень странное.

Последняя защитная стенка на центральном экране почти совсем исчезла. Черные линии, сбившись в кучу вокруг ядра, настолько сгустились, что их масса стала совсем непрозрачной и легонько подрагивала. Мидж отвернулась. Фонтейн стоял очень прямо, глядя прямо перед .

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    Lipids. Preview. Structures of Lipids. Fats, Oils, and Related of Fats and Oils. Hydrogenation of Fats and Oils. Soaps. Detergents. Waxes.

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