Toluidins

It is prepared by the direct nitration of toluene as a 50-60% component of the mixture of isomers. Used for the preparation of o-toluidine. 

Prepared by mononilrating toluene, as a 40% constituent of the mixture of isomers. It is reduced to p-toluidine with iron and hydrochloric acid. 

Required />-Toluidine, 24 g. hydrochloric acid, 55 ml. sodium nitrite, 17 g. 

Dissolve 2 3 drops of o toluidine in a few drops of dil. HCl and add 2 3 drops of ferric chloride solution a green coloration is produced and is slowly replaced by a bluish-green or blue precipitate. 

A) PRIMARY AROMATIC AMINES. RNH. Aniline, o-, m-, and p-toluidine (and other nuclear-substitiited anilines) 1- and 2-naphthylamines. (For note on Aliphatic Amines, cf. p. 375 )... 

Physical properties. Majority are liquids except p toluidine and 1- and 2-naphthylamine. All are colourless when pure, but rapidly darken on exposure to air and light. All are very sparingly soluble in water, but dissolve readily in dilute mineral acids (except the naphthyl-amines, which are only moderately soluble in adds). They form colourless crystalline salts e.g., CjHjNH2,HCl) which are soluble in water these aqueous solutions usually have an add reaction owing to hydrolysis, and give the reactions of both the amine and the acid from which they are derived. Addition of alkali to the acid solution liberates the amine. 

Basic Component. The filtrate from (a), or the HCl extract from b), now contains the basic component in the form of its hydrochloride. Add 30% aqueous NaOH solution until alkaline to litmus. Cool, and scratch the sides of the vessel with a glass rod a white precipitate indicates a solid amine, e.g, p-toluidine or a naphthylamine. Dilute, filter off, wash well with water (recrystallise if necessary), dry and identify. 

Green coloration. Catechol (colour rapidly darkens). [Aniline (pale green), o-toluidine (pale green initially), mono-methylaniline, and diphenylamine, each in dil. HCl.]... 

TEST Aniline 0- toluidine m-> toluidine P-. toluidine I- naphthyl- amine 2- naphthyl- amine mono- methyl- aniline diphenyl- amine dimethyl- aniline triphenyl- amine... 

Many chloroplatinates separate from aqueous solution with water of crystallisation. If this is suspected, the chloroplatinate should be dried to constant weight in the oven before analysis, to ensure elimination of water of crystallisation. Aniline, p-toluidine and pyridine all give anhydrous chloroplatinates, and can be conveniently used in the above determination no attempt should be made to recryrtallise their chloroplatinates. 

Toluidine. Transient green, deep blue and then a deep blue precipitate. Usually a very fast reaction. 

Water 2-methylpiperidine Water 3-metliylpipericline Water 4-methylpiperidine Water P picoline Water aa-Iutidine Glycerol m-toluidine. ... 

Anilides and p-toluidides may also be prepared directly from the acide% by heating them with aniline or p toluidine respectively ... 

Place 1 0 g. of the monobasic acid and 2 g. of aniline or p-toluidine in a dry test-tube, attach a short air condenser and heat the mixture in an oil bath at 140-160° for 2 hours do not reflux too vigorously an acid that boils below this temperature range and only allow steam to escape from the top of the condenser. For a sodium salt, use the proportions of 1 g. of salt to 1 5 g. of the base. If the acid is dibasic, employ double the quantity of amine and a reaction temperature of 180-200° incidentally, the procedure is recommended for dibasic acids since the latter frequently give anhydrides with thionyl chloride. Powder the cold reaction mixture, triturate it with 20-30 ml. of 10 per cent, hydrochloric acid, and recrystallise from dilute alcohol. 

The above simple experiments illustrate the more important properties of the anhydrides of aliphatic acids. For their characterisation, the reaction with aniline or p-toluidine is frequently employed. Alternatively, the anhydride may be hydrolysed with dilute alkali as detailed under Acid Chlorides, Section 111,88, and the resulting acid characterised as in Section 111,85. 

Anilides or p-toluidides of acids from esters. Esters are converted into the corresponding anilides or p-toluidides by treatment with anilino- or with p-toluidino-magnesium bromide, which are readily obtained from any simple Grignard reagent and aniline or p-toluidine ... 

Alternatively, add a solution of 4 5 g. of p-toluidine in dry ether to the Grignard reagent prejjared from 1 0 g. of magnesium as detailed above. Then introduce 1 0 g. (or 0 02 mol) of the ester and proceed as described lOr anihdes. 

Shake for 10-15 minutes. Extract tliealkahiie solution with ether to remove excess of p-toluidine, acidify, filter, and recrystalUse the residue as in (i). 

Dissolve 1 g. of the sulphonic acid or its sodium salt in the minimum volume of boiling water and add a saturated aqueous solution of 1 g. of p-toluidine hydrochloride. Cool, Alter off the precipitate of the p-tolu-idine salt, and recrystallise it from hot water or from dilute ethanol. 

The production of diacetyl derivatives is facilitated by the presence of substituents in the ortho position thus an excellent yield of diacetyl-o-toluidine results when o-toluidine is heated with an excess of the reagent ... 

Boil a mixture of 10 g. (10 ml.) of o-toluidine and 38 g. (35 ml.) of acetic anhydride in a 75 or 100 ml. Claisen flask fitted with a reflux condenser (Fig. Ill, 28, 1, but with trap replaced by a calcium chloride or cotton wool guard tube) for 1 hour. Arrange the flask for distillation under reduced pressure (compare Fig. II, 20, 1) and distil acetic acid and the excess of acetic anhydride pass over first, followed by the diacetyl derivative at 152-153°/20 mm, some mono-acetyl-o-toluidine (1-2 g.) remains in the flask. The yield of diacetyl-o-toluidine is 14-15 g, it is a colourless, somewhat unstable hquid, which slowly sohdifies to yield crystals, m.p. 18°, To prepare the (mono-) acetyl-o-toluidine, warm a mixture of 5 g. 

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