Estimations formaldehyde

One molecule of periodic acid is used for each pair of adjacent hydroxyl groups. Thus by estimating formaldehyde and formic acid and the amount of periodic acid consumed, it is possible to know the number of free adjacent hydroxyl groups. However, if the sugar is in the... 

Table IX shows the calculated values of methyl glyoxal intake for each food item when it is consumed. Even after dilution, coffee provided the most methyl glyoxal intake. It is difficult to estimate formaldehyde or methyl glyoxal intake from soy sauce because its use varies widely.

Formaldehyde-specific IgE antibodies could be detected in only 1/86 serum samples from four groups of formaldehyde-exposed subjects (Kramps et al. 1989). The groups included 28 subjects living or working in places with formaldehyde-containing construction materials (e.g., chipboard) and estimated formaldehyde concentrations ranging from 0.08 to 0.37 ppm, 18 occupationally exposed subjects from an anatomy laboratory and in other unspecified industries where air concentrations were not measured,... 

The MRL was based on a NOAEL of 15 mg/kg/day for gastrointestinal effects in male rats exposed to formaldehyde in drinking water (Til et al. 1989). The LOAEL was 82 mg/kg/day. An uncertainty factor of 100 (10 for extrapolation from animals to humans and 10 for human variability) was applied to the NOAEL to derive the MRL. The Til et al. (1989) study used groups of Wistar rats that received formaldehyde in their drinking water for 2 years. Estimated formaldehyde doses in this study were 0,... 

The only other suggestive evidence of IgE-mediated sensitization to formaldehyde comes from a study of schoolchildren who were exposed to particleboard-paneled classrooms with estimated formaldehyde air... 

Stewart (USA) 1986 Comparison of historical exposures, current exposures, and job titles to develop a final exposure estimate Formaldehyde Cumulative exposure (ppm)... 

Besides the various other substances with toxic effects, polluted air may also contain aldehydes, which are formed as reaction products of hydrocarbon photooxidation. The reactions of aldehydes are not very rapid, so that they are accumulated in concentrations of about 0.2 ppm in the photochemical smog. Formaldehyde and acrolein are the most important compounds in this group. Their irritating nature obviously contributes to the increase of the smog smell and to its irritating effects on the eyes. According to estimates, formaldehyde represents a fraction of 50% out of all the aldehydes in the polluted air. Acrolein is more irritating than formaldehyde and forms about 5% of the aldehydes. 

The compound (III) can however lose ethanol by an internal Claisen ester condensation (p. 264) to give the cyclohexane derivative (IV), which, being the ester of a (3-keto acid, in turn readily undergoes hydrolysis and decarboxylation to give 5,5Hiimethyl cyclohexan-i,3Hiione (V) or Dimedone, a valuable reagent for the detection and estimation of formaldehyde. 

Method, Formaldehyde may be estimated in solution by oxidising it to formic acid by means of a known quantity (in excess) of iodine dissolved in a excess of NaOH solution. The oxidation is, in effect, carried out by the odium hypo-iodite formed by the action of the iodine on the alkali, the formic cid being then neutralised by the alkali present ... 

Noth. The above method can be successfully applied only to dilute solutions of formaldehyde which are free in particular from other alfphatic aldehydes, since the latter, if present, would undergo a similar oxidation. Formaldehyde, if mixed with other aldehydes, should be estimated by quantitative addition of potassium cyanide for details, see advanced text-books of quantitative organic analysis. 

Uses. Furfuryl alcohol is widely used as a monomer in manufacturing furfuryl alcohol resins, and as a reactive solvent in a variety of synthetic resins and appHcations. Resins derived from furfuryl alcohol are the most important appHcation for furfuryl alcohol in both utihty and volume. The final cross-linked products display outstanding chemical, thermal, and mechanical properties. They are also heat-stable and remarkably resistant to acids, alkaUes, and solvents. Many commercial resins of various compositions and properties have been prepared by polymerization of furfuryl alcohol and other co-reactants such as furfural, formaldehyde, glyoxal, resorcinol, phenoHc compounds and urea. In 1992, domestic furfuryl alcohol consumption was estimated at 47 million pounds (38). 

Oxidation of methanol to formaldehyde with vanadium pentoxide catalyst was first patented in 1921 (90), followed in 1933 by a patent for an iron oxide—molybdenum oxide catalyst (91), which is stiU the choice in the 1990s. Catalysts are improved by modification with small amounts of other metal oxides (92), support on inert carriers (93), and methods of preparation (94,95) and activation (96). In 1952, the first commercial plant using an iron—molybdenum oxide catalyst was put into operation (97). It is estimated that 70% of the new formaldehyde installed capacity is the metal oxide process (98). 

Worldwide production capacity in 1989 was estimated to be over 15.5 x 10 t as 37 wt % formaldehyde (98). The United States, Canada, Europe, and Japan account for nearly 70% of the total capacity (98). Worldwide demand for formaldehyde in 1989 was estimated to be about 85—90% of capacity (98). 

Naphthalenesulfonic Acid—Formaldehyde Condensates. The sodium salts of the condensation products of naphthalenesulfonic acid with formaldehyde constitute an important class of compounds which are mainly used in the area of concrete additives (32,33), agricultural formulations, mbber formulations, and synthetic tanning agents. They are also used in photographic materials (34). Hampshire Chemical Co. and Henkel of America, Inc., are the largest suppHers of naphthalene sulfonate in concrete additives (superplasticizer) and reportedly hold 75—80% of this market. It was estimated that naphthalene sulfonate demand from U.S. producers would reach approximately... 

In 1994 estimated naphthalene consumption in western Europe and Japan for the production of alkylnaphthalene sulfonates, naphthalene sulfonate formaldehyde condensates, and synthetic tanning agents was... 

Hawthorne, A., et al. (1987) Models for estimating organic emissions from building materials formaldehyde example. Atmos. Environ. 21, No. 2. Lewis, R. G., et al. (1986) Monitoring for non-occupational exposure to pesticides in indoor and personal respiratory air. Presented at the 79th Annual Meeting of the Air Pollution Control Association, Minneapolis, MN. 

By the mid-1990s world production of aminoplastics was estimated at about 6 000 000 t.p.a. of which more than 5 000 000 t.p.a. were urea-formaldehyde resins. The bulk of the rest were melamine-formaldehyde. Such bald statistics, however, disguise the fact that a considerable amount of aminoplastics used are actually co-condensates of urea, melamine and formaldehyde. 

Example 4.10 A circular plate with a diameter of 0.3 m is to be compression moulded from phenol formaldehyde. If the preform is cylindrical with a diameter of 50 mm and a depth of 36 mm estimate the platen force needed to produce the plate in 10 seconds. The viscosity of the phenol may be taken as 10 Ns/m. ... 

Gaussian also includes a facility for estimating molecular volumes for SCRFsDipole calculations. An energy calculation run with the Volume keyword will produce an estimate value for Uq. For example, here is the output indicating the recommended value for Oq for formaldehyde (RHF/6-31+G ) ... 

The second channel, producing CO, was first observed by Seakins and Leone [64], who estimated 40% branching to this channel. Later measurements by Lockenberg et al. [65] and Preses et al. [66] concluded the branching to CO is 18%. Note that decomposition of formaldehyde formed in reaction (26a) is not a possible source of CO due to the large barrier for formaldehyde decomposition. Marcy et al. [67] recently combined time-resolved Lourier spectroscopy experiments with direct dynamics classical trajectory calculations to examine the mechanism of the CO product channel. They observed two pathways for CO formation, neither of which involve crossing a TS. 

In this chapter, the definitions used by Perrin in his book on pA a prediction (which also includes a very convenient compilation of o values) will be used. One must be alert to the importance of the number of hydrogens directly attached to the carbonyl carbon several groups have pointed out that aldehydes and ketones give separate but parallel lines, with formaldehyde displaced by the same amount again. What this means is that given one equilibrium constant for an aldehyde (or ketone) one may estimate the equilibrium constant for other aldehydes (or ketones) from this value and p for the addition using a value from experiment, if available, or estimated if necessary. This assumes that there is no large difference in steric effects between the reference compound and the unknown of interest. 

What this implies is that given one equilibrium constant for addition of a nucleophile of known 7 to a carbonyl compound, one could estimate the equilibrium constant for addition of another nucleophile to the same carbonyl compound. This requires knowing the slope of the plot of log K versus y this slope is not very sensitive to the nature of the carbonyl compound, but it is at least known that A H2o/ MeOH depends on the electron-withdrawing power of the groups bonded to the carbonyl, and thus more information is needed to estimate an equilibrium constant for strongly electron-withdrawing substituents. From Ritchie s studies of nucleophile addition to trifluoroacetophenone," we can derive a slope for log K versus 7 of 0.42, distinctly less than the value of 1 for formaldehyde or simple benzaldehydes. 

Estimated Free Energy Changes of Selected Biological Reactions Involved in the Anaerobic Degradation of Formaldehyde and Methanol... 

Although the condensation of phenol with formaldehyde has been known for more than 100 years, it is only recently that the reaction could be studied in detail. Recent developments in analytical instrumentation like GC, GPC, HPLC, IR spectroscopy and NMR spectroscopy have made it possible for the intermediates involved in such reactions to be characterized and determined (1.-6). In addition, high speed computers can now be used to simulate the complicated multi-component, multi-path kinetic schemes involved in phenol-formaldehyde reactions (6-27) and optimization routines can be used in conjunction with computer-based models for phenol-formaldehyde reactions to estimate, from experimental data, reaction rates for the various processes involved. The combined use of precise analytical data and of computer-based techniques to analyze such data has been very fruitful. 

---