W. F. Berkowilz Queens College City University of N e w York Flushing, N e w York 11367
Acid Hydrolysis of Nylon 66
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W e were interested in a hydrolysis experiment which would allow isolation of both fragments of a carboxylic acid derivative. The hydrolysis of Nylon 66 reported by Bossert and Brodel interested us hut had several drawbacks, such as the use of Nylon stockings (often of unknown polymeric constitution) and a 6-hr hydrolysis. Consequently we have devised the somewhat different Nylon hydrolysis reported below.
A white precipitate will form immediately. Stir this solid for 5-10 min until it solidifies completely, then crush any lumps and suction filter the mixture. Wash the collected solid (hexamethylenediamine dibenzenesulfonamide-see eqn. (2)) w i t h 10 ml of water and air dry it. Yield: 5-8 g. Recrystallize the diamide from 80-90 ml of hot 95% ethanol. (Yield: 1.5-3.5 g, mp: 152-4'C). Wash the collected solid with 5 ml of cold 95% ethanol and air dry. Problems
1) Calculate the theoretical yield of adipic acid and lfidiaminohexane. The Experimenl: The Hydrolysis of Nylon (Zytel) 2) Calculate the percent of theoretical yield of ndipic acid and diamine which you isolate. HlO +Clk 3) Construct a flaw diagram outlining the "work-up" procedure HO[OC(CHZ)DONH(CH&NH],H --t used to isolate the adipic acid and the diamide. ~HO&(CH;)&O~H ~ [ H S N ( C I I ~ ) ~ N H ~ ] * +(1) C I ~ ~ -4) How would you isolate the free amine, i.e., what work-up procedure would allow you to obtain, from this hydrolysis mixture, pure 1,6-diaminohexane?
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C~HISOLX NaOH
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To a 500-ml round-bottom flask fitted with B reflux condenser rdd 100 ml of conc. HC1, 100 ml water, and 36.7 g (0.15 mole) of Nylon 66 (Zytel). Reflux the mixture for approximately 4 hr, and then set aside for 1week (until the next lah period) during which time crystals of adipic acid will form. The rertcbion is given in eqn. (1). Snd pwiod: Cool the acidic reaction mixture in an ice-water bath (to 5°C) and suction filter the adipic acid (10-12 g ) [Save the liltratel. Wash the solid with 10 ml of cold water and air dry the erykals briefly. Recrystallire the adipic acid from 2,540 ml of hot 30% ethanol (1 part 95% ethanol, 2 parts water). After cooling to room temperature, filter the alcohol solution hy suction and wash the cryst& collected with 10 ml of water and air dry. Yield: 8-10 g, m i : 150-153°C. Cool 25 ml (only) of the acidic filtrate of the reaction mixtnre to 5'C in an ice-water bath. To the cold solution (in a 125 ml flask) add a solution of 12 g (0.3 mole) of sodium hydroxide pellets dissolved in 25 ml of water (careful, this solution will get hot as the NaOH dissolves). After the basified reaction mixture has recooled to room temperature, suction filter, if necessary, and transfer it to a 250-ml separatary funnel. To this, then add 5.5 ml (7.6 g, 0.043 mole) of hensenesulfonyl chloride, replace the st,opper in the separatory funnel, and im: mediately shake the mixture vigorously for 3 min. Be sure to release the pressure from time to time. The mixture will get quite warm, but not too hot to hold. The clear solution which results is then poured into a mixture of 50 g ice and 25 ml conc. HCI contained in s. 400-ml beaker.
536
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Journal of Chemical Education
Discussion
This experiment was checked by 17 undergraduates in our first semester organic chemistry course. The average yield of acid was 8.99 g (6.37-11.80 g), average mp, 147.8-150.5"C (uncor.) (mp ranges: 146-50 to 149.Fr151.5). The average yield of diamide was 2.42 g (1.63-3.65 g), average mp 151.3-153.5°C (uncor.) (mp ranges: 150-3.5 to 153-5'C). Yields and melting points were obtained by the instructor. This experiment offers the following advantages: 1) the nature of the starting material, Dupont "Zytel," Nylon 66 in colorless pellet form, was known without doubt; 2) the length of hydrolysis, 3.5-4.0 hr, fitted our laboratory period; 3) the work-up could easily be encompassed in one lab period of 4 hr by most students (6 of 17 students needed approximately '/rl hr of the following period for isolation of the pure diamide); 4) The experiment illustrates the Hinsberg test and its utilization in an experimental worlc-up; 5) both (solid) products of the reaction may be isolated in good yield and are easily purified. 1 BOSSERT, R. G . , A N D BRODE,W. R., "Lab Text and Notehook for Organic Chemistry," (4th ed.), John Wiley & Sons, Inc., New York, 1968, p. 309. % T h eNylon 66 used for this experiment was Dupont Zytel in colorless pellet form, kindly supplied by The Plastics Department, E. I. du Pont de Nemours and Co., P. 0. Box 1217, Parkersburg, W. Va. 26101.
