Collidines

This reaction consists of the condensation of two molecular equivalents of a 1,3 diketone (or a J3-keto-ester) with one equivalent of an aldehyde and one of ammonia. Thus the interaction of ethyl acetoacetate and acetaldehyde and ammonia affords the 1,4-dihy dro-pyridine derivative (1), which when boiled with dilute nitric acid readily undergoes dehydrogenation and aromatisation" to gb e the diethyl ester of collidine (or 2,4,6-trimethyl-pyridine-3,5 dicarboxylic acid (II)). For the initial condensation the solid aldehyde-ammonia can conveniently be used in place of the separate reagents. 

Gently warm a mixture of 32 g. (32 ml.) of ethyl acetoacetate and 10 g. of aldehyde-ammonia in a 400 ml. beaker by direct heating on a gauze, stirring the mixture carefully with a thermometer. As soon as the reaction starts, remove the heating, and replace it when the reaction slackens, but do not allow the temperature of the mixture to exceed 100-no the reaction is rapidly completed. Add to the mixture about twice its volume of 2A -hydrochloric acid, and stir the mass until the deposit either becomes solid or forms a thick paste, according to the quality of the aldehyde-ammonia employed. Decant the aqueous acid layer, repeat the extraction of the deposit with more acid, and again decant the acid, or filter off the deposit if it is solid. Transfer the deposit to a conical flask and recrystallise it twice from ethanol (or methylated spirit) diluted with an equal volume of water. The i,4-dihydro-collidine-3,5-dicarboxylic diethyl ester (I) is obtained as colourless crystals, m.p. 130-131°. Yield 12 5 g,... 

Fig. 41(A) and (b), p. 65) into which the ethereal extract is allowed to run from a dropping-funnel at approximately the rate at which the solvent is distilling. When the ether has been removed, fit a capillary tube and thermometer, and continue the distillation at water-pump pressure. The diethyl ester of collidine-3,5-dicarboxylic acid (II) distils as a pale golden oil, b.p. i76 178°/i4 mm. Yield, 5 g. from 6 g. of the ester (I). 

Collidine 2i5 d carboxylic acid. Boil a mixture of 5 g. of the ester (II) and 50 ml. of 15% ethanolic potash under reflux for 30 minutes. The dipotassium salt crystallises during the boiling and during the subsequent cooling. Filter off the potassium salt at the pump and wash it with a small quantity of ethanol. Dilute the filtrate with about an equal volume of ether to precipitate a further small crop of the salt. Yield of combined crops 4 5 g. from 5 g. of the estei (I). 

To meet the needs of the advanced students, preparations have now been included to illustrate, for example, reduction by lithium aluminium hydride and by the Meerwein-Ponndorf-Verley method, oxidation by selenium dioxide and by periodate, the Michael, Hoesch, Leuckart and Doebner-Miller Reactions, the Knorr pyrrole and the Hantzsch collidine syntheses, various Free Radical reactions, the Pinacol-Pinacolone, Beckmann and Arbusov Rearrangements, and the Bart and the Meyer Reactions, together with many others. 

The criterion has also been applied qualitatively. Thus, 2,4,6-collidine and 1,2,4,6-tetramethylpyridinium cation can be nitrated under identi-... 

For this series of compounds qualitative information is quite extensive. Application of the criteria discussed in 8.2, in particular comparison with the corresponding methyl quaternary salt, establishment of the rate profile for nitration in sulphuric acid, and consideration of the encounter rate and activation parameters, shows that 2,4,6-collidine is nitrated as its cation. The same is true for the 3-nitration of 2,4- ... 

Present-day nomenclature is partly the result of the conflict and interplay of two functions the need to communicate in speech and on the printed page on the one hand, and the need for archival storage of information and its efficient, reliable retrieval. The former function came first, and laid the basis for the nomenclature most commonly used even today, and gave birth to a wealth of trivial names (i.e. names that give little or no information on structure). These were often coined on the basis of the origin of the substance, as in the case of collidine, obtained from distillation of bones in glue factories, or were derived from a special characteristic, as in the case of skatole, which has a fecal odor. Such names are short and generally euphonious, but they must be memorized they cannot be deduced from the structure. 

Ph3CCl, 2,4,6-collidine, CH2CI2, Bu4N" C104, 15 min, 97% yield. This is an improved procedure for installing the trityl group on polymer-supported nucleosides. 

Hg(C104)2, 2,4,6-collidine, acetone, H2O (9 1), 5 h NH3, dioxane, H2O (1 1). In this case Hg(II) is used to cleave the MTM group, liberating a hydroxyl group, which assists in the cleavage of the carbonate on treatment with ammonia. Cleavage by ammonia is 500 times faster for this hydroxy derivative than for the initial MTM derivative. 

Lil, collidine, reflux, 10 h, quant.Aryl ethyl ethers are cleaved more slowly dialkyl ethers are stable to these conditions. 

Chemical Designations - Synonyms Aldehyde-collidine Aldehydine 5-Ethyl-2-Methylpyridine 5-Ethyl-2-picoline MEP Chemical Formula CjHnN. 

Dissolve 0.3 g ninhydrin (2,2-dihydroxy-l,3-indanedione) in 95 ml 2-propanol and add 5 ml collidine (2,4,6-trimethylpyri-dine) and 5 ml acetic acid (96%). 

Note The reagent can be employed on silica gel and cellulose layers and the dipping solution can also be employed as a spray solution. The addition of collidine... 

Fig. 1 Comparative recordings of the reflectance scans of a mixture of phenylethylamine (1), tyramine (2), serotonin (3) and histamine (4) A. ninhydrin reagent (q.v.), B. ninhydrin — collidine reagent.

Meroquinenine, CgHjjOaN (meroquinene), formed by the oxidation of all four alkaloids and of cinchoninone or quininone and by the hydrolysis of quinenine or cinchenine (p. 489), crystallises from methyl alcohol in needles, m.p. 223-4° (dee.), [ajp -f- 27-5° (H2O). It gives a nitrosoamine, m.p. 67°, and a monoacetyl derivative, m.p. 110°, and can be esterified the ethyl ester hydrochloride has m.p. 165°. When oxidised by chromic acid it yields formic and cincboloiponic acids. On reduction with zinc dust and hydriodic acid, it adds on two atoms of hydrogen forming cincholoipon, CgH jOaN, and when heated with hydrochloric acid at 250-60° gives 3-ethyl-4-methylpyridine ()3-collidine). 

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