Carbon Monoxide Route

As pointed out already above, aromatic polyamides are conventionally prepared by condensing aromatic diacid chlorides and aromatic diamines in polar aprotic solvents. A disadvantage of such a process is that the variety of aromatic polyamides produced is limited by the small number of commercially available diacid chlorides. Moreover, the diacid chlorides are hydrolytically sensitive. 

A process has been suggested that uses carbon monoxide, an aromatic dichloride and a diamine. As catalyst, a palladium complex is used, bis(triphenylphosphine)palladium(II)chloride. The catalyst induces the carbonylation of aryl aromatic chlorides. 

Partially aromatic polyamides consist of aromatic dicarboxylic acid and aliphatic diamine monomer units. Such polyamides are generally characterized by high melting points, high glass transition temperatures, low moisture absorption and, unlike aliphatic polyamides such as nylon 6 and nylon 66, good dimensional stability under moist conditions. 

The combination of high temperature and dimensional stability render 

Partially aromatic PAs can be prepared from the acid, instead of the acid chloride in a multi step process. The first steps are conducted as a solid state polymerization with increasing temperature steps, and optionally feeding monomers after each reaction step. The final steps are proceeding as a melt condensation reaction.  

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A mixture of the two reactants carbon monoxide and hydrogen is called synthesis gas and IS prepared by several processes The most widely used route to synthesis gas employs methane (from natural gas) and gives a 3 1 hydrogen to carbon monoxide ratio... 

The addition of alcohols to form the 3-alkoxypropionates is readily carried out with strongly basic catalyst (25). If the alcohol groups are different, ester interchange gives a mixture of products. Anionic polymerization to oligomeric acrylate esters can be obtained with appropriate control of reaction conditions. The 3-aIkoxypropionates can be cleaved in the presence of acid catalysts to generate acrylates (26). Development of transition-metal catalysts for carbonylation of olefins provides routes to both 3-aIkoxypropionates and 3-acryl-oxypropionates (27,28). Hence these are potential intermediates to acrylates from ethylene and carbon monoxide. 

Acetylene-Based Routes. Walter Reppe, the father of modem acetylene chemistry, discovered the reaction of nickel carbonyl with acetylene and water or alcohols to give acryUc acid or esters (75,76). This discovery led to several processes which have been in commercial use. The original Reppe reaction requires a stoichiometric ratio of nickel carbonyl to acetylene. The Rohm and Haas modified or semicatalytic process provides 60—80% of the carbon monoxide from a separate carbon monoxide feed and the remainder from nickel carbonyl (77—78). The reactions for the synthesis of ethyl acrylate are... 

The stoichiometric and the catalytic reactions occur simultaneously, but the catalytic reaction predominates. The process is started with stoichiometric amounts, but afterward, carbon monoxide, acetylene, and excess alcohol give most of the acrylate ester by the catalytic reaction. The nickel chloride is recovered and recycled to the nickel carbonyl synthesis step. The main by-product is ethyl propionate, which is difficult to separate from ethyl acrylate. However, by proper control of the feeds and reaction conditions, it is possible to keep the ethyl propionate content below 1%. Even so, this is significantly higher than the propionate content of the esters from the propylene oxidation route. 

Reppe s work also resulted in the high pressure route which was estabUshed by BASF at Ludwigshafen in 1956. In this process, acetylene, carbon monoxide, water, and a nickel catalyst react at about 200°C and 13.9 MPa (2016 psi) to give acryUc acid. Safety problems caused by handling of acetylene are alleviated by the use of tetrahydrofuran as an inert solvent. In this process, the catalyst is a mixture of nickel bromide with a cupric bromide promotor. The hquid reactor effluent is degassed and extracted. The acryUc acid is obtained by distillation of the extract and subsequendy esterified to the desked acryhc ester. The BASF process gives acryhc acid, whereas the Rohm and Haas process provides the esters dkecdy. 

Coproductioa of ammonium sulfate is a disadvantage of the formamide route, and it has largely been supplanted by processes based on the direct hydrolysis of methyl formate. If the methanol is recycled to the carbonylation step the stoichiometry corresponds to the production of formic acid by hydration of carbon monoxide, a reaction which is too thermodynamicaHy unfavorable to be carried out directly on an iadustrial scale. 

Synthesis Gas Chemicals. Hydrocarbons are used to generate synthesis gas, a mixture of carbon monoxide and hydrogen, for conversion to other chemicals. The primary chemical made from synthesis gas is methanol, though acetic acid and acetic anhydride are also made by this route. Carbon monoxide (qv) is produced by partial oxidation of hydrocarbons or by the catalytic steam reforming of natural gas. About 96% of synthesis gas is made by steam reforming, followed by the water gas shift reaction to give the desired H2 /CO ratio. 

Other possible chemical synthesis routes for lactic acid include base-cataly2ed degradation of sugars oxidation of propylene glycol reaction of acetaldehyde, carbon monoxide, and water at elevated temperatures and pressures hydrolysis of chloropropionic acid (prepared by chlorination of propionic acid) nitric acid oxidation of propylene etc. None of these routes has led to a technically and economically viable process (6). 

Both dimethyl carbonate [616-38-6] and diphenyl carbonate [102-09-0] have been used, in place of carbon monoxide, as reagents for the conversion of amines into isocyanates via this route (28,29). Alternatively, aniline [62-53-3] toluene diamines (I JJA), and methylene dianilines (MDA) have also been used as starting materials in the carbonylations to provide a wide variety of isocyanate monomers. 

Pyrrohdinone (2-pyrrohdone, butyrolactam or 2-Pyrol) (27) was first reported in 1889 as a product of the dehydration of 4-aminobutanoic acid (49). The synthesis used for commercial manufacture, ie, condensation of butyrolactone with ammonia at high temperatures, was first described in 1936 (50). Other synthetic routes include carbon monoxide insertion into allylamine (51,52), hydrolytic hydrogenation of succinonitnle (53,54), and hydrogenation of ammoniacal solutions of maleic or succinic acids (55—57). Properties of 2-pyrrohdinone are Hsted in Table 2. 2-Pyrrohdinone is completely miscible with water, lower alcohols, lower ketones, ether, ethyl acetate, chloroform, and benzene. It is soluble to ca 1 wt % in aUphatic hydrocarbons. 

A fermentation route to 1-butanol based on carbon monoxide employing the anaerobic bacterium, Butyribacterium methjlotrophicum has been reported (14,15). In contrast to other commercial catalytic processes for converting synthesis gas to alcohols, the new process is insensitive to sulfur contaminants. Current productivities to butanol are 1 g/L, about 10% of that required for commercial viabiUty. Researchers hope to learn enough about the bacteria s control mechanisms to be able to use recombinant DNA to make the cells produce more butanol. 

Control of exhaust emissions for unbumed hydrocarbons and carbon monoxide has followed three routes. 

The most important route for the production of formaldehyde is from methanol, this normally being prepared by interaction of carbon monoxide and hydrogen. 

In densely populated areas, traffic is responsible for massive exhausts of nitrous oxides, soot, polyaromatic hydrocarbons, and carbon monoxide. Traffic emissions also markedly contribute to the formation of ozone in the lower parts of the atmosphere. In large cities, fine particle exposure causes excess mortality which varies between one and five percent in the general population. Contamination of the ground water reservoirs with organic solvents has caused concern in many countries due to the persistent nature of the pollution. A total exposure assessment that takes into consideration all exposures via all routes is a relatively new concept, the significance of which is rapidly increasing. 

They have also developed a route to 2-allenylindole derivatives (98T13929). When prop-2-ynyl carbonates (76) are reacted with 73 in the presence of palladium catalyst, a cross-coupling reaction occurs to give 77a (46%) and 77b (45%). Under a pressurized carbon monoxide atmosphere (10 atm), the palladium-catalyzed reaction of 73 with 78 provides 79a (60%) and 79b (60%) (2000H2201). In a similar reaction, when the substrate is changed to aryl halides (80), 2-aryl-1-methoxyindoles such as 81a (70%) and 81b (60%) are prepared (97H2309). 

The reaction is sensitive to the presence of water, which inhibits the migration of the third alkyl group and leads to dialkyl ketones (see Chapter 12, Section II). The convenience of the hydroboration reaction combined with the use of carbon monoxide at atmospheric pressure provides the most accessible route to many trialkylcarbinols. 

Synthesis gas is an important intermediate. The mixture of carbon monoxide and hydrogen is used for producing methanol. It is also used to synthesize a wide variety of hydrocarbons ranging from gases to naphtha to gas oil using Fischer Tropsch technology. This process may offer an alternative future route for obtaining olefins and chemicals. The hydroformylation reaction (Oxo synthesis) is based on the reaction of synthesis gas with olefins for the production of Oxo aldehydes and alcohols (Chapters 5, 7, and 8). 

Acetic acid is also produced hy the oxidation of acetaldehyde and the oxidation of n-hutane. However, acetic acid from the carhonylation route has an advantage over the other commercial processes because both methanol and carbon monoxide come from synthesis gas, and the process conditions are quite mild. 

A new route to ethylene glycol from ethylene oxide via the intermediate formation of ethylene carbonate has recently been developed by Texaco. Ethylene carbonate may be formed by the reaction of carbon monoxide, ethylene oxide, and oxygen. Alternatively, it could be obtained by the reaction of phosgene and methanol. 

Another route to enantiomcrically pure iron-acyl complexes depends on a resolution of diastereomeric substituted iron-alkyl complexes16,17. Reaction of enantiomerically pure chloromethyl menthyl ether (6) with the anion of 5 provides the menthyloxymethyl complex 7. Photolysis of 7 in the presence of triphenylphosphane induces migratory insertion of carbon monoxide to provide a racemic mixture of the diastereomeric phosphane-substituted menthyloxymethyl complexes (-)-(/ )-8 and ( + )-( )-8 which are resolved by fractional crystallization. Treatment of either diastereomer (—)-(/J)-8 or ( I )-(.V)-8 with gaseous hydrogen chloride (see also Houben-Weyl, Vol 13/9a, p437) affords the enantiomeric chloromethyl complexes (-)-(R)-9 or (+ )-(S)-9 without epimerization of the iron center. 

Treatment of the 1,2-oxazines 52 with carbon monoxide at 1000 psi in the presence of cobalt carbonyl brings about insertion of carbon monoxide to form the 1,3-oxazepines S3 <96TL2713>. A convenient route to P-lactams fused to oxepines is made available by alkene metathesis. Thus reaction of 4-acetoxyazetidin-2-one with ally alcohol in the presence of zinc acetate, followed by iV-allylation of the nitrogen affords the derivative 54 which cyclises by RCM to form the oxazepinone 55 <96CC2231>. The same communication describes a similar synthesis of 1,3-dioxepines. 

Whereas some acyl products, especially RCOMn(CO)5 and RCOCo-(CO)4, easily eliminate carbon monoxide via the reverse of the insertion, others decarbonylate through a different route. For example, the reaction... 

Both oxidative and non-oxidative routes with similar share are followed, yielding hydrogen or water as additional products. As by-products, carbon dioxide and carbon monoxide, methyl formate and formic acid are generated. It is advised to quench the exit stream as formaldehyde decomposition can occur. 

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