Ethyl pimelate

Submitted by Adole Muller and Erich Rolz. Checked by W. H. Carotiiers and W. L. McEwen. 

The crude material, which is a mixture of pimelic acid and unchanged salicylic acid, is esterified by boiling for four hours with 260 cc. of absolute ethyl alcohol and 3 cc. of concentrated sulfuric acid. Two-thirds of the alcohol is then removed by distillation. To the residue, 300 cc. of water and 200 cc. of ether are added, the mixture is shaken and the aqueous layer is removed. The ether solution is washed with two 100-cc. portions of 2 N sodium hydroxide solution to remove the ethyl salicylate (Note 7) and then with water until the disappearance of an alkaline reaction. The ether is evaporated and the residue is distilled under reduced pressure. The ethyl pimelate boils at i53-i56°/24 mm. i48-i52°/22 mm. The yield is 27-30 g. (35-38 per cent of the theoretical amount based upon the salicylic acid used). 

At this time there may be a very small quantity of sodium remaining undissolved. If care is used in adding the water, no trouble with fire or explosion occurs. 

Unless the solutions are kept at approximately the temperatures indicated there is difficulty with the separation. Even with warm solutions the separation is often very slow. 

A large proportion of the isoamyl alcohol used may be recovered for use in subsequent preparations. The moist alcohol from the water extractions is directly distilled and a fraction boiling at 128-135° is collected. The alcohol layer in the forerun is separated and it may either be added to the alcohol from the following run, or subjected to distillation separately and a fraction of the same boiling range collected as before. Alcohol thus recovered is perfectly satisfactory for the preparation of pimelic acid. 

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Ethyl Pimelate (ri, 42) By an improved procedure the acid is obtained in 50 per cent yield. Muller, Monatsh. 6s, 18 (1934). 

Problem 17.39 Ethyl pimelate, CjH,OOC(CH2)5COOCjH reacts with CjH,0 Na (Dieckmaiin condensation) to form a cyclic keto ester, CjHj Oj. Supply a mechanism for its formation and compare the yields in ethanol and ether as solvents. ... 

Ethyl pentadecylate, 16, 37 Ethyl pentanehexacarboxylate, 10, 59 Ethyl phenylacetate, 16, 33 Ethyl -phenylacetoacetate, 18, 36 Ethyl 7-phen ylbut vrate, 18, 25, 26 Ethyl phenylcyanopyruvate, 11, 40 Ethyl (3-phenylethyl ketone, 16, 49 Ethyl phenylmalonate, 16, 33 18, 84 Ethyl phenyloxaloacetate, 16, 33 Ethyl phthalimidomalonate, 14, 58 Ethyl pimelate, 11, 42 17, 91 Ethyl propanetetracarboxylate, 10, 58 Ethyl propionate, 17, 54 Ethyl iso-propylmalonate, 11, 20, 21 Ethyl salicylate, 10, 51 11, 43 Ethyl sebacate, 14, 20 Ethyl sodium phthalimidomalonate, 14, 58... 

Ethyl oxalate, 10, SI 11, 40 Ethyl oxomalonate, 10, S4, no Ethyl pentanehexacarboxylate, 10, 59 Ethyl phenylcyanopyrdvate, 11, 40 Ethyl pimelate, 11, 42 Ethyl propanetetracarboxylate, 10, S8... 

The Dieckmann condensation is an intramolecular reaction by which cyclic P-keto esters are formed using tethered di-esters under basic conditions. The name derives from its originator, Walter Dieckmann, who first reported the reaction in 1894 and demonstrated the formation of ethyl p-ketocyclopentanecarboxylate from ethyl adipate using sodium base and, in a similar fashion, the formation of p-ketocyclohexanecarboxylate from ethyl pimelate. ... 

Wyttenbach, T. von Helden, G. Bowers, M. T. Conformations of alkali ion cationized polyethers in the gas phase Polyethylene glycol and bis[(benzo-15-crown-5)-15-ylm-ethyl] pimelate. Int. J. Mass Spectrom. 1997,165/166, 377-390. 

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