Norman C. Rose
Portland State College Portland, Oregon
Preparation of Terephthaloyl Chloride Prelude to ersatz Nylon
T h e Nylon rope trick described by Morgan and Iiwolek is one of the most intriguing demonstrai tions of organic chemistry ever developed.' The experiment-the preparation from sebacoyl chloride and 1,6-diaminohexane of a Nylon in the form of a film-is an example of a typical reaction of acid chlorides, of the greater nucleophilic character of nitrogen in comparison with oxygen, and of a condensation polymerization, and appeals greatly to students. Even so, the experiment has been incorporated into very few laboratory manuals. One reason for this may be that sebacoy1 chloride and hexamethylenediamiue, the reagents most strongly recommended by Norgan and Kwolek, have to be supplied to the students. The preparation of sebacoyl chloride probably would not be difficult for undergraduate student^,^ but the final purification requires a distillation at a pressure of 30 mm or less, preferably less than 10 mm.8 The highest molecular weight aliphatic diacid chloride that can he readily distilled a t atmospheric pressure is succinyl chloride. However, as Morgan and Kwolek point out and as we observed in our laboratory, succinyl chloride yields a film of a Nylon that is not very tough and cannot easily be pulled into a rope. Morgan and Icwolek made Nylons using other acid chlorides and found that t e r e phthaloyl chloride and piperazine form a tough film. Terephthaloyl chloride can be easily prepared and purified by undergraduate students and converted to a Nylon in less than three hours. The procedure for the preparation of the acid chloride is based on that of de la Rue and I~Iiller.~The filtrai tion of the hot petrolcum ether solution should be done in a hood since the vapors from the solution are irritating to the nose. The other filtrations do not have to be done in a hood. Low-boiling petroleum ether is a very effective solvent for the separation of the acid chloride from unreacted acid and phosphorus halides. In order to obtain a film which can be pulled, it is necessary to recrystallize the acid chloride. The yield of acid chloride is about 1.5 g. Terephthaloyl chloride is a solid a t room temperature, does not react rapidly with moisture in the air, and is not irritating to the nose: characteristics which are preferable to those of the commonly prepared acid chlorides. The original paper by Morgan and Kwolelr should be consulted for its valuable comments on the polym-
erization step. Results in our laboratories indicate that it is essential to use carbon tetrachloride as the solvent for the acid chloride. The Experiment
Preparation of Terephthaloyl Chloride. Rapidly weigh out 6.3 g (0.03 mole) of PC& in a dry beaker. Pour the PCl; into a dry, 200-ml, round-bottom flask equipped with a dry condenser connected to an HC1 trap. Add 2.5 g (0.015 mole) of terephthalic acid to the PCL. After mixing the two solids by shaking, heat them on a steam bath. The solids will turn to a liquid, and the reaction begins. If necessary, swirl the flask to get the solids into the liquid. When most of the solids have reacted (5-10 min), heat the mixture to a gentle reflux for one minute with a small flame. There should be no or little solid remaining. Cool. Add 25 ml of low-boiling petroleum ether (40-60°C). Heat to reflux on a steam bath to dissolve the terephthaloyl chloride. Using a short stem funnel, filter the hot solution in a hood. Cool the filtrate to room temperature and then in an ice bath. Remove the solid by suction filtration. Wash the solid on the filter paper with 5-10 ml of ice-cold low-boiling ligroin. Recrystallize the acid chloride from low-boiling ligroin again. Let the acid chloride air dry for 5-10 min on a watch glass. The melting point reported in the literature is 83-84°C.5 Preparation of the Nylon. Dissolve 0.5 g of terephthaloyl chloride in 50 ml of carbon tetrachloride contained in a 150-ml tall-form beaker. Dissolve 1g of piperazine in 25 ml of water containing 0.6 g of sodium hydroxide. Carefully pour the piperazine down the side of the beaker in such a way that the two solutions do not mix. A film of Nylon will form bet17-een the layers. Pull the center of the film up with a pair of tweezers. Continuous pulling on the rope will form more rope. If the film is not tough enough to pull, recrystallize the remaining acid chloride and then remake the starting solutions. 1 MORGAN, P. W., AND KWOLEK, S. L., J. CH-M.EDUC.,36, P. W., J. CHEM.EDUC., 42, 12 (1965). 182 (1959); and MORGAN, T.,A N D MACURA, K., Ann. C h a . , 548, 226 (1941). ~LIESER, 3 FORDYCE, C. K.,AND JOHNSON, J. R., J . Am. Chew. Sor., 55, 3369 (1933); and LIESERand MACURA, op. a t . nE LA RUE,W., AND MILLER, H., Ann. Chem., 121.86 (1862). LIEBERMANN, C., ANDKARDOS, M., C h a . Ber.,46, 1!)8(1913).
Volume 44, Number 5, May 1967
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