Ester Reaction
Esterification is a chemical reaction between an alcohol and a carboxylic acid, typically catalyzed by an acid or base, to form an ester and water. This reaction is important in the synthesis of fragrances, flavors, and polymers, and is also used in the production of biodiesel. Ester reactions are reversible and can be influenced by factors such as temperature and concentration.
4 Key excerpts on "Ester Reaction"
eBook - ePub- J Fisher, J.R.P. Arnold, Julie Fisher, John Arnold(Authors)
- 2020(Publication Date)
- Taylor & Francis(Publisher)
...Such a process occurs with hydrolysis and with saponification. Ester hydrolysis can readily take place in the presence of an acid catalyst (Figure 4). The mechanism for this reaction has been established by the use of 18 O isotopically enriched water (Section A3); the label is found to reside on the ester at the end of the reaction. Ester formation and hydrolysis are fundamental reactions in biology, where the catalyst is of course enzymic. Animal fats and vegetable oils are esters and hydrolysis is an important process by which they are digested. Figure 4 Ester hydrolysis. Saponification is another ester-linkage breaking process, but takes place in the presence of strong bases (cf. carboxylic acid salt formation) (Figure 5). The saponification of fats and oils is important in the production of soaps (Section M3). Figure 5 Ester saponification. Esters of inorganic acids Carboxylic acid-based esters are extremely important in biology; however, other types of esters are equally important. Just as carboxylic acids react with alcohols to form the corresponding esters, inorganic acids can react to form inorganic esters; the most important of these in biology are those from phosphoric acid (Section F1); As Phosphoric Acid Has Three ‘Oh’ Groups It Is Able To Form Di- And Triesters (The Linkages Also Referred To As Anhydrides); Mono- and diesters are essential to life and represent some of the most important biological molecules. For example, the monophosphate of glucose is the first intermediate in the oxidation of glucose, a key energy source for the body. Like carboxylic acids, phosphoric acid can form dimers and trimers by a dehydration process...
eBook - ePubBiochemistry
An Organic Chemistry Approach
- Michael B. Smith(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
...Neutralization with aqueous H 2 SO 4 in a second step to give two products, acetic acid and propan-2-ol (isopropyl alcohol), as shown in Figure 7.13. FIGURE 7.13 Base hydrolysis of an ester, isopropyl acetate. This two-step process, shown in reaction form for isopropyl acetate to give acetic acid + propan-2-ol, is known as saponification. Saponification means “to make soap” and the term comes from the ancient practice of using wood ashes (rich in potassium hydroxide) to convert animal fat to soap. Animal fat, as well as vegetable oils, are usually a mixture of triglycerides, the triester derivative of fatty acids and glycerol. Under these conditions, basic hydrolysis of all three ester units leads to formation of glycerol and the salt of the fatty acids. The salts of these fatty acid are solids and they are the fundamental constituent of what is known as “soap.” An example is shown in Figure 7.14 for the saponification of cocoa butter (a triglyceride composed of palmitic, oleic, and stearic acid residues), which is extracted from cocoa beans. Basic hydrolysis leads to glycerol (propane-1,2,3-triol) along with the sodium salts of the three fatty acids, sodium palmitate, sodium stearate, and sodium oleate. FIGURE 7.14 Saponification of cocoa butter. Similar acid and base conditions can be used for the hydrolysis of phosphate esters. 32 The glycosidic bonds of disaccharides, trisaccharides and polysaccharides can also be cleaved by hydrolysis facilitated by heating with dilute aqueous acid. The glycoside bond is relatively stable to basic hydrolysis. 32 Kirby, A.J.; Varvoglis, A.G. Journal of the American Chemical Society 1967, 8 9, 415–423. 7.5.2 Esterases An esterase is a hydrolase enzyme that facilitates the reaction of water with esters in a hydrolysis cleavage reaction, giving an acid and an alcohol. There are many different esterases that differ in their substrate specificity, their protein structure, and their biological function...
eBook - ePubBiochemistry Explained
A Practical Guide to Learning Biochemistry
- Thomas Millar(Author)
- 2018(Publication Date)
- CRC Press(Publisher)
...Carboxylic or organic acids contain this functional group. Draw the general structure of an alcohol and ethanol. Answer: Nomenclature : The -OH is called an hydroxyl group – learn this. Q&A 1 : For practice, which of the following are alcohols? A B C D Q&A 2 : Indicate which of the following are acids? A B C D E F G H To form an ester bond, we simply condense (form water) the acid with the alcohol. In the following diagram, carboxylic acid is condensed with alcohol to form an ester bond and water: MAJOR POINT 6 : An ester is formed by condensing an acid with an alcohol. Biochemical examples of ester bonds Clearly from above, biochemicals that contain ester bonds must have basic structural elements of alcohols and acids. Examine the following molecule, glycerol. It comprises 3 carbons with an hydroxyl group at each carbon i.e. a poly-alcohol. Although this molecule rarely occurs biochemically, it is one of the most important structures to learn for biochemistry because it is the structural basis for many other biochemicals. It is exciting because it has the potential to form 3 ester bonds, not just one. To form an ester bond, it needs an acid (or 2 or 3 acids). Q&A 3 : Draw a carboxylic acid with 14 carbons (including the carbon of the carboxyl group) and a single bond between each carbon so that it is saturated with hydrogens. Remember that each carbon can only form 4 bonds. When such a long uncharged chain forms would you expect it to he more water or more lipid soluble? Answer: Lipid soluble, because there is very little charge on such a molecule. Therefore a good name for such an acid would be a fatty acid. Q&A 4 : Draw a fatty acid with 20 carbons with double bonds between C5 and C6, C8 and C9, C11 and C12 and between C14 and C1 5 with carbon 1 being the carbon of the carboxylic acid. This fatty acid is not saturated. It has double bonds so could theoretically take more H atoms to saturate the molecule fully...
eBook - ePub- Michael North(Author)
- 2017(Publication Date)
- CRC Press(Publisher)
...When ester A or thioester B is treated with an enzyme under the conditions specified, the corresponding carboxylic acid is obtained. Provide an explanation for this transformation, which accounts for both the chemical yield and the enantiomeric excess of the products. Hint : for both A and B, H a is particularly acidic. 11. It is sometimes observed that the solid state reaction of a racemate with an achiral compound proceeds at a different rate to the solid state reaction of a single enantiomer of the substance with the same achiral compound. Suggest a reason for this difference in chemical reactivity. Could the same effect be observed in solution phase reactions?...
