EDA formation

Any mechanistic scheme must account for this concurrent production of acetaldehyde and acetic anhydride. A possible mechanism for EDA formation is described in general terms by Scheme II for palladium. 

EDA formation are lower than for acetic anhydride formation by car-bonylation. (c) Selective reductive chemistry occurs and rates are dependent on hydrogen partial pressure. 

When the anhydride was placed under the reductive carbonylation conditions, EDA was produced along with methyl acetate and acetic acid. However, the rate of EDA formation was substantially lower than usual methyl acetate conversions. Also, a mechanism incorporating Fenton s reduction cannot account for excess acetaldehyde along with EDA formation. This cannot be the major path to EDA. 

In addition to the successful reductive carbonylation systems utilizing the rhodium or palladium catalysts described above, a nonnoble metal system has been developed (27). When methyl acetate or dimethyl ether was treated with carbon monoxide and hydrogen in the presence of an iodide compound, a trivalent phosphorous or nitrogen promoter, and a nickel-molybdenum or nickel-tungsten catalyst, EDA was formed. The catalytst is generated in the reaction mixture by addition of appropriate metallic complexes, such as 5 1 combination of bis(triphenylphosphine)-nickel dicarbonyl to molybdenum carbonyl. These same catalyst systems have proven effective as a rhodium replacement in methyl acetate carbonylations (28). Though the rates of EDA formation are slower than with the noble metals, the major advantage is the relative inexpense of catalytic materials. Chemistry virtually identical to noble-metal catalysis probably occurs since reaction profiles are very similar by products include acetic anhydride, acetaldehyde, and methane, with ethanol in trace quantities. 

This enhances the selectivity by preventing EDA formation. The non-volatile catalyst remains in the reactor under a carbonylation atmosphere which maintains its activity. 

The catalyst is generally a palladium compound promoted with a trivalent amine or phosphine in the presence of methyl iodide as described earlier. Systems proven to bias acetaldehyde are utilized, of course (e.g. see Table I, run 12). A yield of 85% acetaldehyde from methyl acetate is typical by this method. It can be utilized in stoichiometric addition to easily prepared acetic anhydride resulting in EDA formation. When considering that the "boiling pot" reaction by-products are recyclable acetic acid, acetic anhydride and small amounts of EDA, the yield to vinyl acetate related products is 95%. 

There are two process alternatives here. The acetaldehyde can be produced in excess acetic anhydride so EDA formation can occur in situ, similar to the work reported by Fenton (26). Alternatively, acetaldehyde can be isolated from acetic anhydride reduction and reacted with the anhydride in a separate step to form the desired EDA. 

Herbal crude materials are heterogeneous and are available as dried materials, powder extracts, or liquid concentrates. According to the DSEHA, manufacture or distribution of dietary supplements does not require EDA registration or approval before hand. However, the product must be identified on the label as a dietary supplement, and the label contents must follow an EDA format. 

A five-step synthesis of ethyl ester of eyelie hydrazonie aeid 314 used in the synthesis of natural produets has been deseribed [94JCA(CC)1867]. The eonden-sation of methoxybutenone with EtCOaCN (t-BuOK, THF, —78°C) is eompleted with the formation of ketoester 310 in 72% yield. The addition of methanol to the latter (Triton B, MeOH, room temperature, 88%) and the reduetion with NaBH4 (EtOH, —78°C) leads to the aleohol 312, yield 90%. The dianion of 312 (EDA, THE, -78°C) reaets with t-butylazodiearboxylate (t-BuOaC—N=N—COaBu-t) to form adduet 313, the treatment of whieh with trifluoroaeetie aeid affords the ester 314 in 55% yield [94JCA(CC)1867]. 

Applieations for EDA Approval to Market a New Drug or an Antiobiotie Drug, Content and format of an Applieation, CER, Title 21, Volume 5, Part 314, Seetion 314.50 (1998). 

Apparently the complex formation with a 71-acceptor is suitable for characterization of the donor ability of the entire -system of the monomers. Simultaneously, it can be derived that the EDA-complex formation is only insignificantly influenced by steric effects. Because the above named variation in structure does not disturb the planarity of the center of the monomer double bond, the interaction of the 71-systems from both donor and coplanar acceptor cannot be limited by steric effects. 

The methyl substitution at a-position leads to an increase of the reactivity of styrene during polymerization as well as EDA-complex formation. However, the methyl substitution in p-position achieves an opposite effect. The strengthened complex formation connected with a further increase of the HOMO is faced with a drastically decreased polymerization rate. This can be explained by the well known steric effect of group hindrance around the p-C-atom under attack 72), as well as the polarity switch in the vinyl double bond. The p-C-atom in the p-methyl styrene possesses a... 

During the cationic homopolymerization, orbital effects as well as charge effects are essential in contrast to the EDA complex formation where apparently orbital effects dominate. The polymerizations are also aided by appearence of negative partial charges at the p-C-atom. 

The validity of this statement is confirmed by the rates of IC1 additions (see Table 12). Because for these additions the formation of a cationic intermediate by direct attack of the electrophile on the double bond is rate determining, their order of rates is comparable to those of polymerizations. It is therefore understandable that the polymerization rates correlate much better with the reactivities of the monomers during an electrophilic addition of cationogenic agents (such as IC1) than with the relatively unspecific EDA complex formation. 

The synthesis of ethylenediamine (EDA) from ethanolamine (EA) with ammonia over acidic t3pes of zeolite catalyst was investigated. Among the zeolites tested in this study, the protonic form of mordenite catalyst that was treated with EDTA (H-EDTA-MOR) showed the highest activity and selectivity for the formation of EA at 603 K, W/F=200 g h mol, and NH3/ =50. The reaction proved to be highly selective for EA over H-EDTA-MOR, with small amounts of ethyleneimine (El) and piperazine (PA) derivatives as the side products. IR spectroscopic data provide evidence that the protonated El is the chemical intermediate for the reaction. The reaction for Uie formation of EDA from EA and ammonia required stronger acidic sites in the mordenite channels for hi er yield and selectivity. 

The common by-products obtained in the transition-metal catalyzed reactions are the formal carbene dimers, diethyl maleate and diethyl fumarate. In accordance with the assumption that they owe their formation to the competition of olefin and excess diazo ester for an intermediate metal carbene, they can be widely suppressed by keeping the actual concentration of diazo compound as low as possible. Usually, one attempts to verify this condition by slow addition of the diazo compound to an excess (usually five- to tenfold) of olefin. This means that the addition rate will be crucial for the yields of cyclopropanes and carbene dimers. For example, Rh6(CO)16-catalyzed cyclopropanation of -butyl vinyl ether with ethyl diazoacetate proceeds in 69% yield when EDA is added during 30 minutes, but it increases to 87 % for a 6 h period. For styrene, the same differences were observed 65). 

There is apparently no analog of the reaction 2eh H2 in liquid ammonia, where eam is very stable. The loss of paramagnetism in concentrated solutions has been interpreted to be either by formation of (eam)2 or by association with metal cation in neither case is the spectral shift drastic. For Na in ethylenedi-amine (EDA), Dye et al. (1972) measured the rate of 2es— (es)2 as 1.7 x 109 M s-1, which is comparable to that of the corresponding reaction in water, 6 x 109 M-1s, although the products are different. A few rate constants have been measured in cesium-EDA systems, but it is not clear whether the electron or an associated form of the electron and the cation is the reactant. 

Since the intensity of the charge-transfer absorption is directly related to the concentration of the EDA complex or contact ion pair in equations (4) and (5), respectively, it can be used as an analytical tool to quantify complex formation in equations (2) and (3). According to the commonly utilized Benesi-Hildeb-rand treatment,16 the formation constants are quantitatively evaluated from the graphical plot of the CT absorbance change (Acr) as the donor is progressively added to a solution of the acceptor (or vice versa) (equation 6)... 

A relatively strong organization of an electron donor by an acceptor is typically indicated by experimental values of KEUA or KC f> > 10 M-1. For intermediate values of the formation constant, i.e., 1 < KE A < 10 m, the donor/acceptor organization is considered to be weak.17 Finally, at the limit of very weak donor/acceptor organizations with KEDA 1, the lifetime of the EDA complex can be on the order of a molecular collision these are referred to as contact charge-transfer complexes.18... 

Table 1 EDA complex formation of enol silyl ethers with various electron acceptors in dichloromethane.

Indeed, the (200-fs) laser excitation of the EDA complexes of various benz-pinacols with methyl viologen (MV2+) confirms the formation of all the transient species in equation (59). A careful kinetic analysis of the decay rates of pinacol cation radical and reduced methyl viologen leads to the conclusion that the ultrafast C—C bond cleavage (kc c = 1010 to 1011 s- ) of the various pinacol cation radicals competes effectively with the back electron transfer in the reactive ion pair. 

According to Mulliken (1952a,b Mulliken and Person, 1969), the formation of the ion radical pair occurs upon the irradiation of the charge-transfer band of the EDA complex (2). The experimental proof of Mulliken theory is... 

In order to establish the generality of ion-radical pair formation by the charge-transfer activation of EDA complexes, let us focus on a few diverse... 

The formation of the monocationic intermediate (ArH)2Fe+ attendant upon the charge-transfer excitation of either the ferrocene or methylan-thracene EDA complex (7a and 7b) is responsible for the photo-induced de-ligation of bis(arene)iron(II), as described in (6). Thus, transient electrochemical studies (Karpinski and Kochi, 1992a,b) show that the catalytic de-ligation of (ArH)2Fe+ proceeds rapidly via a (two-step) electron-transfer chain or ETC process (8). 

The recent time-resolved spectroscopic studies described above (Sections 2 and 3) identify the charge-transfer excitation (/n cr) of aromatic EDA complexes with various types of acceptors (A) to their ion-radical pairs [ArH+-,A ] (Mataga, 1984 Hilinski et al., 1984 Jones, 1988). Such electronic transitions in weak EDA complexes, like those of the halogen acceptors, are mainly associated with the excited states, such as in (32), since the variations in the ground state are minor owing to formation constants K that are not strongly dependent on the arene donor (Briegleb, 1961, pp. 106 ff.). 

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