Adipic acid 1,6-hexanediamine from

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). 

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. 

A synthesis of great industrial interest is the electrochemical anodic reductive dimerisation of two molecules of acrylonitrile to give adiponitrile, from which adipic acid and 1,6-hexanediamine are prepared by hydrolysis and reduction, respectively, of the two nitrile groups. Polycondensation of the resulting products leads to Nylon 66 (Scheme 5.27). 

Carothers next step was to move from polyesters to nylons and to increase the fractional conversion (p) by making salts using the equivalent reaction of 1,6-hexanediamine (hexamethylenediamine) and adipic acid. These salts were recrystallizable from ethanol giving essentially a true 1 1 ratio of reactants. Thus, a high molecular weight polyamide, generally known as simply a nylon, in this case nylon-6,6, was produced from the thermal decomposition of this equimolar salt as shown in structure 4.55. This product has a melting point of 265°C. 

Hexanediamine can also be obtained by the liquid phase catalytic hydrogenation of adiponitrile or adipamide, which is made from adipic acid. 

The repeating units in nylon 66 and in most step reaction polymers consist of residues from both reactants. The following equation shows the synthesis of nylon 66 in this case the reactants are a dicarboxylic acid (adipic acid) and a diamine (1,6-hexanediamine). 

Notice that a water molecule is eliminated when an H atom from the amine group and an —OH group from the carboxyl group are removed. Another adipic acid molecule is then added to the amine group shown on the left, while another hexanediamine molecule is added to the carboxyl group shown on the right. This process continues, linking hundreds of reactants to form a product called nylon 66. 

Adipic acid is also made on an industrial scale through oxidation of cyclohexanone. The number 66 represents the number of carbons in the two different monomeric units of nylon 66 both adipic acid and 1,6-hexanediamine contain six carbon atoms. Nylon 6 is made from only one type of monomeric unit, which also contains six carbon atoms. 

Nylon 66 is an example of a step-growth polymer formed by two different bifunctional monomers adipic acid and 1,6-hexanediamine. It is called nylon 66 because it is a polyamide formed from a six-carbon diacid and a six-carbon diamine. 

Nylon is the common name for polyamides. Polyamides are generally made from reactions of diacids with diamines. The most common polyamide is called nylon 6,6 because it is made by reaction of a six-carbon diacid (adipic acid) with a six-carbon diamine. The six-carbon diamine, systematically named 1,6-hexanediamine, is commonly called hexamethylene diamine. When adipic acid is mixed with hexamethylene diamine, a proton-transfer reaction gives a white solid called nylon salt. When nylon salt is heated to 250° C, water is driven off as a gas, and molten nylon results. Molten nylon is cast into a solid shape or extruded through a spinneret to produce a fiber. 

In the synthesis of nylon 66, hexanedioic acid (adipic acid) and 1,6-hexanediamine (hexamethylenediamine) are dissolved in aqueous ethanol, where they react to form a one-to-one salt called nylon salt. Nylon salt is then heated in an autoclave to 250°C, where the internal pressure rises to about 15 atm. Under these conditions, —COO groups from adipic acid and — NHj+ groups from hexamethylenediamine react with loss of H O to form amide groups. 

As shown, PET is prepared by successive Fischer esterification reactions. Since the polymer is generated via condensation reactions, it is called a condensation polymer. Because PET has repeating ester moieties, the polymer is also classified as a polyester. like PET, nylon 6,6 is also prepared via condensation reactions and is also a condensation polymer. Nylon 6,6 is a polyamide, which is prepared from adipic acid and 1,6-hexanediamine. 

Polyethylene and poly tetrafluoroethylene are both addition polymers in that they are formed by the chemical addition of the monomers making up the large polymer molecules. Other polymers are condensation polymers that join together with the elimination of a molecule of water for each monomer unit joined. A common condensation polymer is nylon, which is formed by the bonding together of two different kinds of molecules. There are several forms of nylon, the original form of which is nylon 66 discovered by Wallace Carothers, a DuPont chemist, in 1937 and made by the polymerization of adipic acid (mentioned as a feedstock that can be made from glucose is Chapter 16, Section 16.6) and 1,6-hexanediamine ... 

Nylon is a polyamide. In industry it is produced by reaction of two difunctional monomers (or comonomers) a dicarboxyUc add and a diamine. The polymer that you are going to study is of great historical significance in polymer chemistry, because it was the first of the pol) amides to be recognized as possessing excellent physical properties for forming very strong fibers. Nylon-6,6 was, in fact, the first commerdally produced synthetic polyamide.The"6,6" nomenclature refers to the number of carbon atoms in each of the two comonomers. Industrially, nylon-6,6 is prepared from 1,6-hexanediamine (hexamethylenediamine) and hexanedioic acid (adipic add) ... 

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