Formaldehyde liberation

The hexitols may be determined quantitatively by periodate oxidation. Either the amount of oxidant consumed or the amount of acid or formaldehyde liberated may be determined. This method will not... 

Another way to oxidize primary alkyl halides to aldehydes is by the use of hexamethylenetetramine followed by water. However, this reaction, called the Sommelet reaction. is limited to benzylic halides. The reaction is seldom useful when the R in RCH2CI is alkyl. The first part of the reaction is conversion to the amine ArCH2NH2 (0-44), which can be isolated. Reaction of the amine with excess hexamethylenetetramine gives the aldehyde. It is this last step that is the actual Sommelet reaction, though the entire process can be conducted without isolation of intermediates. Once the amine is formed, it is converted to an imine (ArCH2N=CH2) with formaldehyde liberated from the reagent. The key step then follows transfer of hydrogen from another mole of the arylamine to the imine ... 

CH2NN02)3 + I2CH3COOH Hexamine is nitrated to Cyclonite, and the 3 mols of formaldehyde liberated react with the AN in the presence of acet anhyd to form a second mole of Cyclonite. According to Bachmann, this reaction appears to be combination of the "nitrolysis reaction and the procedure of Ross Schiessler. However, this reaction is conducted under con- ditions which are different from both of the other reactions. Bachmann s process doubled the y ield of RDX obtainable by the direct nitration of hexamine with HN03 alone. The resulting product, known as Type B RDX, contains as a constant impurity 8-12% HMX (see under Cyclotetramethyl-enetetranitramine)... 

Shrinkage control and fabric smoothness, durable to many home or commercial launderings, are very desirable properties for most textile uses. PERMAFRESH 85 provides high performance results while maintaining a low level of formaldehyde liberation on the treated substrate. 

Formaldehyde liberation from y-methylol groups by alkaline cleavage of the p-y C-C bond has been observed, and the action of hot alkali on lignin to form vanillin by cleavage of the a-p C-C bonds is well known. The simultaneous formation of acetaldehyde in the latter case results from a reverse aldol condensation. Traces of guaiacol found after alkaline hydrolysis of wood may result from cleavage of the C-C bond between the a carbon and the ring. 

The overall objective of this and a companion paper (22) is to define the extent to which board formaldehyde emission is controlled by resin hydrolysis or other processes. In the companion paper I have critically reviewed the literature and presented original Forest Products Laboratory (FPL) data in three related aspects of the formaldehyde emission phenomenon the chemistry of and formaldehyde liberation from formaldehyde-urea and formaldehyde-phenol states the chemistry of and formaldehyde liberation from formaldehyde-cellulose and resin-cellulose states and our knowledge of the board emission mechanism derived from actual board and wood systems. Whereas my oral presentation at the American Chemical Society (ACS) Symposium made use of information from all three of those parts, this written paper, in the interest of saving space, is limited to literature and FPL data dealing with actual wood-containing systems. The Conclusions section of this paper, however, makes use of the results from all three parts of the companion paper. Experimental details of the... 

Overall, therefore, the available literature supports the generally held view that the durability of UF-bonded wood products is governed by the susceptibility of cured UF resin bonds to scission by both hydrolysis and swell/shrink stresses. Note, moreover, that in either case, the most likely product of scission will ultimately be formaldehyde and further that mechanical stress enhances the rates of many chemical reactions (37). In fact, simplistic calculations based on formaldehyde liberated from bond ruptures at least indicate the possibility that formaldehyde from swell/shrink stress rupture could contribute significantly to total emission. Assume, for example, that board failure occurs due to rupture of one chemical bond type which liberates one molecule of formaldehyde and consider two cases (a) a conservative one in which only 5 percent of those bonds rupture in 50 years, i.e., probable board durability greater that 50 years, and (b) a much less conservative case in which 30 percent of those bonds rupture in 20 years, i.e., probably failure in 20 years or less. Case (a) leads to a first order scission rate constant of 3.3 x 10 s and a hypothetical board emission rate (see Appendix 3a) that is below the maximum liberation rate permitted by the German E-1 standard (7). However, Case (b) leads to a first order scission rate constant of 5.7 x 10 s and a hypothetical board emission rate above that allowed by the HUD standard (8). (FormaIdehyde-wood interactions and diffusion effects would... 

Figure 7. Formaldehyde liberation from particleboards and CH20-sorbed wood at 27°C and 33 percent relative humidity (RH) weighing bottle test with -80 mesh materials (o Southern pine impregnated with pH 2 tartaric acid and vapor-equilibrated with CH20/salt solution at pet RH O as before except heated 4 min. 16O°C after CH2O sorption 0 urea-formaldehyde particle board (b) phenol-formaldehyde particleboard, values approximate P = Perforator value at indicated moisture content (MC)).

Interpretation for Comminuted Systems. The similarities and differences noted for the kinetics of formaldehyde removal from UF and PF particleboards and from formaldehyde-sorbed wood are brought out more clearly by plotting relative formaldehyde losses versus time. Loss ratios, i.e., formaldehyde loss by any material divided by the UF board loss at the same time, are shown in Figures 10 and 11 included in Figure 10 are analogous ratios for resin data from formaldehyde liberation (weighing bottle test) and formaldehyde elution by toluene experiments (10). Examination of the data leads to the following additional comments ... 

Figure 9. Formaldehyde liberation in water at 25 C and pH 3 from particleboard and CH20-sorbed wood all materials -80 mesh. (Sodium azide in water at 100 mg/L as preservative symbols and abbreviations as in Figure 7.) (ML85 5436)...

---