Schiff’s reaction

Xylene two changes, 5 min each Mount in Permount, Polymount, or Euparol DNA = blue green RNA = purple or dark blue Total protein—ninhydrin—alloxan— Schiff s reaction (see Jensen, 1952 for Deamination and Acetylation Controls)... 

Schiff s reaction. 10 c.c. of the alcohol (50%) and 4 c.c. of Schiff s reagent (see below r Determination) are shaken together in a test-tube and allowed to stand. The presence of aldehydes is shown by the appearance, either immediately or after some time, of a more or less intense red coloration, which should be observed after about 20 minutes. If no colour appears after this time, the liquid is free from aldehydes. 

Gives some of the tests for acetaldehyde, but more feebly e.g., it restores the colour to SchifF s reagent, gives a yellow resin with NaOH, and responds to the nitroprusside test. With ammoniacal AgN03, it gives a silver minor only after 2 -3 minutes warming. It does not give the iodoform reaction. 

An alternative procedure for the above test is as follows. Mix 2-3 ml. of 2 per cent, aqueous paraperiodic acid solution with 1 drop of dilute sulphuric acid (ca. 2 5N) and add 20-30 mg. of the compound. Shake the mixture for 5 minutes, and then pass sulphur dioxide through the solution until it acquires a pale yellow colour (to remove the excess of periodic acid and also iodic acid formed in the reaction). Add 1-2 ml. of Schiff s reagent (Section 111,70) the production of a violet colour constitutes a positive test. 

This is an example of the Doebner synthesis of quinoline-4-carboxylic acids (cinchoninic acids) the reaction consists in the condensation of an aromatic amine with pyruvic acid and an aldehj de. The mechanism is probably similar to that given for the Doebner-Miller sj nthesis of quinaldiiie (Section V,2), involving the intermediate formation of a dihydroquinoline derivative, which is subsequently dehydrogenated by the Schiff s base derived from the aromatic amine and aldehyde. 

Reaction with primary amines (Section 17 10) Isolated product is an imine (Schiff s base) A carbinolamine inter mediate is formed which undergoes de hydration to an imine... 

Schiff s bases of etbyleneimine dimer are obtained from the reaction of aromatic aldehydes, eg, ben2aldehyde [100-52-7] or furfural [98-01-00] and ethyleneimine (228). 

Pyridoxal Derivatives. Various aldehydes of pyridoxal (Table 3) react with hemoglobin at sites that can be somewhat controlled by the state of oxygenation (36,59). It is thereby possible to achieve derivatives having a wide range of functional properties. The reaction, shown for PLP in Figure 3, involves first the formation of a Schiff s base between the amino groups of hemoglobin and the aldehyde(s) of the pyridoxal compound, followed by reduction of the Schiff s base with sodium borohydride, to yield a covalendy-linked pyridoxyl derivative in the form of a secondary amine. 

Fig. 3. (a) Reaction of pytidoxal 5 -phosphate (PLP) witii an amino-temiinal amino group of hemoglobin (Hb). The reagent is in the form of a Schiff s base with tris(hydroxymethyl)aminomethane [77-86-1] (Tris) buffet, and the reaction is a transamination, (b) The resulting unstable Schiff s base is reduced with... 

An alternative method involves reaction of an a-acylaminoketone (12) with a primary amine and subsequent ring closure of the resultant Schiff s base (13) with phosphoryl chloride. This enables the introduction of a 1-substituent as in (14) to be carried out efficiently, and if the amine were replaced with a monosubstituted hydrazine, the imidazole derivative (IS) resulted (78LA1916). 

Aromatic nitro compounds are often strongly colored. They frequently produce characteristic, colored, quinoid derivatives on reaction with alkali or compounds with reactive methylene groups. Reduction to primary aryl amines followed by diazotization and coupling with phenols yields azo dyestuffs. Aryl amines can also react with aldehydes with formation of Schiff s bases to yield azomethines. 

The acylation of enamines derived from cyclic ketones, which can lead to the acyl ketone or ring expansion (692-694), was studied by NMR and mass spectroscopic analysis of the products (695,696). In a comparative study of the rates of diphenylketene addition to olefins, a pronounced activation was observed in enamines (697). Enamine N- and C-acylation products were obtained from reactions of Schiff s bases (698), vinylogous urethanes (699), cyanamides (699), amides (670,700), and 2-benzylidene-3-methylbenzothiazoline (672) with acid chlorides, anhydrides, and dithio-esters (699). 

Schiff s bases also underwent C or N acylation with isocyanates (698) and isothiocyanates (698,701). Further studies provided 2 1 and 2 2 reaction products of arylisothiocyanates and enamines (702) and polymers derived from enamines and bisisocyanates (703). 

Oxaziranes (1) are produced by the action of peracids on Schiff s bases fEq. (2)], a reaction first described by Krimm in patents. ... 

The preparation of oxaziranes is almost always carried out by reacting a solution of peracetic acid in a volatile inert solvent at temperatures near 0 0 with the Schiff s base. Without any significant variation in the reaction conditions, a large number of oxaziranes has thus been prepared. Table I gives a selection of the fifty or so known oxaziranes. 

All these syntheses form variations of the same reaction. The three-membered ring is formed from an A-halogenoamine with ketone-ammonia mixtures or the Schiff s base 3,4-dihydroisoquinoline. Starting from these first observations the three groups of authors were able to generalize their diaziridine syntheses quickly in the years 1959-1962 they were extended to generally applicable reactions. In numerous variations of the syntheses, large numbers of diaziridincs were prepared. 

The reactions of chloramine are not generally successful with N-chloroalkylamines. Therefore it was surprising that the diaziridine synthesis occurred smoothly from aliphatic Schiff s bases and V-chloro-alkylamines [Eq. (33), Table VII]. As can be seen from examples... 

The rate of the diaziridine formation shows that the chloramine is attacked by the Schiff s base. Although ethereal chloramine solutions are only decomposed after weeks of standing, in the presence of a Schiffs base the chloramine is consumed after a few hours. The Schiff s base therefore does not enter into the reaction merely after the decomposition of the chloramine as it would have to do if formula 39 was an intermediate. Probably the chloramine adds onto the Schiff s base [Eq. (37) ] and ring closure of the geminal addition ]>roduct occurs. ... 

Thus the diazirines could be related by a smooth reaction to a well investigated class of compounds. The three-membered ring structure of the diazirines was thus largely confirmed. They can be obtained from compounds which certainly have a three-membered ring structure [Eq. (54)] and are easily convertible into compounds which have equally well confirmed three-membered ring structures. The structure of the 1-alkyl-diaziridines (43) obtained by the Grignard reaction were confirmed by identification with known compounds, usually prepared by the reaction of Schiff s bases with chloramine [Eq. (32)]. The results of some of these reactions are collected in Table XII. 

It was recently shown that the formation of a Schiff s base is the first step of the reaction between 3-aminopropan-l-ol and an aldehyde. The action of acid chlorides, such as tosyl chloride, on the SchifTs base forms the W-acyl derivative of tetrahydro-1,3-oxazine. 

Schiff s base (j ) derived by reaction of p-chloro-anil ine and borohydride followed by acylation with phenylacetyl chloride produces amide 22,. Selective hydrolysis with HBr followed by alkylation with isopropyl bromide completes the synthesis of lorcainide (20). ... 

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