The presence of the function may be indicated by a characteristic suffix and a location number. This is common for the carbon-carbon double and triple bonds which have the respective suffixes ene and yne. Amines are derivatives of ammonia in which one or more of the hydrogens has been replaced by an alkyl or aryl group. The nomenclature nirbhaya boyfriend death amines is complicated by the fact that several different nomenclature systems exist, and there is no clear preference for one over the others.
When applied to amines these terms refer to the number of alkyl or aryl substituents bonded to the nitrogen atomwhereas in other cases they refer to the nature of an alkyl group. The four compounds shown in the top row of the following diagram are all C 4 H 11 N isomers. This system names amine functions as substituents on the largest alkyl group. The Chemical Abstract Service has adopted a nomenclature system in which the suffix -amine is attached to the root alkyl name.
These CA names are colored magenta in the diagram. Finally, a common system for simple amines names each alkyl substituent on nitrogen in alphabetical order, followed by the suffix -amine. These are the names given in the last row colored black. Many aromatic and heterocyclic amines are known by unique common names, the origins of which are often unknown to the chemists that use them frequently. Since these names are not based on a rational system, it is necessary to memorize them.
There is a systematic nomenclature of heterocyclic compounds, but it will not be discussed here. Nature abounds with nitrogen compounds, many of which occur in plants and are referred to as alkaloids.
Structural formulas for some representative alkaloids and other nitrogen containing natural products are displayed below, and we can recognize many of the basic structural features listed above in their formulas. These will be identified by pressing the " Show Structures " button under the diagram.
Nitrogen atoms bonded to carbonyl groups, as in caffeine, also tend to be planar. In contrast, atropine, coniine, morphine, nicotine and quinine have stereogenic pyramidal nitrogen atoms in their structural formulas think of the non-bonding electron pair as a fourth substituent on a sp 3 hybridized nitrogen.
In quinine this nitrogen is restricted to one configuration by the bridged ring system.Reactions of Amines continued Reactions of Amines continued 4. Because it is unstable, it is prepared immediately before use in the following manner:. Under the acidic conditions of this reaction, all amines undergo reversible salt formation:. Diazonium cations may be described by resonance contributors, as in the bracketed formulas shown below.
The left-hand contributor is dominant because it has greater bonding. For example, if water is the only nucleophile available for reaction, phenols are formed in good yield.
24.7: Reactions of Amines
The nitrosonium cation is not sufficiently electrophilic to react with benzene itself, or even toluene, but highly activated aromatic rings such as amines and phenols are capable of substitution. Once nitrosated, the activating character of the amine nitrogen is greatly diminished; and N-nitrosoaniline derivatives, or indeed any amide derivatives, do not undergo ring nitrosation.
Aryl diazonium salts are important intermediates. Some of the more commonly used substitution reactions are shown in the following diagram. Since the leaving group N 2 is thermodynamically very stable, these reactions are energetically favored.
Those substitution reactions that are catalyzed by cuprous salts are known as Sandmeyer reactions. Fluoride substitution occurs on treatment with BF 4 —a reaction known as the Schiemann reaction. Stable diazonium tetrafluoroborate salts may be isolated, and on heating these lose nitrogen to give an arylfluoride product. The top reaction with hypophosphorus acid, H 3 PO 2is noteworthy because it achieves the reductive removal of an amino or nitro group.
Unlike the nucleophilic substitution reactions, this reduction probably proceeds by a radical mechanism. These aryl diazonium substitution reactions significantly expand the tactics available for the synthesis of polysubstituted benzene derivatives.
Consider the following options:.
A nitro substituent deactivates an aromatic ring and directs electrophilic substitution to meta locations. The following examples illustrate some combined applications of these options to specific cases. You should try to conceive a plausible reaction sequence for each. Once you have done so, you may check suggested answers by clicking on the question mark for each. A resonance description of diazonium ions shows that the positive charge is delocalized over the two nitrogen atoms.
It is not possible for nucleophiles to bond to the inner nitrogen, but bonding or coupling of negative nucleophiles to the terminal nitrogen gives neutral azo compounds. As shown in the following equation, this coupling to the terminal nitrogen should be relatively fast and reversible. In practice it is found that the E-isomer predominates at equilibrium. Unless these azo products are trapped or stabilized in some manner, reversal to the diazonium ion and slow nucleophilic substitution at carbon with irreversible nitrogen loss will be the ultimate course of reaction, as described in the previous section.
For example, if phenyldiazonium bisufate is added rapidly to a cold solution of sodium hydroxide a relatively stable solution of sodium phenyldiazoate the conjugate base of the initially formed diazoic acid is obtained.
Lowering the pH of this solution regenerates phenyldiazoic acid pK a ca. Aryl diazonium salts may be reduced to the corresponding hydrazines by mild reducing agents such as sodium bisulfite, stannous chloride or zinc dust.Amines are formally derivatives of ammoniawherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group  these may respectively be called alkylamines and arylamines; amines in which both types of substituent are attached to one nitrogen atom may be called alkylarylamines.
Important amines include amino acidsbiogenic aminestrimethylamineand aniline ; see Category:Amines for a list of amines. Inorganic derivatives of ammonia are also called amines, such as monochloramine NClH 2. The substituent -NH 2 is called an amino group. Amines can be classified according to the nature and number of substituents on nitrogen. Aliphatic amines contain only H and alkyl substituents. Aromatic amines have the nitrogen atom connected to an aromatic ring.
Amines, alkyl and aryl alike, are organized into three subcategories see table based on the number of carbon atoms adjacent to the nitrogen: . A fourth subcategory is determined by the connectivity of the substituents attached to the nitrogen:. It is also possible to have four organic substituents on the nitrogen. These species are not amines but are quaternary ammonium cations and have a charged nitrogen center.
Quaternary ammonium salts exist with many kinds of anions. Amines are named in several ways. Typically, the compound is given the prefix "amino-" or the suffix: "-amine". The prefix " N -" shows substitution on the nitrogen atom. An organic compound with multiple amino groups is called a diamine, triamine, tetraamine and so forth.
Hydrogen bonding significantly influences the properties of primary and secondary amines. For example, methyl and ethyl amines are gases under standard conditions, whereas the corresponding methyl and ethyl alcohols are liquids. Amines possess a characteristic ammonia smell, liquid amines have a distinctive "fishy" smell. The lone electron pair is represented in this article by a two dots above or next to the N.
The water solubility of simple amines is enhanced by hydrogen bonding involving these lone electron pairs.In these latter two cases there is only one organic group Rso that the terms are used to designate the type of carbon to which the alcohol or halide function is attached.
One system is used for naming relatively simple amines, i. Simple Amines. Simple amines are named according to the number of carbons in the longest continuous chain or ring of carbon atoms present in any of the R groups attached to nitrogen. Numbering, of course, must begin with the carbon immediately attached to the amine function. After identifying the main chain, the amine is named as a derivative of the alkane or cycloalkane having the appropriate number of carbon atoms by deleting the terminal —e of the alkane and replacing it with the suffix — amine.
The common name for this very simple amine is methylamine no separators between methyl and amine. The secondary amine which has one methyl group and one ethyl group attached to nitrogen is named N-methylethanamine the two carbon chain is used as the main chain in preference to the one carbon chain.
Note the usage of the letter N to designate that the methyl substitutent is attached to nitrogen. If one R group is methyl, a second is ethyl, and a third is propyl, the amine would be named N-ethyl-N-methylpropanamine. Note the alphabetic criterion for arranging the methyl and ethyl sequence. More Complex Amines. The substituent name of the —NH 2 is amino. The CH 3 2 N- substituent is, e. The name of the compound. You will recall that the nitrogen atom of ammonia is sp 3 hybridized and there is an unshared pair of electrons in the fourth tetrahedral orbital.
This makes ammonia a base and a nucleophile. Because nitrogen is less electronegative than oxygenammonia is a much stronger base than water and also a much better nucleophile. Amines, which are merely organic derivatives of ammonia, are also tetrahedrally hybridized and are comparably basic and nucleophilic to ammonia.
You might recall that amines are completely neutralized protonated by carboxylic acids. The basicity of amines is often discussed indirectly in terms of the acidity of their respective conjugate acids. Recall that the conjugate acid of a weak base e.
The concept of pK a has already been developed as a measure of the acidity of Bronsted acids, and we will also see that a corresponding concept, pK b can be used as a measure of the basicity of bases and that these two quantities are very closely related. Consider the acid dissociation, in dilute aqueous solution, of ammonia and a representative primary, secondary, and tertiary amine:.With the strong mineral acids e. Salt formation is instantly reversed by strong bases such as NaOH.
This reaction has been used for analytical determination of primary amino groups in a procedure known as the Van Slyke method.
These highly reactive compounds are of great importance in organic synthesis and in the dye industry see dyes.
Chemical Reactions of Amines - Acylation and Basicity
Some nitrosamines are potent cancer-inducing substances, and their possible formation is a serious consideration when nitriteswhich are salts of nitrous acid, are present in foods or pharmaceutical preparations. Tertiary amines give rise to nitrosamines more slowly; an alkyl group is eliminated as an aldehyde or ketonealong with nitrous oxideN 2 O.
Halogenationin which one or more hydrogen atoms of an amine is replaced by a halogen atom, occurs with chlorine, bromine, and iodineas well as with some other reagents, notably hypochlorous acid HClO.
With tertiary amines, an alkyl group may be displaced by a halogen. Amines can burn in air, producing water, carbon dioxide, and either nitrogen or its oxides. Hydrogen peroxide H 2 O 2 and peroxy acids generally add an oxygen atom to the nitrogen of amines.
With primary amines, this step is normally followed by further oxidation, leading to nitroso compoundsRNO, or nitro compoundsRNO 2. The principal reaction of quaternary ammonium compounds is the Hofmann degradationwhich takes place when the hydroxides are strongly heated, generating a tertiary amine; the least-substituted alkyl group is lost as an alkene.
Examples of direct uses of amines and their salts are as corrosion inhibitors in boilers and in lubricating oils morpholineas antioxidants for rubber and roofing asphalt diarylaminesas stabilizers for cellulose nitrate explosives diphenylamineas protectants against damage from gamma radiation diarylaminesas developers in photography aromatic diaminesas flotation agents in miningas anticling and waterproofing agents for textilesas fabric softeners, in paper coating, and for solubilizing herbicides.
Some polyfunctional amines are valuable pharmaceuticals, such as ephedrine and epinephrine adrenalineand anestheticssuch as novocaine. Many important products require amines as part of their syntheses. Methylamine is utilized in the production of the analgesic meperidine trade name Demerol and the photographic developer Metol trademarkand dimethylamine is used in the synthesis of the antihistamine diphenhydramine trade name Benadrylthe solvent dimethylformamide DMFand the rocket propellant 1,1-dimethylhydrazine.
The synthesis of the insect repellent N,N-diethyl-m-toluamide DEET incorporates diethylamine while that of the synthetic fibre Kevlar requires aromatic amines. Polyurethanes are formed from methylenedianiline via its diisocyanate. Other products utilizing amines in their synthesis include spandex, caffeineexplosives e. Article Media. Info Print Print. Table Of Contents. Submit Feedback. Thank you for your feedback. Introduction Nomenclature of amines Properties of amines Physical properties Molecular shape and configuration Occurrence and sources of amines Reactions of amines Addition Substitution Oxidation Elimination Uses of amines.
Load Previous Page. Learn More in these related Britannica articles:. Amine s are functional group compounds that contain at least one nitrogen atom bonded to hydrogen atoms or to alkyl or aryl groups. If the substituents other than hydrogen atoms are alkyl groups, the resulting compounds are termed alkyl amines. If one or more substituents…. Aromatic amines and nitro compounds, for example, aniline, toluidine, and nitrobenzene, produce depression of the central nervous system and methemoglobinemia Table 2.
Methemoglobinemia is a condition in which the ferrous ion in hemoglobin, which is responsible for carrying oxygen, is oxidized to the ferric form. Most of these are stronger bases than ammonia; i.
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More About.Reaction with acids. Aldehydes and ketones react with primary amines to give a reaction product a carbinolamine that dehydrates to yield aldimines and ketimines Schiff bases. Amines react with sulfonyl chlorides to produce sulfonamides. A typical example is the reaction of benzene sulfonyl chloride with aniline. The Hinsberg test, which can distinguish primary, secondary, and tertiary amines, is based upon sulfonamide formation. In the Hinsberg test, an amine is reacted with benzene sulfonyl chloride.
If a product forms, the amine is either a primary or secondary amine, because tertiary amines do not form stable sulfonamides. If the sulfonamide that forms dissolves in aqueous sodium hydroxide solution, it is a primary amine. If the sulfonamide is insoluble in aqueous sodium hydroxide, it is a secondary amine. The sulfonamide of a primary amine is soluble in an aqueous base because it still possesses an acidic hydrogen on the nitrogen, which can be lost to form a sodium salt.
Although you can oxidize all amines, only tertiary amines give easily isolated products. The oxidation of a tertiary amine leads to the formation of an amine oxide. Arylamines tend to be easily oxidized, with oxidation occurring on the amine group as well as in the ring. Reaction with nitrous acid. Nitrous acid is unstable and must be prepared in the reaction solution by mixing sodium nitrite with acid.
Primary amines react with nitrous acid to yield a diazonium salt, which is highly unstable and degradates into a carbocation that is capable of reaction with any nucleophile in solution. Therefore, reacting primary amines with nitrous acid leads to a mixture of alcohol, alkenes, and alkyl halides. Reactions of aromatic diazonium salts. Diazonium salts of aromatic amines are very useful as intermediates to other compounds. Because aromatic diazonium salts are only stable at very low temperatures zero degrees and belowwarming these salts initiates decomposition into highly reactive cations.
These cations can react with any anion present in solution to form a variety of compounds. Previous Preparation of Amines. Next Spectroscopy and Structure. Removing book from your Reading List will also remove any bookmarked pages associated with this title. Are you sure you want to remove bookConfirmation and any corresponding bookmarks? My Preferences My Reading List.
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Learn more Explore this Article Steps. Related Articles. This article deals with studying the chemistry of organic amines and its reactivity.
Learn what amines are. Amines are organic hydrocarbons that are attached to nitrogen in a single bond manner. Amines are very reactive group of compounds. This is so due to the existence of the electron lone pair on the nitrogen atom. The nitrogen atom in amines is relatively of low electro-negativity if we compare it with oxygen. Therefore, the electron pull power of the nitrogen to share it is not so strong as in alcohols. This allows for the lone pair on nitrogen to be manifested in many chemical reactions.
Primary amines are very reactive and they can be synthesized by the reaction of phthalimide with an alkyl halide followed by hydrolysis to form phthalic acid and the primary amine.
Understand how amines react. They usually react with an electrophile a two step manner. Namely, the formed amine from the first reaction with the electrophile continues to react further with another electrophile. This means that one does not expect a single reaction but a multiple reaction of the same amine. Learn about the different function possibilities.