AMINES AND AMIDES

GROUP 6TRINIDAD, RIMA, SEPTIMO, SIABABA, SOBREVEGA, VALDERAMA

Mr. Christian Paul P. dela Cruz

AMINES AND AMIDES16.6 Biological important amines16.7 Nomenclature of amides16.8 Physical properties of amides16.9 Chemical properties of amidesOUTLINE16.6 Other Biologically Important AminesEpinephrine

Epinephrine, or adrenaline, has a molecular structure similar to that of norepinephrine.

The difference is that epinephrine contains an N-methyl group:Epinephrine is more important as a hormone than as a neurotransmitter. It is synthesized in the adrenal gland and acts to increase the blood level of glucose, a key source of energy for body processes. The release of epinephrineusually in response to pain, anger, or fearprovides glucose for a sudden burst of energy. For this reason, epinephrine has been called the fight-or-flight hormone.

Epinephrine also raises blood pressure. It does this by increasing the rate and force of heart contractions and by constricting the peripheral blood vessels. Injectable local anesthetics usually contain epinephrine because it constricts blood vessels in the vicinity of the injection. This prevents the blood from rapidly washing the anesthetic away and prolongs the anesthetic effect in the target tissue. Epinephrine is also used to reduce hemorrhage, treat asthma attacks, and combat anaphylactic shock (collapse of the circulatory system).Amphetamines

Notice that both compounds contain an aromatic ring attached to a substituted ethylamine.That structural arrangement, sometimes referred to as a phenethylamine, is apparently an essential feature of several physiologically active compounds. These structural similarities lead to similar behaviors in the body: Both compounds raise the glucose level in the blood and increase pulse rate and blood pressure. Other closely related phenethylamine compounds, such as Methedrine, also act as powerful nervous system stimulants. Compounds of this type can be thought of as being derived from amphetamine and as a result are sometimes collectively referred to as amphetamines:Amphetamines are used both legally (as prescribed by a physician) and illegally to elevate mood or reduce fatigue. In the drug culture, amphetamine tablets go by such names as bennies, pep pills, reds, red devils, speed, dexies, and uppers. Some amphetamines (known as STP, speed, and mescaline) cause hallucinations. The abuse of such drugs results in severe detrimental effects on both the body and the mind.

Plants are the sources of some of the most powerful drugs known. Numerous primitive tribes in the world possess knowledge about the physiological effects that result from eating or chewing the leaves, roots, flowers or bark of certain plants. The effects vary from plant species to plant species. Some cure diseases; others, such as opium, are addictive drugs. Still others are deadly poisons, such as the leaves of the belladonna plant and the hemlock herb. The substances responsible for these marked physiological effects are often nitrogen-containing compounds called alkaloids. The name, which means alkali-like, reflects the fact that these amine compounds are weakly basicAlkaloids A number of alkaloids are used medicinally. Quinine, for example, is used to treat malaria.

Atropine is used as a preoperative drug to relax muscles and reduce the secretion of saliva in surgical patients, and to dilate the pupil of the eye in patients undergoing eye examinations.

The molecular structures of alkaloids vary from simple to complex. Two common and relatively simple alkaloids are nicotine, which is found in tobacco, and caffeine, which is present in coffee and cola drinks:

Opium, the dried juice of the poppy plant, has been used for centuries as a painkilling drug. It contains numerous alkaloids, including morphine and its methyl ether, codeine. Both are central nervous system depressants, with codeine being much weaker. They exert a soothing effect on the body when administered in sufficient amounts. These properties make them useful as painkillers. Morphine is especially useful in this regard, being one of the most effective painkillers known. Codeine is used in some cough syrups to depress the action of the cough center in the brain. The major drawback to using these drugs is that they are all addictive. Heroin, a derivative of morphine, is one of the more destructive hard drugs used illegally in our society. A substantial number of addicts commit crimes to support their habits.

Simple amides are named after the corresponding carboxylic acids by changing the -ic ending (common names) or the -oic ending (IUPAC names) of the acid to -amide.

Common names are used more often than IUPAC names. Some examples of the assignment of such names follow:16.7 The Nomenclature of Amides

Common names of AmidesAnswers

PropanamideHexanamide

If alkyl groups are attached to the nitrogen atom of amides (substituted amides), the name of the alkyl group precedes the name of the amide, and an italic capital N is used to indicate that the alkyl group is bonded to the nitrogen.

a.CN: N,N-diethylethanmideIN: N,N- diethylacetamide

b.CN: 2-methyl-N-propylpropionamideIN: 2-methyl-N-propylpropanamide

c.CN and IN: N-ethyl-N-phenylbenzamide

d.CN and IN: 2-methyl-N-methylbenzamide

AnswersThe substitution of alkyl or aromatic groups for hydrogen atoms on the nitrogen reduces the number of intermolecular hydrogen bonds that can form and causes the melting points to decrease. Thus, disubstituted amides often have lower melting and boiling points than monosubstituted and unsubstituted amides. Well see in Chapter 19 that hydrogen bonding between amide groups is important in maintaining the shape of protein molecules.

Amides are rather water soluble, especially those containing fewer than six carbon atoms. This solubility results from the ability of amides to form hydrogen bonds with water. Even disubstituted amides do this because of the presence of the carbonyl oxygen (see Figure 16.7).16.8 Physical Properties of Amides

Neutrality Because basicity is the most important property of amines, it is only natural to wonder if amides are also basic. The answer is no. Although they are formed from carboxylic acids and basic amines, amides are neither basic nor acidic; they are neutral. The carbonyl group bonded to the nitrogen has destroyed the basicity of the original amine, and the nitrogen of the amine has replaced the acidic OH of the carboxylic acid.16.9 Chemical Properties of AmidesAmide Hydrolysis The most important reaction of amides is hydrolysis. This reaction corresponds to the reverse of amide formation; the amide is cleaved into two compounds, a carboxylic acid and an amine or ammonia:

As with hydrolysis of carboxylic esters, amide hydrolysis requires the presence of a strong acid or base, and the nature of the final products depends on which of these reactants is used. Notice in the following examples that under acidic conditions, the salt of the amine is produced along with the carboxylic acid, and under basic conditions, the salt of the carboxylic acid is formed along with the amine. Also, notice that heat is required for the hydrolysis of amides.

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