Hexanediamines

Amidation. Heating of the diammonium salt or reaction of the dimethyl ester with concentrated ammonium hydroxide gives adipamide [628-94-4] mp 228°C, which is relatively insoluble in cold water. Substituted amides are readily formed when amines are used. The most industrially significant reaction of adipic acid is its reaction with diamines, specifically 1,6-hexanediamine. A water-soluble polymeric salt is formed initially upon mixing solutions of the two materials then hea ting with removal of water produces the polyamide, nylon-6,6. This reaction has been studied extensively, and the hterature contains hundreds of references to it and to polyamide product properties (31). 

Reduction. Hydrogenation of dimethyl adipate over Raney-promoted copper chromite at 200°C and 10 MPa produces 1,6-hexanediol [629-11-8], an important chemical intermediate (32). Promoted cobalt catalysts (33) and nickel catalysts (34) are examples of other patented processes for this reaction. An eadier process, which is no longer in use, for the manufacture of the 1,6-hexanediamine from adipic acid involved hydrogenation of the acid (as its ester) to the diol, followed by ammonolysis to the diamine (35). 

The nomenclature (qv) of polyamides is fraught with a variety of systematic, semisystematic, and common naming systems used variously by different sources. In North America the common practice is to call type AB or type AABB polyamides nylon-x or nylon-respectively, where x refers to the number of carbon atoms between the amide nitrogens. For type AABB polyamides, the number of carbon atoms in the diamine is indicated first, followed by the number of carbon atoms in the diacid. For example, the polyamide formed from 6-aminohexanoic acid [60-32-2] is named nylon-6 [25038-54-4], that formed from 1,6-hexanediamine [124-09-4] or hexamethylenediamine and dodecanedioic acid [693-23-2] is called nylon-6,12 [24936-74-1]. In Europe, the common practice is to use the designation "polyamide," often abbreviated PA, instead of "nylon" in the name. Thus, the two examples above become PA-6 and PA-6,12, respectively. PA is the International Union of Pure and AppHed Chemistry (lUPAC) accepted abbreviation for polyamides. 

Catalytic hydtogenation is the most efficient method for the large scale manufacture of many aromatic and ahphatic amines. Some of the commercially important amines produced by catalytic hydrogenation include aniline (from nitrobenzene), 1,6-hexanediamine (from adiponitrile), isophoronediamine (from 3-nitro-l,5,5-trimethylcyclohexanecarbonitrile), phenylenediamine (from dinitrobenzene), toluenediamine (from dinitrotoluene), toluidine (from nitrotoluene), and xyhdine (from nitroxylene). As these examples suggest, aromatic amines ate usually made by hydrogenating the... 

Braided Synthetic Nonabsorbable Sutures. Braided synthetic nonabsorbable sutures are made by melt-spinning thermoplastic polymers into fine filaments (yams), and braiding them, with or without a core, to form multifilament sutures in a range of sizes. Nylon-6,6 [32131 -17-2] (7) is a polyamide produced by the condensation polymerization of adipic acid and 1,6-hexanediamine. 

Oligomeric hindered amine light stabilizers are effective thermal antioxidants for polypropylene. Thus 0.1% of A[,Af-bis(2,2,6,6-tetramethyl-4-piperadinyl)-l,6-hexanediamine polymer, with 2,4,6-trichloro-l,3,5-triazine and 2,4,4-trimethyl-2-pentaneainine [70624-18-9] (35) (Fig. 5), protects polypropylene multifilaments against oxidation when exposed at 120°C in a forced-air oven (22) for 47 days. 3,5-Di-/ l -butyl-4-hydroxytoluene [128-37-0] (0.1%) affords protection for only 14 days. 

Chemical Designations - Synonyms 1,6-Diaminoxexane 1,6-Hexanediamine Chemical Formula NH,(CH,),NH3. 

The leader of DuPont s effort was Wallace H. Carothers, who reasoned that he could reproduce the properties of silk by constructing a polymer chain held together, as is silk, by amide bonds. The necessary amide bonds were formed by heating a dicar-boxylic acid with a diamine. Hexanedioic acid (adipic acid) and 1,6-hexanediamine (hexamethylenedi-amine) react to give a salt that, when heated, gives a polyamide called nylon 66. The amide bonds form by a condensation reaction, and nylon 66 is an example of a condensation polymer. 

To 217 grams (0.456 mol) of N,N -bis[1-methyl-3-(2,2,6-trimethylcyclohexyl)propyll-I.B-hexanediamine were added 182 ml (3.04 mols) of formic acid (90%). The resulting colorless solution was cooled, then 91.3 ml (1.043 mols) of formaldehyde (37%) were added. The solution was heated at steam temperature with occasional shaking for 2 hours and then refluxed for 8 hours. The volatiles were distilled off at steam temperature under water vacuum and the residual oil was made strongly alkaline with 50% potassium hydroxide. 

The reaction product was extracted with ether. The ether extract was washed with water, dried and concentrated in vacuo. The residual oil was fractionated in vacuo to obtain N,N -bis[1-methyl-3-(2,2,6-trimethylcydohexyl)propyl] -N,N -dimethyM, 6-hexanediamine, BPo,4 230° to 240°C, no = 1.4833. An aliquot, when treated with an ethanolic hydrogen chloride, gave the crystalline dihydrochloride, MP 183° to 185°C (recrystallized from ethanolacetonitrile). 

To 5 grams of N,N -bis[1-methyi-3-(2,2,6-trimethylcyclohexyl)propyl]-N,N -dimethyl-1,6-hexanediamine dissolved in 100 ml of methanol, at 4°C, were added 100 ml methanol containing 10 grams of methyl chloride. The solution was heated in a closed vessel at 60°C for 15 hours. The colorless solution was concentrated and the resulting white solid crystallized from ethanol-acetonitrile-ether to obtain N,N -bis[1-methyl-3-(2,2,6-trimethylcyclo-hexyOpropyl] -N,N -dimethyl-1,6-hexanediamine bis(methochloride) hemihydrate. 

Hexamethylenediamine (1,6-hexanediamine) is a colorless solid, soluble in both water and alcohol. It is the second monomer used to produce nylon 6/6 with adipic acid or its esters. 

Hexanediamine, a starting material needed for making nylon, can be made from 1,3-butadiene. How would you accomplish this synthesis ... 

The best known step-growth polymers are the polyamides, or nylons, first prepared by Wallace Carothers at the DuPont Company by heating a diamine with a diacid. Por example, nylon 66 is prepared by reaction of adipic acid (hexanedioic acid) with hexamethylenediamine (.1.,6-hexanediamine) at 280 °C. The designation "66" tells the number of carbon atoms in the diamine (the first 6) and the diacid (the second 6). 

Nylon 66 can be drawn from a dish containing two starting materials. The bottom layer is an aqueous solution of 1,6-hexanediamine, and the top layer is adipoyl chloride (a more reactive derivative of adipic acid). Nylon 66 forms at the interface between the two liquids. 

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