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In , a German chemist, Friedrich Whler, obtained urea from the reaction of two inorganic compounds, potassium cyanate and ammonium chloride. Since then, many other organic compounds have been prepared from inorganic materials. Organic chemistry today is the study of compounds in which carbon is the principal element.
Animals, plants, and fossil fuels contain a remarkable variety of carbon com- pounds. What is it about the carbon atom that allows it to form such a variety of com- pounds, a variety that allows the diversity we see in living organisms? The answer lies in the fact that carbon atoms can form four bonds. Carbon atoms have another special property: They can bond together to form chains, rings, spheres, sheets, and tubes of almost any size and can form combinations of single, double, and triple covalent bonds.
This versatility allows the formation of a huge variety of very large organic molecules. These oils are used for their fragrance in perfumes and aromatherapy products.
The oil of bitter almond, for example, is benzaldehyde, the simplest aldehyde of benzene. The functional group in ketones is the carbonyl group, consisting of a carbon atom joined with a double covalent bond to an oxygen atom.
In ketones, the carbonyl group is attached to two alkyl groups and no H atoms. In aldehydes, the carbonyl group is attached to at least one H atom; it is also attached to either another H atom or an alkyl group.
In other words, in an aldehyde, the carbonyl group always occurs at the end of a carbon chain; in a ketone, the carbonyl group occurs in the interior of a carbon chain. Ants, bees, and moths like the gypsy moths shown here, produce and detect minute quantities of ketones to communicate the presence of food or water or the availability of a mate. Naming Aldehydes and Ketones The IUPAC names for aldehydes are formed by taking the parent alkane name, dropping the final -e, and adding the suffix -al.
The simplest aldehyde consists of a carbonyl group with no attached alkyl group; its formula is HCHO. It has only one C atom; thus the parent alkane is methane and the aldehyde is methanal, although it is more often known by its common nameformaldehyde.
The next simplest aldehyde is a carbonyl group with a methyl group attached; this two-carbon aldehyde is called ethanal, also known as acetaldehyde. Ketones are named by replacing the -e ending of the name of the corresponding alkane with -one. If, in a ketone, the carbon chain containing the carbonyl group has five or more carbon atoms, it is necessary to use a numerical prefix to specify the location of the car- bonyl group.
For example, in 2-pentanone, the carbonyl group is the second carbon atom in the carbon chain. The carbonyl group at the end of the chain indicates that the compound is an aldehyde, so will have the suffix -al.
There are four C atoms in the molecule, so the corresponding alkane is butane. The compound is, therefore, butanal. Draw a structural diagram for 3-hexanone. The ending -one indicates that the compound is a ketone, so will have its carbonyl group in the interior of a carbon chain. The prefix hexan- indicates the corresponding alkane is hexane and so has 6 carbons, with the carbonyl group being in the third position.
An aldehyde converts the blue copper II ion in the Fehlings solution to a red precipitate of copper I oxide. A ketone does not react with Fehlings solution, so the solution remains blue. However, the carbonyl group is a strongly polar group due to the four shared electrons in the double CO bond.
Thus, aldehydes and ketones are more soluble in water than are hydrocarbons. The ability of these compounds to mix with both polar and nonpolar substances makes them good solvents Figure 5. Like many ketones, acetone is both volatile and flammable and should be used only in well-ventilated areas.
Figure 4 Many essential oils contain alde- hydes, which contribute their pleasant fragrances. Benzaldehyde is called oil of bitter almond; it is formed by grinding almonds or apricot pits and boiling them in water. In this process, the poi- sonous gas hydrogen cyanide is also produced. Oxidation Reactions Historically, the term oxidation was used to describe any reaction involving oxygen. The term has since been broadened to include all chemical processes that involve a loss of elec- trons.
These processes are always accompanied by a reaction partner that undergoes reduc- tion, or a gain of electrons. This system of tracking electrons is useful in describing the changes in the types of bonds or the number of bonds in a chemical transformation. This further helps us to understand and select the type of reagent to use for a particular reaction. Aldehydes and ketones can be prepared by the controlled oxidation of alcohols. In organic chemistry, the term oxidation reaction generally implies a gain of oxygen or a loss of hydrogen.
The term oxidation in fact encompasses many other chemical processes, and you will learn more about them in Chapter 9. When alcohols are burned in oxygen, complete oxidation occurs and carbon dioxide and water are the only products formed. However, the conditions of oxidation reactions can be controlled to form other prod- ucts. In these reactions, oxygen atoms are supplied by compounds called oxidizing agents. In the following equations, O will be used to indicate the reactive oxygen atom supplied by an oxidizing agent; the involve- ment of the oxidizing agents is not important in discussions here.
Let us examine the transformation of an alcohol to an aldehyde or ketone. Essentially, the reactive O atom removes two H atoms, one from the OH group, and one from the adjacent C atom, resulting in a CO group; a water molecule is also produced.
When a primary alcohol is oxidized, an H atom remains on the C atom, and an aldehyde is produced. It appears that our olfactory receptors respond to the shape of the mole- cules that we smell rather than to their chemical composition. For example, the two hydrocarbons and the ketone shown below all smell like camphor, a component of many perfumes. All three molecules are bowl shaped, a geometrical shape that fits in our receptor sites for camphor-like odours.
Arrange the following compounds in increasing order of predicted boiling points. Tertiary alcohols do not undergo this type of oxidation; no H atom is available on the central C atom.
Hydrogenation Reactions The CO double bond in carbonyl groups can undergo an addition reaction with hydrogen, although not with other reactants. High temperatures and pressures and the presence of a catalyst are needed for this hydrogenation reaction. When the H atoms are added to the carbonyl group, an OH group results, producing an alcohol. This is, in effect, a reversal of the controlled oxidation of alcohols, discussed above.
For example, ethanal forms ethanol and propanone forms 2-propanol. As you can see, because of the type of groups attached to the carbonyl C atom, aldehydes always produce primary alco- hols, and ketones always produce secondary alcohols. The difference in the position of the carbonyl group in aldehydes and ketones accounts for their difference in behaviour with oxidizing agents.
As we will see in the next section when we discuss organic acids, aldehydes can be oxidized to form organic acids; ketones because they have no hydrogen atoms on the carbonyl carbon cannot.
The synthesis pathway from alcohols to aldehydes and then to acids is an important tool in the prepa- ration of many organic substances. Build two dif- ferent structures that use all 9 atoms.
Obtain one additional carbon atom and build as many different structures as possible, using all 10 atoms. Steroids Steroids are unsaturated compounds based on a structure of four rings of carbon atoms. The best-known and most abundant steroid is cholesterol.
Other steroids are ketones, including the male and female sex hormones, testosterone and progesterone, and anti-inflammatory agents such as cortisone. Oral contraceptives include two synthetic steroids.
Some athletes use anabolic steroids to enhance muscle development and physical performance, but such use may cause permanent damage. First, draw the structural formula for butanone. The O represents controlled oxidation using an oxidizing agent such as KM n O 4.
Solution Practice Understanding Concepts 6. Draw structural diagrams and write IUPAC names to illustrate the controlled oxida- tion of the following alcohols. Is the product an aldehyde or a ketone? Predict the relative solubility of the following compounds in water, listing the com- pounds in increasing order of solubility.
Briefly explain the meaning of the term oxidation. Applying Inquiry Skills 9. Design an experimental procedure to prepare an alcohol, starting with acetone. Describe the main steps in the procedure, list experimental conditions needed, and draw structural diagrams and write IUPAC names to represent the reaction used.
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Write an equation for a reaction involving an aldehyde to illustrate a hydrogenation reaction. Explain why no numeral is needed as a prefix in the naming of butanal and butanone.
Draw structural diagrams and write IUPAC names for the product s formed when 1-propanol undergoes the fol- lowing reactions: Giving reasons for your choice, select the compound that: Use a molecular model kit to build models for the following compounds, and write the IUPAC name for each: Suppose that you are given three alcohols: Design an experimental procedure that you could carry out with commonly available materials and equipment that would identify the tertiary alcohol.
Describe the main steps in the procedure and explain your experimental design. Design an experimental procedure for the synthesis of butanone from an alkene. Identify the starting alkene of your choice, describe the steps in the procedure, and include the experimental conditions needed. Your answer should also contain any precautions required in the han- dling and disposal of the materials. Making Connections 8. Many organic compounds have been in everyday use for many years, and are commonly known by nonsystematic names.
Make a list of common names of organic com- pounds found in solvents, cleaners, and other household items. Conduct research using electronic or print sources to find out the chemical names of five of these compounds, identify the functional groups that are present, and discuss the useful properties that these functional groups may impart to the compound.
The smell of formaldehyde was once common in the hall- ways of high schools, as it was used as a preservative of biological specimens. This use has largely been discon- tinued. In cases of severe diabetes, a patients tissues cannot use glucose, and, instead, the body breaks down fat for its energy.
The fats are broken down in the liver and muscles, producing several compounds called ketone bodies, one of which is acetone. Explain why acetone is soluble in these aqueous solutions. Suggest a reason why, like untreated diabetic patients, people who are severely starved or dieting may also have a smell of acetone on their breatha diagnostic symptom of ketosis. Research the symptoms and effects of ketosis and acidosis and how these conditions may be avoided. As with inorganic acids, carboxylic acids can react with compounds containing OH groups to form an organic salt called an ester.
Carboxylic Acids When wine is opened and left in contact with air for a period of time, it will likely turn sour. The alcohol in the wine has turned into vinegar. Grocery stores sell wine vinegars for cooking or for salad dressings. The chemical reaction in this souring process is the oxidation of ethanol, and the vinegar produced belongs to a family of organic com- pounds called carboxylic acids.
Carboxylic acids are generally weak acids and are found in citrus fruits, crab apples, rhubarb, and other foods characterized by a sour, tangy taste.
Sour milk and yogurt con- tain lactic acid, produced by a bacteria culture. If you have ever felt your muscles ache after prolonged exertion, you have experienced the effect of lactic acid in your muscles. The lactic acid is produced when the supply of oxygen cannot keep up with the demand during extended exercise.
The gamey taste of meat from animals killed after a long hunt is due to the high concentration of lactic acid in the muscles.
Carboxylic acids also have distinctive odours that can be used to advantage in law enforcement Figure 1. As car- boxylic acids have distinctive odours, the dogs may follow the characteristic blend of carboxylic acids in a persons sweat.
Trained dogs are also used to seek out illegal drug laboratories by the odour of acetic acid. Acetic acid is formed as a byproduct when mor- phine, collected from opium pop- pies, is treated to produce heroin.
TRYTHIS activity Making Flavoured Vinegar If vinegar a carboxylic acid can be made from ethanol the alcohol resulting from the fermentation of sugars , it should be possible to make a nice flavoured vinegar at home starting with apples, and a good supply of oxygen for oxidation.
Pure them, peel included, in the blender. Pour the pulp into a sieve or a bowl lined with cheesecloth. Strain out most of the pulp. Pour the juice into glass or plastic jars. Replace the lids loosely to maintain a good oxygen supply. Keep at room tem- perature and out of direct sunlight. Stir well each day to increase oxygen access. The yeast nor- mally found in the fruit will start the fermentation process, and vinegar should be produced in three to four weeks, identifiable by smell.
Filter the vinegar through a coffee filter to remove any sedi- ment, then pasteurize it by heating the filled jars loosely lidded in a pan of hot water until the vinegar is between 60C and 70C. Why does it work?
Nelson Chemistry Grade 12 Textbook
To add flavour, tie flavourings such as ginger, garlic, or rasp- berries in a small cheesecloth bag and suspend in the vinegar for several days. Enjoy the final oxidation product on a salad. This functional group combines two other functional groups already familiar to us: The IUPAC name for a carboxylic acid is formed by taking the name of the alkane or alkene with the same number of carbon atoms as the longest chain in the acid.
Remember to count the C atom in the carboxyl group in the total number of the parent chain. The -e ending of the alkane name is replaced with the suffix -oic, followed by the word acid. The simplest carboxylic acid is methanoic acid, HCOOH, commonly called formic acid; the name is derived from the Latin word formica which means ant, the first source of this acid Figure 2.
Methanoic acid is used in removing hair from hides and in coagu- lating and recycling rubber. Ethanoic acid, commonly called acetic acid, is the compound that makes vinegar taste sour. This acid is used extensively in the textile dyeing process and as a solvent for other organic compounds. The simplest aromatic acid is phenylmethanoic acid, better known by its common name, benzoic acid.
Benzoic acid is largely used to produce sodium benzoate, a common preservative in foods and beverages. Some acids contain multiple carboxyl groups.
For example, oxalic acid, which is found naturally in spinach and in the leaves of rhubarb, consists of two carboxyl groups bonded to each other; it is used in commercial rust removers and in copper and brass cleaners. Tartaric acid occurs in grapes; it is often used in recipes that require a solid edible acid to react with baking soda as a leavening agent.
Citric acid is responsible for the sour taste of citrus fruits. Vitamin C, or ascorbic acid, found in many fruits and vegetables, is a cyclic acid. A familiar aromatic acid is acetylsalicylic acid ASA , the active ingredient in Aspirin; you may have experienced its sour taste when swallowing a tablet.
When naming acids with multiple carboxyl groups, the suffix -dioic acid is used for acids with a carboxyl group at each end of the parent chain.
When more carboxyl groups are present, all COOH groups may be named as substituents on the parent chain; in this case, the parent chain does not include the carboxyl C atoms. An example is citric acid, shown below; it is named as a tricarboxylic acid of propane. In some countries, large ants are squeezed directly over a salad to add the tangy ant juice as a dressing.
The water- soluble vitamins are not stored in the body; rather, they are readily excreted in the urine. It is therefore important that we include these vitamins in our daily diet. However, although taking too much vitamin C is not dangerous, taking exces- sive amounts is truly sending money down the drain.
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The prefix propen- indicates that the acid contains three C atoms with one double bond; the end C atom is in the carboxyl group. Since the carboxyl C atom can only form one more single bond with its neighbouring C atom, the double bond is between carbon 2 and carbon 3. Solution The structure represents 2-methylbutanoic acid. Draw a structural diagram for each of the following compounds: However, the two oxygen atoms are not bonded to each other. In fact, the carboxyl group consists of a hydroxyl group OH attached to the C atom of a carbonyl group CO.
Organic Compounds 61 NEL As one would predict from the presence of both carbonyl CO and hydroxyl groups OH , the molecules of carboxylic acids are polar and form hydrogen bonds with each other and with water molecules.
These acids exhibit similar solubility behaviour to that of alcohols; that is, the smaller members one to four carbon atoms of the acid series are soluble in water, whereas larger ones are relatively insoluble. Carboxylic acids have the properties of acids: They also react with organic bases in neutralization reactions to form organic salts, as we will see later, in Chapter 2.
The melting points of carboxylic acids, as Table 1 shows, are higher than those of their corresponding hydrocarbons Figure 3. We can explain this by the increased inter- molecular attractions of the polar carboxyl functional groups.
This explanation is sup- ported by the significantly higher melting points of analogous acids with an abundance of carboxyl groups. Preparing Carboxylic Acids When an alcohol is mildly oxidized, an aldehyde is produced.
Further controlled oxidation of the aldehyde results in the formation of a carboxylic acid, containing a carboxyl group. The general oxidation pathway in this process is from alcohol to aldehyde to carboxylic acid; the functional group in the parent molecule changes from the hydroxyl group to the carbonyl group, then to the carboxyl group.
As you can see in the example below, the dif- ference between the carbonyl group and the carboxyl group is one additional O atom, present in the OH group. In the case of ethanol, the aldehyde formed is ethanal acetalde- hyde , which is further oxidized to ethanoic acid, commonly known as acetic acid.
Human skin con- tains functional groups that react with acids, which is why we can be badly injured by contact with concentrated strong acids. Figure 3 Oxalic acid, found in rhubarb, differs from vinegar in that its molecule contains an additional carboxyl group. This increased polarity explains why oxalic acid is a solid while vinegar is a liquid at the same temperature. Table 1 Melting Points of Some Carboxylic Acids and Their Parent Alkanes Number of Number of Compound Melting point C atoms COOH groups C 1 0 methane 1 1 methanoic acid 8 2 0 ethane 2 1 ethanoic acid 17 2 2 oxalic acid 4 0 butane 4 1 n-butanoic acid -8 4 2 tartaric acid 6 0 hexane 95 6 1 hexanoic acid 13 6 3 citric acid Properties of Carboxylic Acids p.
Compare many properties of a large and a small carboxylic acid, and draw your own conclusions. The clever selection of an oxidizing agent that changes colour as this reaction proceeds is the basis of the breathalyzer test for alcohol. When a measured volume of air containing ethanol passes through the breathalyzer tube, the ethanol is oxidized to acetalde- hyde and then to acetic acid.
The extent of the green colour down the breathalyzer tube provides a measure of the concentration of alcohol in the breath. First, write the structural formula for butanoic acid. Draw a structural diagram and write the IUPAC name of an alcohol that can be used in the synthesis of oxalic ethanedioic acid.
The labels have fallen off three bottles. Bottle A contains a gas, bottle B contains a liquid, and bottle C contains a solid. The labels indicate that the compounds have the same number of carbon atoms, one being an alkane, one an alcohol, and the other a carboxylic acid. Suggest the identity of the contents of each bottle, and give reasons for your answer.
Write a series of chemical equations to illustrate the synthesis of a carboxylic acid from the controlled oxidation of 1-propanol. Name and draw a general structure for the functional group in a carboxylic acid. Explain the effect of the components of this functional group on the molecule.
When a bottle of wine is left open to the air for a period of time, the wine often loses its alcoholic content and starts to taste sour. Write a series of equations to illustrate the reactions. Applying Inquiry Skills 8.
Suppose that you are given three colourless liquids whose identities are unknown. You are told that one is an aldehyde, one a ketone, and the other a carboxylic acid.
What physical and chemical properties would you examine in order to identify each compound?
demonstrate an understanding of the structure of various organic compounds, and of
Give reasons for your strategy. Think about common products in the home and identify several that contain alco- hols other than ethanol. Do these alcohols also turn sour over time? Explain, and illustrate your answer with structural diagrams. Some cosmetic facial creams contain an ingredient manufacturers call alpha hydroxy, which is designed to remove wrinkles.
These compounds are carboxylic acids that contain a hydroxyl group attached to the C atom adjacent to the car- boxyl group. Esterification Carboxylic acids react as other acids do, in neutralization reactions, for example. A car- boxylic acid can react with an alcohol, forming an ester and water.
In this reaction, the alcohol acts as an organic base and the ester formed may be considered an organic salt. This condensation reaction is known as esterification. As we will see later in the chapter, carboxylic acids also react with organic bases other than alcohols to form important biological compounds. The general reaction between a carboxylic acid and an alcohol is represented below. An acid catalyst, such as sulfuric acid, and heat are generally required.
It is interesting to note that, by tracking the oxygen atoms using isotopes, it has been found that the acid contributes the OH group to form the water molecule in the reaction. Esters Esters occur naturally in many plants Figure 5 and are responsible for the odours of fruits and flowers. Synthetic esters are often added as flavourings to processed foods, and as scents to cosmetics and perfumes.
Table 2 shows the main esters used to create certain artificial flavours. H 2 SO 4 heat alcohol OH ROH RC O O R HOH ester an organic compound charac- terized by the presence of a car- bonyl group bonded to an oxygen atom esterification a condensation reac- tion in which a carboxylic acid and an alcohol combine to produce an ester and water Figure 5 The rich scent of the lily is at least partially due to the esters produced in the flower.
Figure 4 Cosmetic treatment with carboxylic acids to remove surface skin may lead to irritation or sun sensitivity. This patient is in the third day of a skin-peeling treatment. Research and draw structural diagrams for these com- pounds. Explain why these alpha hydroxy acids are readily absorbed through the skin. In each case, the ingredients cause the surface of the skin to peel, revealing younger-looking skin. Suggest reasons why physicians recommend daily use of sun protection to accompany the use of these facial creams.
Consequently, the name of an ester has two parts. The first part is the name of the alkyl group from the alcohol used in the esterification reaction.
The second part comes from the acid. The ending of the acid name is changed from -oic acid to - oate. For example, in the reaction of ethanol and butanoic acid, the ester formed is ethyl butanoate, an ester with a banana odour. The functional group for an ester is a carboxyl group in which the H atom is substituted by an alkyl group: The general structural formula for an ester is shown below.
Note that, for an ester, the acid is the first part of its formula as drawn, but is the second part of its name. Draw a structural diagram and write the IUPAC name for the ester formed in the reaction between propanol and benzoic acid. To name the ester: To draw the structure: First, identify the acid four carbonsbutanoic acid and the alcohol two carbons ethanol that may be used in the synthesis of the ester. Then draw structures and include the conditions in the chemical equation.
Solution The ester is methyl ethanoate, and it can be prepared from methanol and ethanoic acid. Write complete structural diagram equations and word equations for the formation of the following esters.
Refer to Table 2 and identify the odour of each ester formed. Name the following esters, and the acids and alcohols from which they could be prepared. What it lacks in comparison to an acid is its OH group; the hydroxyl group is replaced by an OR group. With the loss of the polar OH group, esters are less polar, and therefore are less soluble in water, and have lower melting and boiling points than their parent acids.
Moreover, the acidity of the carboxylic acids is due to the H atom on their OH group, and so esters, having no OH groups, are not acidic. It is the low-molecular-mass esters that we can detect by scent, because they are gases at room temperature. The larger, heavier esters more commonly occur as waxy solids. Hydrolysis When esters are treated with an acid or a base, a reversal of esterification occurs; that is, the ester is split into its acid and alcohol components.
This type of reaction is called hydrolysis. In the general example shown below, the reaction is carried out in a basic solu- tion, and the products are the sodium salt of the carboxylic acid and the alcohol. As we shall see in more detail in the next chapter, fats and oils are esters of long-chain acids Figure 6. When these esters are heated with a strong base such as sodium hydroxide NaOH , a hydrolysis reaction occurs.
The sodium salts of the acids that result are what we call soap. This soap-making reaction is called saponification, from the Latin word for soap, sapon. When certain reactants are used, esters can be formed repeatedly and joined together to form long chains. These large molecules of repeating units are called polymers, and when the repeating units are esters, the polymer is the familiar polyester.
We will learn more about these and other polymers in the next chapter. ROH ester acid alcohol hydrolysis a reaction in which a bond is broken by the addition of the components of water, with the formation of two or more products saponification a reaction in which an ester is hydrolyzed Figure 6 Edible oils such as vegetable oils are liquid glycerol esters of unsaturated fatty acids.
Fats such as shortening are solid glycerol esters of saturated fatty acids. Adding hydrogen to the double bonds of the unsaturated oil converts the oil to a saturated fat. Most saturated fats are solids at room temperature. Synthesis of Esters p. Make some from alcohols and car- boxylic acids, and find out for your- self! COOH carboxyl group ester: COOR alkylated carboxyl group Preparation: In what way is the functional group of an ester different from that of a carboxylic acid?
How does this difference account for any differences in properties? Describe the experimental conditions in the hydrolysis of ethyl formate.
Write a bal- anced equation for the reaction, and name the product s. Draw structural diagrams for each of the following com- pounds: Draw the structures of the compounds formed by conden- sation reactions between the following reactants, and write IUPAC names for each product. Name the carboxylic acid and the alcohol that may be used to produce each of the following compounds: Describe an experimental procedure to carry out the saponification of propyl butanoate.
Explain the evidence that will indicate that the reaction has been completed. In the laboratory synthesis of an ester, what procedure can be used to recover the ester from the other components in the reaction mixture? Explain the strategy behind this pro- cedure.
Making Connections 7. From what you have learned about controlled oxidations in chemical reactions, describe some controlled oxidation reactions that occur in our everyday lives. In what situations are controlled oxidations ideal, and in what situations are uncontrolled oxidations ideal? Working with a partner or a small group, brainstorm and list several occupations that require a knowledge of alcohols, carboxylic acids, or esters.
Research one of these careers and write a brief report on the main strengths and qualities needed, academic training, and job opportunities in the field. Tannic acid, originally obtained from the wood and bark of certain trees, has for centuries been used to tan leather Figure 8.
Explain your answer with reference to the chemical reactions that take place. Design an experimental procedure for the synthesis of an ester, given ethanol and acetic acid. Describe the steps in the procedure, the safety equipment required, and the precautions needed in the handling and disposal of the materials. Making Connections Esters are often referred to as organic salts, and the esterification reaction considered a neutralization reaction.
Use chemical formulas and equations to identify similarities and differences between esters and inorganic salts. Organic Compounds 69 NEL 1. Many of the compounds that are naturally produced by living organisms also contain nitrogen. In fact, many of these nitrogenous organic compounds such as proteins and DNA have essential biological functions.
In this section, we will examine the nitrogenous organic families of amines and amides. Amines can be thought of as ammonia NH 3 with one, two, or all three of its hydro- gens substituted by alkyl groups; these are classified as primary 1 o , secondary 2 o , or tertiary 3 o amines, respectively. The alkyl groups in an amine may be identical or dif- ferent. Amines are organic bases, and can react with carboxylic acids to form nitrogenous organic salts, called amides.
Amide functional groups CON, Figure 1 occur in proteins, the large molecules formed in all living organisms. Amines When organisms decompose, large and complex molecules such as proteins are broken down to simpler organic compounds called amines.
As with many compounds of nitrogen, such as ammonia, NH 3 , amines often have an unpleasant odour. For example, the smell of rotting fish is due to a mixture of amines Figure 2. The putrid odour of decomposing animal tissue is caused by amines appropriately called putrescine and cadaverine, produced by bacteria. Spermine, an amine with its own distinctive aroma, can be isolated from semen. Naming Amines Amines can be named in either of two ways: The R groups may be the same or different, or they may be replaced by H atoms.
Lemon juice is often provided in restaurants to neutralize the taste of these amines, which are weak bases. Consider each molecule as an alkane; the NH 2 group is called an amino group. Thus, the structure in Figure 3 a is a butane with an amino group on C atom 1; it is named 1-aminobutane.
The structure in Figure 3 b is a hexane with an amino group on C atom 3; it is thus 3-aminohexane. Many compounds contain more than one amino group. The molecule cadaverine, for example, is a 5-carbon chain with an amino group at each end: Molecules with 2 amino groups are called diamines, and the IUPAC name for cadaverine is 1,5-diaminopentane.
There is a convenient alternative system of naming amines, in which the names imply an alkyl derivative of ammonia. The structural diagram in Figure 3 a shows an ammonia molecule with one of its H atoms substituted by a butyl group.
Its alternative name is butylamine. The structure in Figure 3 c has two alkyl groups on the N atom: It is named butylmethylamine. Figure 3 d shows an ammonia molecule with all its H atoms substituted by methyl groups; it is trimethylamine. Note that, generally, the alkyl groups are listed alphabetically in the amine name. We mentioned earlier that amines with one, two, or three alkyl groups attached to the central nitrogen atom are referred to, respectively, as primary, secondary, and tertiary amines.
Note that this designation is different from that of alcohols where the attachments of the carbon atom are indicated. NH 2 is an amino group, and NO 2 is a nitro group.
Write two names for the following structure: The longest hydro- carbon chain is propane. The amino group is on C atom 2 of the propane, so it is 2-amino- propane. The amino group has two methyl groups attached, so the amino group is N,N-dimethyl.
Using the alternative system, name the compound as a substituted amine. The three alkyl groups attached to the N atom are methyl, methyl, and isopropyl i-propyl. The alternative name for this compound is dimethyl-i-propylamine. Draw structural diagrams of a a 1 o amine, b a 2 o amine, and c a 3 o amine, each with 3 C atoms in the molecule.
Write two names for each amine. Since there are 3 C atoms, a single alkyl group may be n-propyl or i-propyl. So there are two possible 1 o amines for this formula. Since there are 3 C atoms, one alkyl group must be methyl and the other ethyl. There is only one possible 2 o amine for this formula: Since there are 3 C atoms, each alkyl group must be a methyl group. There is only one pos- sible 3 o amine for this formula. This can be explained by two types of polar bonds in amines: These bonds are polar because N is more electronegative than either C or H.
These polar bonds increase intermolecular forces of attraction, and therefore, higher temperatures are required to melt or to vaporize amines.
The series of amines below all of which have characteristic fishy odours illustrates the effect of hydrogen bonding on boiling point. Where NH bonds are present, hydrogen bonding also occurs with water molecules, accounting for the high solubility of amines in water.
It is worth noting that since NH bonds are less polar than OH bonds, amines boil at lower temperatures than do alco- hols of similar size Table 2. Write two names for each of the following structures one name for e , and indicate whether they are 1 o , 2 o , or 3 o amines. C Amine b. C Alcohol b. People with known allergic reactions carry Epipens syringes containing measured doses of epinephrine to be injected imme- diately to control the extent of an allergic reaction.
For example, the reaction of ammonia with ethyl iodide iodoethane yields ethylamine. Much of the research in organic chemistry is focused on a search for new or improved products. Suppose that you wish to develop a new stain remover, or a more effective drug, or a better-tasting soft drink. What should be the properties of the ingredients of your chosen product?
In the field of biology, complex systems have been developed to classify and name the countless different living organisms. Suggest an effective method of classifying and naming the vast range of organic compounds that exist.
From your knowledge of intramolecular and intermolecular attractions, describe fea- tures in the molecular structure of a compound that would account for its solubility and its melting and boiling points. What does organic mean? Give as many definitions as you can.ROH ester acid alcohol hydrolysis a reaction in which a bond is broken by the addition of the components of water, with the formation of two or more products saponification a reaction in which an ester is hydrolyzed Figure 6 Edible oils such as vegetable oils are liquid glycerol esters of unsaturated fatty acids.
Is the product an aldehyde or a ketone? The evidence is shown in Table 1.
The answer lies in the fact that carbon atoms can form four bonds. This is, in effect, a reversal of the controlled oxidation of alcohols, discussed above.
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