Formaldehyde Elimination

We have studied a number of different anionic methoxycarbonyl clusters, and found them all to undergo loss of HCHO at some point during their fragmentation processes. In some cases, we have eorrelated differences in fragmentation patterns between the various clusters with their macroscopic chemical properties. Confirmation of peak assignments was carried out in some cases using Fourier transform ion cyclotron resonance (FTICR). 

The elimination of an aldehyde or ketone from a coordinated alkoxide is a well known process in coordination chemistry. For example, treatment of metal halide complexes with alcoholie base is a standard method for the preparation of metal hydride complexes (Equation 2). Labelling experiments have shown that the a hydrogen is transformed into the hydride ligand.  

This process has also been observed in cluster chemistry. For example, the cluster anion [Ru3lrH(OMe)(CO)i2] eliminates HCHO under carbonyl loss conditions (prolonged heating) to generate the cluster anion [Ru3lrH2-(CO)i2] - Because fragmentation in the mass spectrometer also involves earbonyl loss, it seems plausible that such a process might be simulated under EDESI-MS conditions. 

As seen for 1 and 2, at the lowest cone voltages, the only peak observed is that 

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Since a small amount of water is always present in novolac resins, it has also been suggested that some decomposition of HMTA proceeds by hydrolysis, leading to the elimination of formaldehyde and amino-methylol compounds (Fig. 7.15).42 Phenols can react with the formaldehyde elimination product to extend the novolac chain or form methylene-bridged crosslinks. Alternatively, phenol can react with amino-methylol intermediates in combination with formaldehyde to produce ortho-or para-hydroxybenzylamines (i.e., Mannich-type reactions). 

Fig. 7-25. Main reactions of the phenolic /8-aryl ether structures during alkali (soda) and kraft pulping (Gierer, 1970). R = H, alkyl, or aryl group. The first step involves formation of a quinone methide intermediate (2). In alkali pulping intermediate (2) undergoes proton or formaldehyde elimination and is converted to styryl aryl ether structure (3a). During kraft pulping intermediate (2) is instead attacked by the nucleophilic hydrosulfide ions with formation of a thiirane structure (4) and simultaneous cleavage of the /3-aryl ether bond. Intermediate (5) reacts further either via a 1,4-dithiane dimer or directly to compounds of styrene type (6) and to complicated polymeric products (P). During these reactions most of the organically bound sulfur is eliminated as elemental sulfur.

First, following the results of the 1,6-dioxa-spiro[2.5]octane rearrangement (5,19), continuous gas phase conditions were applied in a fixed bed reactor and secondly under liquid phase conditions in a slurry reactor. The catalytic experiments carried out showed that two main reactions took place rearrangement of 18 to the aldehyde 19 and a oxidative decarbonylation reaction to the olefine 1,3,3,4-tetramethyl-cyclohex-l-ene 20, which is assumed to be caused by a formaldehyde elimination reaction. Also observed was a deoxygenation reaction to the alkane 1,1,2,5-tetra-methylcyclohexane 21 (Eq. 15.2.7), explained by elimination of CO. There are several other side-products such as 2,2,3,6-tetramethylcyclohex-l-enyl-methanol, ringcontracting compounds and double bond isomers of dimethyl-isopropylene-cyclopentene. 

Aminoplast dispersions, in spite of the accessibility and low cost of raw materials, are not produced industrially, due to the risk of toxic formaldehyde elimination, especially when the resulting aminoplast polymer polyol is used for slabstock foams and, of course, for moulded flexible foams used for seating or interior automotive parts. 

Formaldehyde Elimination from Methoxylated Transition Metal Carbonyl Clusters... 

Formaldehyde Elimination from Methoxylated Transition Metal Carbonyl Clusters Commun. Mass Spec., 2000,14, 311. 

The rate-determining step is K and added formaldehyde eliminates the and paths, leaving PhSSPy. ... 

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