Multi-step Synthesis: Nylon
Multi-step Synthesis Project: Nylon
Introduction
Read about polyamides and step-growth polymers in section 21.9 of your McMurry
textbook (pp 799-902).
Experimental
Synthesis of adipic acid1 Place
0.50 g of sodium tungstate dihydrate (Na2WO4*2H2O)
in a 50 mL round bottom flask containing a stir bar and fitted with a water
cooled condenser. Add approximately 0.5 g of Aliquat 336. This material is a
very viscous liquid that is hard to transfer, so you should break off the tip of
a pipet and weigh the material directly into your round bottom flask. Next, add
11.98 g of 30% hydrogen peroxide and 0.37 g of KHSO4 to
the reaction mixture. Stir, then add 2.00 g of cyclohexene. Please
note that the order of addition of the reagents is important.
Heat the mixture under reflux for one hour while stirring vigorously. About
halfway through the reflux period, rinse down any cyclohexene trapped in the
condenser with a few mL of water, added via pipet. Phase transfer catalysis
depends upon very efficient mixing of the organic and aqueous layers, so it is
important to stir as fast as possible throughout the reaction.
Stop the stirring occasionally to see if there are still two layers present. The
reaction is complete when it no longer separates into two layers.
Use a pipet to transfer the hot reaction mixture into a small beaker, leaving
behind any of the phase transfer catalyst that may have separated. If the
catalyst separates - and it does not always do so - it will stick to the walls
of the flask or form a separate oily layer at the bottom of the flask. It is
better to leave a little of the aqueous solution behind than to risk
contamination of your solution with the phase transfer catalyst.
Cool the beaker containing the reaction mixture rapidly in an ice bath. A
precipitate should form within 20 minutes. Collect the crude product by vacuum
filtration using a Buchner funnel. After the crude material has air dried, weigh
it and determine its melting point
Recrystallize the crude product in a minimum amount of hot water. Determine the
mass and melting point of the recrystallized product, and characterize the
product spectroscopically.
p-Phenylenediamine. 2 Combine
1.4 g p-nitroaniline, 3.5 g tin, and 15 mL concentrated hydrochloric acid in a
round bottom flask. Reflux the mixture for one hour. Filter the mixture to
remove unreacted tin. Add 6M NaOH to the filtrate until the liquid is basic to
litmus paper. Isolate the solid diamine by filtration. Recrystallize the sample
in ethanol. Determine the mass and melting point of your recrystallized product,
and characterize the product spectroscopically.
Adipoyl chloride from adipic acid3. Combine 1.0 g of adipic
acid and 2.0 g of thionyl chloride in a round bottom flask. Add several drops of
dimethylformamide (DMF). Attach a calcium chloride drying tube directly to the
flask, and heat the flask in a 55-65 oC
water bath in the hood. Bubbling or fuming usually begins shortly after the
addition of the DMF. The reaction is sufficiently complete when the bubbling has
slowed down greatly. Remove the excess thionyl chloride by rotary evaporation.
Dissolve the sample in cyclohexane solvent. You will use half of the solution in
the Nylon 6,6 procedure and the other half in the alternate Nylon procedure. Please
note that you should carry out the nylon preparation steps the same day that you
synthesize the adipoyl chloride
Nylon 6,64. Prepare a 5% aqueous solution of
hexamethylenediamine (1,6-hexanediamine). Pour 10 mL of that solution into a 50
mL beaker. Add 10 drops of 20% sodium hydroxide solution. Carefully add 10 mL of
a 5% solution of adipoyl chloride (dissolved in cyclohexane solvent!) to the
hexamethylenediamine by pouring it down the inside wall of the slightly tilted
beaker. Two layers will form, and there will be an immediate formation of a
polymer film at the liquid-liquid interface. Using a copper-wire hook (a 6-inch
piece of wire bent at one end), gently free the walls of the beaker from the
polymer strings. Then hook the mass at the center and slowly raise the wire so
that polyamide forms continuously, producing a rope that can be drawn out for
many feet. The strand can be broken by pulling it faster. Rinse the rope several
times with water and lay it on a paper towel to dry. With the piece of wire,
vigorously stir the remainder of the two-phase system to form additional
polymer. Decant the liquid and wash the polymer thoroughly with water. Allow the
polymer to dry. Do NOT discard
the nylon in the sink. Use a waste container.
Another Nylon. Repeat the procedure given above for Nylon 6,6,
substituting 1,4-phenylenediamine for the hexamethylendiamine.
References
- S. M. Reed and J. E. Hutchison, "An Environmentally Benign Synthesis of
Adipic Acid," J. Chem. Educ. 2000, 77, 1627-8.
- Clarke, H. T.; Hartman, W. W., Organic
Syntheses Volume 9, page 74
- Roberts, R. M.; Gilbert, J. C.; Rodewald, L. B.; Wingrove, A. S. Modern
Experimental Organic Chemistry, 4th ed., Saunders, Fort Worth, 1985, p
717.
- Pavia, D. L.; Lampman, G. M.; Kriz, G. S.; Engel, R. G. Introduction
to Organic Laboratory Techniques: A Microscale Approach 2nd
ed., Saunders, Fort Worth, 1995, pp 414-415.
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