Anilines Anilinium salt

Even though they aie weaker bases, aiylamines, like alkylanines, can be completely protonated by strong acids. Aniline is extracted from an ether solution into 1 M hydrochloric acid by being completely converted to a water-soluble anilinium salt under these conditions. 

The Brpnsted acidic anilinium salt [PhNH3+][ B(C6F5)4] has been developed as a catalyst for the hydroamination and hydroarylation of alkenes, such as styrenes, nor-bomene, cyclic alkenes, and cyclohexadiene, with anilines. The weakly coordinating... 

Trichloroacetic acid decomposes in water, alcohol and aniline and other basic solvents but it does not decompose in non-basic solvents such as benzene, carbon tetrachloride, sulfuric and acetic acid. Furthermore, the ethyl ester of trichloroacetic acid dissolves in alcohol but it does not decompose. It is known that this ester does not ionize in alcohol. Trichloroacetic acid, the sodium salt, the barium salt, and the anilinium salt all decompose in water at the same rate and all give beautiful first order constants throughout the whole course of the reaction. It is known that all these salts... 

In aniline, the anilinium salt decomposed faster towards the end of the reaction, and here also a concentration effect was noticed, the dilute solution giving a higher specific decomposition rate. 

Quaternary anilinium salts (240), obtained from reaction of (pyrrol-l-yl)methanol and the appropriate aniline with trioctylphosphine, react in polar solvents via the azonia-fulvene ion (241) with enamines through a Mannich-type reaction followed by cyclization to give pyrrolizidines 242 and 243124. The ratio between the pyrrolizidines formed varies considerably with ring size of the enamine employed (equation 50). Pyrrolizines have also been obtained by reaction of pyrrole with two equivalents of enamine125 or condensation of some ketones with L-sodium or L-ethyl prolinate126. 

Although protonation of the amine leads to the anilinium salt which is a deactivating substituent, nitration of aniline in nitric acid sulfuric acid yields 60% para and 34% meta substitution, whilst nitration of acetanilide gives 79% para and 19% ortho nitroacetanilides. 

Polyaniline filaments have been synthesized in mordenite and zeolite Y. 3 Aniline was sorbed from hexane solution into the dehydrated zeolites containing different levels of hydroxyl groups (an alternate route is the exchange of anilinium salt into the host, see ref. 93b). Oxidative polymerization was achieved by immersion of the loaded zeolites into an aqueous solution of peroxydisulfate, as demonstrated by spectroscopic identification and recovery of the encapsulated polymer (Figure 10). 

This mesomeric (or M) effect is seen when aniline is placed in a solution of pH 8-14, i.e. when the basic aniline is unionised. When aniline is placed in a solution of pH < 7, the A,max returns to virtually the value obtained for benzene (203 nm). What is happening is that aniline in acidic solution reacts to form the anilinium salt. The lone pair of electrons on the nitrogen is now involved in bond formation to an H+ ion and can no longer function as an auxochrome. The structure of aniline hydrochloride is shown in Figure 7.8. 

Anilinium salts can be converted back to aniline by NaOH. 

First, dissolve the reaction mixture in an organic solvent such as diethyl ether.The ethereal solution can be extracted with an aqueous acid, such as HCI, which reacts with aniline, a base, to form a water-soluble salt. Thus, the ether layer contains nitrobenzene while the aqueous layer contains the anilinium salt. After separating the two layers, the acidic aqueous layer can be basified with NaOH to deprotonate the anilinium ion. Extraction of the basified aqueous layer with diethyl ether, followed by evaporation of the ether, allows aniline to be isolated. 

Template-guided synthesis 2,4) is currently being used increasingly to synthesize water soluble polyaniline. Apofyadd is used as a tenq>late to bind the aniline monomers to form the corresponding anilinium salt. Aniline monomers polymerize to form a conq)lex with the template. The hydrophobic and hydrophilic ends of the tenq)late he in sohibifizing the hydrophobic polyaniline chains. Some of the pofyadds used (25) in the synthesis of polyaniline are polystyrenesulfonic add, poly(aci dic add) and poly(methacrylic acid). 

Ammonium salts contain a nitrogen atom with four bonds that has a positive charge. Four-bonded nitrogen atoms derived from amines are ammonium ions (if they re derived from aniline, they re anilinium ions). If the four bonds are all to carbon atoms, the nitrogen atom is quaternary. Salts contain a cation (named first) and an anion (named last). Typical anions include Cl (chloride), Bi" (bromide), HSO (hydrogen sulfate or bisulfate), and NOj-(nitrate). Figure 13-5 shows two examples of ammonium ions. 

Nitro-N-Etbyl-N-Metbyl Aniline, 02NCHflH4N(CH3XC2H mw 180.21, N13.55% crysts, mp 88° Prepd by beating diethylsulfate with 2-nicro-N,N-dim ethyl aniline to give the quaternary anilinium ethyl sulfate salt which was then heated to give the N-Eihyl-N-Methyl compound 1... 

Salts of amines are generally named by replacing -amine by -ammonium (or -aniline by -anilinium), and adding the name of the anion chloride, nitrate, sulfate, etc.). For example ... 

Aniline is usually sulfonated by baking the salt, anilinium hydrogen sulfate, at 180-200 the chief product is the / -isomer. In this case we cannot discuss orientation on our usual basis of which isomer is formed faster. Sulfonation is... 

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